Component Selection and Nano-Structuring of WS2/MoS2/a-C Thin-Film Coatings for Reduction of Sliding Friction in Difficult Conditions

The possibility of forming new solid-lubricating thin-film coatings consisting of nanosized layers of WS2, MoS2, and amorphous carbon (a-C) with improved antifriction properties is studied. To control the tribological properties of coatings, the conditions for obtaining layers of 2H-WS2 and 2H-MoS2 with a thickness of 5–20 nm with a crystalline laminar structure with a basal orientation to the substrate are determined. Nanolayers are created by reactionary pulsed laser deposition from metal and metal oxide targets in hydrogen sulfide at elevated temperatures. It is shown that, when alternating the deposition processes of the selected materials, no noticeable solid-phase reactions are observed at the interfaces. Tribological tests were carried out at room temperature using the method of sliding a steel ball over a coated disk without lubrication in an atmosphere enriched in nitrogen (relative humidity of ~9%). The structural state of the coatings before and after tribological testing is studied using Raman scattering of light. The lowest friction coefficient of ~0.015 is found for WS2 coatings deposited at 500°C. The tribological properties of the MoS2 coatings turn out to be much worse. The coating consisting of WS2 and carbon nanolayers has a slightly higher friction coefficient (0.021), but it has the best wear resistance.