High-temperature oxidation behavior of GH4169 and Inconel617 nickel-based superalloys in SOFC environment

Field exposure for 5000h combined with weight gain measurement and morphology/composition analysis of oxide film were conducted to examine high temperature oxidation behavior of GH4169 and In617 nickel-based super alloys in SOFC system environment. The In617 alloy has been found to demonstrate excellent oxidation resistance in the SOFC environment because of its high Ni content. An integral and dense NiO oxide film can be developed in the outer layer with a continuous Cr2O3 oxide film formed in inner layer. It indicates that NiO played a crucial role in the formation of an integral and dense oxide film. In contrast, GH4169 alloy failed to develop a continuous and dense oxide film probably due to high Fe content, in which case Fe-dopped chromium oxide (Fe,Cr)2O3 was formed. As a result, the oxide film was loose and porous, leading to relatively poor oxidation resistance.