Investigation of copper/stainless steel multi-metallic materials fabricated by laser metal deposition

The feasibility of fabricating a single component with a copper and stainless steel multi-material structure can broaden its functional properties and offer significant value in engineering design. In an effort to join copper with 304L stainless steel (SS304L) using the laser metal deposition technique, pure copper was deposited on SS304L both directly and via interlayers of a nickel-based alloy Deloro 22 (D22). The microstructure, elemental distribution, bonding strength, microhardness profile, and thermal conductivity/diffusivity of the multi-metallic structures were investigated. The transition zone of the Cu-SS direct joint shows numerous SS304L globules and separated Cu-rich and Fe-rich islands. Tensile testing of the Cu-SS shows poor bonding strength. By adding D22 interlayers, a well bonded and defect-free Cu-D22-SS structure was achieved. Evidence of strong bonding at the Cu-D22 and D22-SS was obtained by tensile testing where samples broke in either the copper or D22 regions. The Cu-D22-SS results in a hardness of 228.7 ? 19.5 HV at the D22 layers. Ascending to the copper layers, a gradual drop of hardness to a steady value of 52.9?56.1 HV was observed. The theoretical prediction shows there is a -100% increase in thermal conductivity and a -370% increase in thermal diffusivity of the Cu-D22-SS system when compared with pure SS304L.