Additive Manufacturing of Copper-Stainless Steel Hybrid Components using Laser-Aided Directed Energy Deposition

Combining dissimilar materials in a single component is an effective solution to integrate diverse material properties into a single part. Copper-stainless steel hybrid components are attracting more and more attention since the high thermal conductivity of copper can greatly enhance the thermal performance of stainless steel, which benefits its applications in many industries. However, direct joining of copper and stainless steel such as SS316 L is challenging since they preserve significant dissimilarities in physical, chemical, and thermo-mechanical properties. This paper aims to fabricate well-bonded copper-SS316 L hybrid parts using a laser-aided directed energy deposition (DED) process. A nickel-based alloy Deloro 22 (D22) is introduced between copper and SS316 L to address the detrimental issues in copper-SS316 L direct joints. Using this technique, defect-free interfaces are achieved at both the D22-SS316 L and copper-D22 transition zones. Tensile testing of Cu-D22-SS316 L and D22-SS316 L hybrid parts shows the fracture occurs at pure copper and SS316 L region, respectively, indicating an excellent bonding at the interfaces. Ascending in the building direction, a transition of grain structure is observed. A significant diffusion zone is obtained at both the D22-SS316 L and the Cu-D22 interfaces. The large diffusion distance results in a smooth variation in microhardness over the dissimilar materials. The microhardness increases from SS316 L to D22 with the highest value of 240 HV and then decreases from D22 to Cu with the lowest value of 63 ± 4 HV. Testing of thermophysical properties of the Cu-D22-SS316 L system indicates there is a ∼300 % increase in thermal diffusivity and a ∼200 % increase in thermal conductivity when compared to pure SS316 L. The significant increase in thermal diffusivity and conductivity validates the enhanced thermal performance of SS316 L when it is joined with pure copper