Influences of iron and iron oxides on ultra-thin carbon-based tribofilm lubrication

A molecular dynamics (MD) simulation was used to investigate the influences of iron/iron oxide surface on the lubrication and tribochemistry of C-based tribofilms mixed with cyclopropane carboxylic acid (CPCa). The results revealed that the best tribological performance was found for mixed 1-decene lubricant confined between iron surfaces. In contrast, Fe3O4 was the most beneficial surface for C-based tribofilm formation as this surface resulted in the most significant number of species and molecules, as well as the largest portion of short C-chain molecules, which are intermediate products generated in C-based tribofilm growth. Interestingly, iron oxides resulted in a larger dissociation rate of C−C and C–H bonds than iron in the current thin-film lubrication. The degree of polymerization, reflected by the number and size of polymerized molecules, increases with CPCa concentration on a pure iron surface, while it decreases with an iron oxide surface.