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The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050℃and analyzed by thermogravimetric analysis (TGA),X-ray diffraction (XRD) and scanning electron microscopy (SEM).The results indicate that a cast Co-base superalloy follows the subparabolic oxidation kinetics at 900 and 1000℃,which are controlled by the growth of the inner Cr-rich layer,and that after oxidation at 1050℃for 200 h,it almost exhibits the linear oxidation kinetics possible due to the volatility of Cr-rich oxide.A mixed scale forms on the alloy after prolonged oxidation.The oxide scale formed at 900 and 1000℃is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at 1050℃is composed of a very discontinuous Cr-rich layer.
The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050 ° C and analyzed by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that a cast Co-base superalloy follows the subparabolic oxidation kinetics at 900 and 1000 ° C, which are controlled by the growth of the inner Cr-rich layer, and that after oxidation at 1050 ° C for 200 h, it almost exhibits the linear oxidation kinetics possible due to the volatility of Cr-rich oxide. A mixed scale forms on the alloy after prolonged oxidation. The oxide scale formed at 900 and 1000 ° C is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at 1050 ° C is composed of a very discontinuous Cr-rich layer.