Effect of high-pressure hydrogen exposure on wear of polytetrafluoroethylene sliding against stainless steel

Abstract

Mechanical components in hydrogen energy systems, such as a fuel cell vehicle and related infrastructures, will operate in high-purity hydrogen. Especially, some seals and valves in fuel cell vehicles should articulate against metal counterface within a pressurized hydrogen gas. However, the effect of high-pressure hydrogen gas on tribological behaviour of materials used in sliding surfaces has not been identified yet. In this study, unfilled polytetrafluoroethylene (PTFE) pins and 316L austenitic stainless-steel discs were exposed to high-pressure hydrogen gas and then the chemical and physical changes in their surface and the tribological characteristics were investigated. The results of an X-ray photoelectron spectrometer analysis of the exposed stainless-steel surface indicated that metal oxides in the passive surface layer of stainless steel can be reduced significantly during the high-pressure hydrogen exposure. Increased metal contents of the stainless surface resulted in enhanced metal fluoride formation and subsequent development of a PTFE transfer film. Consequently, the exposed PTFE specimens showed lower specific wear rate when compared to the unexposed specimen.