Structural and phase transformations, mass transfer, and tribotechnical characteristics of gas-dynamic copper-zinc coatings occurring under sliding friction

The effect of the coating temperature and the displacement of the spray nozzle on the structural and phase transformations in the coating on 40X steel obtained by cold gas-dynamic spraying of a powder mixture of Cu:Zn: Al2O3=35:35:30 (wt%) has been studied. The phase composition of the coating was identified using the method of local X-ray spectral analysis. It was shown that under gas-dynamic spraying there can be five phases garadually occurring in the coating, being formed as a result of solid state transformations under conditions of high-speed impact contact interaction: α - Cu-Zn solid solution; βʹ - CuZn-based solid solution; γ - Cu5Zn8-based solid solution; ε -CuZn3-based solid solution.; η is a solid solution of Zn-Cu. Under sputtering temperatures of 2700and 3600 C, the alpha - Cu-Zn solid solution phase becomes predominant. Tribotechnical tests of a pair of reversible sliding friction steel 40X (coated) – steel SHX15 in an I-20A oil medium have shown that the coupling has high performance at contact pressures of at least 50 MPa. Deformation, diffusion and frictional mass transfer in the zone of contact interaction lead to the realization of the "classical wearlessness" effect, the distinctive feature of which is the formation of a copper-zinc third body with corundum inclusions and capable of direct and reverse coating transfer, providing protection of the surface layers of the friction pair from destruction High wear resistance of the friction pair contacting materials is achieved due to the frictional mass transfer films.