Oxidation of Fe-10Cr in O2 and in O2 + H2O environment at 600 °C: A microstructural investigation

Oxidation of Fe-10Cr in dry and wet O2 was studied at 600 °C for up to 168 h. Oxide microstructure was investigated by STEM/EDX, FIB/SEM and TEM. Oxidation in dry O2 gives a Cr-rich protective (Fe1−xCrx)2O3 scale. The same protective oxide initially forms in O2 + H2O environment, but after an incubation period scale breakdown is triggered by CrO2(OH)2 evaporation that depletes the substrate in Cr and converts (Fe1−xCrx)2O3 to FeCr spinel oxide. Internal oxidation occurs after breakaway. Alternating external and internal oxidation result in the inward-growing scale showing a characteristic banded morphology.