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

Abstract

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.