Oxidation behavior of T92 steel with NiCoCrAlY coating by EB-PVD

Oxidation behavior of NiCoCrAlY coating on T92 steel was investigated in this study. NiCoCrAlY coating was fabricated on T92 steel by electron beam physical vapor deposition (EB-PVD). Isothermal oxidation test was performed at 650 °C for about 300 h. X-ray diffraction (XRD) was employed to characterize the phases in the coating. Scanning electron microscopy (SEM) with energy dispersive spectrum (EDS) was adopted to analyze microstructures and element distribution. Micro-hardness test and high temperature erosion wear test were also done for detecting the properties of T92 steel and substrate with NiCoCrAlY coating. The results showed that the oxidation weight gain of T92 steel and substrate with NiCoCrAlY coating were 1.119 mg/cm2 and 0.325 mg/cm2, respectively. Fe2O3 and Fe3O4 were found on T92 substrate surface, while Al2O3 and Cr2O3 formed on NiCoCrAlY coating surface after oxidation at 650 °C. Elements between coating and substrate diffused during oxidation. The wear rates of T92 substrate and coating of high temperature erosion wear test were respectively 27.82 mg/cm2 and 1.51 mg/cm2. Micro-hardness of T92 steel with coating was about 270 HV. Depositing NiCoCrAlY coating on T92 steel can effectively improve the oxidation resistance.