Wear and Corrosion Properties of Crystalline Ni-W Alloy Coatings Prepared by Electrodeposition

Electroplating Ni-W coatings have been prepared on medium carbon steel substrate by using nickel sulphate and sodium tungstate as precursors. The microstructures, phase compositions and performances of the as-prepared coatings were analyzed by SEM, EDS, AFM, XRD, microhardness tester and wear tester, respectively. The surface morphologies after wearing were observed and the wear mechanism was discussed. The corrosion behaviors of the coatings before and after heat-treatments were evaluated by anodic polarization in 3.5% sodium chloride solution. The results show that no obvious flaws could be found in the Ni-W alloy coatings and there was a good bond with the matrix. The microhardness of the coatings increased with increasing heat treatment temperature, reaching its maximum value for heat treatment at 500°C, and then droped down. Wear resistance of the coatings was found to be better than that of 16 Mn steel and the heat treatment improved the hardness and wear resistance. The corrosion resistance of the heat-treated coatings increased with increasing the annealing temperature, and best corrosion resistance could be obtained at the temperature of 500°C.