Numerical Study of the Effect of Tribofilm Kinetics and its Hardness on the Roughness Evolution of the Substrate in Boundary Lubrication Regime

A tribochemical modelling framework that considers the growth of tribofilm on the contacting surfaces has been used in this work. The model couples a fast contact mechanics model with the thermodynamics of interfaces and captures the growth of the tribofilm on the asperities. The model was shown to be able to capture the dynamics of a tribosystem and the evolution of surface topography. The model considers the effect of plastic deformation and wear in modifying the surface geometries. In a recent work of the authors, (Ghanbarzadeh et al. in Wear 2016) the same numerical model was validated against experiments of the Micropitting Rig (MPR) and the wear, topography and tribofilm thickness results were compared. In this work, while the validation of the model is presented, the effect of tribofilm kinetics and its hardness have been numerically studied to assess the evolution of surface roughness in a rolling sliding contact. Results suggest that the kinetics of the tribofilm growth significantly influences the roughness evolution with higher kinetics resulting in a rougher interface. Similarly the tribofilm hardness affect the roughness evolution and are more influential in the later stages of roughness evolution.