Microtribological performance of Au–MoS2 nanocomposite and Au/MoS2 bilayer coatings

Scratch tests, reciprocating microwear, and scanning wear tests were performed on pure Au, bilayer Au/MoS2, and co-sputtered Au–MoS2 using a nanoindentation instrument in dry air. These different lubrication strategies (i.e. nanocomposite and bilayer coatings) were compared in terms of mechanical properties, friction coefficient, and wear behavior. The results were correlated to the tribofilm formation, which was analyzed using ex situ characterization of the wear track with a Scanning Electron Microscope (SEM), micro-Raman spectrometer, and an atomic force microscope (AFM). It was observed that the nanocomposite Au–MoS2 coatings increased the wear resistance compared to pure Au films, which was explained by the increase in hardness values and the decrease in surface adhesion forces. Similarly for bilayer Au/MoS2 samples, the wear resistance of the Au film was enhanced by the MoS2 top layer, which behaved as a sacrificial layer protecting the Au. ► We investigate two lubrication strategies to improve the microtribological properties of Au. ► Three different microwear experiments helped connect wear resistance to mechanical properties or third body formation. ► Ex situ characterization with SEM and micro-Raman revealed importance of third bodies. ► Nanocomposite Au–MoS2 coating had increased hardness and wear resistance compared to pure Au. ► Sacrificial MoS2 layer on top of the Au increased the wear resistance due to third bodies.