Isothermal oxidation behavior of single crystal superalloy DD6

The isothermal oxidation behavior of the second generation single crystal superalloy DD6 was studied at 1050 °C and 1100 °C in ambient atmosphere. Morphology of oxides was examined by SEM and their composition was analyzed by XRD and EDS. The experimental results show that DD6 alloy obeys subparabolic rate law during oxidation of 100 h at 1050 °C and 1100 °C. The oxide scale exposed at 1050 °C is made up of an outer NiO layer with a small amount of Al2O3 and an inner Al2O3 layer. The oxide scale exposed at 1100 °C is made up of an outer Al2O3 layer with a small amount of NiO, an intermediate layer, mainly composed of Cr2O3 and TaO2, and an inner Al2O3 layer. The γ′-free layer was formed under the oxide scale at two temperatures.