High-temperature oxidation resistance of ultrafine-grained 14 %Cr ODS ferritic steel

Abstract

The long-term oxidation resistance of the Fe-14Cr-2W-0.3Ti-0.3Y 2O3 oxide dispersion strengthened reduced activation ferritic steel was investigated. The results of the long-term oxidation at 750 C for 10000 h in air revealed that the weight gain of the ODS ferritic steel was exceptionally low (<3.5 × 10-3 g/cm-2) and that the long-term oxidation rate follows the parabolic law. The parabolic rate constant, which was calculated from the mass change during the ageing process was equal to 2.0 × 10-9 g2/cm4 h. The scanning electron microscopy (SEM) observations of the cross section of the specimen after being aged for 10000 h revealed an oxide scale with the non-uniform thickness ranging from 2.0 to 5.0 μm enriched with Cr-Mn oxide. On the contrary to the SEM observations of the ODS steel scale following the annealing process at 1350 C, it was revealed that the material had a multi-layer scale with the thickness equal to ~20 μm. The outer layer, with the approximate thickness of 15 μm, was mainly composed of 30Fe-22Cr-8W-2Si-38O (in wt%), whereas the inner part of the layer was predominantly made of 76Fe-14Cr-2W-10O. © 2013 The Author(s).