Substructural Changes in the Surface Layers of Composite Gas-Thermal Cu–(Al–Si) Coatings during Friction under Various Conditions

Abstract

The structure, phase composition, hardness, and tribological properties of composite gas-thermal 50% Cu–50% (Al–Si) coatings under various friction conditions were studied. It has been shown that during the process of high-speed metallization, active interaction of molten aluminum and copper particles occurs, leading to the formation of solid solutions and intermetallic compounds in sprayed coatings. In particular, in 50% Cu–50% (Al–Si) coatings, in addition to the matrix phases of Cu and Al, intermetallic compounds Cu₉Al₄, CuAl₂, and Cu₃Al are recorded. The hardness and microhardness of the composite are 180 HV 1 and 180–190 HV 0.025, respectively. It has been established that a composite coating of 50% Cu–50% (Al–Si) has higher wear resistance under various friction conditions than the widely used coating of CuSn11P-C antifriction bronze, obtained by centrifugal induction surfacing. In particular, in the environment of I-20A lubricant, the wear resistance of the composite coating exceeds the wear resistance of bronze by ≈1.2 times, in the environment of Litol-24 plastic lubricant, by ≈1.4 times, and with dry friction up to ≈2.8 times. It has been shown that during boundary friction, dislocations accumulate in aluminum particles of the composite, while in copper particles at elevated test pressures, a predominant formation of a subgrain structure occurs. Based on the studies conducted, it was concluded that the increased wear resistance of the composite is due to the presence of solid intermetallic compounds in it, solid solution strengthening, the presence of silicon in aluminum interlayers, as well as dislocation strengthening of aluminum interlayers and the formation of a subgrain structure in copper interlayers.