Abstract: By means of observation of microstructure and measurement of the isothermal oxidation kinetics curves，the high temperature oxidation behavior of the single crystal nickel-base superalloy with and without NiCrAlY coading was investigated． The results show that the surface oxidation，internal oxidation and internal nitridation in sub-surface layer of the uncoating superalloy occurs during oxidation at high temperature，the oxides of Al2O3 and Cr2O3 are formed on the surface layer of the alloy． The oxides with Ta-rich and Al-poor are formed in the sub-surface layer，and the internal oxides are observed in the regions near the matrix． The thickness of the Al-poor oxide layer increases as the oxidation temperature increases，thereinto，the Ta-rich phase in the oxides may restrain the element Al in the matrix diffusing outwards，which may decrease the oxidizing rate of the alloy． The mass gain of the alloy oxidized in the initial oxidation stage increases rapidly，and then the kinetics curve of the oxidation displays the undulating feature with increasing time，which is attributed to the formation and scaling off of the oxides on the surface layer． The sputtered NiCrAlY coating effectively improves oxidation resistance of the alloy，and the kinetics curve of the coating alloy displays a less mass change due to no spallation of Al2O3 film formed on the surface，and a few internal ( AlN) aluminum nitrides are observed only in the region near the interface of coating and substrate．
Key words: Single crystal nickel-base superalloy，NiCrAlY coating，isothermal oxidation，internal nitride
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