Friction, wear and surface hardness in abrasion of binary solid-solution alloys in the copper-gold system

The friction coefficient μ, the mass wear rate M and the surface micro-hardness H_D are measured in abrasion of Cu-Au alloys (in the fully abraded, and thus fully work-hardened, surface state), sliding on dry `smooth-cut' steel files at a load of about 1 kg and a speed of a few cm s⁻¹.

μ and M/ρ (where ρ is the density) are found to be nearly the same as for a pure cubic metal of similar H_D, and vary with alloy composition in a nearly parabolic manner analogous to that found by Sachs and Weerts for the shear stress of Ag-Au alloys. The deviations Δμ and Δ(M/ρ) from a Vegard's-law type of linear dependence on composition are approximately proportional to each other and to|Δa|, the lattice dimension deviation from Vegard's law, but they vary non-linearly with ΔH_D. Similar results are indicated for the Cu-Zn and Cu-Ni alloy systems. On this basis the probable μ, M/ρ and H_D can be estimated for abrasion of face-centred-cubic alloys of other binary solid-solution systems. The stored energy in the abraded alloy surface regions is also estimated from μ and M.