In Situ Raman Tribometry for the Formation and Removal Behavior of FeS2 Tribofilm in the Scuffing Process

We developed in situ observation and Raman analysis techniques for frictional interfaces and investigated the formation and removal behavior of the tribofilms that formed from a sulfur-containing extreme pressure (EP) additive on carbon steel. We detected an iron disulfide (FeS2) tribofilm peak during the friction test and simultaneously detected D and G bands attributed to graphite-like products. Once scuffing occurred, both the FeS2 peak and D and G bands disappeared. Therefore, the formation and removal of the tribofilm and carbonization of the additive were detected during the process that led to scuffing. We concluded that in situ Raman tribometry is an effective technique for investigating the formation process of tribofilms and the scuffing mechanism.