High Temperature Oxidation of Type 405, 409’s and 410 Stainless Steels

High temperature oxidation has been made on four chromium steels, i.e. Fe-13.7Cr-0.2Al (405), Fe-11.9Cr-0.7Ti (409-A), Fe-11.8Cr-0.4Ti (409-B) and Fe-12.2Cr (410), in wet oxygen containing up to 10 vol%H2O as well as in dry one between 1173 and 1473 K for 86.4 ks (24 h). All steels show protections at 1173 K irrespective of moisture in the atmosphere except for 405 which has shown a slight degree of breakaway in 10 vol%H2O/O2 mixture. All but 409-B are affected by water vapour at 1273 K in such a way that the oxidation rates are substantially increased and the induction periods before the begining of breakaway are accelerated. The same situation is observed at 1373 K for 409-B which contains a higher content of Si than the other steels tested. The scale structures are double-layered and basically similar to each other, i.e. the outer layer being of type MnCr2O4 and the inner layer is of type (Fe,Cr)2O3. When the steels contain Ti, the internal oxidation of the element occurs. However, no contribution to the adhesion of the scales due to the dispersed internal particles has been observed.