Dry sliding friction and wear properties of zinc-based alloys

The friction and wear of two near-eutectoid and two monotectoid permanent-moulded zinc-based alloys and an SAE 660 bronze for comparison were investigated under dry sliding conditions. To determine the wear mechanisms surface and subsurface microstructures of worn test samples were examined by scanning electron microscopy (SEM). All of the zinc-based alloys had lower coefficients of friction and higher wear resistance than the bronze; the best wear resistance and lowest coefficient of friction were obtained for the ZnAl40Cu2Si1 alloy. Wear resistance increased strongly with hardness and tensile strength and decreased with friction coefficient. Correlation of the experimental results showed that the wear behaviour of the zinc-based alloys was consistent with Archhard’s equation. Layered structures were formed under the wear surfaces of the zinc-based alloy samples during testing. The topmost layer, formed by smearing and embedding of oxidised zinc–aluminium alloy was hard and is considered to have contributed to their low wear rates. Surface and subsurface examinations showed that adhesion and smearing was the main wear mechanism for the zinc-based alloys, while abrasive wear dominated in the case of the SAE 660 bronze.