Comprehensive Study of Surface Layers and Tribological Properties of Antifriction Alloys of the AI-Si-Cu-Sn + Fe System

The paper studies new antifriction aluminum alloys. The effect of small iron additions on the structure and tribological properties of samples was investigated. The tests were carried out using the "drive-roller" scheme with a step-by-step change in pressure. When analyzing the tribological properties, the operating modes were studied both in lubrication and without it. Tests in lubrication simulated the operation of the friction unit under normal conditions. Tests without lubrication simulated an extreme operating mode and were used as an express method for assessing wear resistance. The alloys were studied in the cast state and after heat treatment, as well as before and after tribological tests. It was found that after heat treatment, the silicon and mica phases acquired a rounded shape, and the copper content decreased. An iron-containing phase was isolated, which, due to the addition of manganese, acquired a favorable "skeletal" shape. After testing and lubrication, rounded solid particles were found on the surface of the drive. These particles remain on the surface and roll in the lubricant, creating a kind of protective framework that promotes stable operation of the contact pair. In tests without lubrication (leading to a strong increase in temperature in the friction zone), solid particles, on the contrary, enhance surface destruction, playing the role of an abrasive and promoting scuffing. The study of the block section prepared after testing in lubrication made it possible to estimate the thickness of the near-surface layer (30-40 cm) and showed the redistribution of elements in this layer. It was found that tin is squeezed out of the volume and forms "tracks" in the near-surface layer, elongated along the friction direction. In tests without lubrication, tin melts and is homogenously redistributed in the near-surface layer. It is shown that in tests in lubrication, the resulting film of secondary structures is distributed over the surface in a thin uniform layer with protective properties. During testing without lubrication, the film is uneven in thickness, which contributes to the development of macrorelief and can lead to scoring. It is shown that alloys containing iron (up to 1%) have higher tribological characteristics in modes with and without lubrication.