Plasma remelting and injection method for fabricating metal matrix composite coatings reinforced with tungsten carbide

Tungsten carbide (WC) reinforced metal matrix composites are ideal protective coatings against wear and are widely used for surface coating. However, WC particle dissolution, subsidence, and coating cracking are some of the known challenges limit the application of the coating fabricated by plasma cladding with traditional synchronous feeding. To address this issue, a plasma remelting and injection (PRI) method is proposed to fabricate WC reinforced metal matrix composite coatings. The optimal injection angle of the WC particles was determined by infrared image and geometric calculations, to improve the utilization rate and decrease the dissolution of the particles. The microstructure, hardness, residual stress, and WC particle distribution of the coatings fabricated by the PRI and synchronous-feeding methods were investigated, and the mechanism of WC particle dissolution was analyzed. The results indicate that the WC particles of the synchronous-feeding coating obviously sank to the coating bottom, and transcrystalline cracks appeared inside the WC particles, resulting in serious cracking of the coating. By contrast, the PRI method could effectively avoid the subsidence of WC particles and reduce the thermal damage to WC particles, which increased the coating surface hardness and reduced the residual stress and cracking tendency of the coating.