Influence of Heat Treatment on Microstructure and Corrosion Resistance of Ni-Co Alloy Coating

The Ni-Co alloy coating on Q235 steel surface was prepared by pulse electroplating, and the coating was heat treated at temperature of 300 ℃-500 ℃. Influences of heat treatment on microstructure, hardness and corrosion resistance in3.5%(mass fraction) Na Cl solution of Ni-Co alloy coating were studied by SEM, XRD, hardness meter, and electrochemical analyzing, respectively. The results show that the as-deposited coating consists of nanocrystalline, which possesses higher hardness(605.5HV) and better anticorrosive property. With the increase of heat treatment temperature, the grains of the coating grow and its hardness decreases gradually, but the corrosion resistance performance of the coating first decreases and then increases. After being heat treated, there exists elements diffusion in interface between deposit and matrix, which is useful in improving the interface binding strength and the fatigue resistance of the coating.