Oxidation behaviour of Al2O3-forming Cr-based alloys at elevated temperatures

This work presents oxidation behaviours of Al-bearing Cr-based alloys GA1 (51Cr-22Al-13Mo-9Ta-5Si in at%) and GA2 (40Cr-33Al-13Mo-9Ta-5Si in at%) at 1100–1400 ˚C for up to 24 h. The formation of oxides on the surfaces was influenced by constituent phases; BCC phase was rich in Al and formed only α-Al2O3, complex oxides (Cr2O3, AlTaO4, CrTaO4, and Ta2O5) occurred on top of C14 Laves phase. Sufficient Al content is crucial to the formation of protective α-Al2O3, as GA2 was able to resist severe oxidation at 1400 ˚C with an oxidation weight gain of only 3.3 mg/cm2 after 24 h. [Display omitted] •Al-bearing Cr-based alloys in this work contained BCC matrix and C14 phases.•The BCC phase was rich in Al and formed only α-Al2O3.•Complex oxides formed on top of C14 Laves phase and at phase boundaries.•Increasing Al content can enhance oxidation resistance from 1100 to 1400 °C.