Effects of load and sliding speed on the wear behaviour of plasma sprayed TiC-NiCrBSi coatings

The use of thermally sprayed coatings is a way of reducing wear and frictional losses. However, a limited number of studies have been done on the tribological behaviour of wear resistant coatings. Results of an investigation to evaluate the effects of some wear test conditions on air and vacuum plasma-sprayed (APS and VPS) TiC-NiCrBSi coatings using a pin-on-disk tribometer have been presented in this research. Room temperature tests varying the load and sliding speed have been performed in order to understand the effects of these parameters on the coatings' wear and friction behaviour. Results have shown that load, sliding speed, and the plasma spray process affect the wear resistance and the friction behaviour of thermally sprayed coatings considerably. Higher loads, during sliding, led to higher wear rates for both air and vacuum plasma sprayed coatings. In both systems, APS and VPS, the rate of change of total wear versus load was decreasing. Steady state coefficients of friction were constant with no major transitions in friction behaviours at all the studied loads. Higher sliding speeds led to decreased wear rates for both air and vacuum plasma sprayed coatings. In both systems a transition from a more severe to a milder form of wear seemed to occur at a point between 0.44 and 1 m/s. The trend of the average coefficient of friction during the tests was to decrease with sliding speed, especially after the break-in. VPS processing always resulted in higher wear resistant coatings than the APS coatings. (C) 1998 Elsevier Science S.A. All rights reserved.