Effect of heat treatment on the microstructure and microhardness of cold-sprayed tin bronze coating

Tin bronze (TB) powder was deposited on a stainless steel substrate by cold spraying. Post-deposition heat treatment was conducted in an electrical resistance furnace under nitrogen atmosphere at a temperature of 850 °C for 3 h. The effect of heat treatment on the microstructure and microhardness of cold-sprayed TB coating was investigated. It was found that the as-sprayed TB coating presented a dense microstructure. Heat treatment significantly influenced the microstructure and microhardness of cold-sprayed TB coating. A distinguishable diffusion layer of about 150 μm was formed in the coating near the coating/substrate interface. A compound was precipitated in the diffusion layer. The microhardness in the coating was changed gradually along the coating from the interface to the coating surface after heat treatment. The microhardness in the diffusion layer was high owing to the precipitation of hard phase, while it was much low in other area due to the obvious grain growth during annealing.