Distribution and dissolution of WC particles in surface metal matrix composites produced by plasma melt injection

Surface metal matrix composites (MMCs) were produced by plasma melt injection of tungsten carbide (WC)–17%Co and crushed WC–8%Co particles. Distribution and dissolution of WC particles in the surface MMCs were investigated with an SEM. The results show that ball shaped WC particles are much easier to be injected into the melt pool, while crushed WC particles stay on top of the MMC layer. In a shallow melt pool of the single pass MMC, the carbides are evenly distributed. The WC particles in the second pass MMC that was produced when the substrate was hot sink downwards. More WC particles dissolve in the second pass MMC than in the single pass, while the crushed WC–8%Co particles dissolve only partially because the WC particles are large and they are on top of the melt pool.