Tribofilm formation and characterization of lubricating oils with biofuel soot and inorganic fluorides

A series of tribological experiments have been conducted to characterise and study the formation of tribofilms derived from TiF3 and FeF3 catalysts impregnated in soot-contaminated lubricants. Results showed that inorganic fluorides reduced friction and wear in the specimen contaminated lubricants. With the best results observed when TiF3 was used. There were also indications that the frictional process, when coupled with the fluorides induced a structural change in the soot particles within the contact zones, contributing to the improved tribological performance. The key contributors to the formation of robust tribofilms were adsorption and tribo-chemical reactions. The better tribological response leads to a method for the design of engine lubricants to mitigate against the effects of soot contamination. •Tribological properties of inorganic fluoride derived additives investigated.•TiF3 and FeF3 dispersed in a liquid paraffin base oil and formulated lubricant.•Additives reduced friction and wear in soot contaminated lubricant.•Fluorides assisted in the formation of robust tribofilms, TiF3 produced best results.•Friction coupled with additives changed the structure of the soot particles.