Effect of Al content on the high-temperature oxidation of Co-20Cr-(5, 10)Al oxide dispersion strengthened superalloys

The high-temperature oxidation of Co-based oxide dispersion strengthened (ODS) Co-20Cr-(5, 10) Al-2.4Hf-1.5Y2O3 (wt%) superalloys was investigated at 900 °C and 1000 °C. The 10Al (wt%) superalloys possess better oxidation resistance with the formation of alumina scale than the 5Al (wt%) with a duplex scale of CoCr2O4/Cr2O3 and internal Al2O3. The alumina on the 10Al superalloy is composed of θ- and α-alumina at 900 °C but dominated by α-alumina at 1000 °C. The lower weight gain of 10Al superalloys at 1000 °C than at 900 °C was associated with different growth mechanisms of the Al2O3 scales.