Temperature dependence of oxide scale formation on high-Cr ferritic steels in Ar-H2-H2O

Four high chromium ferritic steels were oxidized in Ar/H-2/H2O at temperatures between 500 and 900 degrees C. Polished specimens of all steels formed iron-rich oxides at temperatures below 600 degrees C, whereas increasing the temperature resulted in local formation of protective chromia scales. As the temperature was raised further, the specimens were totally covered with chromia scales. For the higher chromium steels this was also observed at 900 degrees C but not for the steel with a chromium content of 16%. The temperature dependence of the oxidation rates is governed by the competing diffusion processes in the alloy and the growing scales. (C) 2011 Elsevier Ltd. All rights reserved.