Initial Formation of Reacted Tribofilms on Rough Surfaces Under Boundary EHL

Martin Webster, Spencer Stober, Andy Konicek, Peter W Jacobs, Gary Hunter & Fang Cao (ExxonMobil Corporate Strategic Research)

Simon Medina & Daniele Dini (Imperial Consulting)

Abstract
Tribofilms were formed in tests of steel, reciprocating boundary EHL contacts using model lubricants with single surface active additives.  The extent of tribofilm formation was evaluated post-test by Auger electron spectroscopy with approximately 200 nm X & Y resolution.  The state of contact and the locations of intimate contact were evaluated by elastic half space indentation calculations in combination with measured topography data of similar spatial resolution.  Tribofilm was seen to be correlated with asperities predicted to be intimate contact, but was also observed in areas thought to be outside of intimate contact.  Discussion of various possibilities for tribochemistry outside of intimate contact is discussed including that of stress induced tribochemistry occurring within the lubricant film.