Sliding wear behavior of the supersonic plasma sprayed WC-Co coating in oil containing sand

To improve the wear resistance of the cylinder liner of the engines operating in desert area, the tungsten carbide-based cermet coating (WC-12wt.%Co) was produced using the supersonic plasma spraying technique. The microstructure and phase composition of the as-sprayed coating were evaluated. The effect of sand size in lubricant on the friction and wear behavior of the coating under the lubrication of oil containing sand was investigated on a ball-on-disk tribometer. Characterization of the coating shows that the coating possesses dense microstructure with low level of porosity. The decarburization of WC is limited for the high particle velocity of the supersonic plasma spraying and only a few of W2C phases are observed in the coating. With the higher hardness and the good adhesion with the substrate the sprayed coating exhibits a better wear resistance compared with the gray casting iron used in the current cylinder liner. Micro-structural examination shows that the wear of coating is dominated by micro-cutting, WC particles pull-out and sub-surface indentation-induced sub-surface cracking, while the main wear mechanism of the gray casting iron is micro-cutting and plastic deformation. (C) 2008 Elsevier B.V. All rights reserved.