High temperature oxidation behavior and mechanism of high-velocity arc sprayed FeCrNiAlBSi/Cr3C2 coating

Abstract

High temperature oxidation is mainly responsible for the damage of hot components in boiler tubes, and the application of protective coatings is the most effective solution. In the present study, FeCrNiAlBSi/Cr3C2 coating was deposited on AISI 1020 steel substrate via high-velocity arc spraying (HVAS) process. The high temperature oxidation performance of the coating was investigated at 550, 650, and 750 °C in the atmospheric environment. The phase composition, microstructure, surface and cross-sectional morphology of the coating were characterized by means of x-ray diffraction (XRD), optical microscope (OM) as well as scanning electron microscopy (SEM) which equipped with energy-dispersive spectroscope (EDS), respectively. Oxidation kinetic curves that established by thermo-gravimetric technique were used to evaluate high temperature oxidation mechanism. The results showed that the kinetic curves of the coatings oxidized at different temperatures conformed to the classic parabolic law, and the coatings exhibited much better high temperature oxidation resistance as compared with bare AISI 1020 steel. The coating oxidized at 750 °C showed the largest values for mass gain/area and parabolic rate constant (kp) of 2.86 mg cm−2 and 8.11 × 10–12 g2·cm−4·s−1. As testing temperature increased from 550/650 °C to 750 °C, the oxidation products for the coating transformed from Fe2O3 and Cr2O3 to FeCr2O4. The formation of Cr2O3 and FeCr2O4 may well explained why the FeCrNiAlBSi/Cr3C2 coating exhibited excellent high temperature oxidation resistance.