Tribofilm

Tribofilms (boundary lubricant films,^[1] boundary lubricating films,^[2] tribo-boundary films^[3] or boundary films^[4]) are films that form on tribologically stressed surfaces. Tribofilms are mostly solid surface films that result from a chemical reaction of lubricant components or tribological surfaces.

Tribofilms play an important role in reducing friction and wear in lubricated systems. They form as a result of complex mechanochemical interactions between surface materials and lubricants,^[5] and the study of tribofilm formation processes is a major field of tribology.

Generally, a tribofilm is any film that forms in a tribosystem "as a result of interaction between chemical components of the [lubricant] with the lubricated surface".^[6] The term is mostly used to describe strongly bound films that are formed on tribologically stressed surfaces, such as tribochemical reaction films^[1] (for example produced by ZDDP-containing lubricants^[7][8]) or polymeric and non-sacrificial reaction films (for example formed by complex esters).^[1]