Study on the Characteristics of Transferred Lubricating Thin Films on Ceramic Surfaces Generated in Liquid Nitrogen

Abstract

The ceramic bearings operated in liquid nitrogen are mainly lubricated by the thin films transferred from the PTFE based composite retainers. The thin films on silicon nitride balls surfaces are generated by the friction and interaction among the composite retainer, the balls and the ANSI 440C stainless steel rings. The characteristics of transferred lubricating films on silicon nitride ball surfaces which generated by working in liquid nitrogen at 2.4GPa and 2.8GPa are analyzed. The distribution of thin films on silicon nitride balls surfaces are observed by metallic microscope. The profiles of transferred thin films are measured by atom force microscope. The component and structure of transferred thin films are detected by X-ray photoelectron spectroscopic and Roman spectrometry. The results show that the transferred thin films are interrupted distribution on silicon nitride ball surfaces and the thickness is about half to one micron. The surface layer of transfer films, about 100nm thickness, degraded under heavy load with metal fluoride generation. The bonding strength between the degradation layer and the transfer film is very weak.