The isothermal oxidation behavior of directionally solidified Ni-base superalloy DZ951 at 900, 1000 and 1100 degrees C were investigated. Oxidized alloy was characterized by SEM, EDAX, XRD. A subparabolic time dependence (n = 0.18 at 900 degrees C and n = 0.08 at 1000 degrees C) of the oxide growth rate was determined at relatively low temperature, while alloy nearly followed parabolic law at 1100 degrees C (n = 0.42). The severe composition segregation, which resulted from the solidification process. led to the formation of different scale on the dendritic and interdendritic regions at 900 degrees C, however, this difference disappeared after oxidation at 1000 and 1100T for long time. Furthermore, faceted and needle-shaped AIN precipitates developed in the alloy subsurface region after oxidation at 1100 degrees C for 200h, while no internal corrosion products were found in 900 and 1000 degrees C tests.
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