Influence of laser structural patterning on the tribological performance of C-alloyed W-S coatings

In this paper, we are proposing for the first time the partial laser treatment of a self-lubricating coating in order to optimize its frictional performance from the very first moments of the sliding contact. W-S films alloyed with carbon were deposited by closed field unbalanced magnetron sputtering. The coatings were treated using two types of lasers, with peak emissions in the UV and IR, under different laser power conditions and patterning. The structure, mechanical and tribological properties of the treated coatings were analysed using X-ray diffraction (XRD), Raman spectroscopy, nanoindentation and reciprocating ball-on-disk tribometry. Although XRD diffractograms illustrated an overall amorphous structure in all as-deposited and treated samples, their Raman spectra confirmed the presence of WS2 crystalline phase in some of the treated areas. Furthermore, in the samples where WS2 Raman peaks were detected, the friction coefficient was in the initial part of the test lower than that of untreated coating. Previous crystallization of the W-S phase before tribological testing has a key role for shortening the self-adaption process improving the overall friction performance of the coatings.