Microstructure and Mechanical Performance of Inconel 617 Thin Wall fabricated via Wire Arc Additive Manufacturing

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Maheshwaran, A. Rajesh Kannan, Nallathambi Siva Shanmugam This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6854790/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract This study presents a comprehensive investigation into the microstructural evolution and mechanical performance of an Inconel 617 wall fabricated using the Wire Arc Additive Manufacturing (WAAM) process. Detailed microstructural characterization reveals a gradient in grain morphology along the build direction, driven by variations in thermal history. Equiaxed dendrites and columnar grains due to rapid solidification were noticed near the substrate and are mixed together in the bottom layers, while cellular structures and columnar dendrites are dominant in the middle layers. Elongated columnar dendrites are observed in the upper layers. In addition, Ti(C,N) secondary phases and precipitates such as M 6 C and M 23 C 6 carbides are noticed within the austenitic matrix, are confirmed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The presence of these phases is further confirmed by X-ray diffraction (XRD), which finds their distinctive diffraction peaks. From hardness mapping, the build's average microhardness ranges from 237 HV at the bottom to 211 HV at the top, nearly matching the wrought Inconel 617's characteristics as outlined in ASTM B168-19. Anisotropy is clearly seen from the tensile tests, since the deposition direction achieves a higher average ultimate tensile strength (UTS) of 792 MPa than the build direction, which is 610 MPa. In all orientations, ductile fracture characteristics with dimples and voids are confirmed, suggesting significant plastic deformation before failure. The results demonstrate the importance of building orientation on material performance and validate the feasibility of the WAAM method for fabricating Inconel 617 components free of defects with desirable mechanical and microstructural integrity. Welding WAAM Inconel 617 Microstructure Mechanical properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Inconel 617 is a solid solution-strengthened, nickel-based superalloy engineered for high-temperature structural applications, exhibiting excellent mechanical performance and environmental resistance at temperatures up to ~ 1100°C. Its microstructure is based on a stable face-centered cubic (FCC) matrix, with solid solution strengthening primarily contributed by molybdenum and cobalt, while chromium imparts oxidation and corrosion resistance. The alloy demonstrates superior creep resistance, high-temperature tensile strength, and thermal stability, making it suitable for long-term exposure in aggressive environments. Inconel 617's resistance to carburization, sulfidation, and oxidation, combined with its high-temperature phase stability, renders it a prime candidate for components in advanced ultra-supercritical (A-USC) power plants, gas turbines, heat exchangers, and high-temperature nuclear systems such as Very High Temperature Reactors (VHTRs)[ 1 ] Due to its excellent corrosion resistance and high-temperature strength, Inconel 617 is widely favored for critical components such as boiler tubes, transition ducts in aircraft engines, land-based gas turbines, and catalyst support grids [ 2 ] However, the fabrication of Inconel 617 components with intricate geometries using conventional methods, such as casting and powder metallurgy, remains more economically viable for certain applications due to their established scalability and lower material waste [ 3 ]. Nevertheless, additive manufacturing (AM) technologies offer a compelling alternative for producing geometrically complex Inconel 617 components. AM enables near-net-shape fabrication with high material utilization, reduced production lead times, and the potential for cost savings in low-to-medium volume production[ 4 ]. Additive Manufacturing (AM) is gaining prominence in the production of nickel-based superalloys such as Inconel 617, owing to its capability to fabricate complex, near-net-shape geometries with minimal material waste and significantly reduced lead times. Unlike conventional manufacturing processes, AM enables the production of lightweight, topology-optimized components without the need for extensive tooling or machining. Furthermore, AM offers the potential to engineer tailored microstructures through precise control of solidification dynamics, thereby enhancing the mechanical and thermal properties of the final parts. This technology also supports efficient repair and remanufacturing of high-value components, as well as localized, on-demand production, which is particularly beneficial in high-performance sectors such as aerospace, energy, and nuclear power. AM processes for fabricating three-dimensional components can be broadly classified into powder-fed and wire-fed systems. Wire-fed additive manufacturing techniques are preferred due to their high deposition rates, cost-effectiveness, and superior material utilization. Additionally, they offer enhanced scalability for fabricating large structural components with minimal waste. Among wire-fed technologies, arc-based additive manufacturing (Arc-AM), which includes processes such as Wire Arc Additive Manufacturing (WAAM), is emerging as a cost-effective and scalable approach for producing medium-to-large-scale metallic structures with high deposition rates and comparable structural integrity[ 5 ], [ 6 ]. It also enables flexible fabrication using standard welding equipment and readily available wire feedstock[ 7 ]. WAAM is preferred in aerospace, energy, marine, and defense industries for producing complex metal components with low material waste. Its cost-effectiveness and ability to fabricate near-net-shape parts make it ideal for structural, repair, and tooling applications. WAAM is performed by feeding a metal wire into a molten pool created by an electric arc, typically using a welding process like Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), or Plasma Arc Welding (PAW). The process deposits material layer by layer to build a part. With optimized process parameters, WAAM can produce components exhibiting mechanical properties comparable to those of conventionally manufactured parts, requiring only minimal post-processing to eliminate surface waviness inherent to the deposition process. A wide range of alloys, such as aluminum, steel, titanium, and nickel-based superalloys, have been successfully employed to fabricate high-quality, defect-free structures using WAAM[ 8 ]. Numerous studies have demonstrated the successful fabrication of various nickel-based superalloys via WAAM, including Inconel 625[ 9 ], Inconel 718[ 10 ], Hastelloy C-276[ 11 ], and Waspaloy[ 12 ]. Among the key considerations in selecting suitable feedstock materials for WAAM is the weldability of the alloy, which significantly influences deposition quality and structural integrity. Inconel 625 and Inconel 718 have received the most research attention, primarily due to their excellent weldability, superior corrosion resistance, robust mechanical performance, and widespread applicability across critical industries such as aerospace, energy, and chemical processing. Rodrigues et al.[ 13 ] manufactured Inconel 625 and examined the influence of heat treatments on the microstructural features using in situ synchrotron X-ray diffraction (XRD) and hardness. As-built samples revealed the presence of a γ-matrix with precipitation of γ′, γ′′, and MC carbides. When heat-treated at 750°C for 4 h, the γ′′ phase precipitated, increasing the hardness by 5%. In situ X-ray observations revealed that heat treating at 870°C for 1 h resulted in δ-phase precipitation. Kwak et al.[ 14 ] investigated the anisotropic mechanical behavior of the 601 nickel-based superalloy fabricated via WAAM by employing multiscale tensile testing in conjunction with crystal plasticity modeling, providing insights into the relationship between microstructural orientation and deformation mechanisms. WAAM-CMT fabricated 601 superalloys exhibited a hierarchical microstructure with columnar grains aligned along the build direction and a pronounced [001] crystallographic texture. Despite consistent yield strength across orientations, tensile strength showed directional dependence, highlighting the influence of microstructural anisotropy on mechanical performance. Rajkumar et al.[ 15 ] studied the microstructure, mechanical properties, and corrosion performance of Incoloy 825 produced via WAAM process. Microstructural examination of WAAM-fabricated Incoloy 825 revealed austenitic matrices containing equiaxed, cellular, elongated, and columnar dendrites, with TiC and Laves phases localized in the interdendritic regions, as confirmed by electron microscopy and EDS analysis. These secondary phases notably influenced the hardness distribution (226–262 HV), while the alloy exhibited excellent pitting resistance in 3.5% NaCl solution, with corrosion rates ranging from 0.59 to 0.70 mpy. Anand et al.[ 16 ] examined the Grain refinement in Wire-Arc Additive Manufactured Inconel 82 alloy through controlled heat input. Grain refinement in WAAM-fabricated walls was achieved by adjusting travel speed and applying low-frequency pulse arc, without the use of inoculants or external equipment, resulting in enhanced micro-hardness (275 HV) in a 15-layer wall. The same wall exhibited minimal anisotropy in mechanical properties, with the transverse specimen showing higher UTS (650 MPa), YS (325 MPa), and reduced elongation (52%). Ajithkumar et al.[ 17 ] analyzed the effect of cryogenic treatments on the microstructure and mechanical properties of Inconel 686 fabricated by GMAW-based WAAM process. WAAM fabricated Inconel 686 exhibited coarse microstructures and elemental segregation in the as-built condition, particularly with Mo enrichment in interdendritic regions due to prolonged solidification. Deep Cryogenic Treatments effectively refined the microstructure, eliminated secondary phases, minimized segregation, and significantly improved strength, hardness, and reduced mechanical anisotropy. In reference to this investigation, Hassel et al.[ 18 ] investigated the anisotropy in mechanical properties, and hardness was observed relative to the build direction, with increased strength but reduced elongation at 45° to BD, while properties along BD and 90° were comparable. SEM-based slip line analysis from micro-tensile tests revealed activation of different slip systems depending on orientation, indicating a dominant crystallographic texture; thus, controlled solidification during WAAM can enable directional tailoring of properties by aligning component geometry with grain growth direction. Avinash et al.[ 19 ] fabricated an IN617 wall that exhibited a defect-free build with a hierarchical microstructure comprising cellular, equiaxed, and elongated columnar dendrites aligned along the build direction. EDS analysis confirmed the presence of Ti(C,N) and M₂₃C₆ precipitates within the interdendritic regions of the austenitic matrix. Tafel polarization tests demonstrated low corrosion current density and high corrosion potential, indicating superior electrochemical resistance in 3.5% NaCl solution. Potentiodynamic polarization (PDP) results showed minimal variation in corrosion behavior across different sample locations, with micro-pits ranging from 30 to 100 µm in size. Zhang et al.[ 20 ] examined the influence of pre-strain on the high-temperature oxidation behavior of WAAM-fabricated Inconel 617 at 900°C. A bilayer oxide scale consisting of an inner Al2O3 layer and an outer Cr2O3 layer formed on WAAM-fabricated Inconel 617 after exposure to air at 900°C for 50 h, with minor amounts of (Ti, Ni)-oxides and NiCr2O4 also present. Increasing pre-strain enhanced oxidation resistance by promoting short-circuit diffusion pathways for Cr and Al, leading to faster formation of a denser and more protective oxide scale. Nandi et al.[ 21 ] reported that as-deposited Inconel 617 contains a higher amount of carbides compared to carbonitrides. Furthermore, carbides are more abundant at the 10 mm location from the substrate, whereas carbonitrides are predominantly found closer, at around 1 mm from the substrate. Despite these differences in spatial distribution, the distance from the substrate appears to have minimal impact on the size distribution characteristics of the precipitates. Despite significant progress in the field of WAAM of nickel-based superalloys, the existing literature reveals a lack of comprehensive and cohesive understanding regarding the mechanical and microstructural characteristics of Inconel 617. While several studies have explored the fabrication aspects of Inconel 617 using WAAM, a systematic investigation that correlates its elemental composition, mechanical performance, and microstructural evolution remains limited. In this context, the present study aims to bridge this gap by fabricating an Inconel 617 wall using the GMAW-based WAAM process and conducting a detailed characterization of its elemental distribution, microstructure, and mechanical properties, thereby contributing new insights into the processing-structure-property relationships of this high-performance alloy. 2. Materials and Methods In this study, the GMAW-based WAAM process is employed to deposit Inconel 617 filler wire with a diameter of 1.2 mm. The chemical composition of the wire complies with the AWS A5.14 M:2011 standard, as detailed in Table 1 . Layer-by-layer deposition is performed on an SS347 substrate plate with a thickness of 5 mm. The wall structure is fabricated using an OTC Daihen 6-axis robotic arm, interfaced with a Welbee P500L power source and FD-11 controller. An AF 4012 wire feeder unit is integrated with the robotic system, as illustrated in Fig. 1 . Based on the weld bead geometry and profile obtained, multiple welding trials were conducted to optimize the process parameters, resulting in defect-free, linear weld beads with no porosity. Figure 1 also depicts the six-axis robotic welding setup alongside the as-deposited Inconel 617 WAAM wall. Table 1 Chemical composition of Inconel 617 filler wire as per AWS A5.14 M: 2011 standard Element Ni Cr Co Mo Fe Si Al Ti C wt.% 54.50 22.50 12.0 8.70 0.50 0.30 1.0 0.40 0.1 2.1 Fabrication of WAAM The WAAM-based fabrication requires careful control of bead geometry to ensure dimensional accuracy and build integrity. Among the governing factors, power input plays a critical role in determining the stability and quality of the weld bead. An increase in power input results in elevated heat generation, which enhances the melting rate of the wire feedstock, as described by the relationship Pnet = ηIV, where η denotes the thermal efficiency of the heat source, I is the welding current, and V is the arc voltage[ 22 ]. Achieving a refined and uniform weld bead geometry necessitates the optimization of key process parameters, including welding current, gas flow rate, and travel speed[ 23 ]. During the layer-by-layer deposition process, a dwell time of 60 seconds was introduced between successive layers, as suggested by Kannan et al.[ 24 ] to allow adequate thermal dissipation and minimize heat accumulation, thereby reducing residual stress and distortion. Based on insights from the literature, a series of iterative experimental trials were conducted by varying the current and shielding gas flow rates to identify the optimal process window. The experimental results demonstrated the formation of stable, smooth, and defect-free weld beads with desirable cross-sectional geometry. Using the optimized set of process parameters, a multi-layered Inconel 617 wall was successfully fabricated employing a bi-directional (to-and-fro) deposition strategy. This controlled approach ensured consistent layer stacking and high structural fidelity in the as-deposited WAAM wall. The process variables used for layer deposition are listed in Table 2 . Table 2 Process variables for layer deposition of Inconel 617 WAAM wall. Process variables used for layer deposition Current (Amps) 120 Voltage (V) 14.8 Shielding Gas Pure Argon (99.99%) Gas flow Rate (lpm) 18 Welding speed(mm/min) 100 Bead Thickness(mm) 7 (as deposited) Average height of layers deposited (mm) 3 (approximately) Dwell Time for each layer deposition (seconds) 60 Height of the WAAM wall (mm) 110 (as deposited) Deposition rate (Kg/hr) 1.57 Distance between the torch to work piece 15 mm Angle of the contact tip 90⁰ The WAAM-printed wall in the as-deposited condition measures 7 × 100 × 110 mm (W × L × H). To facilitate mechanical and microstructural characterization, the wall undergoes face milling to remove surface waviness inherent to the as-built condition. After milling, the dimensions of the wall are reduced to 4 × 100 × 105 mm. 2.1 Microstructural Characterization To investigate the microstructural characteristics of the WAAM-fabricated Inconel 617 wall, specimens were extracted from the top, middle, and bottom regions in the as-deposited condition. Following a meticulous grinding and polishing process, samples were chemically etched using a reagent mixture of hydrochloric acid (HCl) and nitric acid (HNO3) to reveal the grain structure, which was initially examined under an optical microscope. For higher-resolution microstructural analysis, a Carl Zeiss Sigma 300 Scanning Electron Microscope (SEM) was employed to observe grain morphology, dendritic structures, and phase boundaries. To identify and quantify the precipitate phases, Energy Dispersive Spectroscopy (EDS) was performed in conjunction with SEM imaging. XRD analysis was conducted using a PANalytical X’Pert3 diffractometer to determine the crystalline phases and secondary precipitates present in the alloy. The XRD scan was carried out using Cu Kα radiation (λ = 1.5406 Å) with operational parameters set at 30 mA and 45 kV. The scan covered a 2θ range of 5° to 90°, with a scan rate of 1°/min and a step time of 47.94 seconds. Additionally, EDS elemental mapping was utilized to assess the spatial distribution of alloying elements and precipitates across different regions of the WAAM wall. 2.2 Mechanical Characterization The mechanical performance of the WAAM-fabricated Inconel 617 wall was systematically assessed through tensile and microhardness testing. Non-standard miniature tensile specimens were extracted in three principal orientations: longitudinal (parallel to deposition), diagonal (inclined), and transverse (perpendicular to deposition) to evaluate anisotropy in mechanical behavior. The use of miniature tensile specimens has been widely validated in the literature as a reliable high-throughput method for predicting representative mechanical properties of additively manufactured superalloys[ 6 ], [ 25 ]. For each orientation, three specimens were tested using a Tinius Olsen H50KL uniaxial tensile testing machine under displacement control at a constant crosshead speed of 1 mm/min. post-fracture surfaces were examined using Scanning Electron Microscopy (SEM) to characterize the failure mechanisms and assess ductile fracture features such as dimples and voids. Vickers microhardness measurements were conducted using a Struers Duramin-4 M1 hardness tester, in accordance with ASTM E92-17 standards. Polished samples from three distinct regions of the build: top, middle, and bottom, were subjected to testing with a 500 g load, a dwell time of 15 seconds, and an indentation spacing of 1 mm to ensure uniform sampling. A schematic representation of the specimen extraction layout is shown in Fig. 2 , providing a visual guide to the orientation and sampling methodology. 3. Results and Discussions Wall structures in industrial applications are expected to possess certain service-related capabilities. WAAM components are generally required to carry loads of various types in which the weld layers are subject to stresses of either a simple or complex character. Moreover, a finished weld is not always as good or as bad as it may appear to be on its surface. It is therefore necessary to find out how satisfactory or sound the weld is. For this purpose, certain testing procedures (as per ASTM standard) have been evolved and standardized to estimate the expected performance of the WAAM wall structure. 3.1 Microstructural Characterization Proper metallurgical bonding, accomplished through WAAM technique improves mechanical strength by producing a durable, cohesive interface between weld layers. 3.1.1 Optical Microscopic Analysis Figure 3 (a-d) presents the microstructural evolution of the Inconel 617 WAAM wall at three distinct locations: the bottom, middle, and top regions. In the bottom layers (layers 2–5), as shown in Fig. 3 d, a combination of equiaxed dendrites and elongated columnar grains is evident. The development of these microstructural features is attributed to the thermal gradients and solidification dynamics during deposition. At the early stages of fabrication, the substrate acts as an effective heat sink, promoting rapid cooling, which in turn facilitates the formation of equiaxed and columnar grains[ 26 ]. These grains typically grow epitaxially along the building direction, oriented parallel to the direction of heat extraction from the weld pool. In the middle layers (approximately layers 15–18), shown in Fig. 3 c, a transitional grain structure is observed, consisting of both columnar dendrites and cellular structures. Additionally, the presence of cellular structures, fine interlocking needle-like grains can be seen nucleating intergranularly. These acellular morphologies influence the mechanical properties of the material, particularly its toughness, due to their ability to deflect cracks and inhibit crack propagation. The middle region is characterized by a transition zone, indicating a shift in grain morphology driven by the altered thermal gradients and cooling rates between successive layers. Figure 3 b illustrates the top region of the Inconel 617 WAAM wall, where the microstructure comprises elongated columnar dendrites. The presence of lathy structures is also noted in this region[ 27 ]. Such morphologies typically form in the final stages of deposition, where thermal gradients are reduced, allowing more uniform solidification structures to develop. The formation of cellular dendrites and laths is often associated with localized compositional variations and segregation during solidification. Nickel-based superalloys like Inconel 617 derive significant mechanical strength and toughness from the precipitation of secondary phases, including MC-type carbides. During solidification, solute elements segregate into interdendritic regions, leading to the formation of carbides such as M 6 C and M 23 C 6 , which contribute to enhanced hardness[ 19 ]. 3.1.2 SEM Analysis Figure 4 illustrates the SEM image and EDS point scan responses obtained from the top (Fig. 4 a), middle (Fig. 4 b), and bottom (Fig. 4 c) regions of the Inconel 617 WAAM wall. The SEM image from the bottom region clearly reveals the presence of columnar dendrites and equiaxed dendrites, which are aligned predominantly perpendicular to the build direction. This epitaxial grain growth pattern is characteristic of WAAM-processed Inconel 617 components and results from the directional solidification driven by steep thermal gradients near the substrate. A similar observation was reported by Ravi et al.[ 28 ] in Inconel 625 WAAM builds, where the directional growth of columnar dendrites was prominent due to consistent heat dissipation into the substrate. In the middle section of the wall, SEM images reveal sharp, needle-like dendritic features and cellular structures. Also, the carbides presence was confirmed within the matrix, indicative of carbide precipitation in this region. These structures are consistent with the morphology of M 23 ​C 6 ​ carbides, as identified by Zhang et al.[ 29 ], who observed elongated needle-like precipitates associated with chromium-rich carbide phases in nickel-based superalloys. These precipitates often nucleate intergranularly and are responsible for enhancing the hardness of the alloy. The top region of the WAAM wall, as observed through SEM-EDS, exhibits localized enrichment of molybdenum and the formation of a distinct secondary phase identified as the Laves phase. The presence of this intermetallic compound is attributed to elemental segregation during rapid solidification. According to Delfino et al.[ 30 ], Laves phases preferentially form in Nb and Mo-rich regions under rapid cooling conditions, which is consistent with the observed microstructure in the topmost layers of the WAAM wall. These microstructural observations confirm the hierarchical distribution of secondary phases across the build height, highlighting the influence of thermal history and solidification conditions on microstructural evolution in WAAM-fabricated Inconel 617. 3.1.3 EDS Analysis EDS analysis clearly confirms the formation of Laves phases in conjunction with carbides and precipitates throughout the WAAM-fabricated Inconel 617 wall. Notably, Ti(C, N) precipitates are predominantly observed in the bottom region of the wall, aligning with the findings reported by Tytko et al.[ 31 ] in their study on the microstructural evolution of Ni-based superalloys. In the middle and top layers, M 23 C 6 and M 6 C carbides are identified. M 6 C, a Mo-rich carbide, and M 23 C 6 , a Cr-rich carbide, both crystallize in a face-centered cubic (FCC) structure and are commonly found in fusion-based processing of Inconel 617, as also noted by Ren et al.[ 32 ]. The presence of these secondary phases has a direct influence on the mechanical performance of the alloy. M 6 C and M 23 C 6 carbides are known to contribute significantly to improvements in tensile strength and hardness by impeding dislocation motion and stabilizing grain boundaries. EDS spectra further reveal localized Mo enrichment at specific sites, often surpassing Ni concentrations, which supports the preferential nucleation of Mo-rich carbides. Additionally, carbides are observed along grain boundaries, a feature that plays a critical role in determining grain boundary strength, grain size stabilization, and the long-term structural integrity of the alloy. The grain boundary precipitation of carbides is beneficial in maintaining microstructural stability during high-temperature service. As reported by Dong et al.[ 33 ], the presence of M 23 C 6 carbides is also associated with enhanced fracture toughness, further underlining their significance in the performance of WAAM-fabricated Inconel 617 components. EDS analysis confirms the presence of Cr-rich (M 23 C 6 ) and Mo-rich (M 6 C) carbides, along with Ti(C, N) precipitates, within the WAAM-fabricated Inconel 617 wall. The corresponding EDS spectrums and composition of these carbides are presented in Fig. 5 a-c and Table 3 . These secondary phases are distributed across various regions of the build wall, corresponding to distinct thermal histories during layer-by-layer deposition. Elemental segregation contributing to the formation of these carbides and precipitates was evaluated at specific locations using spot EDS analysis. The localized chemical compositions obtained from these regions are summarized in Table 3 , providing clear evidence of elemental enrichment, particularly of Cr, Mo, and Ti, at sites where precipitate phases have formed. These compositional findings further support the identification of the observed phases and their potential roles in influencing the alloy’s mechanical and thermal stability. Table 3 Elements present in precipitates and carbides present in the Inconel 617 WAAM wall. Element in wt% Ni Cr Mo Co C Ti N Phases Ti (C, N) 19.63 11.45 3.08 4.64 9.26 40.76 1.20 M 23 C 6 47.89 21.50 5.06 10.26 12.37 0.70 0.01 M6C 14.91 18.74 19.73 4.56 29.48 1.02 0.79 3.1.4 EDS Elemental Mapping The elemental distribution of the WAAM-fabricated Inconel 617 alloy analyzed using EDS, and the corresponding elemental maps are presented in Fig. 6 . The chemical composition, detailed in the accompanying table, aligns well with the nominal specification for Inconel 617, confirming the chemical reliability of the WAAM deposition process. Nickel (Ni) and Chromium (Cr), the two principal constituents of Inconel 617, are present in relatively high weight percentages of 37% and 30%, respectively. Their distribution appears uniform across the scanned area, indicating effective melting and solidification behavior during WAAM processing. This homogeneity is essential for ensuring consistent corrosion resistance and mechanical strength throughout the deposited wall. Cobalt (Co), Molybdenum (Mo), and Manganese (Mn), present at 10%, 7%, and 6% respectively, also exhibit uniform dispersion. These elements play significant roles in solid-solution strengthening and high-temperature creep resistance. Their even distribution further affirms the metallurgical soundness of the WAAM process and suggests minimal macro-segregation. Titanium (Ti) and Nitrogen (N), though present in relatively small quantities (6% and 1%, respectively), exhibit localized clustering in the elemental maps. These regions likely correspond to the formation of secondary strengthening phases such as titanium carbonitrides (Ti(C, N)). This observation is consistent with earlier EDS point analysis and XRD results, which confirm the presence of M6C and M23C6 carbides, as well as Ti-based carbonitrides in the microstructure. The presence of bright, isolated features in the Ti and N maps suggests precipitate formation, particularly in interdendritic regions or near grain boundaries. In addition, Mo-rich precipitates are noticed within the dendritic regions. Such precipitates contribute to the overall strength and thermal stability of the material, particularly in high-temperature applications. The minimal evidence of elemental segregation implies that thermal gradients during deposition were well managed, limiting elemental redistribution. 3.1.5 XRD Analysis XRD was performed on specimens extracted from the bottom (B), middle (M), and top (T) regions of the Inconel 617 wall produced via WAAM, as shown in Fig. 7 . The peaks are plotted between the obtained 2θ values and the interplanar spacing as per Bragg’s law of diffraction[ 34 ]. The diffraction patterns from all three locations exhibit dominant peaks at approximately 2θ ≈ 44.5° and 51.8°, corresponding to the (111) and (200) planes of the face-centered cubic (FCC) γ-Ni matrix. These consistent peak positions across the build height confirm the preservation of the primary FCC phase with the formation of secondary or intermetallic phases during the WAAM process. Notable variations were observed in the relative peak intensities and widths across the different build regions. The bottom region (WAAM 617(B)) displays the highest peak intensity and the sharpest peaks among the three, indicating a well-ordered crystalline structure with comparatively equiaxed and columnar dendrites along with minimal lattice strain. This is corroborated to the increased heat dissipation into the substrate, which encourages higher cooling rates and makes it easier for grains to grow during solidification. Conversely, the intermediate region (WAAM 617(M)) shows somewhat wider diffraction peaks and moderate peak intensities, indicating the existence of more diverse grain orientations and maybe higher microstrain. This is probably because of the intricate heat cycling that occurs in this area as a result of the multiple layers of deposition, which causes partial recrystallization and grain refining. Peak intensity is lowest, and peak broadening is most noticeable in the top region (WAAM 617(T)). These characteristics point to longer dendrites or increased residual stresses, which are most likely brought on by the final layers of deposition's quick cooling and the lack of further thermal exposure. Grain coarsening can be inhibited, and microstructural refinement increases under such circumstances. The spectra derived from this study resemble the peaks found by Ren et al.[ 35 ]. A progressive shift from coarse, strain-free grains to finer, more strained microstructures is shown in the downward trend in peak intensity and upward trend in peak broadening. Significant outcomes for the mechanical behavior and performance homogeneity of the manufactured component result from these findings, which are in line with the thermal gradients inherent in the WAAM process. 3.2 Mechanical Characterization Mechanical testing of WAAM wall structure is vital for confirming the reliability, durability and strength of added weld layers, ensuring that it should meet the operational requirements and industry standards. 3.2.1 Micro Hardness The microhardness mapping along the build direction was examined at three distinct regions: the bottom, middle, and top of the WAAM-fabricated Inconel 617 wall. As shown in Fig. 8 , a clear gradient in hardness is observed, with values decreasing progressively from the bottom to the top of the wall. With values ranging from roughly 230 to 245 HV, the bottom section has the maximum hardness. The quick cooling and solidification that takes place close to the SS347 substrate during the first deposition passes are responsible for this increased hardness. Increased carbide precipitation and microstructural refinement are encouraged in this zone by the larger temperature gradients and more frequent reheating from later layers, both of which enhance hardness. The intermediate region, on the other hand, has more consistent and moderate hardness values, typically falling between 215–220 HV. This relative consistency indicates that a more homogenized microstructure is produced by the thermal cycling that occurs in this area as a result of the deposition of numerous consecutive layers both above and below. Grain boundary hardening effects and residual stress can be minimized by heat treatment, producing a somewhat lower but more stable hardness profile. In the top region, the hardness ranges from about 200 to 210 HV, which is the last part of the wall to be placed. This region's decreased hardness is probably caused by slower cooling rates, which encourage grain coarsening and lower dislocation density. Furthermore, the possibility of secondary phase precipitation or additional microstructural refinement is limited by the lack of extra thermal cycles in the upper layers. The observed gradient highlights the significance of managing cooling conditions and thermal input during deposition, with higher hardness values at the bottom and lower values at the top. Furthermore, the microhardness was influenced by the secondary phase distribution along the build direction. These results indicate that in order to produce a more uniform microstructure and mechanical property distribution in WAAM-fabricated Inconel 617 components, post-deposition heat treatment or interpass thermal control techniques would be required. 3.2.2 Tensile Characteristics The engineering stress versus strain response of the WAAM-fabricated Inconel 617 wall, tested in three different orientations, is illustrated in Fig. 9 . The average ultimate tensile strength (UTS) recorded for specimens extracted in the longitudinal, diagonal, and transverse directions is 792 ± 50 MPa, 658 ± 25 MPa, and 610 ± 2 MPa, respectively. These results clearly indicate anisotropic tensile behavior, with superior mechanical performance in the longitudinal (deposition path) direction compared to the diagonal and transverse (build direction) orientations. The enhanced tensile properties in the longitudinal direction are attributed to the inherent grain structure developed during the WAAM process. The microstructure in this orientation typically consists of elongated columnar grains aligned parallel to the direction of material deposition. This alignment favors load transfer along the grain direction, thereby increasing resistance to deformation and enhancing tensile strength[ 6 ], [ 7 ]. In contrast, specimens tested in the transverse direction are oriented perpendicular to the grain growth, intersecting columnar and interdendritic regions that act as preferential sites for crack initiation and propagation under tensile loading. Consequently, transverse specimens exhibit lower tensile strength due to early failure originating in these microstructural discontinuities. These findings agree with previous reports by Weber et al.[ 36 ]. Hassel et al.[ 18 ], which demonstrates that WAAM-fabricated components generally exhibit higher tensile strength in inclined or longitudinal orientations than in the perpendicular (transverse) direction. Such behavior is characteristic of additively manufactured materials, where directionally solidified structures contribute to pronounced anisotropy in mechanical properties. Furthermore, when compared to the wrought counterpart of Inconel 617 (UTS = 655 MPa, YS = 240 MPa, as specified in ASTM B168-19), the WAAM-fabricated wall exhibits comparable or superior tensile performance, particularly in the longitudinal direction. This enhancement can be linked to process-induced microstructural features such as directional solidification and repeated thermal cycling, which may lead to localized strengthening effects. The orientation-dependent tensile behavior of WAAM-processed Inconel 617 is primarily governed by the columnar grain morphology and thermal history during deposition. These results highlight the importance of considering build orientation in the design and application of WAAM-fabricated components. 3.2.3 Fracture Morphology The fractured surfaces were examined using SEM and are shown in Fig. 10 a-c. The fractography images clearly indicate a significant difference in ductility between the build direction and the deposition direction. Specifically, the longitudinal specimens exhibit fewer voids and dimples compared to both the diagonal and transverse specimens, indicating a lower extent of plastic deformation during the tensile test. The crack initiation and propagation observed during the room temperature tensile tests reveal a ductile failure mode, characterized by substantial plastic deformation prior to fracture. The presence of dimples and voids on the fractured surfaces, as shown in Fig. 10 , corresponds to the plastic deformation mechanisms active during testing. These features are consistent with those reported in the literature[ 1 ]. 4. Conclusions The present study focused on the fabrication of a nickel-based superalloy Inconel 617 wall using the WAAM process, followed by detailed microstructural and mechanical characterization. Based on the experimental findings, the following key conclusions are drawn: The Inconel 617 WAAM wall was successfully fabricated without observable macro-defects. Microstructural analysis revealed a graded structure along the build direction, consisting of columnar grains, equiaxed dendrites, and cellular dendrites, indicative of directionally solidified microstructures. SEM analysis confirmed the presence of columnar dendrites and identified the distribution of secondary phases such as carbides and Laves phase across the transverse cross-section. EDS analysis further revealed the presence of Ti(C,N) precipitates and carbides of types M 6 C and M₂₃C₆ situated between dendritic arms. These findings were corroborated by XRD analysis, which confirmed the crystalline presence of M₆C, M₂₃C₆ carbides, and Ti(C,N) precipitates. Microhardness measurements along the build direction showed a decreasing trend from bottom to top, with values ranging from 211 HV to 237 HV. This gradient reflects the thermal history of the WAAM process and its influence on microstructural refinement and precipitation hardening. Tensile testing demonstrated pronounced anisotropy in mechanical behavior, with the longitudinal (deposition) direction exhibiting the highest tensile strength. This is attributed to the alignment of columnar grains along the deposition path, which facilitates superior load-bearing capability compared to the diagonal and transverse orientations. Fractographic analysis revealed dimpled rupture surfaces and the presence of microvoids across all orientations, indicative of ductile fracture behavior accompanied by substantial plastic deformation. Overall, the study confirms that the WAAM process can produce high-quality Inconel 617 components with desirable microstructural features and competitive mechanical properties. However, the observed anisotropy suggests that mechanical performance is direction-dependent, necessitating consideration of building orientation in component design and post-processing strategies. Declarations Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References J. Sun, W. Ren, P. Nie, J. Huang, K. Zhang, and Z. Li, “Study on the weldability, microstructure and mechanical properties of thick Inconel 617 plate using narrow gap laser welding method,” Mater Des , vol. 175, Aug. 2019, doi: 10.1016/j.matdes.2019.107823. S. Thayumanavan, R. Santhanakrishnan, and T. D. B. 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Arulmani, “Microstructure and mechanical properties of Inconel-625 slab component fabricated by wire arc additive manufacturing,” Materials Science and Technology (United Kingdom) , vol. 36, no. 16, pp. 1785–1795, Nov. 2020, doi: 10.1080/02670836.2020.1836737. Z. Zhang, R. Ding, C. Liu, L. Yu, and Y. Liu, “The precipitates evolution with related element interaction and redistribution during long-term high-temperature aging of Alloy 617,” Mater Charact , vol. 199, May 2023, doi: 10.1016/j.matchar.2023.112783. F. H. S. Delfino et al. , “Mechanical and corrosion characteristics of heat-treated wire arc additive manufactured parts of Inconel ® 625 superalloy,” Progress in Additive Manufacturing , 2024, doi: 10.1007/s40964-024-00772-0. D. Tytko, P. P. Choi, J. Klöwer, A. Kostka, G. Inden, and D. Raabe, “Microstructural evolution of a Ni-based superalloy (617B) at 700 °c studied by electron microscopy and atom probe tomography,” Acta Mater , vol. 60, no. 4, pp. 1731–1740, Feb. 2012, doi: 10.1016/j.actamat.2011.11.020. W. Ren, Y. Chen, L. Lan, F. Lu, and Z. Li, “Thermal Exposure Effect on the Microstructural and Mechanical Properties of a Laser-Welded Inconel 617 Joint in an Air Environment,” J Mater Eng Perform , vol. 30, no. 6, pp. 4328–4340, Jun. 2021, doi: 10.1007/s11665-021-05747-8. C. Dong, Z. Liu, X. Wang, Z. Liu, Z. Chen, and H. Bao, “Formation behavior of long needle-like M23C6 carbides in a nickel-based alloy without γ’ phase during long time aging,” J Alloys Compd , vol. 821, Apr. 2020, doi: 10.1016/j.jallcom.2019.153259. V. Murugabalaji, M. Rout, H. Soni, and B. N. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6854790","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":483334176,"identity":"f4b0604e-0327-427c-88cd-a11f17110a3e","order_by":0,"name":"S. Maheshwaran","email":"","orcid":"","institution":"National Institute of Technology Tiruchirappalli","correspondingAuthor":false,"prefix":"","firstName":"S.","middleName":"","lastName":"Maheshwaran","suffix":""},{"id":483334177,"identity":"99319ea4-a1a2-466b-9c91-e024fb57a6bd","order_by":1,"name":"A. Rajesh Kannan","email":"","orcid":"","institution":"Incheon National University","correspondingAuthor":false,"prefix":"","firstName":"A.","middleName":"Rajesh","lastName":"Kannan","suffix":""},{"id":483334178,"identity":"9d9e6d69-5e86-413e-98cf-e3997ea652d3","order_by":2,"name":"Nallathambi Siva Shanmugam","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAApklEQVRIiWNgGAWjYFACxgYGhgoGHjCbh3gtZxh4eNiI1wLS1QZUTbQWc/7DbRI/592RsZdvYHzwto0ILZYzEtske7c9AzmM2XAuMVoMbjA2G/BuOwzSwibNS5SW8webDf/OAWth/02clgOJjY95GyC2MBOn5QZQi8wxoJZjic2Sc84R5bDjDw6+qTlsz958+OCHN2VEaEECoDgdBaNgFIyCUUAdAADSZzHEBsVwIwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-5882-2272","institution":"National Institute of Technology Tiruchirappalli","correspondingAuthor":true,"prefix":"","firstName":"Nallathambi","middleName":"Siva","lastName":"Shanmugam","suffix":""}],"badges":[],"createdAt":"2025-06-09 13:09:54","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6854790/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6854790/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":86652646,"identity":"f7494b6b-f026-48da-ab67-cb9cfe952ce0","added_by":"auto","created_at":"2025-07-14 09:54:52","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":575326,"visible":true,"origin":"","legend":"\u003cp\u003eThe six-axis robotic welding system used to fabricate the Inconel 617 wall via WAAM.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/02afafe4aa3f8f5eeb926c95.png"},{"id":86652644,"identity":"717beb59-46ad-4360-ba03-73c34006e5a2","added_by":"auto","created_at":"2025-07-14 09:54:52","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":92238,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic layout of sample extraction on Inconel 617WAAM wall.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/8c6a184f763df90b63e10476.png"},{"id":86655072,"identity":"f2d79ef0-53a7-453f-b1d3-c8934a7efab5","added_by":"auto","created_at":"2025-07-14 10:10:52","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":273141,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructural images of Inconel 617 WAAM printed wall along the build direction: \u0026nbsp;(a) macrostructure, (b) top, (c) middle, and (d) bottom regions.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/1e7932cf7dff17758b5f5c6d.png"},{"id":86653700,"identity":"0207cbbe-780d-4663-8148-8dd6fe4868df","added_by":"auto","created_at":"2025-07-14 10:02:52","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":537101,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of WAAM fabricated Inconel 617 wall along the building direction at (a) top, (b) middle, and (c) bottom.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/539014ac6f7b988086f0d5bf.png"},{"id":86652654,"identity":"bd814b00-dbdf-4f55-afa3-d47093596afe","added_by":"auto","created_at":"2025-07-14 09:54:52","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":95492,"visible":true,"origin":"","legend":"\u003cp\u003eEDS spectrum confirming the traces of various secondary phases in the Inconel 617 wall fabricated via WAAM; (a)Ti(C, N), (b)M\u003csub\u003e6\u003c/sub\u003eC, and (c) M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/74e1dd9d7f1dc7d699e7186c.png"},{"id":86653702,"identity":"15b12ebf-880c-4624-bd1b-0f002e1695de","added_by":"auto","created_at":"2025-07-14 10:02:53","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":477169,"visible":true,"origin":"","legend":"\u003cp\u003eEDS elemental mapping of the WAAM-fabricated Inconel 617 wall showing the distribution of major alloying elements.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/22fe67918c337d9d18e3a427.png"},{"id":86652660,"identity":"bf4117ab-b467-4dc6-a68f-ccde1eeff67c","added_by":"auto","created_at":"2025-07-14 09:54:53","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":162186,"visible":true,"origin":"","legend":"\u003cp\u003eXRD peaks for Inconel 617 WAAM wall on top, middle, and bottom regions.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/e06ca4079eeb8a57c232e58c.png"},{"id":86652653,"identity":"14143f1c-182c-4512-bd62-eed109fafe69","added_by":"auto","created_at":"2025-07-14 09:54:52","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":194952,"visible":true,"origin":"","legend":"\u003cp\u003eOutcomes of Vickers Micro hardness for Inconel 617 WAAM printed wall.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/aa13c60a1796b78345d21097.png"},{"id":86652659,"identity":"fc662870-2537-4250-b516-8bb4a5e7b248","added_by":"auto","created_at":"2025-07-14 09:54:53","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":212443,"visible":true,"origin":"","legend":"\u003cp\u003eTensile outcomes in all three orientations of the Inconel 617 WAAM wall.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/99f74dce4e1b409e11e1766a.png"},{"id":86653704,"identity":"361c75d7-b502-44c1-900f-be69540ad2e1","added_by":"auto","created_at":"2025-07-14 10:02:53","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":420550,"visible":true,"origin":"","legend":"\u003cp\u003eFractured surface of Inconel 617 WAAM wall in all directions (The fractured specimen is represented in the inset image).\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/101a3bc6d4f0bb8084065147.png"},{"id":86656341,"identity":"04a74d65-ef9e-4a78-a312-ea8f3fb85200","added_by":"auto","created_at":"2025-07-14 10:19:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3782341,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6854790/v1/b3d2722a-98bd-4e17-b167-e1452d5937da.pdf"}],"financialInterests":"","formattedTitle":"Microstructure and Mechanical Performance of Inconel 617 Thin Wall fabricated via Wire Arc Additive Manufacturing","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eInconel 617 is a solid solution-strengthened, nickel-based superalloy engineered for high-temperature structural applications, exhibiting excellent mechanical performance and environmental resistance at temperatures up to ~\u0026thinsp;1100\u0026deg;C. Its microstructure is based on a stable face-centered cubic (FCC) matrix, with solid solution strengthening primarily contributed by molybdenum and cobalt, while chromium imparts oxidation and corrosion resistance. The alloy demonstrates superior creep resistance, high-temperature tensile strength, and thermal stability, making it suitable for long-term exposure in aggressive environments. Inconel 617's resistance to carburization, sulfidation, and oxidation, combined with its high-temperature phase stability, renders it a prime candidate for components in advanced ultra-supercritical (A-USC) power plants, gas turbines, heat exchangers, and high-temperature nuclear systems such as Very High Temperature Reactors (VHTRs)[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] Due to its excellent corrosion resistance and high-temperature strength, Inconel 617 is widely favored for critical components such as boiler tubes, transition ducts in aircraft engines, land-based gas turbines, and catalyst support grids [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] However, the fabrication of Inconel 617 components with intricate geometries using conventional methods, such as casting and powder metallurgy, remains more economically viable for certain applications due to their established scalability and lower material waste [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Nevertheless, additive manufacturing (AM) technologies offer a compelling alternative for producing geometrically complex Inconel 617 components. AM enables near-net-shape fabrication with high material utilization, reduced production lead times, and the potential for cost savings in low-to-medium volume production[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditive Manufacturing (AM) is gaining prominence in the production of nickel-based superalloys such as Inconel 617, owing to its capability to fabricate complex, near-net-shape geometries with minimal material waste and significantly reduced lead times. Unlike conventional manufacturing processes, AM enables the production of lightweight, topology-optimized components without the need for extensive tooling or machining. Furthermore, AM offers the potential to engineer tailored microstructures through precise control of solidification dynamics, thereby enhancing the mechanical and thermal properties of the final parts. This technology also supports efficient repair and remanufacturing of high-value components, as well as localized, on-demand production, which is particularly beneficial in high-performance sectors such as aerospace, energy, and nuclear power. AM processes for fabricating three-dimensional components can be broadly classified into powder-fed and wire-fed systems. Wire-fed additive manufacturing techniques are preferred due to their high deposition rates, cost-effectiveness, and superior material utilization. Additionally, they offer enhanced scalability for fabricating large structural components with minimal waste. Among wire-fed technologies, arc-based additive manufacturing (Arc-AM), which includes processes such as Wire Arc Additive Manufacturing (WAAM), is emerging as a cost-effective and scalable approach for producing medium-to-large-scale metallic structures with high deposition rates and comparable structural integrity[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. It also enables flexible fabrication using standard welding equipment and readily available wire feedstock[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. WAAM is preferred in aerospace, energy, marine, and defense industries for producing complex metal components with low material waste. Its cost-effectiveness and ability to fabricate near-net-shape parts make it ideal for structural, repair, and tooling applications. WAAM is performed by feeding a metal wire into a molten pool created by an electric arc, typically using a welding process like Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), or Plasma Arc Welding (PAW). The process deposits material layer by layer to build a part. With optimized process parameters, WAAM can produce components exhibiting mechanical properties comparable to those of conventionally manufactured parts, requiring only minimal post-processing to eliminate surface waviness inherent to the deposition process.\u003c/p\u003e \u003cp\u003eA wide range of alloys, such as aluminum, steel, titanium, and nickel-based superalloys, have been successfully employed to fabricate high-quality, defect-free structures using WAAM[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Numerous studies have demonstrated the successful fabrication of various nickel-based superalloys via WAAM, including Inconel 625[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], Inconel 718[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], Hastelloy C-276[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], and Waspaloy[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Among the key considerations in selecting suitable feedstock materials for WAAM is the weldability of the alloy, which significantly influences deposition quality and structural integrity. Inconel 625 and Inconel 718 have received the most research attention, primarily due to their excellent weldability, superior corrosion resistance, robust mechanical performance, and widespread applicability across critical industries such as aerospace, energy, and chemical processing. Rodrigues et al.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] manufactured Inconel 625 and examined the influence of heat treatments on the microstructural features using in situ synchrotron X-ray diffraction (XRD) and hardness. As-built samples revealed the presence of a γ-matrix with precipitation of γ\u0026prime;, γ\u0026prime;\u0026prime;, and MC carbides. When heat-treated at 750\u0026deg;C for 4 h, the γ\u0026prime;\u0026prime; phase precipitated, increasing the hardness by 5%. In situ X-ray observations revealed that heat treating at 870\u0026deg;C for 1 h resulted in δ-phase precipitation. Kwak et al.[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] investigated the anisotropic mechanical behavior of the 601 nickel-based superalloy fabricated via WAAM by employing multiscale tensile testing in conjunction with crystal plasticity modeling, providing insights into the relationship between microstructural orientation and deformation mechanisms. WAAM-CMT fabricated 601 superalloys exhibited a hierarchical microstructure with columnar grains aligned along the build direction and a pronounced [001] crystallographic texture. Despite consistent yield strength across orientations, tensile strength showed directional dependence, highlighting the influence of microstructural anisotropy on mechanical performance. Rajkumar et al.[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] studied the microstructure, mechanical properties, and corrosion performance of Incoloy 825 produced via WAAM process. Microstructural examination of WAAM-fabricated Incoloy 825 revealed austenitic matrices containing equiaxed, cellular, elongated, and columnar dendrites, with TiC and Laves phases localized in the interdendritic regions, as confirmed by electron microscopy and EDS analysis. These secondary phases notably influenced the hardness distribution (226\u0026ndash;262 HV), while the alloy exhibited excellent pitting resistance in 3.5% NaCl solution, with corrosion rates ranging from 0.59 to 0.70 mpy. Anand et al.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] examined the Grain refinement in Wire-Arc Additive Manufactured Inconel 82 alloy through controlled heat input. Grain refinement in WAAM-fabricated walls was achieved by adjusting travel speed and applying low-frequency pulse arc, without the use of inoculants or external equipment, resulting in enhanced micro-hardness (275 HV) in a 15-layer wall. The same wall exhibited minimal anisotropy in mechanical properties, with the transverse specimen showing higher UTS (650 MPa), YS (325 MPa), and reduced elongation (52%). Ajithkumar et al.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] analyzed the effect of cryogenic treatments on the microstructure and mechanical properties of Inconel 686 fabricated by GMAW-based WAAM process. WAAM fabricated Inconel 686 exhibited coarse microstructures and elemental segregation in the as-built condition, particularly with Mo enrichment in interdendritic regions due to prolonged solidification. Deep Cryogenic Treatments effectively refined the microstructure, eliminated secondary phases, minimized segregation, and significantly improved strength, hardness, and reduced mechanical anisotropy.\u003c/p\u003e \u003cp\u003eIn reference to this investigation, Hassel et al.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] investigated the anisotropy in mechanical properties, and hardness was observed relative to the build direction, with increased strength but reduced elongation at 45\u0026deg; to BD, while properties along BD and 90\u0026deg; were comparable. SEM-based slip line analysis from micro-tensile tests revealed activation of different slip systems depending on orientation, indicating a dominant crystallographic texture; thus, controlled solidification during WAAM can enable directional tailoring of properties by aligning component geometry with grain growth direction. Avinash et al.[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] fabricated an IN617 wall that exhibited a defect-free build with a hierarchical microstructure comprising cellular, equiaxed, and elongated columnar dendrites aligned along the build direction. EDS analysis confirmed the presence of Ti(C,N) and M₂₃C₆ precipitates within the interdendritic regions of the austenitic matrix. Tafel polarization tests demonstrated low corrosion current density and high corrosion potential, indicating superior electrochemical resistance in 3.5% NaCl solution. Potentiodynamic polarization (PDP) results showed minimal variation in corrosion behavior across different sample locations, with micro-pits ranging from 30 to 100 \u0026micro;m in size. Zhang et al.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] examined the influence of pre-strain on the high-temperature oxidation behavior of WAAM-fabricated Inconel 617 at 900\u0026deg;C. A bilayer oxide scale consisting of an inner Al2O3 layer and an outer Cr2O3 layer formed on WAAM-fabricated Inconel 617 after exposure to air at 900\u0026deg;C for 50 h, with minor amounts of (Ti, Ni)-oxides and NiCr2O4 also present. Increasing pre-strain enhanced oxidation resistance by promoting short-circuit diffusion pathways for Cr and Al, leading to faster formation of a denser and more protective oxide scale. Nandi et al.[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] reported that as-deposited Inconel 617 contains a higher amount of carbides compared to carbonitrides. Furthermore, carbides are more abundant at the 10 mm location from the substrate, whereas carbonitrides are predominantly found closer, at around 1 mm from the substrate. Despite these differences in spatial distribution, the distance from the substrate appears to have minimal impact on the size distribution characteristics of the precipitates.\u003c/p\u003e \u003cp\u003eDespite significant progress in the field of WAAM of nickel-based superalloys, the existing literature reveals a lack of comprehensive and cohesive understanding regarding the mechanical and microstructural characteristics of Inconel 617. While several studies have explored the fabrication aspects of Inconel 617 using WAAM, a systematic investigation that correlates its elemental composition, mechanical performance, and microstructural evolution remains limited. In this context, the present study aims to bridge this gap by fabricating an Inconel 617 wall using the GMAW-based WAAM process and conducting a detailed characterization of its elemental distribution, microstructure, and mechanical properties, thereby contributing new insights into the processing-structure-property relationships of this high-performance alloy.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eIn this study, the GMAW-based WAAM process is employed to deposit Inconel 617 filler wire with a diameter of 1.2 mm. The chemical composition of the wire complies with the AWS A5.14 M:2011 standard, as detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Layer-by-layer deposition is performed on an SS347 substrate plate with a thickness of 5 mm. The wall structure is fabricated using an OTC Daihen 6-axis robotic arm, interfaced with a Welbee P500L power source and FD-11 controller. An AF 4012 wire feeder unit is integrated with the robotic system, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Based on the weld bead geometry and profile obtained, multiple welding trials were conducted to optimize the process parameters, resulting in defect-free, linear weld beads with no porosity. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e also depicts the six-axis robotic welding setup alongside the as-deposited Inconel 617 WAAM wall.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical composition of Inconel 617 filler wire as per AWS A5.14 M: 2011 standard\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eAl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eTi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ewt.%\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Fabrication of WAAM\u003c/h2\u003e \u003cp\u003eThe WAAM-based fabrication requires careful control of bead geometry to ensure dimensional accuracy and build integrity. Among the governing factors, power input plays a critical role in determining the stability and quality of the weld bead. An increase in power input results in elevated heat generation, which enhances the melting rate of the wire feedstock, as described by the relationship Pnet\u0026thinsp;=\u0026thinsp;ηIV, where η denotes the thermal efficiency of the heat source, I is the welding current, and V is the arc voltage[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Achieving a refined and uniform weld bead geometry necessitates the optimization of key process parameters, including welding current, gas flow rate, and travel speed[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. During the layer-by-layer deposition process, a dwell time of 60 seconds was introduced between successive layers, as suggested by Kannan et al.[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] to allow adequate thermal dissipation and minimize heat accumulation, thereby reducing residual stress and distortion. Based on insights from the literature, a series of iterative experimental trials were conducted by varying the current and shielding gas flow rates to identify the optimal process window. The experimental results demonstrated the formation of stable, smooth, and defect-free weld beads with desirable cross-sectional geometry. Using the optimized set of process parameters, a multi-layered Inconel 617 wall was successfully fabricated employing a bi-directional (to-and-fro) deposition strategy. This controlled approach ensured consistent layer stacking and high structural fidelity in the as-deposited WAAM wall. The process variables used for layer deposition are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eProcess variables for layer deposition of Inconel 617 WAAM wall.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eProcess variables used for layer deposition\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCurrent (Amps)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVoltage (V)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eShielding Gas\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePure Argon (99.99%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGas flow Rate (lpm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWelding speed(mm/min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBead Thickness(mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (as deposited)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAverage height of layers deposited (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (approximately)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDwell Time for each layer deposition (seconds)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight of the WAAM wall (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e110 (as deposited)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDeposition rate (Kg/hr)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance between the torch to work piece\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAngle of the contact tip\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e90⁰\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe WAAM-printed wall in the as-deposited condition measures 7 \u0026times; 100 \u0026times; 110 mm (W \u0026times; L \u0026times; H). To facilitate mechanical and microstructural characterization, the wall undergoes face milling to remove surface waviness inherent to the as-built condition. After milling, the dimensions of the wall are reduced to 4 \u0026times; 100 \u0026times; 105 mm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Microstructural Characterization\u003c/h2\u003e \u003cp\u003eTo investigate the microstructural characteristics of the WAAM-fabricated Inconel 617 wall, specimens were extracted from the top, middle, and bottom regions in the as-deposited condition. Following a meticulous grinding and polishing process, samples were chemically etched using a reagent mixture of hydrochloric acid (HCl) and nitric acid (HNO3) to reveal the grain structure, which was initially examined under an optical microscope. For higher-resolution microstructural analysis, a Carl Zeiss Sigma 300 Scanning Electron Microscope (SEM) was employed to observe grain morphology, dendritic structures, and phase boundaries. To identify and quantify the precipitate phases, Energy Dispersive Spectroscopy (EDS) was performed in conjunction with SEM imaging. XRD analysis was conducted using a PANalytical X\u0026rsquo;Pert3 diffractometer to determine the crystalline phases and secondary precipitates present in the alloy. The XRD scan was carried out using Cu Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring;) with operational parameters set at 30 mA and 45 kV. The scan covered a 2θ range of 5\u0026deg; to 90\u0026deg;, with a scan rate of 1\u0026deg;/min and a step time of 47.94 seconds. Additionally, EDS elemental mapping was utilized to assess the spatial distribution of alloying elements and precipitates across different regions of the WAAM wall.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Mechanical Characterization\u003c/h2\u003e \u003cp\u003eThe mechanical performance of the WAAM-fabricated Inconel 617 wall was systematically assessed through tensile and microhardness testing. Non-standard miniature tensile specimens were extracted in three principal orientations: longitudinal (parallel to deposition), diagonal (inclined), and transverse (perpendicular to deposition) to evaluate anisotropy in mechanical behavior.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe use of miniature tensile specimens has been widely validated in the literature as a reliable high-throughput method for predicting representative mechanical properties of additively manufactured superalloys[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. For each orientation, three specimens were tested using a Tinius Olsen H50KL uniaxial tensile testing machine under displacement control at a constant crosshead speed of 1 mm/min. post-fracture surfaces were examined using Scanning Electron Microscopy (SEM) to characterize the failure mechanisms and assess ductile fracture features such as dimples and voids. Vickers microhardness measurements were conducted using a Struers Duramin-4 M1 hardness tester, in accordance with ASTM E92-17 standards. Polished samples from three distinct regions of the build: top, middle, and bottom, were subjected to testing with a 500 g load, a dwell time of 15 seconds, and an indentation spacing of 1 mm to ensure uniform sampling. A schematic representation of the specimen extraction layout is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, providing a visual guide to the orientation and sampling methodology.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussions","content":"\u003cp\u003eWall structures in industrial applications are expected to possess certain service-related capabilities. WAAM components are generally required to carry loads of various types in which the weld layers are subject to stresses of either a simple or complex character. Moreover, a finished weld is not always as good or as bad as it may appear to be on its surface. It is therefore necessary to find out how satisfactory or sound the weld is. For this purpose, certain testing procedures (as per ASTM standard) have been evolved and standardized to estimate the expected performance of the WAAM wall structure.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Microstructural Characterization\u003c/h2\u003e \u003cp\u003eProper metallurgical bonding, accomplished through WAAM technique improves mechanical strength by producing a durable, cohesive interface between weld layers.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e3.1.1 Optical Microscopic Analysis\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a-d) presents the microstructural evolution of the Inconel 617 WAAM wall at three distinct locations: the bottom, middle, and top regions. In the bottom layers (layers 2\u0026ndash;5), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, a combination of equiaxed dendrites and elongated columnar grains is evident. The development of these microstructural features is attributed to the thermal gradients and solidification dynamics during deposition. At the early stages of fabrication, the substrate acts as an effective heat sink, promoting rapid cooling, which in turn facilitates the formation of equiaxed and columnar grains[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. These grains typically grow epitaxially along the building direction, oriented parallel to the direction of heat extraction from the weld pool. In the middle layers (approximately layers 15\u0026ndash;18), shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, a transitional grain structure is observed, consisting of both columnar dendrites and cellular structures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAdditionally, the presence of cellular structures, fine interlocking needle-like grains can be seen nucleating intergranularly. These acellular morphologies influence the mechanical properties of the material, particularly its toughness, due to their ability to deflect cracks and inhibit crack propagation. The middle region is characterized by a transition zone, indicating a shift in grain morphology driven by the altered thermal gradients and cooling rates between successive layers. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb illustrates the top region of the Inconel 617 WAAM wall, where the microstructure comprises elongated columnar dendrites. The presence of lathy structures is also noted in this region[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Such morphologies typically form in the final stages of deposition, where thermal gradients are reduced, allowing more uniform solidification structures to develop. The formation of cellular dendrites and laths is often associated with localized compositional variations and segregation during solidification. Nickel-based superalloys like Inconel 617 derive significant mechanical strength and toughness from the precipitation of secondary phases, including MC-type carbides. During solidification, solute elements segregate into interdendritic regions, leading to the formation of carbides such as M\u003csub\u003e6\u003c/sub\u003eC and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e, which contribute to enhanced hardness[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2 SEM Analysis\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the SEM image and EDS point scan responses obtained from the top (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea), middle (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), and bottom (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) regions of the Inconel 617 WAAM wall. The SEM image from the bottom region clearly reveals the presence of columnar dendrites and equiaxed dendrites, which are aligned predominantly perpendicular to the build direction. This epitaxial grain growth pattern is characteristic of WAAM-processed Inconel 617 components and results from the directional solidification driven by steep thermal gradients near the substrate. A similar observation was reported by Ravi et al.[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] in Inconel 625 WAAM builds, where the directional growth of columnar dendrites was prominent due to consistent heat dissipation into the substrate. In the middle section of the wall, SEM images reveal sharp, needle-like dendritic features and cellular structures. Also, the carbides presence was confirmed within the matrix, indicative of carbide precipitation in this region. These structures are consistent with the morphology of M\u003csub\u003e23\u003c/sub\u003e​C\u003csub\u003e6\u003c/sub\u003e​ carbides, as identified by Zhang et al.[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], who observed elongated needle-like precipitates associated with chromium-rich carbide phases in nickel-based superalloys. These precipitates often nucleate intergranularly and are responsible for enhancing the hardness of the alloy. The top region of the WAAM wall, as observed through SEM-EDS, exhibits localized enrichment of molybdenum and the formation of a distinct secondary phase identified as the Laves phase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe presence of this intermetallic compound is attributed to elemental segregation during rapid solidification. According to Delfino et al.[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], Laves phases preferentially form in Nb and Mo-rich regions under rapid cooling conditions, which is consistent with the observed microstructure in the topmost layers of the WAAM wall. These microstructural observations confirm the hierarchical distribution of secondary phases across the build height, highlighting the influence of thermal history and solidification conditions on microstructural evolution in WAAM-fabricated Inconel 617.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e3.1.3 EDS Analysis\u003c/h2\u003e \u003cp\u003eEDS analysis clearly confirms the formation of Laves phases in conjunction with carbides and precipitates throughout the WAAM-fabricated Inconel 617 wall. Notably, Ti(C, N) precipitates are predominantly observed in the bottom region of the wall, aligning with the findings reported by Tytko et al.[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] in their study on the microstructural evolution of Ni-based superalloys. In the middle and top layers, M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e and M\u003csub\u003e6\u003c/sub\u003eC carbides are identified. M\u003csub\u003e6\u003c/sub\u003eC, a Mo-rich carbide, and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e, a Cr-rich carbide, both crystallize in a face-centered cubic (FCC) structure and are commonly found in fusion-based processing of Inconel 617, as also noted by Ren et al.[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The presence of these secondary phases has a direct influence on the mechanical performance of the alloy. M\u003csub\u003e6\u003c/sub\u003eC and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e carbides are known to contribute significantly to improvements in tensile strength and hardness by impeding dislocation motion and stabilizing grain boundaries.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eEDS spectra further reveal localized Mo enrichment at specific sites, often surpassing Ni concentrations, which supports the preferential nucleation of Mo-rich carbides. Additionally, carbides are observed along grain boundaries, a feature that plays a critical role in determining grain boundary strength, grain size stabilization, and the long-term structural integrity of the alloy. The grain boundary precipitation of carbides is beneficial in maintaining microstructural stability during high-temperature service. As reported by Dong et al.[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], the presence of M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e carbides is also associated with enhanced fracture toughness, further underlining their significance in the performance of WAAM-fabricated Inconel 617 components.\u003c/p\u003e \u003cp\u003eEDS analysis confirms the presence of Cr-rich (M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e) and Mo-rich (M\u003csub\u003e6\u003c/sub\u003eC) carbides, along with Ti(C, N) precipitates, within the WAAM-fabricated Inconel 617 wall. The corresponding EDS spectrums and composition of these carbides are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-c and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. These secondary phases are distributed across various regions of the build wall, corresponding to distinct thermal histories during layer-by-layer deposition. Elemental segregation contributing to the formation of these carbides and precipitates was evaluated at specific locations using spot EDS analysis. The localized chemical compositions obtained from these regions are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, providing clear evidence of elemental enrichment, particularly of Cr, Mo, and Ti, at sites where precipitate phases have formed. These compositional findings further support the identification of the observed phases and their potential roles in influencing the alloy\u0026rsquo;s mechanical and thermal stability.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eElements present in precipitates and carbides present in the Inconel 617 WAAM wall.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eElement in wt%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eTi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cb\u003ePhases\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTi (C, N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e40.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e1.20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e47.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e21.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e12.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM6C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e14.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e19.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e29.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e3.1.4 EDS Elemental Mapping\u003c/h2\u003e \u003cp\u003eThe elemental distribution of the WAAM-fabricated Inconel 617 alloy analyzed using EDS, and the corresponding elemental maps are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The chemical composition, detailed in the accompanying table, aligns well with the nominal specification for Inconel 617, confirming the chemical reliability of the WAAM deposition process. Nickel (Ni) and Chromium (Cr), the two principal constituents of Inconel 617, are present in relatively high weight percentages of 37% and 30%, respectively. Their distribution appears uniform across the scanned area, indicating effective melting and solidification behavior during WAAM processing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis homogeneity is essential for ensuring consistent corrosion resistance and mechanical strength throughout the deposited wall. Cobalt (Co), Molybdenum (Mo), and Manganese (Mn), present at 10%, 7%, and 6% respectively, also exhibit uniform dispersion. These elements play significant roles in solid-solution strengthening and high-temperature creep resistance. Their even distribution further affirms the metallurgical soundness of the WAAM process and suggests minimal macro-segregation. Titanium (Ti) and Nitrogen (N), though present in relatively small quantities (6% and 1%, respectively), exhibit localized clustering in the elemental maps. These regions likely correspond to the formation of secondary strengthening phases such as titanium carbonitrides (Ti(C, N)). This observation is consistent with earlier EDS point analysis and XRD results, which confirm the presence of M6C and M23C6 carbides, as well as Ti-based carbonitrides in the microstructure. The presence of bright, isolated features in the Ti and N maps suggests precipitate formation, particularly in interdendritic regions or near grain boundaries. In addition, Mo-rich precipitates are noticed within the dendritic regions. Such precipitates contribute to the overall strength and thermal stability of the material, particularly in high-temperature applications. The minimal evidence of elemental segregation implies that thermal gradients during deposition were well managed, limiting elemental redistribution.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.1.5 XRD Analysis\u003c/h2\u003e \u003cp\u003eXRD was performed on specimens extracted from the bottom (B), middle (M), and top (T) regions of the Inconel 617 wall produced via WAAM, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The peaks are plotted between the obtained 2θ values and the interplanar spacing as per Bragg\u0026rsquo;s law of diffraction[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The diffraction patterns from all three locations exhibit dominant peaks at approximately 2θ\u0026thinsp;\u0026asymp;\u0026thinsp;44.5\u0026deg; and 51.8\u0026deg;, corresponding to the (111) and (200) planes of the face-centered cubic (FCC) γ-Ni matrix. These consistent peak positions across the build height confirm the preservation of the primary FCC phase with the formation of secondary or intermetallic phases during the WAAM process. Notable variations were observed in the relative peak intensities and widths across the different build regions. The bottom region (WAAM 617(B)) displays the highest peak intensity and the sharpest peaks among the three, indicating a well-ordered crystalline structure with comparatively equiaxed and columnar dendrites along with minimal lattice strain. This is corroborated to the increased heat dissipation into the substrate, which encourages higher cooling rates and makes it easier for grains to grow during solidification. Conversely, the intermediate region (WAAM 617(M)) shows somewhat wider diffraction peaks and moderate peak intensities, indicating the existence of more diverse grain orientations and maybe higher microstrain. This is probably because of the intricate heat cycling that occurs in this area as a result of the multiple layers of deposition, which causes partial recrystallization and grain refining. Peak intensity is lowest, and peak broadening is most noticeable in the top region (WAAM 617(T)). These characteristics point to longer dendrites or increased residual stresses, which are most likely brought on by the final layers of deposition's quick cooling and the lack of further thermal exposure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGrain coarsening can be inhibited, and microstructural refinement increases under such circumstances. The spectra derived from this study resemble the peaks found by Ren et al.[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. A progressive shift from coarse, strain-free grains to finer, more strained microstructures is shown in the downward trend in peak intensity and upward trend in peak broadening. Significant outcomes for the mechanical behavior and performance homogeneity of the manufactured component result from these findings, which are in line with the thermal gradients inherent in the WAAM process.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Mechanical Characterization\u003c/h2\u003e \u003cp\u003eMechanical testing of WAAM wall structure is vital for confirming the reliability, durability and strength of added weld layers, ensuring that it should meet the operational requirements and industry standards.\u003c/p\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Micro Hardness\u003c/h2\u003e \u003cp\u003eThe microhardness mapping along the build direction was examined at three distinct regions: the bottom, middle, and top of the WAAM-fabricated Inconel 617 wall. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, a clear gradient in hardness is observed, with values decreasing progressively from the bottom to the top of the wall. With values ranging from roughly 230 to 245 HV, the bottom section has the maximum hardness. The quick cooling and solidification that takes place close to the SS347 substrate during the first deposition passes are responsible for this increased hardness. Increased carbide precipitation and microstructural refinement are encouraged in this zone by the larger temperature gradients and more frequent reheating from later layers, both of which enhance hardness. The intermediate region, on the other hand, has more consistent and moderate hardness values, typically falling between 215\u0026ndash;220 HV. This relative consistency indicates that a more homogenized microstructure is produced by the thermal cycling that occurs in this area as a result of the deposition of numerous consecutive layers both above and below.\u003c/p\u003e \u003cp\u003eGrain boundary hardening effects and residual stress can be minimized by heat treatment, producing a somewhat lower but more stable hardness profile. In the top region, the hardness ranges from about 200 to 210 HV, which is the last part of the wall to be placed. This region's decreased hardness is probably caused by slower cooling rates, which encourage grain coarsening and lower dislocation density. Furthermore, the possibility of secondary phase precipitation or additional microstructural refinement is limited by the lack of extra thermal cycles in the upper layers. The observed gradient highlights the significance of managing cooling conditions and thermal input during deposition, with higher hardness values at the bottom and lower values at the top. Furthermore, the microhardness was influenced by the secondary phase distribution along the build direction. These results indicate that in order to produce a more uniform microstructure and mechanical property distribution in WAAM-fabricated Inconel 617 components, post-deposition heat treatment or interpass thermal control techniques would be required.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 Tensile Characteristics\u003c/h2\u003e \u003cp\u003eThe engineering stress versus strain response of the WAAM-fabricated Inconel 617 wall, tested in three different orientations, is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. The average ultimate tensile strength (UTS) recorded for specimens extracted in the longitudinal, diagonal, and transverse directions is 792\u0026thinsp;\u0026plusmn;\u0026thinsp;50 MPa, 658\u0026thinsp;\u0026plusmn;\u0026thinsp;25 MPa, and 610\u0026thinsp;\u0026plusmn;\u0026thinsp;2 MPa, respectively. These results clearly indicate anisotropic tensile behavior, with superior mechanical performance in the longitudinal (deposition path) direction compared to the diagonal and transverse (build direction) orientations. The enhanced tensile properties in the longitudinal direction are attributed to the inherent grain structure developed during the WAAM process. The microstructure in this orientation typically consists of elongated columnar grains aligned parallel to the direction of material deposition. This alignment favors load transfer along the grain direction, thereby increasing resistance to deformation and enhancing tensile strength[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In contrast, specimens tested in the transverse direction are oriented perpendicular to the grain growth, intersecting columnar and interdendritic regions that act as preferential sites for crack initiation and propagation under tensile loading. Consequently, transverse specimens exhibit lower tensile strength due to early failure originating in these microstructural discontinuities. These findings agree with previous reports by Weber et al.[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHassel et al.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], which demonstrates that WAAM-fabricated components generally exhibit higher tensile strength in inclined or longitudinal orientations than in the perpendicular (transverse) direction. Such behavior is characteristic of additively manufactured materials, where directionally solidified structures contribute to pronounced anisotropy in mechanical properties. Furthermore, when compared to the wrought counterpart of Inconel 617 (UTS\u0026thinsp;=\u0026thinsp;655 MPa, YS\u0026thinsp;=\u0026thinsp;240 MPa, as specified in ASTM B168-19), the WAAM-fabricated wall exhibits comparable or superior tensile performance, particularly in the longitudinal direction. This enhancement can be linked to process-induced microstructural features such as directional solidification and repeated thermal cycling, which may lead to localized strengthening effects. The orientation-dependent tensile behavior of WAAM-processed Inconel 617 is primarily governed by the columnar grain morphology and thermal history during deposition. These results highlight the importance of considering build orientation in the design and application of WAAM-fabricated components.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.2.3 Fracture Morphology\u003c/h2\u003e \u003cp\u003eThe fractured surfaces were examined using SEM and are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea-c. The fractography images clearly indicate a significant difference in ductility between the build direction and the deposition direction. Specifically, the longitudinal specimens exhibit fewer voids and dimples compared to both the diagonal and transverse specimens, indicating a lower extent of plastic deformation during the tensile test. The crack initiation and propagation observed during the room temperature tensile tests reveal a ductile failure mode, characterized by substantial plastic deformation prior to fracture. The presence of dimples and voids on the fractured surfaces, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e, corresponds to the plastic deformation mechanisms active during testing. These features are consistent with those reported in the literature[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe present study focused on the fabrication of a nickel-based superalloy Inconel 617 wall using the WAAM process, followed by detailed microstructural and mechanical characterization. Based on the experimental findings, the following key conclusions are drawn:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe Inconel 617 WAAM wall was successfully fabricated without observable macro-defects. Microstructural analysis revealed a graded structure along the build direction, consisting of columnar grains, equiaxed dendrites, and cellular dendrites, indicative of directionally solidified microstructures.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSEM analysis confirmed the presence of columnar dendrites and identified the distribution of secondary phases such as carbides and Laves phase across the transverse cross-section. EDS analysis further revealed the presence of Ti(C,N) precipitates and carbides of types M\u003csub\u003e6\u003c/sub\u003eC and M₂₃C₆ situated between dendritic arms. These findings were corroborated by XRD analysis, which confirmed the crystalline presence of M₆C, M₂₃C₆ carbides, and Ti(C,N) precipitates.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eMicrohardness measurements along the build direction showed a decreasing trend from bottom to top, with values ranging from 211 HV to 237 HV. This gradient reflects the thermal history of the WAAM process and its influence on microstructural refinement and precipitation hardening.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTensile testing demonstrated pronounced anisotropy in mechanical behavior, with the longitudinal (deposition) direction exhibiting the highest tensile strength. This is attributed to the alignment of columnar grains along the deposition path, which facilitates superior load-bearing capability compared to the diagonal and transverse orientations.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eFractographic analysis revealed dimpled rupture surfaces and the presence of microvoids across all orientations, indicative of ductile fracture behavior accompanied by substantial plastic deformation.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eOverall, the study confirms that the WAAM process can produce high-quality Inconel 617 components with desirable microstructural features and competitive mechanical properties. However, the observed anisotropy suggests that mechanical performance is direction-dependent, necessitating consideration of building orientation in component design and post-processing strategies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDeclaration of competing interest\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJ. Sun, W. Ren, P. Nie, J. Huang, K. Zhang, and Z. Li, \u0026ldquo;Study on the weldability, microstructure and mechanical properties of thick Inconel 617 plate using narrow gap laser welding method,\u0026rdquo; \u003cem\u003eMater Des\u003c/em\u003e, vol. 175, Aug. 2019, doi: 10.1016/j.matdes.2019.107823.\u003c/li\u003e\n\u003cli\u003eS. Thayumanavan, R. Santhanakrishnan, and T. D. B. 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Zhou, X. Lin, N. Kang, W. Huang, and Z. Wang, \u0026ldquo;Mechanical properties and precipitation behavior of the heat-treated wire + arc additively manufactured 2219 aluminum alloy,\u0026rdquo; \u003cem\u003eMater Charact\u003c/em\u003e, vol. 171, Jan. 2021, doi: 10.1016/j.matchar.2020.110735.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Welding, WAAM, Inconel 617, Microstructure, Mechanical properties","lastPublishedDoi":"10.21203/rs.3.rs-6854790/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6854790/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents a comprehensive investigation into the microstructural evolution and mechanical performance of an Inconel 617 wall fabricated using the Wire Arc Additive Manufacturing (WAAM) process. Detailed microstructural characterization reveals a gradient in grain morphology along the build direction, driven by variations in thermal history. Equiaxed dendrites and columnar grains due to rapid solidification were noticed near the substrate and are mixed together in the bottom layers, while cellular structures and columnar dendrites are dominant in the middle layers. Elongated columnar dendrites are observed in the upper layers. In addition, Ti(C,N) secondary phases and precipitates such as M\u003csub\u003e6\u003c/sub\u003eC and M\u003csub\u003e23\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003e carbides are noticed within the austenitic matrix, are confirmed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The presence of these phases is further confirmed by X-ray diffraction (XRD), which finds their distinctive diffraction peaks. From hardness mapping, the build's average microhardness ranges from 237 HV at the bottom to 211 HV at the top, nearly matching the wrought Inconel 617's characteristics as outlined in ASTM B168-19. Anisotropy is clearly seen from the tensile tests, since the deposition direction achieves a higher average ultimate tensile strength (UTS) of 792 MPa than the build direction, which is 610 MPa. In all orientations, ductile fracture characteristics with dimples and voids are confirmed, suggesting significant plastic deformation before failure. The results demonstrate the importance of building orientation on material performance and validate the feasibility of the WAAM method for fabricating Inconel 617 components free of defects with desirable mechanical and microstructural integrity.\u003c/p\u003e","manuscriptTitle":"Microstructure and Mechanical Performance of Inconel 617 Thin Wall fabricated via Wire Arc Additive Manufacturing","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-14 09:54:47","doi":"10.21203/rs.3.rs-6854790/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-07-15T09:29:20+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-10T07:16:31+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Welding in the World","date":"2025-07-07T18:44:07+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-13T06:14:02+00:00","index":"","fulltext":""},{"type":"submitted","content":"Welding in the World","date":"2025-06-12T02:07:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"dc31d167-01a0-4905-a8a1-58d7e49c8c2c","owner":[],"postedDate":"July 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-11-03T16:41:57+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-14 09:54:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6854790","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6854790","identity":"rs-6854790","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}