Microstructure and electrochemical properties of nanostructured WC-10Co-4Cr coating prepared by HVOF spraying

A nanostructured WC-10Co-4Cr coating was deposited on the substrate of AISI 1045 steel by means of high-velocity oxygen-fuel (HVOF) thermal spraying process. The detailed microstructures and phase composition of the coating were analyzed by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimeter (DSC) and high-resolution transmission electron microscope (HRTEM). It was revealed that the amorphous phase, nanoclusters and carbides, including W2C and WC were present in the coating. The coating with low porosity of 0.85% had a dense structure and good thermostability. The temperature of the amorphous phase transforming into the nanocrystalline structure was 645 °C. Corrosion behavior of the coatings was investigated by electrochemical measurement. The results showed that the coating exhibited better corrosion resistance than the hard chromium coating in 3.5 wt.% NaCl solution.