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

Abstract

MoS 2 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 MoS 2 solid film lubricant is investigated using a pin-on-disk tribometer. MoS 2 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 MoS 2 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 MoS 2 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 MoS 2 film was also conducted.

Tribological Properties of 2D Materials and Composites—A Review of Recent Advances

“…Solid-film lubrication is highly dependent on the environment. The chemical and physical interactions between the film and the surrounding environment greatly affect the tribological performance [ 43 , 44 , 45 ]. Table 2 shows the effect of some environmental factors such as humidity and temperature on the lubricating properties of some of the widely used solid lubricants.…”

“…The solid-lubricating properties of these transition materials are known to deteriorate due to the adsorption of atmospheric humidity, the presence of oxygen, and at higher temperatures [ 43 , 102 , 103 ]. Studies have reported an increase in friction at room temperature due to adsorption of water, which notably does not promote oxidation of MoS 2 .…”