Preparation and characterisation of low-friction TiB2-based coatings by incorporation of C or MoS2

Hard, low-friction, TiB2-based coatings incorporating C or MoS2 have been synthesised by magnetron co-sputtering from TIB2 and C or MoS2 targets. The coating microstructure was characterised by glancing angle X-ray diffractometry and photoelectron spectroscopy. The friction coefficient was measured using pin-ore-disk tribometry and hardness by nanoindentation. Our TiB2-C coatings were found to consist of two phases, diamond-like carbon (DLC) and a hexagonal TiB2 type structure into which carbon is incorporated. A friction-reducing effect was observed only at C concentrations above 66%, where a significant quantity of DLC phase was able to form. For TiB2-MoS2 coatings, a reduced friction was observed, even at low concentrations of MoS2. With both types of lubricants, a trade-off between hardness and friction coefficient was found. Coatings exhibiting a relatively high hardness of 20 GPa and friction coefficients as low as 0.05 could be obtained by choosing a suitable composition. Low friction could be obtained for temperatures as high as 400 degrees C for the TiB2-MoS2 coatings, whilst the TiB2-C coatings exhibited a sharp increase in friction coefficient above 150 degrees C. (C) 1998 Elsevier Science S.A.