Composition and structure-property relationship of low friction, wear resistant TiN-MoSx composite coating deposited by pulsed closed-field unbalanced magnetron sputtering

Effect of MoSx content has been studied in TiN-MoSx composite coating deposited by closed-field unbalanced magnetron sputtering (CFUBMS) using separate MoS2 and Ti target in N-2 gas environment. Pulsed dc power was applied for both the targets as well as for substrate biasing. Crystallographic orientation and structure of the coating was analysed by grazing incidence X-ray diffraction (GIXRD) technique. The surface morphology and coating fractograph were studied with field emission scanning electron microscopy (FESEM) whereas the composition of the coating was determined by energy dispersive spectroscopy (EDS) by X-ray. Scratch adhesion test, Vickers microhardness test and pin-on-disc test with cemented carbide (WC-6%Co) ball were carried out to investigate mechanical and tribological properties of the coating. Increase in MoSx content (from 6.22 wt.% to 30.43 wt.%) was found to be associated with decrease in grain size (from 63 nm to 24 nm). Maximum hardness of 32 GPa was obtained for TiN-MoSx composite coating. Film substrate adhesion was also observed to depend on MoS. content of the composite coating. Significant improvement in tribological properties was observed. With optimal MoSx content, it was possible to achieve low friction (mu=0.02-0.04) and wear resistant (wear coefficient=5.5 x 10(-16) m(3)/Nm) composite solid lubricant coating. (C) 2008 Elsevier B.V. All rights reserved.