High-temperature oxidation behavior of HVOF-sprayed rare earth-modified WC–12Co coating

In this study, the CeO2-modified WC–12Co coatings were deposited on Q345 steel substrate using high-velocity oxygen fuel (HVOF) spraying. Oxidation behavior of the modified coatings was analyzed in the range of 450–900 °C for different oxidation time to investigate the effects of oxidation time and temperature on the coatings. The oxidation kinetics and oxidation mechanism of the modified coatings were clarified. The results show that the oxides are mainly composed of WO3 and CoWO4 within 450–750 °C while the phases are different at 900 °C. The CeO2-modified coatings have good oxidation resistance when the oxidation temperature is below 550 °C and the oxidation mechanism changes due to the occurrence of anomalous oxidation above 650 °C. Moreover, the oxidation mass gain curves obey approximately a parabolic law in the temperature range of 450–650 °C at the initial stage but the later oxidation proceeds by a linear law. In addition, based on the analysis of micromorphology and component of the prepared coating, the role of rare earth (RE) additives is obtained during high-temperature oxidization.