Solid lubricant behavior of MoS and WSe-based nanocomposite coatings.

Tribological coatings made of MoS and WSe phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30-40% relative humidity, RH) and dry nitrogen (RH<7%) environments using the same tribometer and testing conditions. A nanostructural study using advanced transmission electron microscopy of the initial coatings and examination of the counterfaces after the friction test using different analytical tools helped to elucidate what governs the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSe film (specific wear rate of 2 × 10 mm Nm and a friction coefficient of 0.03-0.05) was compared with that of the well-established MoS lubricant material.