Wear Mechanisms of PTFE in Humidified Hydrogen Gas

PTFE is used as sealing material of machine elements in hydrogen utilizing machine systems, such as fuel cell vehicles and related infrastructures. It is necessary to know the tribological property of sealing materials in hydrogen gas to realize safety and reliability of machine elements operated in hydrogen environment. In this study, humidity in gases was focused on and its effects on the friction and wear of rubbing pair of PTFE pin and AISI 316L disk was investigated in pin-on-disk wear apparatus. The result indicated that the humidity in hydrogen gas had little effect on the friction coefficient between PTFE and AISI 316L. However, the specific wear rate of unfilled PTFE was clearly affected by the humidity. The amount of PTFE transfer film formed on the stainless surface gradually decreased with decreasing the humidity in hydrogen gas. The similar results could be obtained in inert argon gas as well. Water molecules remained in gaseous environments would be included in the formation process of PTFE transfer film affect on formation of PTFE transfer film. The humidity in hydrogen gas should be regulated to ensure the tribological behavior of the PTFE/stainless sliding pair being used in the hydrogen environment.