Effect of WC content on the interface microstructure of nickel/tungsten carbide composite brazing coating

Nickel/tungsten carbide composite coating has high wear resistance, corrosion resistance, and high hardness characteristics. It is widely used in shield machine parts, rotary blade, and other fields. In order to improve the lifespan of the hydraulic machinery overflow components, the nickel/tungsten carbide composite brazing coating was successfully prepared. It was combined with the surface of austenitic stainless steel by brazing coating method with thermal radiation in vacuum furnace. In the joint, WC particles and nickel-based powder brazing alloys were used as coating materials. The microstructure and interfacial behavior of the brazing coating were analyzed with the scanning electron microscopy, X-ray diffractometer, and metallographic microscopy. The results show that the interface between WC hard-phase and nickel-based brazing alloy achieved mechanical and metallurgical bonding. There is certain component diffusion between the brazing coating and steel substrate. And the thickness of narrowest diffusion area is about 100 μm. When the WC content is lower than 25wt.%, the brazing coating has better wettability on the steel substrate. The internal denseness of the coating stays in high level. Meanwhile, the minimum porosity in the composite coating can be kept at 1.08%.