Oxidation behaviour of NiCrAlY coatings on Ni-based superalloy

NiCrAlY coatings were prepared on cast Ni-based IN100 superalloy using arc ion plating, leading to a dense structure. The surface became smoother after vacuum heat treatment. The oxidation kinetic curves of the IN100 alloy and the coating were obtained. The results indicate that NiCrAlY coating gains more weight after cyclic than after isothermal oxidation and no oxide spallation was evident. The oxidation resistance of IN100 superalloy when exposed to either isothermal or cyclic oxidation was markedly improved by coating with NiCrAlY. The oxide scales mainly consisted of α-Al2O3 and Cr2O3 at 900°C. In the initial oxidation stage at 1000°C, three kinds of oxides, NiO, Cr2O3 and α-Al2O3, formed simultaneously. With further oxidation, not only is the thickness of the oxide scale increased, but complex reactions also occurred.