Influence of the chemical composition and local atomic packing of nanostructured MoS$_x$ and MoSe$_x$ solid lubricant coatings on their tribological properties under complicated conditions

The results of a comparative study of the friction and wear of MoS$_x$ and MoSe$_x$ thin film coatings that was carried out in an oxidizing medium (a mixture of argon and air) at a temperature of -100$^{\circ}$C are presented. The films were obtained by pulsed laser deposition from MoS$_2$, MoSe$_2$, and Mo targets in vacuum and H$_2$S. It was established that Se-containing coatings significantly exceeded the S-containing coatings in terms of wear resistance and provided a friction coefficient of $\sim$0.09. The properties of MoS$_x$ films depended on the S concentration, which determines the local packing of atoms in the amorphous structure of the film. The coefficient of friction for MoS$_3$ films after running-in turned out to be half as much as that for MoS$_2$ films, and its value was 0.08.