TEM and nanomechanical studies on tribological surface modifications formed on roller bearings under controlled lubrication conditions

The chemical composition and microstructure of reaction layers formed under the presence of lubricants with low wear protection, high wear and fatigue protection, and high wear but low fatigue protection on thrust cylindrical roller bearings made of 100Cr6 steel were analysed by transmission electron microscopy. Thin cross sections prepared by the focused ion beam technique were investigated. The nanomechanical properties of the different tribological layers were analysed by static and dynamic nanoindentation. Our results indicate that wear protection not only relies on the lubricant induced formation of a reaction layer, but also on the properties of the combined system of a reaction layer and an underlying tribomutation layer. The formation and structure of the layer system varies with the chemical nature of the basic oil. Our investigations show that its ability to protect against wear and fatigue strongly depends on the oil viscosity and the additives.