Wear behaviour of silicon carbide / electroless nickel composite coatings at high temperatures
Résumé
The present paper reports the results obtained from sliding wear tests performed at both room temperature and high temperature (100 and 300°C) on silicon carbide/nickel composite coatings annealed at 400°C in argon. The coatings were deposited industrially on AISI 1020 steel discs by using a proprietary self catalysing chemical reduction process (Hardex). The tests were conducted without lubrication in argon, employing a ball on disc tribometer. A load of 5 N was used at a constant sliding speed of 0·1 ms-1. The mating pair was an alumina ball of 6 mm diameter. For the tests performed at 25°C, the effect of heat treatment contributed to an improvement in the coating wear resistance of nearly 135%, when compared to the as deposited conditions. It was determined that the set of the experimental conditions for the wear test performed at high temperature, i.e. the load used, the nature of the mating surface, and the low velocity of the test, added to a small coating thickness to particle size ratio, created very severe conditions, which caused coating removal. Wear rates nearly 23 and 11·6 times larger were obtained for the heat treated coatings tested at 100 and 300°C, respectively when compared with the wear resistance of the heat treated coatings tested at 25°C.