Water Vapor Effects on Corrosion of Fe–Cr and Fe–Cr–Ni Alloys Containing Silicon in CO2 Gas at 818 °C
Model alloys Fe–20Cr and Fe–20Cr–20Ni, with and without Si additions (0.1, 0.2 and 0.5 wt%), were exposed to Ar–20CO2–20H2O gas at 818 °C. All undoped alloys underwent breakaway corrosion, resulting in iron-rich oxide scales and internal carbide precipitates. Silicon addition significantly improved both oxidation and carburization resistance in wet CO2, by forming a layer of silica beneath the chromia scale. Silicon-bearing austenitic alloys underwent scale spallation on cooling from reaction. The contributions of thermal and growth stresses to spallation, and of growth stresses to the onset of breakaway are discussed.
KeywordsAlloy Silicon Water vapor High temperature corrosion
Financial support from the Australian Research Council’s Discovery Program is gratefully acknowledged.
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