The Effect of Lubricant Additives on Hydrogen Permeation Under Rolling Contact

This study describes the effects of lubricant additives on the permeation of hydrogen into high-strength-bearing steel in rolling contact conditions. Oil-lubricated tests were conducted in a hydrogen atmosphere under high temperature/pressure. Trioctylphosphate and zinc dialkyldithiophosphate (ZDDP) were used as lubricant additives. Thermal desorption spectrometry (TDS) was performed to measure the amount of permeated hydrogen immediately after the rolling contact tests. TDS analysis suggested that ZDDP is very efficient at preventing hydrogen permeation into the substrate. Auger electron spectroscopy revealed the generation of a protective chemical tribofilm containing zinc, sulphur, oxygen and phosphorus at the interface. This tribofilm should be responsible for the lower rates of hydrogen permeation into the bearing steel.