Tribochemical Interactions of Moly Dimer and ZDDP Additives With CrN Coating and Bearing Steel While Sliding Against Cast Iron in Boundary Lubrication Conditions

In recent years, use of low friction non-ferrous coatings under boundary lubrication condition has become a challenge to meet the increasing demand of fuel economy in automotive applications. In this study, chromium nitride (CrN) was chosen as a non-ferrous coating and experiments were performed in a pin-on-plate reciprocating tribotester to produce the tribofilm. An atomic force microscope (AFM) was used to record high resolution topographical images while chemical analysis of the tribofilm was performed using X-ray photoelectron spectroscopy (XPS). Both AFM and XPS analyses give evidence of the formation of ZDDP and Moly Dimer derived tribofilm. This paper will also focus on the synergistic or antagonistic effect of ZDDP with Moly Dimer additive in the tribological performance of CrN coating.