Chemical and Structural Effects on the Lubrication Properties of Sputtered MoS2Films

Abstract

Lubricating films of MoS₂ have been prepared by sputter deposition onto steel substrates maintained at different temperatures. The surface chemical compositions and bulk structural properties of the films before and after rubbing for various periods of time in dry nitrogen gas were determined by x-ray photoelectron spectroscopy and X-ray diffraction, respectively. Film thickness, density, and morphology measurements were also made. Differences in these properties for the films prepared under different conditions provide some insight into the mechanism(s) of lubrication and failure of the films. On the basis of the reported results, it is proposed that lubrication by MoS₂ films occurs through a process of intercrystallite slip and that there is an optimum crystallite size that provides maximum wear life under any particular set of application (use) conditions. Methods for improving film performance based on particle/crystallite size and lattice spacing arguments and on the electronic properties of MoS₂ and related compounds are suggested.