Examination of the tribolayer formation of a self-lubricant W–S–C sputtered coating

A W–S–C self-lubricating coating was deposited by d.c. magnetron sputtering from carbon and tungsten disulfide targets on steel substrates. The coating showed a carbon content of 42 at% and a S/W ratio of 1.26. The film was characterized (structure, hardness, adhesion) and tribologically tested using a pin-on-disk device. The load and number of cycles were varied and the corresponding wear tracks were thoroughly investigated by several techniques. Moreover, the wear tracks were monitored with Raman spectroscopy including in-situ measurements. The W–S–C coating exhibited friction and wear decreasing with the applied load. It has been demonstrated that the running-in process is related with changes in the Raman spectra on the wear tracks.