Hydrogen assisted rolling contact fatigue due to lubricant degradation and formation of white etching areas.

Abstract RCF tests were conducted on bearings lubricated with three different lubricants: a gearbox oil, a MAC fluid and PFPE oil. The decomposition of the MAC fluid and PFPE was investigated by FTIR and NMR. Gearbox oil tests showed flaking and networks of subsurface cracks with partial intercrystalline crack growth. Cross-sectional analysis revealed the formation of WEAs. FEM correlated the damage with stress fields. The results of the MAC lubricated tests showed surface flaking and intercrystalline crack growth in the subsurface. The PFPE lubricated bearings showed no signs of hydrogen induced damage. Post-experimental hydrogen analysis of the bearings indicated an increased hydrogen concentration in the samples lubricated with the gearbox oil and MAC compared to those lubricated with PFPE. Highlights • Post RCF hydrogen analysis showed concentration variation with various lubricants. • Hydrogen evolution in RCF tests was associated with lubricant decomposition. • The levels of hydrogen in bearings was correlated with damage telltale signs. • Failure patterns were correlated to stress fields obtained from FEM. [ABSTRACT FROM AUTHOR]