The influence of HVOF powder feedstock characteristics on the abrasive wear behaviour of CrxCy-NiCr coatings

CrxCy-NiCr cermet coatings are commonly utilised in industry as a means to provide wear resistance in high temperature environments. Such coatings are usually deposited by thermal spraying. In this work, CrxCy-NiCr coatings h ave been deposited using a Miller Thermal/UTP Top Gun high velocity oxy-fue l spray system from three commercially available powders, namely a sintered and crushed powder, a blended powder and a composite powder. The character istics of the powder feedstock have a strong influence on the coating micro structures, although the coating microstructure is often very different to that of the powder due to processes that occur during spraying and rapid so lidification of the splats. Coating microstructures were assessed by X-ray diffraction, scanning electron microscopy and microhardness measurements. The abrasive wear performance of the coatings was assessed using a dry sand -rubber wheel test with both alumina and silica abradents. It was found tha t, under all conditions, the coating deposited from the blended powder exhi bited the highest wear rates and the coating deposited from the composite p owder exhibited the lowest wear rates. Wear mechanisms were assessed by SEM examination of the wear surfaces and cross-sections through the wear scars and understood in terms of the different coating microstructures. (C) 2001 Elsevier Science B.V. All rights reserved.