Oxidation resistance of iron-based coatings by supersonic arc spraying at high temperature

The high-temperature oxidation behavior of three kinds of iron-based coatings prepared by supersonic arc spraying (HVAS) was investigated in this paper. The characterization of the microstructures, surface morphologies and chemical compositions for the coatings before and after high temperature oxidation at 800 °C and 900 °C were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscope (EDS) and X-ray diffraction (XRD). It was illustrated that the FeCrAlTiCRE coating had the best high temperature oxidation resistance among the three coatings. After high-temperature oxidation, a dense and compact oxide layer was formed on the surface of FeCrAlTiCRE coating, which was composed of Cr2O3 and Al2O3. The oxide film of FeCrAlTiCRE coating was mainly composed of Fe2O3 after 100 h oxidation at 800 °C, while it was of Fe3O4, Cr2O3 and Al2O3 after exposure at 900 °C for 100 h. The oxide film formed on the surface of FeCr(C, RE) coating was mainly composed of Cr2O3 and spinel crystal FeCr2O4 which also showed protective effect for the coating at high temperature. The oxide layer on the Fe(Cr3C2, RE) coating was mainly composed of loose and porous Fe3O4 and a small amount of Cr2O3 because there were little Cr and Al. The oxidation mechanism, thermodynamic and kinetic analysis during the failure process was discussed.