Indication of chromium oxide hydroxide evaporation during oxidation of 304L at 873 K in the presence of 10% water vapor

The oxidation of type 304L stainless steel was investigated at 873 K in the presence of O-2 and O-2+10% H2O. Oxidation time varied between 1 and 672 h r. The oxidized samples were investigated by a number of surface-analytical techniques including grazing-angle XRD, SEM/EDX, auger spectroscopy, SIMS and XPS. Oxidation in dry oxygen results in the formation a corundum-type o xide (Me2O3) with additional formation of spinel oxides after prolonged exp osure. The oxide layer contained mainly chromium, with smaller amounts of F e and Mn. Oxidation in the presence of water vapor results in an oxide that contains more Fe and less Cr, the outer part of the oxide being depleted i n Cr. In the presence of water vapor, a mass loss is detected after prolong ed exposure. We show that the mass loss is caused by chromium evaporation. The volatile species is suggested to be CrO2(OH)(2).