材料期刊网

The isothermal-oxidation behavior of a single-crystal (SC) Ni-base superalloy was studied over the temperature range from 900 to 1100 degrees C and analyzed by OM, TGA, XRD, EDX, SEM and EPMA. The alloy obeyed a subparabolic rate law during oxidation at 900 and 1000 degrees C, whereas the alloy showed parabolic behavior at 1100 degrees C exposure. The variations in the chemical composition due to segregation, which resulted from the solidi. cation process, led to the formation of different kinds of oxide scale on the dendritic and interdendritic areas during oxidation at 900 and 1000 degrees C, while the alloy exhibited relatively uniform oxidation at 1100 degrees C. The growth mechanism of the scale is discussed.