Correlation between performance and boundary layers in high speed bearings lubricated with polymer-enhanced greases

In this paper the effect of greases enhanced with polymer additives on the tribological behavior of high speed angular contact bearings is investigated. Bearing test results indicate lower operating temperatures for grease enhanced with dispersing polyalkylmethacrylate in relation to plain reference grease. The effect of the additives on the boundary layers was investigated by means of nano indentations on the raceways. It could be shown that the loading–unloading curves differ significantly, depending on the nature of the reaction/boundary layers on the raceways. Additionally, ToF-SIMS with depth profiling (time of flight secondary ion mass spectroscopy) helped to analyze the composition of the boundary layers. The profiling showed significantly different reaction layers with beneficial layers resulting from grease enhanced with dispersing PAMA.