Formation of Anti-Wear Films in Rolling Bearings due to Run-in Procedures

Rolling bearings are essential parts in most drive trains. Their improvement is required for further increase of reliability and efficiency of the entire system. One possibility to reduce friction losses is the use of lubricants with lower viscosity. This may lead to boundary friction conditions. An increased risk of wear exists under these conditions and can cause a premature failure. Therefore wear protecting additives are added to the lubricant to build up antiwear films. They are also called tribofilms. These films prevent rolling bearing contacts from adhesive wear and protect the interacting surfaces. Tribofilms are not formed under all operating condition. The prediction of their existence and performance is complex. In former studies Wolf [1] showed that tribofilms can be built up very fast in run-in processes. These tribofilms have high potential in wear protection under extreme boundary friction. A systematic investigation of run-in conditions corresponding to tribofilm build-up has not been done yet. Therefore the tribofilm composition due to run-in processes and their wear behavior is examined with cylindrical roller thrust bearings. Different run-in procedures are analyzed systematically. The benefits can be adopted for the later use in drive trains. This study is funded by the German Research Foundation (DFG) to find efficient run-in procedures, possibilities for environmental protection by lower additive concentration and a better understanding of antiwear film formation.