Dependency of deposition behavior, microstructure and properties of cold sprayed Cu on morphology and porosity of the powder

Effect of the Cu feedstock morphology and microstructure on cold spray deposition behavior and coating microstructure was investigated in this study. Deposition efficiency, coating porosity, electrical conductivity and corrosion behavior of coatings sprayed with conventional gas atomized Cu (GA Cu) powder and electrolytic porous and dendritic Cu (E Cu) powder sprayed coating were comparatively studied. Correlation of the detailed pore structure with electrical conductivity and corrosion resistance were examined. It is found that, under the same conditions, E Cu powder shows a high deposition efficiency (DE) of 70.5% while GA Cu powder yields a low DE of only 34.4%. Although both the coatings have relatively low porosity of ~ 0.5%, GA Cu coating presents a much higher in-plane electrical conductivity of 73% of IACS, but a poorer corrosion resistance than E Cu coating. Detailed pore structrue examination indicates that the numerous intra-splat interfaces arising from the inter-branch gaps in E Cu powder introduce extra contact electrical resistance to the E Cu coating and thus lead to low electrical conductivity. In the GA coating, the inter-particle pores connected by poorly bonded inter-particle boundaries provide fast pathway for corrosive medium and consequently result in a poor corrossion resistance.