Modelling Friction Reduction Based on Molybdenum Disulphide Tribofilm Formation and Removal in Boundary Lubrication

Abstract

Molybdenum dialkyldithiocarbamate is a highly effective friction modifier lubricant additive in boundary lubrication, owing to the formation of a MoS2 nanosheet lattice structure that significantly reduces friction. The friction reduction behaviour is linked to the MoS2 amount and coverage buildup at the contacting interface, however, accurately predicting friction reduction based on a semi-deterministic model incorporating MoS2 formation and removal remains challenging. In this study, a Raman map collection methodology was developed for accurate quantitative analysis of MoS2 tribofilms. The growth rate of MoS2 tribofilms was determined by coupling tribochemical experimental data with sophisticated numerical models. A full numerical procedure was implemented under rubbing of two rough surfaces at different temperatures. The results demonstrated localised MoS2 tribofilms buildup. The friction coefficients show a close agreement with the measurements. The developed model can be adapted to diverse experimental setups and surface geometries.