Continuous and cyclic oxidation of T91 ferritic steel under steam

The oxidation behaviour of T91 ferritic steel in steam has been studied under isothermal and non-isothermal conditions within a temperature range between 575 and 700 degreesC. Isothermal treatments resulted in parabolic oxidation kinetics. Three clearly defined oxide layers constituted the oxide scales. The innermost layer was a (Fe,Cr)(3)O-4. The intermediate layer was porous magnetite (Fe3O4) followed by a compact thinner layer of hematite (Fe2O3). Under non-isothermal conditions the oxide scales were irregular and evidently cracked. An increase of the oxidation temperature produces an acceleration of the oxidation process, causing an increase of the oxide scale thickness that depends on the temperature increase and the exposure time. (C) 2003 Elsevier Ltd. All rights reserved.