Multimaterial design strategies and microstructural characterization of stainless steel 316-Inconel 718 developed by wire-based Directed Energy Deposition

Multimaterial design strategies and microstructural characterization of stainless steel 316-Inconel 718 developed by wire-based Directed Energy Deposition | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Multimaterial design strategies and microstructural characterization of stainless steel 316-Inconel 718 developed by wire-based Directed Energy Deposition JULIA UREÑA ALCÁZAR, Marta Álvarez-Leal This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4416707/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Oct, 2024 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted 5 You are reading this latest preprint version Abstract The combination of different material properties to face severe conditions has been always demanded by different industrial sectors. For instance, in gas turbine components, excellent mechanical properties at high temperatures and corrosive environments are required. Traditionally, this has been achieved by conventional manufacturing of multiple materials with several steps and joining processes. However, manufacturing the entire component within the same process by additive manufacturing and the combination of two different materials is presented as a potential via to explore. In this research, the additive manufacturing of stainless steel (SS316L) and Nickel-based Inconel superalloy (IN718) multimaterial through different design strategies approaches has been developed and investigated by wire-based Laser Directed Energy Deposition (DED) technology. Direct transition between materials was applied and three multimaterial sandwich structures (S1, S2 and S3) were designed and successfully manufactured. The microstructure obtained in the three different regions (IN718, IN718/SS316 and SS316) was evaluated in both XY and XZ build directions. Rockwell C hardness was measured along the cross-sections of all samples to compare the different properties of the three samples developed. Defective microstructural features like big porosity, cracks or lack-of-fusion at the SS316/IN718 interphases were not evidenced for S2 and S3 strategies. Multimaterial samples showed very fine microstructures corresponding to the DED processing, and secondary phases such as intermetallic-compounds or carbides were not found. Smooth transitions between materials were obtained which also led to a gradient in microstructure and hardness properties. S3 sample showed the highest hardness value, being the IN718 value even higher compared to conventional IN718 material. Multimaterial Additive Manufacturing (AM) Laser Directed Energy Deposition (L-DED) processing wire-based IN718/SS316 Microstructure Hardness Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction Multimaterial combinations are widely present in our daily life and most of them are nature-inspired multimaterial structures. Design and innovative processing methods for optimized multimaterial are being investigated by selecting application-specific combinations of compositional structures of two materials [ 1 ]. The stainless steel (SS316L)-nickel-based superalloy Inconel 718 (IN718) multimaterial has increased its attraction to be investigated together in multimaterial structures due to their different properties in the same manufacturing process [ 2 ]. SS316/IN718 was selected for this study due to their useful combination properties for both strength and corrosion resistance at elevated temperature. With this IN718/SS316 multimaterial, high wear and corrosion resistance at high temperature will be provided by IN718 when required whereas weight and cost reduction will be locally achieved by applying SS316 material. Gas turbine components, high-end automobile engine valve stems or coating are different applications where such material properties combination is highly interesting [ 3 ]. Different fusion welding processes by applying heat with or without pressure or filler materials are usually found among the most common conventional methods for joining similar or dissimilar metals. This is the conventional route for manufacturing a part composed of different metallic materials. However, in order to avoid or minimize the crack-formation or embrittlement, these conventional joining processes employ intermediate layers for separating two dissimilar metals or high energy-sources. Nevertheless, some innovative joining processes like Friction Stir Welding (FSW) are also an alternative joining method for welding dissimilar materials in the solid state by severe plastic deformation using a harder tool. In this way, mechanical bonding occurs between both metallic alloys to join without an energy-source or melting steps[ 4 ]. However, metallic multimaterial manufacturing can be suitably performed with some Additive Manufacturing (AM) processes in which different metallic materials are able to be melted through a controlled electron or laser beam energy-source. Therefore, in addition to the advantages of multimaterials, the fact of manufacturing them by AM results in merits like: i) developing metallic multimaterials as a single-step process without the necessity of joining pos-processing methods; ii) enabling design freedom for customization; iii) cost-effective and environmental-friendly manufacturing solutions with a reduced amount of raw material and material waste as well as reduced production costs saving energy, time and steps [ 5 ]. DED systems, also known as Laser Metal Deposition (LMD) processing, are AM processes in which a nozzle mounted on a multi-axis arm deposits molten material in powder or wire format layer by layer onto a build plate at a specific angle. The energy-source can be a laser, electron beam or plasma arc and it is used to create beads, tracks and layers of solid materials upon solidification of the melt pool on the substrate [ 5 ], [ 6 ]. Among the main advantages found in wire-based DED technologies; the higher material deposition rate compared to powder bed fusion, the bigger size of the final component or the lower heat transference are highlighted [ 7 ]. However, due to DED being a fusion-process, the common problems of processinng dissimilar materials with different physico-chemical properties must be addressed. To the best of our knowledge, the valuable researches found about this topic seems to be mostly related to powder-based DED processing, L-PBF processing or WAAM technology but very few publications are available about the double wire DED manufacturing. Thus, exploring the IN718/SS316 multimaterial manufacturing via wire-based DED processing in this research will contribute to widening the state-of-the-art with innovative knowledge. In this work, three IN718/SS316 multimaterial samples manufactured by wire-based DED technology with different sandwich design strategies (two, three or four layers per material) were developed. Cross-sections, microstructure in both build directions and hardness properties were evaluated in the different regions (IN718-segments, IN718/SS316 interphases and SS316-segments) to compare the material behaviour of the three multimaterial strategies employed. The effect of a number of layers per material on the interphases and adjacent layers is studied to better understand the service life of a part additively manufactured in this multimaterial by wire-based DED technology. 2 Experimental procedure Wire metals of low-carbon stainless steel 316LS (SS316) and nickel-based superalloy Inconel 718 (IN718) were employed to process the SS316/IN718 multimaterial. The stainless steel SS316L is a standard low-carbon austenitic steel containing molybdenum, which makes excellent durability, biocompatibility and corrosion resistance, particularly against pitting and crevice corrosion in chloride environments [ 4 ]. The IN718 superalloy is a high-strength alloy widely used in high-temperature applications due to its good mechanical properties and excellent corrosion resistance. Therefore, both materials were used for the manufacturing of the SS316/IN718 by means of 1 mm diameter wires as starting materials. The elemental composition of the SS316 stainless steel and IN718 nickel-based superalloy wires are listed in Table 1 . MELTIO was the supplier for both materials as well as the manufacturer of the double wire-based DED technology used in this research. Table 1 Chemical composition of the starting wire SS316 and IN718 materials for the LMD processing. Material Chemical composition (wt. %) C Mn Si Ni Cr Mo Cu Ferrite Fe Ti Al Nb + Ta SS316 0.01 1.8 0.9 12.2 18.4 2.6 0.12 7 - - - - IN718 0.05 0.2 0.2 Balance 19 3 - - 20 0.9 0.5 5.2 The multimaterial SS316/IN718 was processed using the innovative Meltio M450 Directed Energy Deposition (DED) technology. This additive manufacturing technology is equipped with a multi-laser deposition head system capable of processing two different wires simultaneously (Fig. 1 ). The Laser DED additive manufacturing system, equipped with a 1.2 kW laser system composed of 6 (200 W) fiber coupled diode lasers of 976 nm wavelength was used to manufacture the samples. Argon with a purity higher than 99.996% was used as shielding gas during the whole 3D processing. The process parameters combination selected for the manufacturing of small cubes of 25 mm wide and 25 mm tall for the three design multimaterial strategies is summarized in Table 2 . Table 2 DED process parameters for SS316/IN718 multimaterial manufacturing. DED process parameters for SS316/IN718 multimaterial Material Print speed (mm/min) Layer height (mm) Laser power (W) Track spacing (mm) Gas flow (L/min) SS316 600 1 1100 1 10 IN718 450 1 1100 1 10 The multimaterial strategies sandwich SS316/IN718 for manufacturing small cubes of 25 mm wide and 25 mm tall designed by three different strategies are schematically represented in Fig. 2 using S1 (two layers multimaterial strategy), S2 (three layers multimaterial strategy) and S3 (four layers multimaterial strategy). All of them are composed of SS316 and IN718 direct transition material gradients, represented in grey and blue color, respectively. The microstructural analysis was carried out by optical microscopy (Axiolab A1 equipped with an AxioCam ERc, Carl Zeiss ICS and ZeissCore software) after cross-sectioning and surface preparation by standard metallographic techniques to evaluate the density level of the different materials processed. The surface of the specimens was ground successively from 600 to 4000 grit with SiC papers, followed by polishing with 1 µm diamond suspension and finally with colloidal silica suspension. The as-polished samples were chemically etched for a few seconds to reveal the microstructures by using a solution of Vilella and HCl for the stainless-steel segments and a diluted solution of FeCl3 for the Inconel regions. Hardness Rockwell C values of the developed samples were measured using a Wilson Rockwell C hardness tester. A loading force of 150 Kg and 15 s indentation time were effective for achieving accurate measurements for the SS316 and IN718 segments as well as SS316/IN718 interphases. 3 Results and discussion The three SS316/IN718 multimaterial sandwich specimens designed are shown in Fig. 3 . This multimaterial design can be applicable to bimetallic structures where dual functionalities are required. Three different material gradients were created where the material layer disposition was different. Two, three and four layers per material have been considered as the three different multimaterial strategies S1, S2 and S3, respectively, to be studied. Distribution of the specimens along the build plate and the successful result of the manufacturing process by DED technology are represented. The process parameters for the manufacturing and the detailed multimaterial strategies were described in Table 2 and Fig. 2 , respectively. First, Fig. 4 shows the cross-section of the additive manufactured samples processed by DED technology along with the design considered for each multimaterial strategy. In Fig. 4 -a the multimaterial sandwich strategy considered (S1) is composed of two IN718 layers and two SS316 layers, consecutively, from the bottom to the surface with eight IN718/SS316 interphases. Secondly, in Fig. 4 -b the multimaterial sandwich strategy considered (S2) was composed of three IN718 layers and three SS316 layers, consecutively, from the bottom to the surface with six IN718/SS316 interphases. Finally, in Fig. 4 -c was represented the multimaterial sandwich strategy S3, which was composed of four IN718 layers and four SS316 layers, consecutively, from the bottom to the surface with five IN718/SS316 interphases. In the S1 strategy (Fig. 4 -a), some defects were found repeatably at the interphase. In fact, all of them were originated at the border of the IN718 layer and they were propagated to the SS316 layer. Some of the defects caused by the DED process could have occurred due to low or excessive heat input. Irregular lack-of-fusion defects are usually attributed to an insufficient heat input since some cracks can appear due to a higher heat input as reported also by [ 8 ]. However, in this multimaterial study the presence of some cracks can be also related to supercooling, thermal and residual stress concentration as well as the CTE difference between dissimilar materials. However, in Fig. 4 -b it can be noticed how the presence of these defects in almost depreciable, similar to Fig. 4 -c, which can be attributed to the fact of depositing more than two consecutive layers of the different materials. This behaviour can be correlated with the thermal behaviour responses of the three multimaterial strategies employed. In the case of the samples manufactured with S2 and S3 strategies, three and four material layers, respectively, are deposited and melted of each SS316 and IN718 material. In contrast, the gradient generated in the sample manufactured with the S1 multimaterial strategy is composed of two consecutive layers of both alloys. This seems to have a major impact on the thermal gradient response between layers. Therefore, although 2 layers per material transition could be built, the thermal and residual stresses formed in the previous interphase region could affect the subsequent layer through close contact during the change of material. Furthermore, the pores and cracks induced during the cooling of the IN718 layer can propagate at the IN718/SS316 interphase and move into the nearby SS316 layer with no defects. This was also evidenced by other authors where similar defects were found in functionally graded materials with 3–4 layers and even 1 layer per compositional transition manufactured by DED technology [ 3 ], [ 8 ]. As shown in Fig. 5 , related to the optical microstructure along the XY direction of DED samples processed through direct transition (i.e. S2 and S3), it can be seen (from left to right) the microstructure of the different regions: IN718-segment, IN718/SS316 interphase and SS316-segment. Microstructural examination of the built specimens was observed in two different areas, at the middle-region of the sample (Fig. 5 -a) and at the upper-area of the sample (Fig. 5 -b). A microstructural gradient was obtained throughout the sample in both areas analyzed. First, in Fig. 5 -a, deep melt pool signs were observed at low magnification as a consequence of high thermal gradients which caused different grain growth directions in the IN718-segment. It is known that the dimensions of the melt pool are associated with thermal conductivity, thermal diffusivity, cooling rate, and solidification front velocity as described in another study [ 8 ]. These thermal gradients, provoked by the consecutive cooling rate changes, originated a microstructure partially formed by columnar and equiaxed dendrites as it was observed at higher magnifications. Then, a smooth transition zone was identified at the IN718/SS316 interphase, meaning a successful union of both dissimilar materials by a good combination of DED-process parameters between them. At the SS316-segment, the main microstructure features found were austenite and ferrite composed of a mix of cellular and dendritic structures; showing an important region of columnar dendrites. This type of microstructure is usually attributed to the additive manufacturing process itself since they are not continuous processes. Each layer is solidified during its material layer deposition, but also experiences partial melting and solidification steps with the subsequent layer deposition as it was reported in other research [ 9 ]. Regarding the microstructure size of SS316 and IN718, it is important to highlight that this feature is one of the main microstructural differences between materials processed by Additive Manufacturing (AM) compared to the same conventional alloys. A very fine microstructure was obtained defined by the rapid cooling rate commonly found in the DED processing compared to conventional methods. An average grain size between 5 µm (equiaxed grains) and 20 µm (columnar and elongated grains) was achieved in the samples studied in this research, whereas coarser microstructure with grain sizes between 30–50 µm was reported for the same conventional materials by other authors [ 10 ]. Regarding the microstructure obtained at the surface or upper-area (Fig. 5 -b), it was very similar to that obtained for the IN718-segment in the previous region (middle-area), but very different from the conventionally IN718 manufactured, as expected. A great proportion of localized columnar structure was seen in IN718 at lower augments when fabricated using laser-DED with mixed regions of equiaxed grains. The reason for partial mixing could be related to the lower heat input of the DED processing together with a faster cooling rate which provides less time for the diffusion of elements like Mo and Cr to both sides [ 4 ]. In the transition IN718/SS316, a transition in microstructure was also revealed from equiaxed dendrites to more elongated dendrites, but in both cases with very fine microstructure, and free from defects like cracks, segregation, lack of fusion or delamination. In the case of the SS316-segment an important difference was observed between the surface (upper-area) and the middle-area. SS316-upper region appeared to show finer grains composed of a cellular structure with very well defined and small grain sizes (3–5 µm) compared to the microstructure shown in the middle-region of the sample. This could be explained due to the solidification rate achieved at the latest layers (upper-area, surface) since no partial remelting is happening on subsequent layers as occurs at the middle-region. In both areas examined no compositional segregation was identified by optical microscopy, which could lead to cracks at the IN718/SS316 interphase. Microstructure results in the cross-section (XZ build direction) of two adjacent layers in the SS316/IN718 sample additively manufactured by DED employing S3 multimaterial strategy were also investigated (Fig. 6 ). In Fig. 6 -a very fine columnar and equiaxed dendrites were grown in the SS316-region from the melt pool signs which can be seen more in detail in Fig. 6 -b. Microstructure mainly composed of cellular and columnar austenite grains was found partially mixed. Figure 6 c-d (IN718-segment) exhibited very similar microstructure features as in the XY plane, but in this case marks corresponding to the melt pools and transition layers were found parallel to the build direction. Very fine columnar grains showed an average grain size of 30 µm length and 2–3 µm wide while equiaxed grains were mostly around 5 µm. Figure 7 shows the average Rockwell C hardness values obtained along the cross-section of the three samples additively manufactured according to the S1, S2 and S3 multimaterial design strategies employed in this study. It can be also seen the cross-sections where the material gradient can be observed in detail in each sample. The indentation measurements can also be seen together with the identification of each layer by means of a small square in blue (IN718), grey (SS316) or dark blue color (IN718/SS316 interphase). It can be seen that the hardness values of the three multimaterial strategies employed followed a similar correlation between their different material regions. The hardness of the IN718-segments was higher in all cases followed by the IN718/SS316 regions and SS316-segments, as expected. Therefore, a hardness transition was obtained in all samples in agreement with the material gradient also shown in the cross-sections of samples. The IN718 / IN718/SS316 / SS316 hardness transition gradient found for S1, S2 and S3 was: (19 / 13 / 9 HRC), (21 / 8 / 8 HRC) and (55 / 34 / 9 HRC), respectively. The hardness values for the SS316-segments in all samples seem to be quite stable around 8–9 HRC. However, it can be noticed how the values of hardness for both IN718-segments and IN718/SS316 regions increased from S1 to S3 samples. In fact, this hardness increase is significantly high in the sample developed by S3 multimaterial strategy; reaching values of 55 HRC and 34 HRC for IN718-segments and IN718/SS316 regions, respectively. These values are also in correlation with the detailed results obtained from the cross-sections (Fig. 4 ) where it was found that although the three strategies can be successfully manufactured, S1 (two layers per material) showed more presence of cracks propagated defects associated with a higher concentration of thermal and residual stresses between layers. Nevertheless, S2 (three layers per material) and S3 (four layers per material) samples did not show defects between subsequent layers. This means that although S2 and S3 are suitable as multimaterial strategies for developing graded IN718/SS316 materials, from the hardness point of view, S3 is the multimaterial strategy which offers the transition hardness with the highest values accompanied with very good microstructure properties. Moreover, hardness values obtained in S3 sample for IN718-region (55 ± 6 HRC) and IN718/SS316 interphases (34 ± 1 HRC) are significantly higher compared to results reported for conventional IN718 alloy (28 HRC) and IN718/SS420 mixtures (15–18 HRC) as well as for IN718-DED (33 HRC) [ 9 ], [ 10 ]. From the IN718/SS316 hardness value of the S3 sample, it can be pointed out the high hardness together with the low deviation value, which indicates the quite stable hardness value achieved across all the interphases analyzed. This consistent properties and behavior of adjacent layers in dissimilar structures can significantly affect the improving service life and prevent the premature failure of multimaterial parts manufactured in this combination of material [ 7 ]. This successful hardness property transition obtained together with no defects or element segregation could also result in a gradient in mechanical properties. Moreover, a specific heat treatment of solution plus aging-2 steps to increase the IN718 mechanical properties could be carried out. This heat treatment has been identified and studied in a previous work with IN718 samples manufactured throughout same DED technology as the one employed in this study. Enhanced mechanical behavior of up to 55% in the yield strength from 660 MPa to 1025 MPa was previously demonstrated for IN718 samples processed by DED technology [ 11 ]. Thus, the same heat treatment could be conducted in the samples developed in this research to study the effect on hardness properties and gradient transition. 4 Conclusions In this study, the additive manufacturing wire-based DED process was used to manufacture three SS316-IN718 multimaterial samples by different multimaterial sandwich strategies. Three different strategies were designed following a different number of consecutive layers of the same material: S1 (two layers multimaterial strategy), S2 (three layers multimaterial strategy) and S3 (four layers multimaterial strategy). In all of them, the direct transition was considered between both materials and cross-sections, microstructure and hardness properties were evaluated. The three strategies were successfully manufactured, although the sample processed with two layers per material (S1) showed the presence of cracks propagated defects associated with a higher concentration of thermal and residual stresses between layers. Nevertheless, S2 (three layers per material) and S3 (four layers per material) samples did not show defects between adjacent layers. Microstructural assessments were carried out in the XY direction in the middle-region and upper-area of sample S3 and along the cross-section (XZ build direction) of two adjacent IN718 and SS316 layers. A smooth transition was found in both build directions at the IN718/SS316 interphase with a very fine microstructure attributed to the high cooling rate of the DED processing compared to conventional methods. A partial microstructure with a mean grain size between 5 µm (equiaxed grains) and 20 µm (columnar and elongated grains) was achieved in the IN718-regions. At the SS316-regions, the main microstructure features found were austenite composed of a mix of cellular and dendritic structures. In the case of the XY build direction, a low proportion of ferrite was also identified, whereas a very well-defined cellular structure was found at the XZ build direction. In general, in all the IN718/SS316 interphases evaluated, a transition in microstructure was also revealed from equiaxed dendrites to more elongated ones, with very fine microstructure, and free from defects like cracks, segregation, lack of fusion or delamination. Hardness evaluation along the cross-section of the samples showed that in addition to good microstructure in S2 and S3 samples, the highest values of hardness in the three areas IN718-region, IN718/SS316 and SS316-region were shown in the four layers multimaterial strategy (S3 sample). The transition hardness found in S3 sample IN718 (55 HRC) / IN718/SS316 (34 HRC) / SS316 (9 HRC) was also accompanied by very good microstructure properties. IN718 hardness values were even higher than the conventional material. Comparison of hardness variations along the build direction of the samples processed with 2, 3 or 4 layers per material showed the hardness changes associated with the behaviour of the adjacent layers, which gives helpful information about the possible service life of the multimaterial part. Chemical composition, hardness and mechanical testing should be also further investigated to better understand the behaviour of these multimaterial samples. Declarations Acknowledgment The authors would like to express sincere gratitude to all the members (A. Fraile-Marin, M. Pastor, J. Batres and A. Medina) of the Advanced Materials Department from the Technology Centre of Metal-mechanical and Transport (CETEMET) for their cooperation and involvement in the research project entitled MULTIMAT 3D “Industrial research of multimaterial additive manufacturing technology applied to metallic 3d printing for the manufacturing of parts in the transport sector” (PTQ2020-011030). Funding This project is part of the National Spanish Call Torres Quevedo 2020 (PTQ2020-011030) funded by the Spanish Ministry of Science and Innovation (MCIN) in collaboration with the Spanish State Investigation Agency (AEI), MCIN/AEI/10.13039/501100011033, together with the European Union “NextGenerationEU/PRTR”. Author contribution Julia Ureña: main project researcher; conceptualization; data curation; formal analysis; investigation; methodology; roles/writing-original draft; writing-review and editing. Marta Álvarez-Leal: investigation; roles/writing-review and editing. Ethics approval: Not Applicable. Conflict of interest: The authors declare no competing interests. Consent to participate: All authors agreed to participate in this manuscript. Consent for publication: All authors agreed to submit the manuscript. Data availability: The data of the results are available from the corresponding author on reasonable request. Code availability: Not Applicable. References Nazir A et al (2023) Multi-material additive manufacturing: A systematic review of design, properties, applications, challenges, and 3D printing of materials and cellular metamaterials. Mater Des 226:111661. 10.1016/j.matdes.2023.111661 Zhang W, Wang J, Zhu X, Lu X, Ling X (2024) A functionally graded material from stainless steel 304 to Fe–40Al fabricated by dual wire arc additive manufacturing, J. Mater. Res. Technol. , vol. 28, no. April, pp. 3566–3572, 10.1016/j.jmrt.2023.12.268 Carroll BE et al (2016) Functionally graded material of 304L stainless steel and inconel 625 fabricated by directed energy deposition: Characterization and thermodynamic modeling. Acta Mater 108:46–54. 10.1016/j.actamat.2016.02.019 Senthil TS, Ramesh Babu S, Puviyarasan M, Dhinakaran V (2021) Mechanical and microstructural characterization of functionally graded Inconel 825 - SS316L fabricated using wire arc additive manufacturing, J. Mater. Res. Technol. , vol. 15, pp. 661–669, Nov. 10.1016/j.jmrt.2021.08.060 Godec D, Gonzalez-gutierrez J, Nordin A, Pei E, Ureña J (2022) A Guide to Additive Manufacturing. Springer Nature, Springer Tracts in Additive Manufacturing, Feenstra DR, Banerjee R, Fraser HL, Huang A, Molotnikov A, Birbilis N (2021) Critical review of the state of the art in multi-material fabrication via directed energy deposition. Curr Opin Solid State Mater Sci 25(4):100924. 10.1016/j.cossms.2021.100924 Ghanavati R, Naffakh-Moosavy H (2021) Additive manufacturing of functionally graded metallic materials: A review of experimental and numerical studies. J Mater Res Technol 13:1628–1664. 10.1016/j.jmrt.2021.05.022 Kim SH et al (2021) Selective compositional range exclusion via directed energy deposition to produce a defect-free Inconel 718/SS 316L functionally graded material. Addit Manuf 47:102288. 10.1016/j.addma.2021.102288 Ghanavati R, Naffakh-Moosavy H, Moradi M (2021) Additive manufacturing of thin-walled SS316L-IN718 functionally graded materials by direct laser metal deposition. J Mater Res Technol 15:2673–2685. 10.1016/j.jmrt.2021.09.061 Aydogan B, O’Neil A, Sahasrabudhe H (2020) Microstructural and mechanical characterization of stainless steel 420 and Inconel 718 multi-material structures fabricated using laser directed energy deposition, J. Manuf. Process. , vol. 68, no. November pp. 1224–1235, 2021, 10.1016/j.jmapro.2021.06.031 Alvarez-Leal M, Rodriguez-Alabanda O, Romero PE, Molero E, Ureña J (2023) Development and Processing of Inconel 718 Tools for Friction Stir Welding Additively Manufactured by Laser Metal Deposition, in Proceedings of the XV Ibero-American Congress of Mechanical Engineering , Springer International Publishing, pp. 334–340. 10.1007/978-3-031-38563-6_49 Cite Share Download PDF Status: Published Journal Publication published 25 Oct, 2024 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Editorial decision: Major Revisions Needed 02 Jul, 2024 Reviewers agreed at journal 22 May, 2024 Reviewers invited by journal 22 May, 2024 Editor assigned by journal 22 May, 2024 First submitted to journal 20 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4416707","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":305659047,"identity":"18634d73-35e3-4552-9943-46ef9a756b7b","order_by":0,"name":"JULIA UREÑA ALCÁZAR","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACxgYILUe6FmMGBmYQbUC81sQGorUwN/CYffi4wy69v73/4KMbFX8Y+PkPEHIYj/HMmWeSc2ecOcxsnHPGgEFyRgJhLcy8bcy5GySS2aRz2wwYDG4QcBhYy9+2+nQD+cfsv3P/GTDYnyfCYcyMbYcTDCSY2ZhzG4C2MBByWDNbMWNv23HDGWeSjaVzjhnzSNwgoMWwvXkzw8+2ann+9oMPP+fUyMnx9xNwmGEzmgAPfvVAIE9QxSgYBaNgFIwCAE29OlpLx/UmAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-3740-3079","institution":"Technology Centre of Metal-Mechanical and Transport (CETEMET)","correspondingAuthor":true,"prefix":"","firstName":"JULIA","middleName":"UREÑA","lastName":"ALCÁZAR","suffix":""},{"id":305659048,"identity":"06592486-9317-4da3-bb41-af9576ebbc8e","order_by":1,"name":"Marta Álvarez-Leal","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Marta","middleName":"","lastName":"Álvarez-Leal","suffix":""}],"badges":[],"createdAt":"2024-05-14 05:42:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4416707/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4416707/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00170-024-14694-2","type":"published","date":"2024-10-25T15:56:58+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":57694606,"identity":"16053ae2-7890-4a0e-aba6-28a084c961dc","added_by":"auto","created_at":"2024-06-04 12:13:16","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":456916,"visible":true,"origin":"","legend":"\u003cp\u003eDetail images of the M450 double wire LMD device used for the additive manufacturing of the SS316/IN718 multimaterial.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/f6401f26d5cc4634400d69c2.png"},{"id":57694003,"identity":"9e34d0b2-9129-42f6-acd5-5e968255c5ca","added_by":"auto","created_at":"2024-06-04 12:05:16","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":269453,"visible":true,"origin":"","legend":"\u003cp\u003eMultimaterial strategies sandwich design for SS316/IN718 additive manufacturing by DED: S1 (two layers multimaterial strategy); S2 (three layers multimaterial strategy) and S3 (four layers multimaterial strategy). Detailed views of the three different gradients created.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/0f6be9dbf09c253dba2dd060.png"},{"id":57694007,"identity":"8067d45c-427e-4987-b2c0-333f7c13e5f7","added_by":"auto","created_at":"2024-06-04 12:05:17","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":484918,"visible":true,"origin":"","legend":"\u003cp\u003eDesign and manufacturing of the three SS316/IN718 multimaterial sandwich strategies by DED technology: S1 (two layers multimaterial strategy); S2 (three layers multimaterial strategy); and S3 (four layers multimaterial strategy).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/04290ef2d77f7e94d248d623.png"},{"id":57694005,"identity":"a2d4520d-22da-4aa3-98ca-8cd4eaf2a0b0","added_by":"auto","created_at":"2024-06-04 12:05:16","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1677578,"visible":true,"origin":"","legend":"\u003cp\u003eCross-section results of the three manufactured SS316/IN718 multimaterial sandwich strategies by DED technology. XZ build direction analysis of: a) S1 (two layers multimaterial strategy); b) S2 (three layers multimaterial strategy); and c) S3 (four layers multimaterial strategy) samples.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/a4d33153907fb414b38bc4c4.png"},{"id":57694009,"identity":"de887527-a779-411e-b70c-6fd308f19d15","added_by":"auto","created_at":"2024-06-04 12:05:17","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":577726,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure results of the manufactured SS316/IN718 multimaterial (S3) sample employing direct transition by DED technology. XY plane of the IN718-region, SS316/IN718 interphase and SS316-regions found at: a) middle-region and b) upper-area.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/9cf787d7a917bae26d9a518b.png"},{"id":57694607,"identity":"04a79355-f010-489d-8ef7-a7f0db3b536f","added_by":"auto","created_at":"2024-06-04 12:13:17","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1546194,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure results in the build direction (XZ plane) at the interface of two adjacent layers in the SS316/IN718 multimaterial (S3) sample manufactured employing direct transition by DED technology. a) SS316-region, b) SS316-region (detailed view), c) IN718-region, d) IN718-region (detailed view) showing the smooth transition at the SS316/IN718 interphase.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/51d2cb9752bd63e59ff51ff4.png"},{"id":57694608,"identity":"e5916f07-c239-48da-8579-623f5c9f8c47","added_by":"auto","created_at":"2024-06-04 12:13:17","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":365749,"visible":true,"origin":"","legend":"\u003cp\u003eRockwell C hardness results of the three SS316/IN718 multimaterial sandwich strategies additively manufactured via DED technology. Measurements performed in the cross-section of: a) S1 (two layers multimaterial strategy); b) S2 (three layers multimaterial strategy); and c) S3 (four layers multimaterial strategy) samples.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/d469a66eea2a9a9dd577a381.png"},{"id":67681750,"identity":"e979bd69-e8ef-4841-a3c3-daab9b28ea8c","added_by":"auto","created_at":"2024-10-28 16:09:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6625339,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4416707/v1/2b27f0f4-582c-4859-ac80-459b01389d05.pdf"}],"financialInterests":"","formattedTitle":"Multimaterial design strategies and microstructural characterization of stainless steel 316-Inconel 718 developed by wire-based Directed Energy Deposition","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eMultimaterial combinations are widely present in our daily life and most of them are nature-inspired multimaterial structures. Design and innovative processing methods for optimized multimaterial are being investigated by selecting application-specific combinations of compositional structures of two materials [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The stainless steel (SS316L)-nickel-based superalloy Inconel 718 (IN718) multimaterial has increased its attraction to be investigated together in multimaterial structures due to their different properties in the same manufacturing process [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. SS316/IN718 was selected for this study due to their useful combination properties for both strength and corrosion resistance at elevated temperature. With this IN718/SS316 multimaterial, high wear and corrosion resistance at high temperature will be provided by IN718 when required whereas weight and cost reduction will be locally achieved by applying SS316 material. Gas turbine components, high-end automobile engine valve stems or coating are different applications where such material properties combination is highly interesting [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDifferent fusion welding processes by applying heat with or without pressure or filler materials are usually found among the most common conventional methods for joining similar or dissimilar metals. This is the conventional route for manufacturing a part composed of different metallic materials. However, in order to avoid or minimize the crack-formation or embrittlement, these conventional joining processes employ intermediate layers for separating two dissimilar metals or high energy-sources. Nevertheless, some innovative joining processes like Friction Stir Welding (FSW) are also an alternative joining method for welding dissimilar materials in the solid state by severe plastic deformation using a harder tool. In this way, mechanical bonding occurs between both metallic alloys to join without an energy-source or melting steps[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, metallic multimaterial manufacturing can be suitably performed with some Additive Manufacturing (AM) processes in which different metallic materials are able to be melted through a controlled electron or laser beam energy-source. Therefore, in addition to the advantages of multimaterials, the fact of manufacturing them by AM results in merits like: i) developing metallic multimaterials as a single-step process without the necessity of joining pos-processing methods; ii) enabling design freedom for customization; iii) cost-effective and environmental-friendly manufacturing solutions with a reduced amount of raw material and material waste as well as reduced production costs saving energy, time and steps [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDED systems, also known as Laser Metal Deposition (LMD) processing, are AM processes in which a nozzle mounted on a multi-axis arm deposits molten material in powder or wire format layer by layer onto a build plate at a specific angle. The energy-source can be a laser, electron beam or plasma arc and it is used to create beads, tracks and layers of solid materials upon solidification of the melt pool on the substrate [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Among the main advantages found in wire-based DED technologies; the higher material deposition rate compared to powder bed fusion, the bigger size of the final component or the lower heat transference are highlighted [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, due to DED being a fusion-process, the common problems of processinng dissimilar materials with different physico-chemical properties must be addressed.\u003c/p\u003e \u003cp\u003eTo the best of our knowledge, the valuable researches found about this topic seems to be mostly related to powder-based DED processing, L-PBF processing or WAAM technology but very few publications are available about the double wire DED manufacturing. Thus, exploring the IN718/SS316 multimaterial manufacturing via wire-based DED processing in this research will contribute to widening the state-of-the-art with innovative knowledge.\u003c/p\u003e \u003cp\u003eIn this work, three IN718/SS316 multimaterial samples manufactured by wire-based DED technology with different sandwich design strategies (two, three or four layers per material) were developed. Cross-sections, microstructure in both build directions and hardness properties were evaluated in the different regions (IN718-segments, IN718/SS316 interphases and SS316-segments) to compare the material behaviour of the three multimaterial strategies employed. The effect of a number of layers per material on the interphases and adjacent layers is studied to better understand the service life of a part additively manufactured in this multimaterial by wire-based DED technology.\u003c/p\u003e"},{"header":"2 Experimental procedure","content":"\u003cp\u003eWire metals of low-carbon stainless steel 316LS (SS316) and nickel-based superalloy Inconel 718 (IN718) were employed to process the SS316/IN718 multimaterial. The stainless steel SS316L is a standard low-carbon austenitic steel containing molybdenum, which makes excellent durability, biocompatibility and corrosion resistance, particularly against pitting and crevice corrosion in chloride environments [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The IN718 superalloy is a high-strength alloy widely used in high-temperature applications due to its good mechanical properties and excellent corrosion resistance. Therefore, both materials were used for the manufacturing of the SS316/IN718 by means of 1 mm diameter wires as starting materials. The elemental composition of the SS316 stainless steel and IN718 nickel-based superalloy wires are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. MELTIO was the supplier for both materials as well as the manufacturer of the double wire-based DED technology used in this research.\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 the starting wire SS316 and IN718 materials for the LMD processing.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" 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=\"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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"12\" nameend=\"c13\" namest=\"c2\"\u003e \u003cp\u003eChemical composition (wt. %)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eFerrite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eTi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eAl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eNb\u0026thinsp;+\u0026thinsp;Ta\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS316\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e18.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIN718\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBalance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e5.2\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 multimaterial SS316/IN718 was processed using the innovative Meltio M450 Directed Energy Deposition (DED) technology. This additive manufacturing technology is equipped with a multi-laser deposition head system capable of processing two different wires simultaneously (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Laser DED additive manufacturing system, equipped with a 1.2 kW laser system composed of 6 (200 W) fiber coupled diode lasers of 976 nm wavelength was used to manufacture the samples. Argon with a purity higher than 99.996% was used as shielding gas during the whole 3D processing. The process parameters combination selected for the manufacturing of small cubes of 25 mm wide and 25 mm tall for the three design multimaterial strategies is summarized 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\u003eDED process parameters for SS316/IN718 multimaterial manufacturing.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eDED process parameters for SS316/IN718 multimaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c7\" namest=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePrint speed\u003c/p\u003e \u003cp\u003e\u003cem\u003e(mm/min)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLayer height\u003c/p\u003e \u003cp\u003e\u003cem\u003e(mm)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLaser power\u003c/p\u003e \u003cp\u003e\u003cem\u003e(W)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTrack spacing\u003c/p\u003e \u003cp\u003e\u003cem\u003e(mm)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eGas flow\u003c/p\u003e \u003cp\u003e\u003cem\u003e(L/min)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSS316\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIN718\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e10\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 multimaterial strategies sandwich SS316/IN718 for manufacturing small cubes of 25 mm wide and 25 mm tall designed by three different strategies are schematically represented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e using S1 (two layers multimaterial strategy), S2 (three layers multimaterial strategy) and S3 (four layers multimaterial strategy). All of them are composed of SS316 and IN718 direct transition material gradients, represented in grey and blue color, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe microstructural analysis was carried out by optical microscopy (Axiolab A1 equipped with an AxioCam ERc, Carl Zeiss ICS and ZeissCore software) after cross-sectioning and surface preparation by standard metallographic techniques to evaluate the density level of the different materials processed. The surface of the specimens was ground successively from 600 to 4000 grit with SiC papers, followed by polishing with 1 \u0026micro;m diamond suspension and finally with colloidal silica suspension. The as-polished samples were chemically etched for a few seconds to reveal the microstructures by using a solution of Vilella and HCl for the stainless-steel segments and a diluted solution of FeCl3 for the Inconel regions. Hardness Rockwell C values of the developed samples were measured using a Wilson Rockwell C hardness tester. A loading force of 150 Kg and 15 s indentation time were effective for achieving accurate measurements for the SS316 and IN718 segments as well as SS316/IN718 interphases.\u003c/p\u003e"},{"header":"3 Results and discussion","content":"\u003cp\u003eThe three SS316/IN718 multimaterial sandwich specimens designed are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. This multimaterial design can be applicable to bimetallic structures where dual functionalities are required. Three different material gradients were created where the material layer disposition was different. Two, three and four layers per material have been considered as the three different multimaterial strategies S1, S2 and S3, respectively, to be studied. Distribution of the specimens along the build plate and the successful result of the manufacturing process by DED technology are represented. The process parameters for the manufacturing and the detailed multimaterial strategies were described in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFirst, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the cross-section of the additive manufactured samples processed by DED technology along with the design considered for each multimaterial strategy. In Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e-a the multimaterial sandwich strategy considered (S1) is composed of two IN718 layers and two SS316 layers, consecutively, from the bottom to the surface with eight IN718/SS316 interphases. Secondly, in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e-b the multimaterial sandwich strategy considered (S2) was composed of three IN718 layers and three SS316 layers, consecutively, from the bottom to the surface with six IN718/SS316 interphases. Finally, in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e-c was represented the multimaterial sandwich strategy S3, which was composed of four IN718 layers and four SS316 layers, consecutively, from the bottom to the surface with five IN718/SS316 interphases.\u003c/p\u003e \u003cp\u003eIn the S1 strategy (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e-a), some defects were found repeatably at the interphase. In fact, all of them were originated at the border of the IN718 layer and they were propagated to the SS316 layer. Some of the defects caused by the DED process could have occurred due to low or excessive heat input. Irregular lack-of-fusion defects are usually attributed to an insufficient heat input since some cracks can appear due to a higher heat input as reported also by [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, in this multimaterial study the presence of some cracks can be also related to supercooling, thermal and residual stress concentration as well as the CTE difference between dissimilar materials.\u003c/p\u003e \u003cp\u003eHowever, in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e-b it can be noticed how the presence of these defects in almost depreciable, similar to Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e-c, which can be attributed to the fact of depositing more than two consecutive layers of the different materials. This behaviour can be correlated with the thermal behaviour responses of the three multimaterial strategies employed. In the case of the samples manufactured with S2 and S3 strategies, three and four material layers, respectively, are deposited and melted of each SS316 and IN718 material. In contrast, the gradient generated in the sample manufactured with the S1 multimaterial strategy is composed of two consecutive layers of both alloys. This seems to have a major impact on the thermal gradient response between layers. Therefore, although 2 layers per material transition could be built, the thermal and residual stresses formed in the previous interphase region could affect the subsequent layer through close contact during the change of material. Furthermore, the pores and cracks induced during the cooling of the IN718 layer can propagate at the IN718/SS316 interphase and move into the nearby SS316 layer with no defects. This was also evidenced by other authors where similar defects were found in functionally graded materials with 3\u0026ndash;4 layers and even 1 layer per compositional transition manufactured by DED technology [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, related to the optical microstructure along the XY direction of DED samples processed through direct transition (i.e. S2 and S3), it can be seen (from left to right) the microstructure of the different regions: IN718-segment, IN718/SS316 interphase and SS316-segment.\u003c/p\u003e \u003cp\u003eMicrostructural examination of the built specimens was observed in two different areas, at the middle-region of the sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e-a) and at the upper-area of the sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e-b). A microstructural gradient was obtained throughout the sample in both areas analyzed. First, in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e-a, deep melt pool signs were observed at low magnification as a consequence of high thermal gradients which caused different grain growth directions in the IN718-segment. It is known that the dimensions of the melt pool are associated with thermal conductivity, thermal diffusivity, cooling rate, and solidification front velocity as described in another study [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. These thermal gradients, provoked by the consecutive cooling rate changes, originated a microstructure partially formed by columnar and equiaxed dendrites as it was observed at higher magnifications. Then, a smooth transition zone was identified at the IN718/SS316 interphase, meaning a successful union of both dissimilar materials by a good combination of DED-process parameters between them. At the SS316-segment, the main microstructure features found were austenite and ferrite composed of a mix of cellular and dendritic structures; showing an important region of columnar dendrites. This type of microstructure is usually attributed to the additive manufacturing process itself since they are not continuous processes. Each layer is solidified during its material layer deposition, but also experiences partial melting and solidification steps with the subsequent layer deposition as it was reported in other research [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding the microstructure size of SS316 and IN718, it is important to highlight that this feature is one of the main microstructural differences between materials processed by Additive Manufacturing (AM) compared to the same conventional alloys. A very fine microstructure was obtained defined by the rapid cooling rate commonly found in the DED processing compared to conventional methods. An average grain size between 5 \u0026micro;m (equiaxed grains) and 20 \u0026micro;m (columnar and elongated grains) was achieved in the samples studied in this research, whereas coarser microstructure with grain sizes between 30\u0026ndash;50 \u0026micro;m was reported for the same conventional materials by other authors [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding the microstructure obtained at the surface or upper-area (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e-b), it was very similar to that obtained for the IN718-segment in the previous region (middle-area), but very different from the conventionally IN718 manufactured, as expected. A great proportion of localized columnar structure was seen in IN718 at lower augments when fabricated using laser-DED with mixed regions of equiaxed grains. The reason for partial mixing could be related to the lower heat input of the DED processing together with a faster cooling rate which provides less time for the diffusion of elements like Mo and Cr to both sides [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the transition IN718/SS316, a transition in microstructure was also revealed from equiaxed dendrites to more elongated dendrites, but in both cases with very fine microstructure, and free from defects like cracks, segregation, lack of fusion or delamination.\u003c/p\u003e \u003cp\u003eIn the case of the SS316-segment an important difference was observed between the surface (upper-area) and the middle-area. SS316-upper region appeared to show finer grains composed of a cellular structure with very well defined and small grain sizes (3\u0026ndash;5 \u0026micro;m) compared to the microstructure shown in the middle-region of the sample. This could be explained due to the solidification rate achieved at the latest layers (upper-area, surface) since no partial remelting is happening on subsequent layers as occurs at the middle-region. In both areas examined no compositional segregation was identified by optical microscopy, which could lead to cracks at the IN718/SS316 interphase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eMicrostructure results in the cross-section (XZ build direction) of two adjacent layers in the SS316/IN718 sample additively manufactured by DED employing S3 multimaterial strategy were also investigated (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e-a very fine columnar and equiaxed dendrites were grown in the SS316-region from the melt pool signs which can be seen more in detail in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e-b. Microstructure mainly composed of cellular and columnar austenite grains was found partially mixed. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec-d (IN718-segment) exhibited very similar microstructure features as in the XY plane, but in this case marks corresponding to the melt pools and transition layers were found parallel to the build direction. Very fine columnar grains showed an average grain size of 30 \u0026micro;m length and 2\u0026ndash;3 \u0026micro;m wide while equiaxed grains were mostly around 5 \u0026micro;m.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows the average Rockwell C hardness values obtained along the cross-section of the three samples additively manufactured according to the S1, S2 and S3 multimaterial design strategies employed in this study. It can be also seen the cross-sections where the material gradient can be observed in detail in each sample. The indentation measurements can also be seen together with the identification of each layer by means of a small square in blue (IN718), grey (SS316) or dark blue color (IN718/SS316 interphase).\u003c/p\u003e \u003cp\u003eIt can be seen that the hardness values of the three multimaterial strategies employed followed a similar correlation between their different material regions. The hardness of the IN718-segments was higher in all cases followed by the IN718/SS316 regions and SS316-segments, as expected. Therefore, a hardness transition was obtained in all samples in agreement with the material gradient also shown in the cross-sections of samples. The IN718 / IN718/SS316 / SS316 hardness transition gradient found for S1, S2 and S3 was: (19 / 13 / 9 HRC), (21 / 8 / 8 HRC) and (55 / 34 / 9 HRC), respectively.\u003c/p\u003e \u003cp\u003eThe hardness values for the SS316-segments in all samples seem to be quite stable around 8\u0026ndash;9 HRC. However, it can be noticed how the values of hardness for both IN718-segments and IN718/SS316 regions increased from S1 to S3 samples. In fact, this hardness increase is significantly high in the sample developed by S3 multimaterial strategy; reaching values of 55 HRC and 34 HRC for IN718-segments and IN718/SS316 regions, respectively. These values are also in correlation with the detailed results obtained from the cross-sections (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) where it was found that although the three strategies can be successfully manufactured, S1 (two layers per material) showed more presence of cracks propagated defects associated with a higher concentration of thermal and residual stresses between layers. Nevertheless, S2 (three layers per material) and S3 (four layers per material) samples did not show defects between subsequent layers. This means that although S2 and S3 are suitable as multimaterial strategies for developing graded IN718/SS316 materials, from the hardness point of view, S3 is the multimaterial strategy which offers the transition hardness with the highest values accompanied with very good microstructure properties. Moreover, hardness values obtained in S3 sample for IN718-region (55\u0026thinsp;\u0026plusmn;\u0026thinsp;6 HRC) and IN718/SS316 interphases (34\u0026thinsp;\u0026plusmn;\u0026thinsp;1 HRC) are significantly higher compared to results reported for conventional IN718 alloy (28 HRC) and IN718/SS420 mixtures (15\u0026ndash;18 HRC) as well as for IN718-DED (33 HRC) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFrom the IN718/SS316 hardness value of the S3 sample, it can be pointed out the high hardness together with the low deviation value, which indicates the quite stable hardness value achieved across all the interphases analyzed. This consistent properties and behavior of adjacent layers in dissimilar structures can significantly affect the improving service life and prevent the premature failure of multimaterial parts manufactured in this combination of material [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. This successful hardness property transition obtained together with no defects or element segregation could also result in a gradient in mechanical properties. Moreover, a specific heat treatment of solution plus aging-2 steps to increase the IN718 mechanical properties could be carried out. This heat treatment has been identified and studied in a previous work with IN718 samples manufactured throughout same DED technology as the one employed in this study. Enhanced mechanical behavior of up to 55% in the yield strength from 660 MPa to 1025 MPa was previously demonstrated for IN718 samples processed by DED technology [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Thus, the same heat treatment could be conducted in the samples developed in this research to study the effect on hardness properties and gradient transition.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eIn this study, the additive manufacturing wire-based DED process was used to manufacture three SS316-IN718 multimaterial samples by different multimaterial sandwich strategies. Three different strategies were designed following a different number of consecutive layers of the same material: S1 (two layers multimaterial strategy), S2 (three layers multimaterial strategy) and S3 (four layers multimaterial strategy). In all of them, the direct transition was considered between both materials and cross-sections, microstructure and hardness properties were evaluated.\u003c/p\u003e \u003cp\u003eThe three strategies were successfully manufactured, although the sample processed with two layers per material (S1) showed the presence of cracks propagated defects associated with a higher concentration of thermal and residual stresses between layers. Nevertheless, S2 (three layers per material) and S3 (four layers per material) samples did not show defects between adjacent layers.\u003c/p\u003e \u003cp\u003eMicrostructural assessments were carried out in the XY direction in the middle-region and upper-area of sample S3 and along the cross-section (XZ build direction) of two adjacent IN718 and SS316 layers. A smooth transition was found in both build directions at the IN718/SS316 interphase with a very fine microstructure attributed to the high cooling rate of the DED processing compared to conventional methods. A partial microstructure with a mean grain size between 5 \u0026micro;m (equiaxed grains) and 20 \u0026micro;m (columnar and elongated grains) was achieved in the IN718-regions. At the SS316-regions, the main microstructure features found were austenite composed of a mix of cellular and dendritic structures. In the case of the XY build direction, a low proportion of ferrite was also identified, whereas a very well-defined cellular structure was found at the XZ build direction. In general, in all the IN718/SS316 interphases evaluated, a transition in microstructure was also revealed from equiaxed dendrites to more elongated ones, with very fine microstructure, and free from defects like cracks, segregation, lack of fusion or delamination.\u003c/p\u003e \u003cp\u003eHardness evaluation along the cross-section of the samples showed that in addition to good microstructure in S2 and S3 samples, the highest values of hardness in the three areas IN718-region, IN718/SS316 and SS316-region were shown in the four layers multimaterial strategy (S3 sample). The transition hardness found in S3 sample IN718 (55 HRC) / IN718/SS316 (34 HRC) / SS316 (9 HRC) was also accompanied by very good microstructure properties. IN718 hardness values were even higher than the conventional material. Comparison of hardness variations along the build direction of the samples processed with 2, 3 or 4 layers per material showed the hardness changes associated with the behaviour of the adjacent layers, which gives helpful information about the possible service life of the multimaterial part. Chemical composition, hardness and mechanical testing should be also further investigated to better understand the behaviour of these multimaterial samples.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgment\u003c/p\u003e\n\u003cp\u003eThe authors would like to express sincere gratitude to all the members (A. Fraile-Marin, M. Pastor, J. Batres and A. Medina) of the Advanced Materials Department from the Technology Centre of Metal-mechanical and Transport (CETEMET) for their cooperation and involvement in the research project entitled MULTIMAT 3D \u0026ldquo;Industrial research of multimaterial additive manufacturing technology applied to metallic 3d printing for the manufacturing of parts in the transport sector\u0026rdquo; (PTQ2020-011030).\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis project is part of the National Spanish Call Torres Quevedo 2020 (PTQ2020-011030) funded by the Spanish Ministry of Science and Innovation (MCIN) in collaboration with the Spanish State Investigation Agency (AEI), MCIN/AEI/10.13039/501100011033, together with the European Union \u0026ldquo;NextGenerationEU/PRTR\u0026rdquo;.\u003c/p\u003e\n\u003cp\u003eAuthor contribution\u003c/p\u003e\n\u003cp\u003eJulia Ure\u0026ntilde;a: main project researcher; conceptualization; data curation; formal analysis; investigation; methodology; roles/writing-original draft; writing-review and editing. Marta \u0026Aacute;lvarez-Leal: investigation; roles/writing-review and editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval:\u003c/strong\u003e Not Applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate:\u003c/strong\u003e All authors agreed to participate in this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u0026nbsp;\u003c/strong\u003eAll authors agreed to submit the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability:\u0026nbsp;\u003c/strong\u003eThe data of the results are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability:\u003c/strong\u003e Not Applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNazir A et al (2023) Multi-material additive manufacturing: A systematic review of design, properties, applications, challenges, and 3D printing of materials and cellular metamaterials. Mater Des 226:111661. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.matdes.2023.111661\u003c/span\u003e\u003cspan address=\"10.1016/j.matdes.2023.111661\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang W, Wang J, Zhu X, Lu X, Ling X (2024) A functionally graded material from stainless steel 304 to Fe\u0026ndash;40Al fabricated by dual wire arc additive manufacturing, \u003cem\u003eJ. Mater. Res. Technol.\u003c/em\u003e, vol. 28, no. April, pp. 3566\u0026ndash;3572, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jmrt.2023.12.268\u003c/span\u003e\u003cspan address=\"10.1016/j.jmrt.2023.12.268\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarroll BE et al (2016) Functionally graded material of 304L stainless steel and inconel 625 fabricated by directed energy deposition: Characterization and thermodynamic modeling. Acta Mater 108:46\u0026ndash;54. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.actamat.2016.02.019\u003c/span\u003e\u003cspan address=\"10.1016/j.actamat.2016.02.019\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSenthil TS, Ramesh Babu S, Puviyarasan M, Dhinakaran V (2021) Mechanical and microstructural characterization of functionally graded Inconel 825 - SS316L fabricated using wire arc additive manufacturing, \u003cem\u003eJ. Mater. Res. Technol.\u003c/em\u003e, vol. 15, pp. 661\u0026ndash;669, Nov. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jmrt.2021.08.060\u003c/span\u003e\u003cspan address=\"10.1016/j.jmrt.2021.08.060\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGodec D, Gonzalez-gutierrez J, Nordin A, Pei E, Ure\u0026ntilde;a J (2022) A Guide to Additive Manufacturing. Springer Nature, Springer Tracts in Additive Manufacturing,\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeenstra DR, Banerjee R, Fraser HL, Huang A, Molotnikov A, Birbilis N (2021) Critical review of the state of the art in multi-material fabrication via directed energy deposition. Curr Opin Solid State Mater Sci 25(4):100924. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cossms.2021.100924\u003c/span\u003e\u003cspan address=\"10.1016/j.cossms.2021.100924\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhanavati R, Naffakh-Moosavy H (2021) Additive manufacturing of functionally graded metallic materials: A review of experimental and numerical studies. J Mater Res Technol 13:1628\u0026ndash;1664. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jmrt.2021.05.022\u003c/span\u003e\u003cspan address=\"10.1016/j.jmrt.2021.05.022\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim SH et al (2021) Selective compositional range exclusion via directed energy deposition to produce a defect-free Inconel 718/SS 316L functionally graded material. Addit Manuf 47:102288. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.addma.2021.102288\u003c/span\u003e\u003cspan address=\"10.1016/j.addma.2021.102288\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhanavati R, Naffakh-Moosavy H, Moradi M (2021) Additive manufacturing of thin-walled SS316L-IN718 functionally graded materials by direct laser metal deposition. J Mater Res Technol 15:2673\u0026ndash;2685. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jmrt.2021.09.061\u003c/span\u003e\u003cspan address=\"10.1016/j.jmrt.2021.09.061\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAydogan B, O\u0026rsquo;Neil A, Sahasrabudhe H (2020) Microstructural and mechanical characterization of stainless steel 420 and Inconel 718 multi-material structures fabricated using laser directed energy deposition, \u003cem\u003eJ. Manuf. Process.\u003c/em\u003e, vol. 68, no. November pp. 1224\u0026ndash;1235, 2021, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jmapro.2021.06.031\u003c/span\u003e\u003cspan address=\"10.1016/j.jmapro.2021.06.031\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlvarez-Leal M, Rodriguez-Alabanda O, Romero PE, Molero E, Ure\u0026ntilde;a J (2023) Development and Processing of Inconel 718 Tools for Friction Stir Welding Additively Manufactured by Laser Metal Deposition, in \u003cem\u003eProceedings of the XV Ibero-American Congress of Mechanical Engineering\u003c/em\u003e, Springer International Publishing, pp. 334\u0026ndash;340. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/978-3-031-38563-6_49\u003c/span\u003e\u003cspan address=\"10.1007/978-3-031-38563-6_49\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Multimaterial, Additive Manufacturing (AM), Laser Directed Energy Deposition (L-DED) processing, wire-based, IN718/SS316, Microstructure, Hardness","lastPublishedDoi":"10.21203/rs.3.rs-4416707/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4416707/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe combination of different material properties to face severe conditions has been always demanded by different industrial sectors. For instance, in gas turbine components, excellent mechanical properties at high temperatures and corrosive environments are required. Traditionally, this has been achieved by conventional manufacturing of multiple materials with several steps and joining processes. However, manufacturing the entire component within the same process by additive manufacturing and the combination of two different materials is presented as a potential via to explore.\u003c/p\u003e \u003cp\u003eIn this research, the additive manufacturing of stainless steel (SS316L) and Nickel-based Inconel superalloy (IN718) multimaterial through different design strategies approaches has been developed and investigated by wire-based Laser Directed Energy Deposition (DED) technology. Direct transition between materials was applied and three multimaterial sandwich structures (S1, S2 and S3) were designed and successfully manufactured. The microstructure obtained in the three different regions (IN718, IN718/SS316 and SS316) was evaluated in both XY and XZ build directions. Rockwell C hardness was measured along the cross-sections of all samples to compare the different properties of the three samples developed. Defective microstructural features like big porosity, cracks or lack-of-fusion at the SS316/IN718 interphases were not evidenced for S2 and S3 strategies. Multimaterial samples showed very fine microstructures corresponding to the DED processing, and secondary phases such as intermetallic-compounds or carbides were not found. Smooth transitions between materials were obtained which also led to a gradient in microstructure and hardness properties. S3 sample showed the highest hardness value, being the IN718 value even higher compared to conventional IN718 material.\u003c/p\u003e","manuscriptTitle":"Multimaterial design strategies and microstructural characterization of stainless steel 316-Inconel 718 developed by wire-based Directed Energy Deposition","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-04 12:05:12","doi":"10.21203/rs.3.rs-4416707/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2024-07-02T06:51:41+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-05-22T20:57:29+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-22T20:35:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-22T06:27:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2024-05-20T05:40:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"485c1d88-a724-40a5-808d-7210a3be4c0a","owner":[],"postedDate":"June 4th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-10-28T15:59:59+00:00","versionOfRecord":{"articleIdentity":"rs-4416707","link":"https://doi.org/10.1007/s00170-024-14694-2","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2024-10-25 15:56:58","publishedOnDateReadable":"October 25th, 2024"},"versionCreatedAt":"2024-06-04 12:05:12","video":"","vorDoi":"10.1007/s00170-024-14694-2","vorDoiUrl":"https://doi.org/10.1007/s00170-024-14694-2","workflowStages":[]},"version":"v1","identity":"rs-4416707","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4416707","identity":"rs-4416707","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}