Effect of Heat Treatment on the Phase Composition of Copper-Zinc Coating on Steels

The structure of a copper–zinc coating deposited onto steel 40Kh at 450°C by the method of gas-dynamic spraying of a mechanical mixture of copper, zinc and corundum particles with 2-mm displacement of the sprayer nozzle is studied. The coated specimens are heat treated in a furnace at 420 – 430°C for at most 180 min. The structure and the chemical composition of the coating are studied by the methods of x-ray diffraction phase analysis and microscopic spectrum analysis. It is shown that the spraying is accompanied by diffusion of copper into zinc, which yields an electron-type solid solution based on Cu5Zn8 (a γ-phase). After the heat treatment at 420 – 430°C for 180 min the coating contains a solid solution of zinc in copper (an α-phase) and an electron-type solid solution based on CuZn (a γ′-phase). The chemical and phase compositions of the coating correspond to duplex brass L65.