MOS2 tribofilm distribution from low viscosity lubricants and its effect on friction

Abstract The current study analyses the friction performance of low viscosity fully-formulated oils containing the Molybdenum Dialkyl Dithiocarbamate (MoDTC) friction modifier at different concentrations. The MoDTC friction modifier is known to produce MoS2 sheets in the tribocontact providing a low coefficient of friction under boundary lubrication conditions. However, there is a little knowledge around the quantitative relationship between the concentration of MoDTC in the oil and MoS2 amount and distribution in the contact. The study uses Raman spectroscopy mapping capability to characterise the tribofilm formed from different chemistry lubricants and under different tribological conditions as defined by the lambda ratio. After qualitative and quantitative chemical surface characterisation a discussion is presented to highlight some important aspects to relate the formed MoS2 sheets, their spatial distribution in tribofilms and the subsequent tribological performance.