Abstract: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.

Key words: single crystal superalloy; DD6 alloy; high temperature oxidation