Influence of Surface Layers Modified with Copper on the Performance of Steel–Steel Sliding Friction Couples

The features of the structural and tribotechnical characteristics of copper alloys and coatings during friction of a steel–steel pair are analyzed. Copper-based coatings obtained by gas-dynamic spraying have been experimentally studied. The wear resistance and microgeometric characteristics of the surface of steels with coatings of the composition Cu : Al₂O₃ = 55 : 45 (wt %) and Cu : Zn : Al₂O₃ = 35 : 35 : 30 (wt %) are determined. A coating is formed from a powder mixture of copper and corundum, mainly consisting of copper. Corundum is present in the form of particles with a size of 0.05 μm² in an amount of less than 1%. The coating has a high performance when tested under friction and wear conditions: wear intensity I_h (coating) ≈ (1.1–1.5) × 10^–10 and I_h (counterbody) ≈ (0.3–0.4) × 10^–11 under friction in I-20A mineral oil; I_h (coatings) ≈ (2–5) × 10^–10 and I_h (counterbodies) ≈ 0.2 × 10^–11 during friction in Litol-24 grease. Heat treatment of such a coating causes diffusion of zinc into copper with the formation of a solid solution of zinc in copper (α-phase) and an electron-type solid solution based on CuZn is also formed. The mechanism of contact interaction of steel coated with Cu–Zn–Al₂O₃ in a pair with ShKh15 steel is based on the process of mass transfer in the zone of surface plastic deformation, which minimizes the level of surface destruction of the pair as a whole, reducing it to practical wearlessness at high external pressures. Deformation, diffusion, and mass transfer in the zone of contact interaction during friction point to the effect of “classical wearlessness,” a distinctive feature of which is the formation of a copper-zinc third body interspersed with corundum, which has the ability to transfer from the sample on the counterbody and vice versa, providing protection of the surface layers from destruction but not a servovite copper film (with a special structural state). High wear resistance of friction pair materials is achieved due to frictional mass transfer films.