Preparation and Property of Gradient Ni–W–ZrO2 Composite Coating on LY12 Alloy

Combining a technology of a composite coating and a new development idea of a functionally gradient deposits, a kind of novel gradient nickel–tungsten–zirconium dioxide (Ni–W–ZrO 2 ) composite coating was successfully prepared on LY12 alloy substrate by using concentration of sodium tungstate varying as 20 g/L, 50 g/L, 80 g/L, 120 g/L, 160 g/L, and 200 g/L in the bath. The results showed that the W content of as-deposited gradient Ni–W–ZrO 2 composite coating was gradually increased to 50.50 wt% along the coating growth direction, its structure transitioned from amorphous to crystal line, and the tungsten nickel (Ni 4 W) phase was precipitated after heat treatment at 400 °C for 1 h. In addition, the wear and oxidation resistance, and anti-corrosion of gradient Ni–W–ZrO 2 composite coating were generally enhanced with increase in heat treatment temperature. Moreover, the wear resistance, oxidation and corrosion resistance of gradient Ni–W–ZrO 2 composite coating achieved optimal values after heat treatment at 400 °C for 1 h for the gradient structure and high W content.