Wear and corrosion mechanisms of Ni-WC coatings modified with different Y2O3 by laser cladding on AISI 4145H steel

In order to evaluate the effect of rare earth Y2O3 on the wear and corrosion properties of WC-Ni composite coatings, X-ray diffraction, scanning electron microscopy(SEM), electrochemical polarization curve, electrochemical impedance spectroscopy (EIS), and friction and wear tests were used to analyze the metallographic structure, corrosion characteristics in simulated seawater and friction and wear principle of the composite coatings. Results of SEM revealed that the microstructure of the Y2O3 added coatings was refined with the grains changing smaller and the impurity disappearing. The EIS results proved that the addition of Y2O3 brought a positive influence on the corrosion resistance by reducing the capacitance and increasing the R (f) and R (c). The hardness of the coatings with Y2O3 addition tends to be smooth without wild fluctuation, and the coating with 0.5 wt% Y2O3 owned the hardness values reaching 850 HV. With the addition of rare earth elements, the coefficient of fiction values decreased, reaching the lowest (0.3418) at the content of Y2O3 of 0.5 wt%. The surface of the coating without Y2O3 appears grooved due to the abrasive wear; the coatings with Y2O3 did not suffer serious wear and tear. The coating with 0.5 wt% Y2O3 exhibited the best corrosion resistance and wear resistance properties in all the specimens.