Effect of vacuum heat treatment on microstructure and microhardness of cold sprayed Cu-4Cr-2Nb alloy coating

The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250°C to 950°C with a step of 100°C for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr₂Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr₂Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350°C, and then decreases with further increasing temperature up to 950°C. This fact can be attributed to the microstructure evolution during the heat treatment.