Effect of Humidity on Friction of Molybdenum Disulfide Films Produced by Thermal Evaporation on Titanium Substrates

MoS2 is one of the most advanced solid lubricants that have been used in many machineries. In this work, the effect of humidity on the friction of MoS2 solid film lubricant is investigated using a pin-on-disk tribometer. MoS2 film was coated by a thermal evaporation method on a titanium substrate. Steel and aluminum pins were used for the evaluation of friction coefficient of MoS2 films using a tribometer. The tests showed that with an increase in humidity, the coefficient of friction also increased. In practical applications at high humidity levels, the MoS2 films could be covered by condensed water molecules. Therefore, an experiment to understand the effect of water film on the variation of friction coefficient was also conducted. The results showed that the coefficient of friction remained constant for experiments using both aluminum and steel pins, and then the coefficient of friction increased once the water film was evaporated by the heat generated due to friction. An optical and XRD characterization of the MoS2 film was also conducted.