Effect of running-in conditions on the super low EHD sliding friction of Si3N4 ball and WC plate in glycerol-water solution.

Abstract

In water-based ultralow or super low friction experiments, a running-in period before achieving the ultralow or super low friction is necessary and important. However, the effect of the change in contact geometry has not been fully realised. In this paper, a series of running-in tests on a Si3N4 ball and a WC plate have been performed in glycerol-water mixtures with different concentrations. The shape of the wear scars and the chemical compositions of the worn surfaces were characterised in detail. A numerical EHD and mixed lubrication model was established to comprehensively analyze the effects of geometric profiles, surface roughness, and working / lubrication conditions on ultralow or super low sliding friction. The experiment and simulation results of the study have provided an in-depth understanding of the mechanism of super low friction of liquid lubricated sliding point contacts.