Antiwear tribofilm growth in rolling bearings under boundary lubrication conditions

Zinc dialkyldithiophosphates (ZDDP) are applied as a lubricant additive for wear protection in rolling bearing applications. Chemical interactions between the additive and the bearing material lead to the formation of a tribofilm on the bearing surfaces in contact. In the present study, tribofilm growth is evaluated with cylindrical roller thrust bearings operated in the boundary lubrication regime. The influence of lubrication conditions and the slide roll ratio on tribofilm formation is studied in a bearing test rig. It is found that higher slide roll ratios hinder the tribofilm from growing at the beginning of a test and accelerate tribofilm growth after an initial film is formed.