Corrosion Behavior of WC-CoCr Coatings Prepared by High Velocity Oxygen Fuel Spraying

WC-CoCr coatings were fabricated on Q235 steel by high velocity oxygen fuel (HVOF) spraying. The phase composition, microstructure and microhardness of the coatings were analyzed by X-ray diffraction, scanning electron microscope and microhardness tester. Electrochemical tests were carried out to compare the corrosion resistance of HVOF sprayed WC-CoCr coating to that of hard chromium coating via a Parstat 2273 advanced electrochemical system. The results showed that WC-CoCr coating had a thickness of 180 μm with few pores, and the average microhardness of the coating was about 1 300 HV. The corrosion resistance of WC-CoCr coating was better than that of hard chromium coating in 3.5% (mass fraction) NaCl solution and 1 mol/L HCl solution. However, the corrosion resistance of WC-CoCr coating was worse than that of hard chromium coating in 1 mol/L NaOH solution, which was due to the severe passivation of hard chromium coating.