Additive Manufacturing of Stainless Steel -- Copper Functionally Graded Materials via Inconel 718 Interlayer

The joining of dissimilar materials is becoming increasingly prevalent to integrate different material properties to enhance design flexibility and overall performance. This study introduced an innovative approach to additively manufacture copper on 316L stainless steel (SS316L) via Inconel 718 interlayers using directed energy deposition (DED). The novel multi-material structure was studied both experimentally and theoretically. The microstructure, tensile properties, microhardness, and thermal performance of the structure were characterized. Residual stress distribution over the structure was revealed by experimental-validated numerical modeling. The result exhibits that defect-free structures with excellent interfacial bonding can be achieved by introducing Inconel 718 interlayers. The bonding strength of copper-Inconel 718 and Inconel 718-SS316L exceeds the ultimate tensile strength of copper (257 ± 23 MPa) and SS316L (525 ± 25 MPa), respectively. A ∼125% increment in thermal conductivity and ∼450% increment in thermal diffusivity were achieved in the hybrid structure when compared with these of SS316L, indicating a significant enhancement in thermal performance. A peak longitudinal tensile residual stress of 137 MPa and compressive stress of 94 MPa is seen at the Inconel 718-SS316L and copper-Inconel 718 interfaces, respectively. This study provides a new strategy to make stainless steel-copper functionally graded materials using DED to offer diverse properties