A new approach to prepare fully dense Cu with high conductivities and anti-corrosion performance by cold spray

A novel approach has been developed to cold spray fully dense Cu deposits by using a mixed feedstock. The feedstock is composed of two raw powders with remarkably dissimilar microstructure and hardness: a hard and dense gas-atomized Cu powder (GA Cu) and a soft and porous electrolytic Cu powder (E Cu). It was found that when high velocity impact occurs between dissimilar Cu particles, the plastic deformation shows an asymmetrical feature and the strain is mainly concentrated on the soft side. This asymmetrical deformation behavior ensures that all the inter-particle space can be filled by the deformed soft particles and leads to a fully dense microstructure. An increment of ∼44% in deposition efficiency was achieved for the mixed feedstock as compared with the GA Cu powder. A high in-plane electrical conductivity of 79 %IACS (73 and 56 %IACS for GA coating and E coating, respectively) and high through thickness thermal conductivity of 285.6 W m⁻¹ K⁻¹ (207.1 and 133.8 W m⁻¹ K⁻¹ for GA coating and E coating, respectively) were achieved. The coating prepared by mixed powders shows an excellent corrosion resistance, comparable with that of the bulk Cu. This work gives a new strategy to improve the inter-particle bonding and get fully dense metallic deposits by feedstock design rather than spraying condition optimization.