Electroless Nickel Deposition On WC-12Ni Powders And Study On Corrosion Resistance Of The HVOF Coatings

WC-Ni cemented carbide is one of the important wear-resistant and corrosion-resistant protective coating materials with their excellent comprehensive properties with combination of high strength and good toughness as well as the good heat resistance and corrosion resistance.Coating a nickel layer on the surface of sprayed cemented carbide powders is an effective way to improve the wettability between the reinforced hard phase and the metal matrix and reduce the decarburization of WC due to oxidation during thermal spray,thus improving the coating performance.In this work,electroless nickel coating of different thickness and N i-Mo S₂/WS₂ co-deposition on WC-12Ni powders were carried out and high-velocity oxygen-fuel(HVOF)were used to prepare the corresponding cemented carbide coatings on a stainless-steel substrate.The electrochemical corrosion behaviors of the coatings were characterized through measurement of the polarization curve,Mott Schottky curve and AC impedance spectroscopy.The influence of coated nickel layer thickness on the powder surface,ratio of fuel oil,solid lubricant addition as well as the nickel salt types used for electroless plating were discussed based on the experimental results.The experimental results showed that the thickness of coated nickel layer on the WC-12Ni powders,the type of electroless nickel plating salt,the doping of solid lubricant and the ratio of fuel oil all have important effects on the corrosion resistance of WC-Ni cemented carbide coatings.When the thickness of nickel coating is about 1.4?m,the ratio of oxygen flow rate 876 to kerosene flow rate22.7 is adopted for spraying,WS₂ solid lubricant particles are added,and acetate is used for electroless nickel plating,the corrosion resistance of the coatings is the best.The conclusion of the experiment can provide a useful experimental basis for the engineering application of nickel-coated cemented carbide powders.