Friction and wear behaviour of composite MoS2-TiO2 coating material in dry sliding contact

Molybdenum disulphide (MoS2) is widely used in tribological applications because of its solid lubricating properties. However, its performance needs to be further improved. In this work, an attempt has been made to improve the tribological performance of MoS2 coating by incorporating TiO2 nanoparticles as a reinforcement material into the MoS2 base matrix. The effects of crystallite size and wt.% addition of TiO2 onto the tribological properties of composite MoS2-TiO2 have been studied. Prior to application of the coating onto the substrate surface, it was pre-treated by phosphating which leads to improvement in the porosity and helps to enhance the bond strength between the coating and steel substrate. A tribological study of composite pure MoS2 coating and MoS2-TiO2 coating was carried out using the pin-on-disc test rig at different operating conditions (contact pressure, speed and temperature). It was observed that composite MoS2-TiO2 coating exhibits excellent tribological properties as compared to pure MoS2 coating. In addition, crystallite size of TiO2 and its different weight% significantly affect the tribological properties of the composite coating. Among all samples of composite MoS2-TiO2 coating, the sample C (27.69 nm crystallite size) with 15% wt. of TiO2 depicts the lowest friction coefficient and wear rate. The influence of temperature and coating thickness on the tribological properties of composite coating has been studied. The frictional coefficient has been reduced, and the wear rate increased with an increase in temperature of the coated pin surface. The similar kind of trend has been observed with respect to the coating thickness.