Abstract: The corrosion behavior of DD5 single crystal alloy in moist air and NaCl aerosol at 750 °C and 900 °C was investigated. At 750 °C, (Ni, Co)O is the main initial corrosion product, and the (Ni, Co)O formed on the γ phase is significantly thicker than that on the γ’ phase. After 168 h of corrosion, a bi-layer oxide scale consisting of an external (Ni, Co)O layer and an internal (Cr, Al)₂O₃ layer was finally formed, and the internal corrosion product was Al₂O₃. At 900 °C, although a thicker (Ni, Co)O layer was formed after 1 min of corrosion, the oxide scale finally developed into a multi-layer structure of (Ni, Co)O/spinel((Ni, Co)(Cr, Al)₂O₄)/Ta₂O₅/Al₂O₃. The continuous internal Al₂O₃ layer formed at 900 °C effectively reduced the corrosion rate than that at 750 °C. The corrosion mechanism of the alloy at 750 °C and 900 °C was also comprehensively discussed.

Key words: Ni-based single crystal alloy, NaCl aerosol atmosphere, High temperature corrosion, Temperature-dependent corrosion behavior