Mechanical properties and corrosion protection of DED-Arc additively manufactured high-strength low-alloy steel components coated with Low-Pressure Cold Spray

Mechanical properties and corrosion protection of DED-Arc additively manufactured high-strength low-alloy steel components coated with Low-Pressure Cold Spray | 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 Mechanical properties and corrosion protection of DED-Arc additively manufactured high-strength low-alloy steel components coated with Low-Pressure Cold Spray Marc Müggenburg, Hossein Mokhtarian, Heli Koivuluoto, Hendrik Jahns, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6566148/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract The Directed Energy Deposition-Arc (DED-Arc) process, using high-strength low-alloy (HSLA) feedstock wire, presents a promising solution for fabricating large-scale steel connectors in civil engineering. Due to the use of carbon steel feedstock wire, corrosion protection of the 3D-printed components is necessary. Therefore, this study investigates Low-Pressure Cold Spray (LPCS) as a method for applying zinc-based coatings. Two sets of thin walls were 3D-printed: one set uncoated and one set coated with LPCS Zn + Al 2 O 3 coating. This LPCS coating was successfully deposited on untreated and on grit-blasted DED-Arc surfaces. Coating thicknesses exceeding 300 µm as well as electrochemical polarisation analysis confirmed sufficient corrosion resistance of the coated as-built specimens. To evaluate the influence of the surface condition and the coating process on the mechanical behaviour, dog-bone tensile specimens were extracted from the walls, 3D-scanned and subsequently mechanically tested. Structured-light scanning of the geometry revealed different scatter of the specimens’ thickness based on their orientation with respect to the build direction. Uniaxial quasi-static tensile tests, combined with a four-camera Digital Image Correlation (DIC) system, were performed both on specimens with machined surfaces and with LPCS Zn + Al 2 O 3 coating on the as-built surface. While the machined specimens exhibited nearly isotropic behaviour, the coated as-built specimens showed pronounced anisotropy with comparable mechanical properties to uncoated as-built specimens from literature when excluding the coating thickness from the load-bearing cross-section. The LPCS Zn + Al 2 O 3 coating led to a reduction of the corrosion rate by two thirds compared to uncoated HSLA DED-Arc. Wire Arc Additive Manufacturing (WAAM) Directed Energy Deposition-Arc (DED-Arc) High-strength low-alloy (HSLA) steel Corrosion resistance Low-Pressure Cold spray (LPCS) Digital Image Correlation (DIC) Quasi-static tensile testing Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1 Introduction Directed Energy Deposition using an electric arc (DED-Arc), also referred to as Wire Arc Additive Manufacturing (WAAM), is a wire-based additive manufacturing process that offers high deposition rates while allowing freedom of material and design, as well an integration into digital construction workflows [ 1 – 3 ]. DED-Arc has been applied in civil engineering to produce structural components such as nodes [ 4 ], joints between semi-finished parts [ 5 ] and load-bearing elements [ 6 ]. However, the process still faces several challenges, including quantifying the influence of the characteristic as-built surface topography with its surface undulations resulting in anisotropic material behaviour depending on the build direction together with a high geometric variability across components [ 7 – 9 ]. The digital process steps of the DED-Arc process enable geometry-optimized component design, based on individual load cases [ 10 , 11 ]. High-strength low-alloy (HSLA) steels are well suited for DED-Arc manufacturing due to their favourable strength-to-weight ratio, their good weldability and low material cost. The characterisation of the mechanical performance of HSLA components with as-built surfaces is subject of ongoing research [ 12 – 15 ]. To further enable the reliable and long-term use of DED-Arc components made from carbon steel in load-bearing structures, both the mechanical performance as well as the corrosion protection must be ensured [ 16 , 17 ]. For civil engineering applications, reliable corrosion protection is essential to ensure the long-term integrity of load-bearing components. A common conventional method to achieve corrosion protection is hot-dip galvanizing (HDG), in which steel components are immersed in molten zinc to form a metallurgically bonded coating, providing cathodic protection through a layer with high zinc content [ 18 , 19 ]. However, applying HDG to DED-Arc components with their process inherent complex surface topography, can lead to variations in coating thickness as the solidification behaviour is affected by gravity, surface topography. In addition, the HDG process may affect the mechanical properties of DED-Arc components, with a reduction in fatigue resistance attributed to the uneven growth of the zinc layer and the formation of microcracks in the intermetallic δ-phase [ 20 , 21 ]. As the surface topography of DED-Arc components complicates the formation of a homogeneous and defect-free zinc layer, these limitations highlight the need for coating technologies that allow for greater process control and better compatibility with digitally fabricated geometries. Therefore, this study investigates the use of a Cold Spray (CS) process for corrosion protection of DED-Arc components made of HSLA material. CS is a solid-state coating process within the group of thermal spray technologies, in which metal powder particles are accelerated by compressed gas and deposited onto a substrate by mechanical impact [ 22 ]. The coating build-up relies on the plastic deformation of the particles upon impact and occurs without significant thermal input, making the process particularly suitable for temperature-sensitive substrates [ 23 ]. The corrosion resistance of CS coatings is achieved with coating materials that protect the substrate by anodic [ 24 ] or cathodic [ 25 – 28 ] protection. In addition to corrosion protection, CS has been used for component repair [ 29 ], additive manufacturing [ 30 ], and the production of non-equilibrium alloys [ 31 ]. CS processes can be categorized into High-Pressure Cold Spray (HPCS) and Low-Pressure Cold Spray (LPCS), which differ in gas pressure, preheating temperature, and carrier gas and coating material selection [ 32 ]. The LPCS process is particularly suitable for coating DED-Arc components in civil engineering applications, as it relies on compressed air instead of inert gases, operates at lower process temperatures, requires less complex infrastructure, and enables flexible integration into digital workflows. Zinc-based powders, such as pure Zn and Zn + Al 2 O 3 mixtures, are used as coating materials for atmospheric corrosion protection [ 33 ], where corrosion resistance is achieved through cathodic protection based on the sacrificial behaviour of the zinc. So far, no systematic investigations have addressed the application of LPCS coatings to DED-Arc components made from HSLA steel. Given the high surface undulations resulting from the DED-Arc process, both the protective performance of the coating and its influence on the mechanical behaviour of the substrate require further evaluation. As a first step in combining these two digitally controlled processes, this study aims to characterize the corrosion protection and mechanical performance of LPCS Zn + Al 2 O 3 coated DED-Arc HSLA steel specimens under uniaxial quasi-static tensile loading. The results provide an initial basis for assessing the compatibility of LPCS coatings with DED-Arc components in structural applications for civil engineering. 2 Materials and Methods 2.1 Printing of walls and Low-Pressure Cold Spray coating Multiple thin-walled samples were printed at Tampere University (TAU) using a Directed Energy Deposition with electric arc (DED-Arc) system. The feedstock material used was Voestalpine Böhler 3D print AM80 HD (10NiMnMoCr8-7-6) wire with a diameter of 1.2 mm. The chemical composition of the HLSA material is given in Table 1 Table 1 Chemical composition of Voestalpine Böhler 3Dprint AM80 HD based on EN 10204 type 3.1 certificate C Si Mn Cr Ni Mo 0.09 0.40 1.70 0.35 2.00 0.60 The DED-Arc system shown in Fig. 1 consisted of an ABB IRB4600 robotic arm mounted on an ABB IRBP positioning table. As power source, a Fronius Cold Metal Transfer system (CMT Advanced 4000R) was used. As a shielding gas 92% Argon and 8% CO 2 (M20 according to ISO 14175 [ 34 ]) was used with a flow rate of 16 L/min to prevent oxidation of the molten pool. A Keller infrared pyrometer was employed to monitor the interpass temperature, and a C300 Cavitar welding camera was used for visual process control and to observe the process for defects and interruptions during printing. The DED-Arc material was deposited on S355 mild steel substrates dimensions of 300 mm × 200 mm × 20 mm without preheating by employing a bidirectional deposition strategy to produce walls with a length of 200 mm and a height of 160 mm. The welding torch was held perpendicular to the deposition direction at a fixed contact tip to work distance (CTWD) of 15 mm. The wire feed rate was set to 2 m/min and the travel speed to 24 cm/min. Deposition was performed in CMT Mode G3Si1-1643 (synergic program) with an average current of 96 A and an average voltage of 14.2 V, corresponding to an energy input of 3.4 kJ/cm. The layer height resulted in approximately 1.8 mm and the interpass temperature was kept below 200°C throughout the process. The Low-Pressure Cold Sprayed (LPCS) Zn + Al 2 O 3 coating for selected DED-Arc walls was performed at TAU using a LPCS system (Dymet 304K) mounted into an industrial robot (ABB), as shown in Fig. 2 (left). The Zn + Al 2 O 3 feedstock powder (K-00-11), supplied by Obninsk Center for Powder Spraying, consisted of a 50:50 vol.-% mixture of spherical Zn particles and blocky Al 2 O 3 particles. The LPCS coatings were applied in four consecutive layers using compressed air with an air pressure of 6 bar, an air preheating temperature of 540°C, a spray distance of 10 mm and a traverse speed of 5 m/min. Preliminary tests were carried out by producing coating on the unprocessed as-built surface of the DED-Arc walls as well as on selected parts of the surface that were manually polished and/or grit-blasted with Al 2 O 3 grits (Mesh 24) before coating build-up, see Fig. 2 (middle). Based on these preliminary tests, it was decided to grit blast the DED-Arc walls prior to the coating production to increase adhesion and to clean the surfaces, see Fig. 2 (right). Particle velocities were recorded with a HiWatch CS2 diagnostic camera. The structures were characterized using a field emission electron microscope (FESEM, Zeiss UltraPlus) whereas coating thicknesses were evaluated from coating cross-sections by an optical microscope (Leica DM2500) and by magnetic induction measurements using an eXacto FN Type 180–1102 of ElektroPhysik. In addition, coating hardness was measured with Vickers hardness tester (Matsuzawa MMT-X7) with a load of 100 g and the results were given as an average of ten measurements with a standard deviation. 2.2 Specimen preparation, 3D-scanning and geometry data-processing A total of 42 dog-bone tensile specimens with dimensions in Fig. 3 (right) were extracted via CNC milling at Technische Universität Braunschweig (TUBS) from six different DED-Arc manufactured walls. Each set of specimens was taken from a separate wall. Specimen orientations were defined as horizontal (θ = 0°, deposition direction), vertical (θ = 90°, build direction), and diagonal (θ = 45° to the baseplate), see Fig. 3 (left). This enables the assessment of material anisotropy in the quasi-static uniaxial tensile tests. Table 2 summarizes the number of specimens per orientation and surface condition. Specimens with machined surfaces were milled to a constant thickness of 3.0 mm, whereas the surface condition of the as-built specimens with LPCS Zn + Al 2 O 3 coating remained unmodified, see Fig. 3 (right). Table 2 Number of specimens per surface condition and specimen orientation Surface condition Specimen orientation Vertical ( θ = 90°) Diagonal ( θ = 45°) Horizontal ( θ = 0°) machined 9 5 8 LPCS Zn + Al 2 O 3 Coated as-built 8 4 8 Prior to specimen extraction, all wall surfaces were 3D scanned at the Institute of Geodesy and Photogrammetry of TUBS using a Hexagon StereoScan neo R16.2 structured-light scanner mounted with Schneider-Kreuznach MAKRO-SYMMAR 5.6/80 lenses with a field of view (FOV) of 730 × 440 mm. Additionally, all coated as-built specimens were scanned after their extraction. Surface topology data from the structured light scans were analysed using CloudCompare v2.13.beta and MATLAB 2022b. To remove the influence of point density, the scan data were rasterized onto a uniform grid with a step size of 0.1 mm. Filtering operations were conducted according to DIN EN ISO 16610-1:2015 [ 35 ]and a low-pass Gaussian filter, ‘L-filter’ based on DIN EN ISO 25178-2:2022 [ 36 ] was applied to the scan data and the long-wave result above the cut-off wavelength was extracted. A low-pass Gaussian filter (L-filter) with a cut-off wavelength of 0.6 mm, corresponding to one-third of the layer height, was applied to remove scanning artefacts as well as high-frequency noise without introducing significant smoothing effects. The use of a cut-off wavelength around half the layer height has been shown to effectively capture the characteristic surface profile while avoiding excessive smoothing [ 9 ]. The thickness was subsequently determined as the distance between the top and bottom as-built surfaces of the parallel range of the specimen. 2.3 Corrosion resistance evaluation Electrochemical polarisation measurements were conducted using a G 750 Potentiostat (Gamry Instruments) to characterise the corrosion performance of the coatings. The corrosion current density i corr and corrosion potential E corr were determined via Tafel extrapolation on potentiodynamic polarisation curves using the Gamry Echem Analyst software and corrosion rate was calculated from the data. Prior to testing, the coating surfaces were polished to ensure reproducibility. All measurements were performed in a 3.5% NaCl solution, employing an Ag/AgCl reference electrode and Pt was used as a counter electrode in a three-electrode setup. Coated samples were immersed in the test solution until establishing a stable open circuit potential (OCP). Polarisation measurements were performed over a potential range of -300 mV to + 1000 mV vs. OCP with a 0.167 mV/s potential sweep rate. 2.4 Uniaxial quasi-static tensile testing and data processing Uniaxial quasi-static tensile tests were performed at materialTUBS in displacement control according to DIN EN ISO 6892-1:2019 [ 37 ] at room temperature using a servo-hydraulic testing machine (MTS 318.25) equipped with a 250 kN load cell (MTS 661.22D-01). For the Digital Image Correlation (DIC), a stochastic black-and-white pattern with a structure size of approx. 130 µm was applied using a printed water transfer film for the machined specimens and with acrylic airbrush paint for the coated as-built specimens. The DIC setup consists of a biplanar four-camera system (Q-400, Dantec Dynamics) with Schneider-Kreuznach Tourmaline 2.8/50 C objectives and 5 MP Baumer VCXG-51M cameras was used for all tests. Axial force and displacement were recorded at a frequency of 100 Hz, while the DIC system acquired the image data at 20 Hz. The force signal was synchronized with the DIC system via an analogue input. The strain reconstruction and evaluation were conducted in MATLAB 2022b based on displacement fields extracted from DIC image data using Istra 4D (Dantec Dynamics). The engineering strain was calculated as the spatial derivative of the displacement fields. An equivalent engineering strain, representative of the specimen’s global deformation, was obtained by averaging results from multiple longitudinal virtual strain gauges spaced 0.5 mm apart across the specimen width on both sides of the specimens. Singular strain fields obtained from Istra 4D were subsequently processed using an ACSP 19×19 local regression filter. Engineering stress was calculated from the measured force and the mean cross-sectional area of each specimen, determined from the structured light scans. For coated specimens, the cold spray coating thickness was subtracted from the mean specimen thickness, ensuring that only the cross-sectional area of the uncoated as-built DED-Arc HSLA base material was used for the evaluation. To characterize the transition from elastic to plastic behaviour using a singular value, the Proof stress ratio \(\:{{\mu\:}}_{\text{p}}\) was determined with Eq. ( 1 ) as the ratio between the stress at 0.03% plastic strain σ 0.03 and the 0.2% proof stress \(\:{R}_{p,0.2}\) [ 38 ]. $$\:{\mu\:}_{p}=\frac{{\sigma\:}_{0.03}}{{R}_{p,0.2}}$$ 1 Lower values of the proof stress ratio \(\:{\mu\:}_{p}\) indicate an earlier onset of plasticity and a smoother transition from the elastic to plastic regime of the stress-strain curve. 3 Results 3.1 Microstructural evaluation of LPCS coating The LPCS Zn + Al 2 O 3 coating was successfully produced on the different prepared surfaces of the DED-Arc structures, as shown in Fig. 2 (right). While the coating was already formed continuously on the untreated as-built surface, there were oxide residuals present from the DED-Arc fabrication process ( Fig. 4 (left)), which can reduce the adhesion of the coating to the substrate. Therefore, the surface was grit-blasted in order to clean it and to remove the oxides as well as to improve surface roughness for further optimal coating production. LPCS Zn + Al 2 O 3 coating on grit-blasted DED-Arc surface was dense and well-adhered, see Fig. 4 (middle). In the coating structure, the Zn particles are displayed light grey and the hard, blocky Al 2 O 3 particles are displayed in black and they were embedded into the metallic structure. High deformation of Zn particles during the particle impacts on the substrate and on the previous particles as well as fracturing of the Al 2 O 3 particles can be seen in Fig. 4 (right). The coatings demonstrated high density and strong interfacial bonding. The LPCS coating on the grit-blasted DED-Arc walls led to a coating thickness exceeding 300 µm, indicating sufficient thickness for corrosion protection. Mean particle velocity and mean particle size were measured as 472 m/s and 16 µm, respectively. Schmidt et al. [ 39 ] have modelled critical velocity for Zn as 360 to 380 m/s so particle velocity of Zn + Al 2 O 3 powder was higher than the critical velocity of Zn, which promoted successful particle bonding during coating build-up. Hardness of the LPCS Zn + Al 2 O 3 coating was 66 ± 3 HV 0,1 , which is relatively high even the measurements were targeted to the Zn areas in the coating. This indicated high plastic deformation of the Zn particles and high work hardening, which is typical for cold sprayed coating structures. This coating had high hardness compared to an as-cast Zn (~ 38 HV 0,1 ) and a hot-rolled Zn (~ 40 HV 0,1 ) [ 40 ], which indicated high deformation during high-velocity particle impacts 3.2 Geometrical characterisation To quantify the influence of build orientation and the coating process on the geometric characteristics of the specimens, both the total thickness of the coated as-built specimens and the thickness of the LPCS Zn + Al 2 O 3 coating layer were evaluated. As shown in in Fig. 5 (middle) and summarized in Table 3 , the highest average specimen thickness was obtained for vertically oriented specimens, followed by diagonal and then the horizontal specimens. Differences of up to 0.4 mm were observed between the median wall thicknesses. The standard deviation is the highest for vertically oriented specimens with σ = 0.24 mm, indicating increased geometric variability for specimens in build direction. As the specimens of each orientation were extracted from a distinct DED-Arc wall, orientation-dependent variations in thickness can also be attributed to differences between the respective wall geometries. The corresponding coating thicknesses are summarized in Table 3 and in Fig. 5 (right). The median coating thickness, ranging from 426.8 µm for horizontal to 502.0 µm for diagonal specimens, are comparable across all orientations and the distributions show no direct dependence on the specimen orientation. Together with similar standard deviations between 76.0 µm and 117.7 µm, these results demonstrate that the LPCS process produces a consistent and uniform coating build-up. As the DED-Arc walls were coated prior to specimen extraction, the coating thicknesses reflect the uniformity of the LPCS process across the entire wall surface and no effect of specimen orientation can observed. Table 3 Thickness of the as-built LPCS Zn + Al 2 O 3 specimens and respective coating thicknesses Specimen Orientation Coated as-built specimen thickness [mm] Coating thickness [µm] Median Std. Median Std. Vertical ( θ = 90°) 6.17 0.24 437.8 76.0 Diagonal ( θ = 45°) 6.10 0.16 502.0 117.7 Horizontal ( θ = 0°) 5.75 0.19 426.8 90.7 3.3 Electrochemical polarisation behaviour Figure 6 displays the polarisation curves of uncoated DED-Arc steel and of LPCS Zn + Al 2 O 3 coatings tested in 3.5 wt% NaCl solution. The coated specimens exhibited a significantly more negative corrosion potential E corr (–1250 mV) compared to the uncoated DED-Arc wall (–550 mV), indicating their function as sacrificial anodes within the material system. The corresponding corrosion rate (CR) of the coated surface was 0.1 mm/year, whereas the uncoated DED-Arc HLSA steel showed a rate of 0.29 mm/year. These results confirm the cathodic protection provided by the LPCS Zn + Al 2 O 3 coating, which protects the steel substrate through sacrificial and selective corrosion behaviour of Zn in the test environment. 3.4 Results of uniaxial quasi-static tensile tests To assess the influence of surface condition and build orientation on the mechanical properties, a series of uniaxial quasi-static tensile tests were performed. In total, 42 uniaxial quasi-static tensile tests were conducted (see Table 2 ). For all specimens, the respective nominal (engineering) stress-engineering strain-curves are displayed with markers indicating the fracture points of each test. 3.4.1 Mechanical properties of specimens with machined surface Figure 7 shows the stress–strain curves of the machined specimens, including the initial range up to the 0.2% Proof stress (left) and the full deformation behaviour (left). The mechanical properties extracted from the stress–strain curves are quantified in Fig. 8 and in Table 4 (Annex). The stress–strain response follows the characteristic rounded shape of HSLA material and shows very limited orientation dependence, reflecting a nearly isotropic mechanical behaviour. There are only minor differences depending on the orientation in the elastic–plastic transition. Specifically, the stress–strain curves of the horizontal specimens exhibit a slightly sharper transition from the elastic to plastic regime, with reduced curvature in the yield region compared to the vertical and diagonal specimens. This observation is reflected in the proof stress ratio µ p , which is highest for the horizontal specimens (median: 0.947), followed by the diagonal (0.881), and lowest for the vertical specimens (0.865), indicating a more abrupt onset of plastic deformation in the horizontal orientation and slightly higher stresses after reaching the 0.2% Proof stress. The mechanical properties display a high consistency across all orientations with the Youngs modulus E being almost identical between vertical, diagonal and horizontal specimens and the ultimate tensile strength R m ranging from 880 MPa to 889 MPa for all machined specimens. The large values of the Elongation after fracture A indicate a ductile behaviour and while it is comparable for horizontal (18.6%) and diagonal (18.5%) specimens the Elongation A is slightly lower for vertical specimens (17.1%) in addition with a slightly higher standard deviation for specimens of this direction. Only the 0.2% Proof stress shows a minor orientation dependence for which the median value is approximately 5% higher for horizontal specimens (771 MPa) than for vertical (727 MPa) and diagonal (727 MPa) specimens. 3.4.2 Mechanical properties of coated as-built specimens The engineering stress–strain curves of the coated as-built specimens are shown in Fig. 9 for the initial range up to the 0.2% proof stress (left) as well as for the full range (left). The corresponding mechanical properties are summarized in Fig. 10 and in Table 5 (Annex), while selected DIC strain fields are presented in Fig. 11 . The stress–strain curves in Fig. 9 display a clear orientation dependence of the mechanical response of the coated as-built specimens, which is already evident in the initial deformation range before reaching the 0.2% Proof stress. The shape and progression of the curves differ significantly between specimen groups, with horizontal specimens exhibiting a sharp elastic–plastic transition as indicated by a proof stress ratio of µ p = 0.983, while diagonal and vertical specimens show more gradual transitions. Additionally, vertical specimens show an earlier onset of plasticity and an earlier failure point. The observed anisotropy is further confirmed by the extracted mechanical properties, which exhibit a clear orientation-dependent trend: the 0.2% Proof stress R p0.2 , the tensile strength R m , and the elongation after fracture A all decrease with increasing build orientation angle θ , i.e. from horizontal to diagonal to vertical specimens. Specifically, the median proof stress decreases from 792.4 MPa (horizontal) to 652.5 MPa (vertical), the tensile strength from 860.1 MPa to 765.0 MPa, and the elongation from 0.149 to 0.073. The highest Young’s modulus E is observed for the diagonal specimens (204.4 GPa). Among all orientations, the vertical specimens consistently exhibit the highest scatter in mechanical properties. Additional insight into the local behaviour is obtained from the engineering strain e distributions in Fig. 11 which are derived from the DIC data of the tests at reaching integral yielding at the 0.2% Proof stress. In the results for the vertical specimen (top), a distinct layer-wise strain localization is visible perpendicular to the build (and loading) direction. Local strain concentrations exceed 3.0%, indicating considerable early plastic deformation. A similar pattern is visible in the diagonal specimen (middle), but rotated according to the specimen orientation by 45°. In contrast, the horizontal specimen (bottom) shows a more homogeneous strain distribution and there are no clear visible effects of the layer-wise built-up present. The high accumulation of local strains highlights the influence of the as-built surface characteristics on the load bearing behaviour and therefore the mechanical properties. 4 Discussion Dense microstructures and strong interfacial bonding were achieved for the LPCS Zn + Al 2 O 3 coating on grit-blasted DED-Arc surfaces. Comparable results were reported by Koivuluoto et al. [ 33 ] for LPCS coatings produced on steel substrates under similar process conditions. Grit blasting of the DED-Arc surface prior to coating was deemed necessary to achieve high adhesion and uniform coating build-up. In contrast, coatings deposited directly onto the untreated as-built surfaces exhibited reduced deposition efficiency, as indicated by lower coating thicknesses. The presence of residual oxides on the untreated surfaces, visible in Fig. 4 (left), is assumed to have promoted increased particle rebound, thereby limiting particle deformation and bonding during the LPCS process. Notably, coating thicknesses still exceeded approx. 300 µm. The LPCS process enables the build-up of comparatively thick zinc coatings, see Fig. 5 (right), with the final thickness being scalable by adjusting the number of spray passes. In the uniaxial tensile testing, after reaching the yield stress, small cracks appeared in the LPCS Zn + Al 2 O 3 coating. However, the coating adhered well to the specimen’s surfaces until close to reaching the tensile strength when flaking occurred around the fracture zone, most likely originating from a difference in strain ratio between substrate and coating. The machined specimens tested in this study exhibited median 0.2% proof stresses of 768 MPa (horizontal), 733 MPa (diagonal), and 728 MPa (vertical), closely matching the values reported by Jahns et al. [ 15 ] for machined HSLA specimens (R p0.2 =765 MPa, 729 MPa, and 730 MPa). Similar agreement was found for ultimate tensile strength and elongation after fracture. These results confirm that the LPCS process, does not affect the mechanical properties of the DED-Arc HSLA material itself. The LPCS-coated as-built specimens displayed pronounced anisotropy in their mechanical response. A continuous decrease in the median 0.2% proof stress, tensile strength, and elongation with increasing build orientation angle was observed. Specifically, the 0.2% proof stress decreased from 792 MPa (horizontal) to 652 MPa (vertical), tensile strength from 860 MPa to 765 MPa, and elongation after fracture from 0.149 to 0.073, see Fig. 10 . This orientation-dependent behaviour reflects the characteristic influence of the layer-by-layer DED-Arc manufacturing process and aligns in general with results reported by Jahns et al. [ 41 ] for uncoated as-built HSLA DED-Arc specimens. As summarized in Fig. 12 , R p0.2 ranged from 740 MPa (horizontal) to 686 MPa (vertical), and elongation from 0.165 to 0.076 The tensile strength exhibited a similar anisotropic trend, decreasing from 862 MPa to 853 MPa across the build orientations. Also, the proof stress ratio slightly decreased with increasing build angle, indicating an earlier onset of plastic deformation in specimens with vertical orientation. These comparable results and the trends in the mechanical responses confirm, that the LPCS coating does not alter characteristic the mechanical response of as-built DED-Arc components. For hot-dip galvanization (HDG) of mild steel DED-Arc specimens, Voelkel et al. [ 20 ] showed that HDG with pure zinc does not significantly affect the yield strength of mild steel DED-Arc when the zinc layer is excluded from the load-bearing cross-section. However, a slight reduction in tensile strength and a decrease in elongation at fracture (from 0.268 to 0.213) were observed, attributed to the formation of brittle intermetallic δ- and ζ-phase within the zinc layer during the HDG process. Kühne et al. [ 21 ] further demonstrated that thin-film galvanizing with a Zn–5Al alloy resulted in nearly unchanged tensile properties of mild steel DED-Arc, with a minor increase of the elongation at fracture (0.233) compared to the uncoated state (0.229). However, both studies did not address the corrosion protection performance of the hot-dip galvanised DED-Arc components. 5 Conclusion This study investigated the applicability of Low-Pressure Cold Sprayed (LPCS) coatings for corrosion protection of steel components manufactured by Directed Energy Deposition using an electric arc (DED-Arc). Multiple thin-walled structures were 3D-printed from high-strength low-alloy (HSLA) feedstock. Three of the walls were coated with a Zn + Al 2 O 3 powder using a robot-guided LPCS system. Prior to the coating production, the as-built surfaces were grit-blasted to remove oxide residues from the deposition process and to enhance coating adhesion. The microstructure of both the HSLA base material and the LPCS Zn + Al 2 O 3 coating was examined using optical and electron microscopy. Additionally, electrochemical polarisation analysis was carried out to assess the corrosion protection capability of the coating system. Subsequently, a total of 44 dog-bone tensile specimens were extracted by CNC milling from the manufactured walls. The specimens were extracted horizontal (θ = 0°), diagonal (θ = 45°), and vertical (θ = 90°) with respect to the deposition direction to assess build-direction-dependent material behaviour. A total of 22 specimens were further machined to a constant thickness of t = 3 mm, while the other 22 specimens were left in the coated as-built state without modification of the surface. Prior to mechanical testing, all coated specimens were geometrically characterized using a structured-light scanning system to evaluate the total specimen thickness and magnetic induction measurements to obtain the thickness of the applied Zn + Al 2 O 3 coating. The geometrical characterization served as a base for determining the effective load-bearing cross-sections of the DED-Arc material and assessing the coating uniformity across different specimen orientations. To quantify the influence of the LPCS coating process on the mechanical properties of DED-Arc components, uniaxial quasi-static tensile tests were performed on all specimens, with high-resolution deformation data acquired using a four-camera Digital Image Correlation (DIC) system. The evaluation focused on orientation-dependent variations in mechanical behaviour. The main outcomes of this conducted research are as follows: Zn + Al 2 O 3 coating was successfully deposited on grit-blasted as-built DED-Arc HSLA surfaces using the LPCS process, resulting in dense material built-up with median coating thicknesses between 430 and 500 µm. Electrochemical polarisation analysis showed that the LPCS Zn + Al 2 O 3 coating provides sufficient corrosion protection for HLSA DED-Arc components, reducing corrosion rate to 0.1 mm/year compared to 0.29 mm/year for uncoated material. Geometric analysis of coated as-built specimens revealed that both total specimen thickness and coating thickness distribution remained consistent for specimens extracted with different orientations from thin walls. Uniaxial quasi-static tensile tests on specimens with machined surface showed isotropic material properties of the DED-Arc HSLA substrate material. LPCS Zn + Al 2 O 3 coated as-built specimens exhibited orientation-dependent mechanical properties, with yield strength, ultimate tensile strength, and elongation after fracture decreasing from horizontal (θ = 0°) to vertical (θ = 90°) specimen orientation. When excluding the Zn + Al 2 O 3 coating thickness from the load-bearing cross-sectional area, the mechanical properties are comparable to those for uncoated as-built specimens from literature. The systematic experimental framework and dataset developed in this study provide an initial basis for evaluating the use of LPCS Zn + Al 2 O 3 coatings on DED-Arc structural steel components. The findings contribute to a systematic understanding of the interaction between both processes. Future research should build upon this work by investigating fatigue performance under cyclic loading conditions of coated as-built specimens and by investigating the applicability of the combined processes to large-scale structural components for civil engineering applications. Declarations Ethical Approval Not applicable Consent to participate Not applicable Consent to publish Not applicable Competing Interests The authors declare that they have no conflict of interest. Acknowledgements The authors would like to thank Mr. Jarkko Lehti and Mr. Anssi Metsähonkala of Tampere University for LPCS coating production and M.Sc Pentti Kalliotiura for assisting with the coating evaluation. This work has used the facilities of Tampere Microscopy Center, Tampere, Finland. Additionally, Mr. Tatu Leppänen and Dr. Jussi Larjo of Oseir Ltd. (Finland) are acknowledged for measurements of in-flight particle properties. CRediT authorship contribution statement M.M.: Visualization, Investigation, Formal analysis, Data curation, Writing – original draft. H.M.: Supervision, Resources, Conceptualization, Funding acquisition, Writing – review & editing. H.K.: Formal analysis, Supervision, Conceptualization, Writing – original draft. H.J.: Software, Methodology, Data curation. R.J.: Formal analysis, Data curation, Writing – review & editing. S.P.: Writing – review & editing, Data curation. E.H.: Investigation, Data curation. M.A.: Investigation, Data curation. K.T.: Supervision, Resources. J.U.: Supervision, Project administration, Funding acquisition, Conceptualization, Writing – review & editing. Funding The research presented in this paper is being conducted within the project ‘‘Wire Arc Additive Manufacturing (WAAM) of Complex and Refined Steel Components (A07)’’. The project is part of the collaborative research centre ‘‘Additive Manufacturing in Construction”, funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - project number 414265976 - TRR 277. Suraj Panicker received funding by the Walter Ahlström Foundation. Great thanks are expressed to the Institute of Geodesy and Photogrammetry for using the structured-light stereo scanner, which is funded by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – project number 461109100. Data availability statement The data can be accessed under DOI: 10.5281/zenodo.15183281, see [42]. Declaration of Generative AI and AI-assisted technologies in the writing process During the preparation of this work the authors used ChatGPT (based on GPT-4o -OpenAI) in order to reorganise the notes and improve the manuscript readability. 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Müggenburg M, Mokhtarian H, Koivuluoto H , et al. Dataset to: Mechanical properties and corrosion protection of DED-Arc additively manufactured high-strength low-alloy steel components coated with Low-Pressure Cold Spray. Zenodo; 2025. Supplementary Files Appendix.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 03 Jun, 2025 Reviewers invited by journal 01 Jun, 2025 Editor invited by journal 27 May, 2025 Editor assigned by journal 09 May, 2025 First submitted to journal 07 May, 2025 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. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6566148","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":464848865,"identity":"0373ddc7-dfbd-4575-af16-3e82a378deb6","order_by":0,"name":"Marc 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05:34:29","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":923458,"visible":true,"origin":"","legend":"\u003cp\u003eStress-strain curves for specimens with machined surface, initial range (left), full range (right)\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/71e124a4b3b03e046b65ab19.png"},{"id":84184704,"identity":"765a82eb-b92d-42b8-ac4f-645ea36e6f1f","added_by":"auto","created_at":"2025-06-09 05:10:21","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":100031,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of mechanical properties from uniaxial tensile tests of machined specimens, V – vertical, D – diagonal, H – horizontal specimen orientation\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/bc80c98d6cffda674d311a62.png"},{"id":84185997,"identity":"10893b4a-160a-4c97-b072-e8836c228d5f","added_by":"auto","created_at":"2025-06-09 05:34:32","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":957829,"visible":true,"origin":"","legend":"\u003cp\u003eStress-strain curves for as-built specimens coated with LPCS Zn+Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, initial\u0026nbsp; range (left), full range (right)\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/6c0b828f3a65d5d9184f9896.png"},{"id":84184700,"identity":"23ca3279-13b5-4ff2-9427-de2e5e772e39","added_by":"auto","created_at":"2025-06-09 05:10:21","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":99679,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of mechanical properties from uniaxial tensile tests of as-built with LPCS Zn+Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e specimens, V – vertical, D – diagonal, H – horizontal specimen orientation\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/a682e79db9170e446e0608b8.png"},{"id":84184709,"identity":"409864bd-4108-45e9-8719-60aef3de312c","added_by":"auto","created_at":"2025-06-09 05:10:21","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":4477792,"visible":true,"origin":"","legend":"\u003cp\u003eEngineering strain distribution from DIC at reaching integral yielding point of coated as-built specimens with different specimen orientation, vertical orientation (top), diagonal orientation (middle), horizontal orientation (bottom)\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/48da65f49cebb3ee36819123.png"},{"id":84184701,"identity":"ed7b0111-05aa-4b6d-88ab-8e4bd6c8bd19","added_by":"auto","created_at":"2025-06-09 05:10:21","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":96727,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of mechanical properties from uniaxial tensile tests of as-built with LPCS Zn+Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e specimens, V – vertical, D – diagonal, H – horizontal specimen orientation; derived from Jahns et al. \u003cem\u003e[41]\u003c/em\u003e (With permission from the authors.)\u003c/p\u003e","description":"","filename":"image12.png","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/5575fa636873c45e929ef28c.png"},{"id":84186967,"identity":"d94fb397-42f1-4523-b04a-2c205f166e35","added_by":"auto","created_at":"2025-06-09 05:42:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":12779293,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/9aad3250-04d7-440d-814c-35d59eef96b6.pdf"},{"id":84184699,"identity":"76edc288-37ad-4d84-ac3f-f03ea7960878","added_by":"auto","created_at":"2025-06-09 05:10:21","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16740,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix.docx","url":"https://assets-eu.researchsquare.com/files/rs-6566148/v1/d4c53bc56d712ba9e7f30a59.docx"}],"financialInterests":"","formattedTitle":"Mechanical properties and corrosion protection of DED-Arc additively manufactured high-strength low-alloy steel components coated with Low-Pressure Cold Spray","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eDirected Energy Deposition using an electric arc (DED-Arc), also referred to as Wire Arc Additive Manufacturing (WAAM), is a wire-based additive manufacturing process that offers high deposition rates while allowing freedom of material and design, as well an integration into digital construction workflows [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. DED-Arc has been applied in civil engineering to produce structural components such as nodes [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], joints between semi-finished parts [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] and load-bearing elements [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, the process still faces several challenges, including quantifying the influence of the characteristic as-built surface topography with its surface undulations resulting in anisotropic material behaviour depending on the build direction together with a high geometric variability across components [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The digital process steps of the DED-Arc process enable geometry-optimized component design, based on individual load cases [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHigh-strength low-alloy (HSLA) steels are well suited for DED-Arc manufacturing due to their favourable strength-to-weight ratio, their good weldability and low material cost. The characterisation of the mechanical performance of HSLA components with as-built surfaces is subject of ongoing research [\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. To further enable the reliable and long-term use of DED-Arc components made from carbon steel in load-bearing structures, both the mechanical performance as well as the corrosion protection must be ensured [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. For civil engineering applications, reliable corrosion protection is essential to ensure the long-term integrity of load-bearing components. A common conventional method to achieve corrosion protection is hot-dip galvanizing (HDG), in which steel components are immersed in molten zinc to form a metallurgically bonded coating, providing cathodic protection through a layer with high zinc content [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, applying HDG to DED-Arc components with their process inherent complex surface topography, can lead to variations in coating thickness as the solidification behaviour is affected by gravity, surface topography. In addition, the HDG process may affect the mechanical properties of DED-Arc components, with a reduction in fatigue resistance attributed to the uneven growth of the zinc layer and the formation of microcracks in the intermetallic δ-phase [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAs the surface topography of DED-Arc components complicates the formation of a homogeneous and defect-free zinc layer, these limitations highlight the need for coating technologies that allow for greater process control and better compatibility with digitally fabricated geometries. Therefore, this study investigates the use of a Cold Spray (CS) process for corrosion protection of DED-Arc components made of HSLA material. CS is a solid-state coating process within the group of thermal spray technologies, in which metal powder particles are accelerated by compressed gas and deposited onto a substrate by mechanical impact [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The coating build-up relies on the plastic deformation of the particles upon impact and occurs without significant thermal input, making the process particularly suitable for temperature-sensitive substrates [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The corrosion resistance of CS coatings is achieved with coating materials that protect the substrate by anodic [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] or cathodic [\u003cspan additionalcitationids=\"CR26 CR27\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] protection. In addition to corrosion protection, CS has been used for component repair [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], additive manufacturing [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], and the production of non-equilibrium alloys [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. CS processes can be categorized into High-Pressure Cold Spray (HPCS) and Low-Pressure Cold Spray (LPCS), which differ in gas pressure, preheating temperature, and carrier gas and coating material selection [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe LPCS process is particularly suitable for coating DED-Arc components in civil engineering applications, as it relies on compressed air instead of inert gases, operates at lower process temperatures, requires less complex infrastructure, and enables flexible integration into digital workflows. Zinc-based powders, such as pure Zn and Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e mixtures, are used as coating materials for atmospheric corrosion protection [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], where corrosion resistance is achieved through cathodic protection based on the sacrificial behaviour of the zinc.\u003c/p\u003e \u003cp\u003eSo far, no systematic investigations have addressed the application of LPCS coatings to DED-Arc components made from HSLA steel. Given the high surface undulations resulting from the DED-Arc process, both the protective performance of the coating and its influence on the mechanical behaviour of the substrate require further evaluation. As a first step in combining these two digitally controlled processes, this study aims to characterize the corrosion protection and mechanical performance of LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coated DED-Arc HSLA steel specimens under uniaxial quasi-static tensile loading. The results provide an initial basis for assessing the compatibility of LPCS coatings with DED-Arc components in structural applications for civil engineering.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Printing of walls and Low-Pressure Cold Spray coating\u003c/h2\u003e \u003cp\u003eMultiple thin-walled samples were printed at Tampere University (TAU) using a Directed Energy Deposition with electric arc (DED-Arc) system. The feedstock material used was Voestalpine B\u0026ouml;hler 3D print AM80 HD (10NiMnMoCr8-7-6) wire with a diameter of 1.2 mm. The chemical composition of the HLSA material is given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\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 Voestalpine B\u0026ouml;hler 3Dprint AM80 HD based on EN 10204 type 3.1 certificate\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSi\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\u003eCr\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\u003eMo\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.60\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 DED-Arc system shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e consisted of an ABB IRB4600 robotic arm mounted on an ABB IRBP positioning table. As power source, a Fronius Cold Metal Transfer system (CMT Advanced 4000R) was used. As a shielding gas 92% Argon and 8% CO\u003csub\u003e2\u003c/sub\u003e (M20 according to ISO 14175 [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]) was used with a flow rate of 16 L/min to prevent oxidation of the molten pool. A Keller infrared pyrometer was employed to monitor the interpass temperature, and a C300 Cavitar welding camera was used for visual process control and to observe the process for defects and interruptions during printing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe DED-Arc material was deposited on S355 mild steel substrates dimensions of 300 mm \u0026times; 200 mm \u0026times; 20 mm without preheating by employing a bidirectional deposition strategy to produce walls with a length of 200 mm and a height of 160 mm. The welding torch was held perpendicular to the deposition direction at a fixed contact tip to work distance (CTWD) of 15 mm. The wire feed rate was set to 2 m/min and the travel speed to 24 cm/min. Deposition was performed in CMT Mode G3Si1-1643 (synergic program) with an average current of 96 A and an average voltage of 14.2 V, corresponding to an energy input of 3.4 kJ/cm. The layer height resulted in approximately 1.8 mm and the interpass temperature was kept below 200\u0026deg;C throughout the process.\u003c/p\u003e \u003cp\u003eThe Low-Pressure Cold Sprayed (LPCS) Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating for selected DED-Arc walls was performed at TAU using a LPCS system (Dymet 304K) mounted into an industrial robot (ABB), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (left). The Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e feedstock powder (K-00-11), supplied by Obninsk Center for Powder Spraying, consisted of a 50:50 vol.-% mixture of spherical Zn particles and blocky Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e particles. The LPCS coatings were applied in four consecutive layers using compressed air with an air pressure of 6 bar, an air preheating temperature of 540\u0026deg;C, a spray distance of 10 mm and a traverse speed of 5 m/min. Preliminary tests were carried out by producing coating on the unprocessed as-built surface of the DED-Arc walls as well as on selected parts of the surface that were manually polished and/or grit-blasted with Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e grits (Mesh 24) before coating build-up, see Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (middle). Based on these preliminary tests, it was decided to grit blast the DED-Arc walls prior to the coating production to increase adhesion and to clean the surfaces, see Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (right).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eParticle velocities were recorded with a HiWatch CS2 diagnostic camera. The structures were characterized using a field emission electron microscope (FESEM, Zeiss UltraPlus) whereas coating thicknesses were evaluated from coating cross-sections by an optical microscope (Leica DM2500) and by magnetic induction measurements using an eXacto FN Type 180\u0026ndash;1102 of ElektroPhysik. In addition, coating hardness was measured with Vickers hardness tester (Matsuzawa MMT-X7) with a load of 100 g and the results were given as an average of ten measurements with a standard deviation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Specimen preparation, 3D-scanning and geometry data-processing\u003c/h2\u003e \u003cp\u003eA total of 42 dog-bone tensile specimens with dimensions in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (right) were extracted via CNC milling at Technische Universit\u0026auml;t Braunschweig (TUBS) from six different DED-Arc manufactured walls. Each set of specimens was taken from a separate wall. Specimen orientations were defined as horizontal (θ\u0026thinsp;=\u0026thinsp;0\u0026deg;, deposition direction), vertical (θ\u0026thinsp;=\u0026thinsp;90\u0026deg;, build direction), and diagonal (θ\u0026thinsp;=\u0026thinsp;45\u0026deg; to the baseplate), see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (left). This enables the assessment of material anisotropy in the quasi-static uniaxial tensile tests.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e summarizes the number of specimens per orientation and surface condition. Specimens with machined surfaces were milled to a constant thickness of 3.0 mm, whereas the surface condition of the as-built specimens with LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating remained unmodified, see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (right).\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\u003eNumber of specimens per surface condition and specimen orientation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSurface condition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eSpecimen orientation\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVertical\u003c/p\u003e \u003cp\u003e(\u003cem\u003eθ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;90\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDiagonal\u003c/p\u003e \u003cp\u003e(\u003cem\u003eθ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;45\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHorizontal\u003c/p\u003e \u003cp\u003e(\u003cem\u003eθ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003emachined\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003cp\u003eCoated as-built\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8\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\u003ePrior to specimen extraction, all wall surfaces were 3D scanned at the Institute of Geodesy and Photogrammetry of TUBS using a Hexagon StereoScan neo R16.2 structured-light scanner mounted with Schneider-Kreuznach MAKRO-SYMMAR 5.6/80 lenses with a field of view (FOV) of 730 \u0026times; 440 mm. Additionally, all coated as-built specimens were scanned after their extraction. Surface topology data from the structured light scans were analysed using CloudCompare v2.13.beta and MATLAB 2022b. To remove the influence of point density, the scan data were rasterized onto a uniform grid with a step size of 0.1 mm. Filtering operations were conducted according to DIN EN ISO 16610-1:2015 [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]and a low-pass Gaussian filter, \u0026lsquo;L-filter\u0026rsquo; based on DIN EN ISO 25178-2:2022 [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] was applied to the scan data and the long-wave result above the cut-off wavelength was extracted. A low-pass Gaussian filter (L-filter) with a cut-off wavelength of 0.6 mm, corresponding to one-third of the layer height, was applied to remove scanning artefacts as well as high-frequency noise without introducing significant smoothing effects. The use of a cut-off wavelength around half the layer height has been shown to effectively capture the characteristic surface profile while avoiding excessive smoothing [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The thickness was subsequently determined as the distance between the top and bottom as-built surfaces of the parallel range of the specimen.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Corrosion resistance evaluation\u003c/h2\u003e \u003cp\u003eElectrochemical polarisation measurements were conducted using a G 750 Potentiostat (Gamry Instruments) to characterise the corrosion performance of the coatings. The corrosion current density i\u003csub\u003ecorr\u003c/sub\u003e and corrosion potential E\u003csub\u003ecorr\u003c/sub\u003e were determined via Tafel extrapolation on potentiodynamic polarisation curves using the Gamry Echem Analyst software and corrosion rate was calculated from the data. Prior to testing, the coating surfaces were polished to ensure reproducibility. All measurements were performed in a 3.5% NaCl solution, employing an Ag/AgCl reference electrode and Pt was used as a counter electrode in a three-electrode setup. Coated samples were immersed in the test solution until establishing a stable open circuit potential (OCP). Polarisation measurements were performed over a potential range of -300 mV to +\u0026thinsp;1000 mV vs. OCP with a 0.167 mV/s potential sweep rate.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Uniaxial quasi-static tensile testing and data processing\u003c/h2\u003e \u003cp\u003eUniaxial quasi-static tensile tests were performed at materialTUBS in displacement control according to DIN EN ISO 6892-1:2019 [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] at room temperature using a servo-hydraulic testing machine (MTS 318.25) equipped with a 250 kN load cell (MTS 661.22D-01). For the Digital Image Correlation (DIC), a stochastic black-and-white pattern with a structure size of approx. 130 \u0026micro;m was applied using a printed water transfer film for the machined specimens and with acrylic airbrush paint for the coated as-built specimens. The DIC setup consists of a biplanar four-camera system (Q-400, Dantec Dynamics) with Schneider-Kreuznach Tourmaline 2.8/50 C objectives and 5 MP Baumer VCXG-51M cameras was used for all tests. Axial force and displacement were recorded at a frequency of 100 Hz, while the DIC system acquired the image data at 20 Hz. The force signal was synchronized with the DIC system via an analogue input.\u003c/p\u003e \u003cp\u003eThe strain reconstruction and evaluation were conducted in MATLAB 2022b based on displacement fields extracted from DIC image data using Istra 4D (Dantec Dynamics). The engineering strain was calculated as the spatial derivative of the displacement fields. An equivalent engineering strain, representative of the specimen\u0026rsquo;s global deformation, was obtained by averaging results from multiple longitudinal virtual strain gauges spaced 0.5 mm apart across the specimen width on both sides of the specimens. Singular strain fields obtained from Istra 4D were subsequently processed using an ACSP 19\u0026times;19 local regression filter. Engineering stress was calculated from the measured force and the mean cross-sectional area of each specimen, determined from the structured light scans. For coated specimens, the cold spray coating thickness was subtracted from the mean specimen thickness, ensuring that only the cross-sectional area of the uncoated as-built DED-Arc HSLA base material was used for the evaluation. To characterize the transition from elastic to plastic behaviour using a singular value, the Proof stress ratio \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{{\\mu\\:}}_{\\text{p}}\\)\u003c/span\u003e\u003c/span\u003e was determined with Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) as the ratio between the stress at 0.03% plastic strain σ\u003csub\u003e0.03\u003c/sub\u003e and the 0.2% proof stress \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{R}_{p,0.2}\\)\u003c/span\u003e\u003c/span\u003e [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{\\mu\\:}_{p}=\\frac{{\\sigma\\:}_{0.03}}{{R}_{p,0.2}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eLower values of the proof stress ratio \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\mu\\:}_{p}\\)\u003c/span\u003e\u003c/span\u003e indicate an earlier onset of plasticity and a smoother transition from the elastic to plastic regime of the stress-strain curve.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Microstructural evaluation of LPCS coating\u003c/h2\u003e\n \u003cp\u003eThe LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating was successfully produced on the different prepared surfaces of the DED-Arc structures, as shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e (right). While the coating was already formed continuously on the untreated as-built surface, there were oxide residuals present from the DED-Arc fabrication process (\u003cstrong\u003eFig.\u0026nbsp;4\u003c/strong\u003e (left)), which can reduce the adhesion of the coating to the substrate. Therefore, the surface was grit-blasted in order to clean it and to remove the oxides as well as to improve surface roughness for further optimal coating production. LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating on grit-blasted DED-Arc surface was dense and well-adhered, see \u003cstrong\u003eFig.\u0026nbsp;4\u003c/strong\u003e (middle). In the coating structure, the Zn particles are displayed light grey and the hard, blocky Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e particles are displayed in black and they were embedded into the metallic structure. High deformation of Zn particles during the particle impacts on the substrate and on the previous particles as well as fracturing of the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e particles can be seen in \u003cstrong\u003eFig.\u0026nbsp;4\u003c/strong\u003e (right). The coatings demonstrated high density and strong interfacial bonding. The LPCS coating on the grit-blasted DED-Arc walls led to a coating thickness exceeding 300 \u0026micro;m, indicating sufficient thickness for corrosion protection. Mean particle velocity and mean particle size were measured as 472 m/s and 16 \u0026micro;m, respectively. Schmidt et al. [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e] have modelled critical velocity for Zn as 360 to 380 m/s so particle velocity of Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e powder was higher than the critical velocity of Zn, which promoted successful particle bonding during coating build-up.\u003c/p\u003e\n \u003cp\u003eHardness of the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating was 66\u0026thinsp;\u0026plusmn;\u0026thinsp;3 HV\u003csub\u003e0,1\u003c/sub\u003e, which is relatively high even the measurements were targeted to the Zn areas in the coating. This indicated high plastic deformation of the Zn particles and high work hardening, which is typical for cold sprayed coating structures. This coating had high hardness compared to an as-cast Zn (~\u0026thinsp;38 HV\u003csub\u003e0,1\u003c/sub\u003e) and a hot-rolled Zn (~\u0026thinsp;40 HV\u003csub\u003e0,1\u003c/sub\u003e) [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e], which indicated high deformation during high-velocity particle impacts\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Geometrical characterisation\u003c/h2\u003e\n \u003cp\u003eTo quantify the influence of build orientation and the coating process on the geometric characteristics of the specimens, both the total thickness of the coated as-built specimens and the thickness of the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating layer were evaluated. As shown in in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (middle) and summarized in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, the highest average specimen thickness was obtained for vertically oriented specimens, followed by diagonal and then the horizontal specimens. Differences of up to 0.4 mm were observed between the median wall thicknesses. The standard deviation is the highest for vertically oriented specimens with \u0026sigma;\u0026thinsp;=\u0026thinsp;0.24 mm, indicating increased geometric variability for specimens in build direction. As the specimens of each orientation were extracted from a distinct DED-Arc wall, orientation-dependent variations in thickness can also be attributed to differences between the respective wall geometries.\u003c/p\u003e\n \u003cp\u003eThe corresponding coating thicknesses are summarized in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e and in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (right). The median coating thickness, ranging from 426.8 \u0026micro;m for horizontal to 502.0 \u0026micro;m for diagonal specimens, are comparable across all orientations and the distributions show no direct dependence on the specimen orientation. Together with similar standard deviations between 76.0 \u0026micro;m and 117.7 \u0026micro;m, these results demonstrate that the LPCS process produces a consistent and uniform coating build-up. As the DED-Arc walls were coated prior to specimen extraction, the coating thicknesses reflect the uniformity of the LPCS process across the entire wall surface and no effect of specimen orientation can observed.\u003c/p\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThickness of the as-built LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e specimens and respective coating thicknesses\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSpecimen Orientation\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eCoated as-built\u003c/p\u003e\n \u003cp\u003especimen thickness [mm]\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eCoating thickness [\u0026micro;m]\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStd.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMedian\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStd.\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical\u003c/p\u003e\n \u003cp\u003e(\u003cem\u003e\u0026theta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;90\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e437.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e76.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDiagonal\u003c/p\u003e\n \u003cp\u003e(\u003cem\u003e\u0026theta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;45\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e502.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e117.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHorizontal\u003c/p\u003e\n \u003cp\u003e(\u003cem\u003e\u0026theta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0\u0026deg;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e426.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e90.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Electrochemical polarisation behaviour\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e displays the polarisation curves of uncoated DED-Arc steel and of LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coatings tested in 3.5 wt% NaCl solution. The coated specimens exhibited a significantly more negative corrosion potential E\u003csub\u003ecorr\u003c/sub\u003e (\u0026ndash;1250 mV) compared to the uncoated DED-Arc wall (\u0026ndash;550 mV), indicating their function as sacrificial anodes within the material system. The corresponding corrosion rate (CR) of the coated surface was 0.1 mm/year, whereas the uncoated DED-Arc HLSA steel showed a rate of 0.29 mm/year. These results confirm the cathodic protection provided by the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating, which protects the steel substrate through sacrificial and selective corrosion behaviour of Zn in the test environment.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Results of uniaxial quasi-static tensile tests\u003c/h2\u003e\n \u003cp\u003eTo assess the influence of surface condition and build orientation on the mechanical properties, a series of uniaxial quasi-static tensile tests were performed. In total, 42 uniaxial quasi-static tensile tests were conducted (see Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). For all specimens, the respective nominal (engineering) stress-engineering strain-curves are displayed with markers indicating the fracture points of each test.\u003c/p\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e3.4.1 Mechanical properties of specimens with machined surface\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows the stress\u0026ndash;strain curves of the machined specimens, including the initial range up to the 0.2% Proof stress (left) and the full deformation behaviour (left). The mechanical properties extracted from the stress\u0026ndash;strain curves are quantified in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and in Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e (Annex).\u003c/p\u003e\n \u003cp\u003eThe stress\u0026ndash;strain response follows the characteristic rounded shape of HSLA material and shows very limited orientation dependence, reflecting a nearly isotropic mechanical behaviour. There are only minor differences depending on the orientation in the elastic\u0026ndash;plastic transition. Specifically, the stress\u0026ndash;strain curves of the horizontal specimens exhibit a slightly sharper transition from the elastic to plastic regime, with reduced curvature in the yield region compared to the vertical and diagonal specimens. This observation is reflected in the proof stress ratio \u0026micro;\u003csub\u003ep\u003c/sub\u003e, which is highest for the horizontal specimens (median: 0.947), followed by the diagonal (0.881), and lowest for the vertical specimens (0.865), indicating a more abrupt onset of plastic deformation in the horizontal orientation and slightly higher stresses after reaching the 0.2% Proof stress. The mechanical properties display a high consistency across all orientations with the Youngs modulus \u003cem\u003eE\u003c/em\u003e being almost identical between vertical, diagonal and horizontal specimens and the ultimate tensile strength \u003cem\u003eR\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e ranging from 880 MPa to 889 MPa for all machined specimens. The large values of the Elongation after fracture \u003cem\u003eA\u003c/em\u003e indicate a ductile behaviour and while it is comparable for horizontal (18.6%) and diagonal (18.5%) specimens the Elongation \u003cem\u003eA\u003c/em\u003e is slightly lower for vertical specimens (17.1%) in addition with a slightly higher standard deviation for specimens of this direction. Only the 0.2% Proof stress shows a minor orientation dependence for which the median value is approximately 5% higher for horizontal specimens (771 MPa) than for vertical (727 MPa) and diagonal (727 MPa) specimens.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e3.4.2 Mechanical properties of coated as-built specimens\u003c/h2\u003e\n \u003cp\u003eThe engineering stress\u0026ndash;strain curves of the coated as-built specimens are shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e for the initial range up to the 0.2% proof stress (left) as well as for the full range (left). The corresponding mechanical properties are summarized in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e and in Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (Annex), while selected DIC strain fields are presented in Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eThe stress\u0026ndash;strain curves in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e display a clear orientation dependence of the mechanical response of the coated as-built specimens, which is already evident in the initial deformation range before reaching the 0.2% Proof stress. The shape and progression of the curves differ significantly between specimen groups, with horizontal specimens exhibiting a sharp elastic\u0026ndash;plastic transition as indicated by a proof stress ratio of \u0026micro;\u003csub\u003ep\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.983, while diagonal and vertical specimens show more gradual transitions. Additionally, vertical specimens show an earlier onset of plasticity and an earlier failure point. The observed anisotropy is further confirmed by the extracted mechanical properties, which exhibit a clear orientation-dependent trend: the 0.2% Proof stress \u003cem\u003eR\u003c/em\u003e\u003csub\u003ep0.2\u003c/sub\u003e, the tensile strength \u003cem\u003eR\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e, and the elongation after fracture \u003cem\u003eA\u003c/em\u003e all decrease with increasing build orientation angle \u003cem\u003e\u0026theta;\u003c/em\u003e, i.e. from horizontal to diagonal to vertical specimens. Specifically, the median proof stress decreases from 792.4 MPa (horizontal) to 652.5 MPa (vertical), the tensile strength from 860.1 MPa to 765.0 MPa, and the elongation from 0.149 to 0.073. The highest Young\u0026rsquo;s modulus \u003cem\u003eE\u003c/em\u003e is observed for the diagonal specimens (204.4 GPa). Among all orientations, the vertical specimens consistently exhibit the highest scatter in mechanical properties.\u003c/p\u003e\n \u003cp\u003eAdditional insight into the local behaviour is obtained from the engineering strain \u003cem\u003ee\u003c/em\u003e distributions in Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e which are derived from the DIC data of the tests at reaching integral yielding at the 0.2% Proof stress.\u003c/p\u003e\n \u003cp\u003eIn the results for the vertical specimen (top), a distinct layer-wise strain localization is visible perpendicular to the build (and loading) direction. Local strain concentrations exceed 3.0%, indicating considerable early plastic deformation. A similar pattern is visible in the diagonal specimen (middle), but rotated according to the specimen orientation by 45\u0026deg;. In contrast, the horizontal specimen (bottom) shows a more homogeneous strain distribution and there are no clear visible effects of the layer-wise built-up present. The high accumulation of local strains highlights the influence of the as-built surface characteristics on the load bearing behaviour and therefore the mechanical properties.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eDense microstructures and strong interfacial bonding were achieved for the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating on grit-blasted DED-Arc surfaces. Comparable results were reported by Koivuluoto et al. [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] for LPCS coatings produced on steel substrates under similar process conditions. Grit blasting of the DED-Arc surface prior to coating was deemed necessary to achieve high adhesion and uniform coating build-up. In contrast, coatings deposited directly onto the untreated as-built surfaces exhibited reduced deposition efficiency, as indicated by lower coating thicknesses. The presence of residual oxides on the untreated surfaces, visible in \u003cb\u003eFig.\u0026nbsp;4\u003c/b\u003e (left), is assumed to have promoted increased particle rebound, thereby limiting particle deformation and bonding during the LPCS process. Notably, coating thicknesses still exceeded approx. 300 \u0026micro;m. The LPCS process enables the build-up of comparatively thick zinc coatings, see Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e (right), with the final thickness being scalable by adjusting the number of spray passes.\u003c/p\u003e \u003cp\u003eIn the uniaxial tensile testing, after reaching the yield stress, small cracks appeared in the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating. However, the coating adhered well to the specimen\u0026rsquo;s surfaces until close to reaching the tensile strength when flaking occurred around the fracture zone, most likely originating from a difference in strain ratio between substrate and coating. The machined specimens tested in this study exhibited median 0.2% proof stresses of 768 MPa (horizontal), 733 MPa (diagonal), and 728 MPa (vertical), closely matching the values reported by Jahns et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] for machined HSLA specimens (R\u003csub\u003ep0.2\u003c/sub\u003e =765 MPa, 729 MPa, and 730 MPa). Similar agreement was found for ultimate tensile strength and elongation after fracture. These results confirm that the LPCS process, does not affect the mechanical properties of the DED-Arc HSLA material itself. The LPCS-coated as-built specimens displayed pronounced anisotropy in their mechanical response. A continuous decrease in the median 0.2% proof stress, tensile strength, and elongation with increasing build orientation angle was observed. Specifically, the 0.2% proof stress decreased from 792 MPa (horizontal) to 652 MPa (vertical), tensile strength from 860 MPa to 765 MPa, and elongation after fracture from 0.149 to 0.073, see Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e. This orientation-dependent behaviour reflects the characteristic influence of the layer-by-layer DED-Arc manufacturing process and aligns in general with results reported by Jahns et al. [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e] for uncoated as-built HSLA DED-Arc specimens. As summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e12\u003c/span\u003e, R\u003csub\u003ep0.2\u003c/sub\u003e ranged from 740 MPa (horizontal) to 686 MPa (vertical), and elongation from 0.165 to 0.076 The tensile strength exhibited a similar anisotropic trend, decreasing from 862 MPa to 853 MPa across the build orientations. Also, the proof stress ratio slightly decreased with increasing build angle, indicating an earlier onset of plastic deformation in specimens with vertical orientation. These comparable results and the trends in the mechanical responses confirm, that the LPCS coating does not alter characteristic the mechanical response of as-built DED-Arc components.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor hot-dip galvanization (HDG) of mild steel DED-Arc specimens, Voelkel et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] showed that HDG with pure zinc does not significantly affect the yield strength of mild steel DED-Arc when the zinc layer is excluded from the load-bearing cross-section. However, a slight reduction in tensile strength and a decrease in elongation at fracture (from 0.268 to 0.213) were observed, attributed to the formation of brittle intermetallic δ- and ζ-phase within the zinc layer during the HDG process. K\u0026uuml;hne et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] further demonstrated that thin-film galvanizing with a Zn\u0026ndash;5Al alloy resulted in nearly unchanged tensile properties of mild steel DED-Arc, with a minor increase of the elongation at fracture (0.233) compared to the uncoated state (0.229). However, both studies did not address the corrosion protection performance of the hot-dip galvanised DED-Arc components.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThis study investigated the applicability of Low-Pressure Cold Sprayed (LPCS) coatings for corrosion protection of steel components manufactured by Directed Energy Deposition using an electric arc (DED-Arc). Multiple thin-walled structures were 3D-printed from high-strength low-alloy (HSLA) feedstock. Three of the walls were coated with a Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e powder using a robot-guided LPCS system. Prior to the coating production, the as-built surfaces were grit-blasted to remove oxide residues from the deposition process and to enhance coating adhesion. The microstructure of both the HSLA base material and the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating was examined using optical and electron microscopy. Additionally, electrochemical polarisation analysis was carried out to assess the corrosion protection capability of the coating system. Subsequently, a total of 44 dog-bone tensile specimens were extracted by CNC milling from the manufactured walls. The specimens were extracted horizontal (θ\u0026thinsp;=\u0026thinsp;0\u0026deg;), diagonal (θ\u0026thinsp;=\u0026thinsp;45\u0026deg;), and vertical (θ\u0026thinsp;=\u0026thinsp;90\u0026deg;) with respect to the deposition direction to assess build-direction-dependent material behaviour. A total of 22 specimens were further machined to a constant thickness of t\u0026thinsp;=\u0026thinsp;3 mm, while the other 22 specimens were left in the coated as-built state without modification of the surface. Prior to mechanical testing, all coated specimens were geometrically characterized using a structured-light scanning system to evaluate the total specimen thickness and magnetic induction measurements to obtain the thickness of the applied Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating. The geometrical characterization served as a base for determining the effective load-bearing cross-sections of the DED-Arc material and assessing the coating uniformity across different specimen orientations. To quantify the influence of the LPCS coating process on the mechanical properties of DED-Arc components, uniaxial quasi-static tensile tests were performed on all specimens, with high-resolution deformation data acquired using a four-camera Digital Image Correlation (DIC) system. The evaluation focused on orientation-dependent variations in mechanical behaviour. The main outcomes of this conducted research are as follows:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eZn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating was successfully deposited on grit-blasted as-built DED-Arc HSLA surfaces using the LPCS process, resulting in dense material built-up with median coating thicknesses between 430 and 500 \u0026micro;m.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eElectrochemical polarisation analysis showed that the LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating provides sufficient corrosion protection for HLSA DED-Arc components, reducing corrosion rate to 0.1 mm/year compared to 0.29 mm/year for uncoated material.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eGeometric analysis of coated as-built specimens revealed that both total specimen thickness and coating thickness distribution remained consistent for specimens extracted with different orientations from thin walls.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eUniaxial quasi-static tensile tests on specimens with machined surface showed isotropic material properties of the DED-Arc HSLA substrate material.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eLPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coated as-built specimens exhibited orientation-dependent mechanical properties, with yield strength, ultimate tensile strength, and elongation after fracture decreasing from horizontal (θ\u0026thinsp;=\u0026thinsp;0\u0026deg;) to vertical (θ\u0026thinsp;=\u0026thinsp;90\u0026deg;) specimen orientation. When excluding the Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating thickness from the load-bearing cross-sectional area, the mechanical properties are comparable to those for uncoated as-built specimens from literature.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe systematic experimental framework and dataset developed in this study provide an initial basis for evaluating the use of LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coatings on DED-Arc structural steel components. The findings contribute to a systematic understanding of the interaction between both processes. Future research should build upon this work by investigating fatigue performance under cyclic loading conditions of coated as-built specimens and by investigating the applicability of the combined processes to large-scale structural components for civil engineering applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthical Approval\u003c/h2\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003ch2\u003eConsent to participate\u003c/h2\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003ch2\u003eConsent to publish\u003c/h2\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003ch2\u003eCompeting Interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003ch2\u003eAcknowledgements\u003c/h2\u003e\n\u003cp\u003eThe authors would like to thank Mr. Jarkko Lehti and Mr. Anssi Mets\u0026auml;honkala of Tampere University for LPCS coating production and M.Sc Pentti Kalliotiura for assisting with the coating evaluation. This work has used the facilities of Tampere Microscopy Center, Tampere, Finland. Additionally, Mr. Tatu Lepp\u0026auml;nen and Dr. Jussi Larjo of Oseir Ltd. (Finland) are acknowledged for measurements of in-flight particle properties.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eCRediT authorship contribution statement\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003eM.M.:\u003c/strong\u003e Visualization, Investigation, Formal analysis, Data curation, Writing \u0026ndash; original draft. \u003cstrong\u003eH.M.:\u003c/strong\u003e Supervision, Resources, Conceptualization, Funding acquisition, Writing \u0026ndash; review \u0026amp; editing. \u003cstrong\u003eH.K.:\u0026nbsp;\u003c/strong\u003eFormal analysis, Supervision, Conceptualization, Writing \u0026ndash; original draft. \u003cstrong\u003eH.J.:\u003c/strong\u003e Software, Methodology, Data curation. \u003cstrong\u003eR.J.:\u003c/strong\u003e Formal analysis, Data curation, Writing \u0026ndash; review \u0026amp; editing. \u003cstrong\u003eS.P.:\u003c/strong\u003e Writing \u0026ndash; review \u0026amp; editing, Data curation. \u003cstrong\u003eE.H.:\u003c/strong\u003e Investigation, Data curation. \u003cstrong\u003eM.A.:\u003c/strong\u003e Investigation, Data curation. \u003cstrong\u003eK.T.:\u0026nbsp;\u003c/strong\u003eSupervision, Resources. \u003cstrong\u003eJ.U.:\u003c/strong\u003e Supervision, Project administration, Funding acquisition, Conceptualization, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThe research presented in this paper is being conducted within the project \u0026lsquo;\u0026lsquo;Wire Arc Additive Manufacturing (WAAM) of Complex and Refined Steel Components (A07)\u0026rsquo;\u0026rsquo;. The project is part of the collaborative research centre \u0026lsquo;\u0026lsquo;Additive Manufacturing in Construction\u0026rdquo;, funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - project number 414265976 - TRR 277. Suraj Panicker received funding by the Walter Ahlstr\u0026ouml;m Foundation. Great thanks are expressed to the Institute of Geodesy and Photogrammetry\u0026nbsp;for using the structured-light stereo scanner, which is funded by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) \u0026ndash; project number 461109100.\u003c/p\u003e\n\u003ch2\u003eData availability statement\u003c/h2\u003e\n\u003cp\u003eThe data can be accessed under DOI: 10.5281/zenodo.15183281, see [42].\u003c/p\u003e\n\u003cp\u003eDeclaration of Generative AI and AI-assisted technologies in the writing process\u003c/p\u003e\n\u003cp\u003eDuring the preparation of this work the authors used ChatGPT (based on GPT-4o -OpenAI) in order to reorganise the notes and improve the manuscript readability. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the published article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eUnglaub J, M\u0026uuml;ggenburg M, Jahns H, Kloft H, Hensel J, Thiele K. Towards a Digital Twin to Enable First Time Right DED-Arc Components. In: Lowke D, Freund N, B\u0026ouml;hler D, Herding F, editors. Fourth RILEM International Conference on Concrete and Digital Fabrication: Digital Concrete 2024. 1st ed. 2024. Cham: Springer Nature Switzerland; Imprint Springer 2024; 439\u0026ndash;46.\u003c/li\u003e\n\u003cli\u003eReisch RT, Janisch L, Tresselt J, Kamps T, Knoll A. Prescriptive Analytics - A Smart Manufacturing System for First-Time-Right Printing in Wire Arc Additive Manufacturing using a Digital Twin. 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Surface Engineering 2022; 38(4): 324\u0026ndash;65\u003cbr\u003e [https://doi.org/10.1080/02670844.2022.2073424]\u003c/li\u003e\n\u003cli\u003eFaccoli M, Cornacchia G, Maestrini D, Marconi GP, Roberti R. Cold Spray Repair of Martensitic Stainless Steel Components. J Therm Spray Tech 2014; 23(8): 1270\u0026ndash;80\u003cbr\u003e [https://doi.org/10.1007/s11666-014-0129-7]\u003c/li\u003e\n\u003cli\u003eKoivuluoto H, N\u0026auml;kki J, Vuoristo P. Corrosion Properties of Cold-Sprayed Tantalum Coatings. J Therm Spray Tech 2009; 18(1): 75\u0026ndash;82\u003cbr\u003e [https://doi.org/10.1007/s11666-008-9281-2]\u003c/li\u003e\n\u003cli\u003eXu L, Cui C, Lu Q, Yang H, Zhang W. Characterization of microstructural and corrosion behavior of cold sprayed Zn11Al3Mg alloy coating. Surface and Coatings Technology 2023; 471: 129890\u003cbr\u003e [https://doi.org/10.1016/j.surfcoat.2023.129890]\u003c/li\u003e\n\u003cli\u003eBalani K, Laha T, Agarwal A, Karthikeyan J, Munroe N. 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Zenodo; 2025.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Wire Arc Additive Manufacturing (WAAM), Directed Energy Deposition-Arc (DED-Arc), High-strength low-alloy (HSLA) steel, Corrosion resistance, Low-Pressure Cold spray (LPCS), Digital Image Correlation (DIC), Quasi-static tensile testing","lastPublishedDoi":"10.21203/rs.3.rs-6566148/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6566148/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Directed Energy Deposition-Arc (DED-Arc) process, using high-strength low-alloy (HSLA) feedstock wire, presents a promising solution for fabricating large-scale steel connectors in civil engineering. Due to the use of carbon steel feedstock wire, corrosion protection of the 3D-printed components is necessary. Therefore, this study investigates Low-Pressure Cold Spray (LPCS) as a method for applying zinc-based coatings. Two sets of thin walls were 3D-printed: one set uncoated and one set coated with LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating. This LPCS coating was successfully deposited on untreated and on grit-blasted DED-Arc surfaces. Coating thicknesses exceeding 300 \u0026micro;m as well as electrochemical polarisation analysis confirmed sufficient corrosion resistance of the coated as-built specimens. To evaluate the influence of the surface condition and the coating process on the mechanical behaviour, dog-bone tensile specimens were extracted from the walls, 3D-scanned and subsequently mechanically tested. Structured-light scanning of the geometry revealed different scatter of the specimens\u0026rsquo; thickness based on their orientation with respect to the build direction. Uniaxial quasi-static tensile tests, combined with a four-camera Digital Image Correlation (DIC) system, were performed both on specimens with machined surfaces and with LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating on the as-built surface. While the machined specimens exhibited nearly isotropic behaviour, the coated as-built specimens showed pronounced anisotropy with comparable mechanical properties to uncoated as-built specimens from literature when excluding the coating thickness from the load-bearing cross-section. The LPCS Zn\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating led to a reduction of the corrosion rate by two thirds compared to uncoated HSLA DED-Arc.\u003c/p\u003e","manuscriptTitle":"Mechanical properties and corrosion protection of DED-Arc additively manufactured high-strength low-alloy steel components coated with Low-Pressure Cold Spray","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-09 05:10:16","doi":"10.21203/rs.3.rs-6566148/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-06-03T20:04:20+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-01T18:17:14+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Welding in the World","date":"2025-05-28T02:52:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-09T14:11:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"Welding in the World","date":"2025-05-07T11:00:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2d226266-7e90-43a4-ba80-f56c96679f02","owner":[],"postedDate":"June 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-11-08T05:35:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-09 05:10:16","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6566148","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6566148","identity":"rs-6566148","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}