Friction and wear of copper samples in the steady friction state

The effect of sliding velocity and load on the friction and wear of Cu–steel pairs was studied. Elasto-hydrodynamic (EHL), mixed (ML) and boundary lubrication (BL) regions were analyzed using the Stribeck curve. The lubrication number of Schipper, Z, was used in the analysis of the Stribeck curve. Steady friction states were observed in the mixed EHL and BL regions, however two types of the ML region are revealed. The first type is the stable ML range. The second one is the range of unstable friction and wear when a decrease of the lubricant film leads to abrupt change of all controlled parameters. It was found that a transition to the unstable ML region occurs within a narrow range of Z parameter. Wear modes in the lubrication regions were studied. Deformation hardening in the lubricant regimes is discussed.