Sliding wear behavior of tungsten carbide thermal spray coatings for replacement of chromium electroplate in aircraft applications

Tungsten carbide (WC) thermal spray coatings have gained increased acceptance for commercial aircraft applications driven by the desire to replace chromium electroplate due to environmental and economic considerations. In order to confidently replace electroplated chrome with WC thermal spray coatings in aircraft applications, the coatings must demonstrate fatigue and wear characteristics as good as or better than those of electroplated chrome. Previous research in this area has shown that the fatigue life of the WC thermal spray coatings can be improved by inducing compressive residual stresses in the coating. This paper compares the wear characteristics of several types of WC thermal spray coatings with those of electroplated chrome in sliding wear tests using the “block-on-ring” procedures described in the ASTM G77 standard. Wear results are interpreted in terms of coating residual stresses and in terms of x-ray diffraction (XRD) and scanning electron microscope (SEM) analyses.