Microstructure and Electrochemical Properties of Cr₃C₂-NiCr Coating and Nickel-based Coating by HVOF Spraying

Cr3C2-NiCr coating and nickel-based coating were prepared on Q235 steel by high velocity oxy-fuel (HVOF) thermal spraying, the microstructures of coatings were analyzed by scanning election microscopy(SEM). The corrosion resistance of the two as-sprayed coatings in the solution of mass fraction of 3.5%NaCl was evaluated by the electrochemical method. The result showed that the Cr3C2-NiCr coating exhibited high consistency and a layered structure, the carbides evenly distributed among the matrix. The carbides in nickel-based coating had smaller particles size and they evenly distributed among the matrix too. The porosity of Cr3C2-NiCr coating and nickel-based coating was 1.6%, 1.1% respectively. The electrochemical impedance spectroscopy (EIS) data and polarization curve indicated both of the two coatings had a quite good corrosion resistance in 3.5%NaCl solution. In comparison of Cr3C2-NiCr coating, nickel-based coating had a better corrosion resistance.