High temperature oxidation of Fe22Cr-alloy

The isothermal and constant heating rate oxidation behaviour of the alloy F e78Cr22 was examined in air with 1% H2O and in 7% H-2/93% Ar with 1% or 12% H2O. The measurements were performed in the temperature range 700-1300 deg reesC. The effect of surface treatment prior to oxidation was examined. A C r2O3 scale developed slowly up to 900 degreesC. At 1100 degreesC a catastro phic oxidation was observed after heat treatment for 70 h in air with 1% H2 O and in 7% H-2/93% Ar with 12% H2O. The scale developed in these cases con sisted of iron rich oxides such as Fe2O3 or FeCr2O4, in contrast to the mor e protective Cr2O3 scale seen under other test conditions. Possible causes for the catastrophic oxidation are discussed.