Effects of Fe on oxidation of Ni-20Cr and Ni-30Cr alloys at 800 °C in dry CO2 gas

Model alloys Ni-(20, 30)Cr (wt %) alloyed with (0, 1, 5, 15 %) Fe were exposed to flowing Ar-20 %CO2 gas at 800 degrees C. Samples were electropolished before reaction to avoid surface cold work effects on alloys diffusion. The oxidation resistance of 20Cr alloys gradually increased with increasing alloy Fe levels. All 30Cr alloys formed external chromia scales, but Ni-30Cr-(1, 5)Fe alloys underwent severe scale spallation. The effects of Fe additions on the formation and spallation of chromia scale are discussed in terms of alloy diffusion processes.