Paper III (i) Reduction in friction coefficient in sliding ceramic surfaces by in-situ formation of solid lubricant coatings

Abstract

Research investigations on the tribological performance of advanced structural ceramics have shown that the coefficients of friction of these materials are generally larger than 0.5 under unlubricated sliding conditions. The aim of this research was to explore whether the high friction coefficient of ceramic materials can be reduced by solid lubrication. The ceramic materials chosen for this investigation were alumina and silicon nitride using graphite intercalated with NiCl 2 as the solid lubricant. Friction coefficients as low as 0.17 were observed when intercalated graphite was used as a solid lubricant with either alumina or silicon nitride. The worn surfaces of the steel counterface, alumina and silicon nitride were examined under a scanning electron microscope and chemically analyzed using energy dispersive spectroscopy, micro-Raman spectroscopy and micro-Fourier transform infrared spectroscopy to gain a better understanding of the mechanism of friction reduction. It was concluded that the reduction in friction is related to the formation of transfer films which consist of a mixture of materials from the surfaces in contact.