Oxidation Behavior of a Cast Polycrystalline Ni-Base Superalloy in Air: At 900 and 1000 °C
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The oxidation behavior of a cast polycrystalline Ni-base superalloy was studied at 900 and 1000 °C and analyzed by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and SEM. The results indicate that the cast Ni-base superalloy exhibits subparabolic oxidation kinetics, which are controlled by the growth of the inner Al-rich layer. A mixed scale forms on the alloy after prolonged oxidation. The oxide scale formed on the γ matrix is composed of an outer layer of spinel and a uniform inner, compact Al-rich layer. The oxidation behavior on the region overlying MC carbide precipitates is slightly different from that in the γ matrix. The difference is explained by the big difference in composition between MC carbide and γ matrix.
KeywordsCast polycrystalline Ni-base superalloy Oxidation Kinetics Microstructure
Financial support of the National Sciences Foundation of China (Grant No. 50501024) is gratefully acknowledged. The authors are indebted to Drs. J. X. Yang and L. N. Wang for experimental assistance.
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