A new type of tribological coating for machine elements based on carbon, molybdenum disulphide and titanium diboride

In this study, solid lubricant films containing molybdenum disulphide, carbon, and titanium diboride (MoS2:C:TiB2) were deposited onto steel substrates by a non-reactive d.c. magnetron sputtering process. Adhesion was examined as a function of sputter-etching parameters and design of the interface between TiB2 intermediate layer and MoS2:C:TiB2 top layer. Optimum adhesion was achieved by a short sputter etching process at high r.f. power in combination with a smoothly graded interface. The tribological behaviour of the optimized coating was then examined at ambient air in dependence of relative humidity (RH). The friction coefficient turned out to be nearly independent of RH. The wear rate at low RH was about 5×10−8 mm3/Nm. However, wear rate increased significantly with RH.