Microstructure and Properties of Ni60/WC-10Co4Cr Composite Coatings by High Velocity Air Fuel Spraying

Ni60/WC-10Co4Cr composite coatings were prepared by high velocity air fuel spraying with air as combustion gas by taking Ni60 alloy powder and WC-10Co4Cr powder as raw materials. The microstructure, abrasive wear resistance and corrosion resistance of the coatings with different mass fractions (20%, 40%, 60%) of WC-10Co4Cr were studied and were compared with those of the electroplated hard chromium layer. The results show that Ni60/WC-10Co4Cr composite coatings were composed of nickel-based solid solution (NiCr), chromium carbides (Cr₂₃C₆ and Cr₇C₃), borides (Cr₂B) and WC. The coatings were tightly bonded to the substrate, and the porosity was lower than 1%. With the increase of the content of WC-10Co4Cr, the content of hard WC phase and the hardness of the composite coatings increased, and the abrasive wear volume loss decreased significantly, indicating that the abrasive wear resistance increased. With increasing content of WC-10Co4Cr, the free corrosion potential decreased, and the free corrosion current density increased, indicating the corrosion resistance decreased. The composite coating with 60wt% WC-10Co4Cr had the best performance; its wear resistance was equivalent to that of electroplated hard chromium layer, its corrosion resistance was better than that of electroplated hard chromium layer, and its hardness was slightly lower than that of electroplated hard chromium layer. It was feasible to replace electroplated hard chromium layer with this coating with 60wt% WC-10Co4Cr.