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 180μm with few pores,and the average microhardness of the coating was about 1 300HV.The corrosion resistance of WC-CoCr coating was better than that of hard chromium coating in 3.5%(mass fraction)NaCl solution and 1mol/L HCl solution.However,the corrosion resistance of WC-CoCr coating was worse than that of hard chromium coating in1mol/L NaOH solution,which was due to the severe passivation of hard chromium coating.