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<p>Fabricating dissimilar metal functionally graded materials (FGMs) such as Al–SS316L remains a challenge due to metallurgical incompatibility and brittle intermetallic formation in fusion-based additive manufacturing. This study demonstrates the development of Al–SS316L FGMs using a hybrid manufacturing approach that combines Wire Arc Additive Manufacturing (WAAM) and Cold Spray Additive Manufacturing (CSAM). In this work, SS316L wall fabricated by WAAM was coated with a 3&#xa0;mm thick coating of aluminum (Al) by cold spray to create a graded structure. Post-deposition heat treatment at 350&#xa0;°C/2&#xa0;h and 450&#xa0;°C/1&#xa0;h was carried out to reduce work hardening effect and enhance densification without promoting intermetallic formation at the interface. Microstructural analysis revealed that the as-sprayed aluminum coating exhibited a typical splat morphology with the presence of intersplat porosity, which got significantly densified upon heat treatment, reducing porosity from 4.2 ± 1.3 to 1.5 ± 0.5%. Microhardness measurements showed significant work hardening in the as-sprayed coating (48.3 HV<sub>0.05</sub> ± 5) compared to the feedstock powder (23.9 HV<sub>0.01</sub>). After heat treatment, the hardness decreased, reaching 30.1 HV<sub>0.05</sub> ± 3.5 at 350&#xa0;°C/2&#xa0;h and further reducing to 25.1 HV<sub>0.05</sub> ± 3.5 at 450&#xa0;°C/1&#xa0;h, which is close to the original feedstock hardness. In comparison, the WAAM-fabricated SS316L sample showed a considerably hardness of 188 HV<sub>0.3</sub> ± 6, consistent with its fusion-based processing and dense microstructure. Fracture surface analysis indicated a transition from inter-splats decohesion in the as-sprayed state to few micro-void coalescences at 450&#xa0;°C/1&#xa0;h, confirming improved cohesion of the Al layer. Scratch test demonstrated that heat treatment reduced the coefficient (COF) and improved scratch stability, reflecting improved cohesion of the coatings. EDS map and line scans across the CS–WAAM interface confirmed the absence of intermetallic compounds, ensuring interface integrity. This hybrid approach offers a viable pathway for fabricating metallic FGMs with tailored properties for different applications. The novelty of this work lies in the development of a hybrid additive manufacturing route using WAAM and CS as primary processes, followed by heat-treatment as a secondary process to develop FGMs.</p>

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Development and characterization of functionally graded Al–SS316L material via hybrid cold spray and wire arc additive manufacturing

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • Pawan Kumar,
  • Jitendra Kumar,
  • Harpreet Singh

摘要

Fabricating dissimilar metal functionally graded materials (FGMs) such as Al–SS316L remains a challenge due to metallurgical incompatibility and brittle intermetallic formation in fusion-based additive manufacturing. This study demonstrates the development of Al–SS316L FGMs using a hybrid manufacturing approach that combines Wire Arc Additive Manufacturing (WAAM) and Cold Spray Additive Manufacturing (CSAM). In this work, SS316L wall fabricated by WAAM was coated with a 3 mm thick coating of aluminum (Al) by cold spray to create a graded structure. Post-deposition heat treatment at 350 °C/2 h and 450 °C/1 h was carried out to reduce work hardening effect and enhance densification without promoting intermetallic formation at the interface. Microstructural analysis revealed that the as-sprayed aluminum coating exhibited a typical splat morphology with the presence of intersplat porosity, which got significantly densified upon heat treatment, reducing porosity from 4.2 ± 1.3 to 1.5 ± 0.5%. Microhardness measurements showed significant work hardening in the as-sprayed coating (48.3 HV0.05 ± 5) compared to the feedstock powder (23.9 HV0.01). After heat treatment, the hardness decreased, reaching 30.1 HV0.05 ± 3.5 at 350 °C/2 h and further reducing to 25.1 HV0.05 ± 3.5 at 450 °C/1 h, which is close to the original feedstock hardness. In comparison, the WAAM-fabricated SS316L sample showed a considerably hardness of 188 HV0.3 ± 6, consistent with its fusion-based processing and dense microstructure. Fracture surface analysis indicated a transition from inter-splats decohesion in the as-sprayed state to few micro-void coalescences at 450 °C/1 h, confirming improved cohesion of the Al layer. Scratch test demonstrated that heat treatment reduced the coefficient (COF) and improved scratch stability, reflecting improved cohesion of the coatings. EDS map and line scans across the CS–WAAM interface confirmed the absence of intermetallic compounds, ensuring interface integrity. This hybrid approach offers a viable pathway for fabricating metallic FGMs with tailored properties for different applications. The novelty of this work lies in the development of a hybrid additive manufacturing route using WAAM and CS as primary processes, followed by heat-treatment as a secondary process to develop FGMs.