Effect of microstructure and micromechanics on wear/wear-corrosion mechanism of laser-repaired Ni-WC coating

Repairing drilling tools with laser cladding technology becomes a meaningful way to reduce costs and increase efficiency. The relationship between the wear/wear corrosion mechanism and micromechanics of laser-repaired Ni-WC coating was investigated. It is found that the received Ni-WC coating was mainly composed of γ-Ni, WC, W2C, and a small amount of CrC and MoC. In dry environment, the surface fatigue crack gradually propagates and develops along the surface as the load increases, forming a peeling phenomenon on the surface. Conversely, the water film was formed as lubrication to reducing the formation of peeling in wet environment. It is found that the wear and damage of the laser-repaired Ni-WC coating in wet environment is lower than that in dry environment. The effect of water film and water cooling on wear of the laser-repaired Ni-WC coating is higher than that of corrosion. In addition, a thin oxide interfacial layer is found under dry sliding at the boundary of WC particle with the maximum width of about 3 μm, leading to low microhardness (H) / elastic modulus (E) of the oxide interfacial layer, which weakens the wear resistance of WC particles in laser-repaired Ni-WC coating.