High temperature oxidation of commercial austenitic stainless steels

Abstract

An investigation has been carried out into the oxidation behaviour of 310 stainless steel and 321 stainless steel in oxygen at 800 and 1000°C. Both steels contain sufficient chromium to ensure development of a protective Cr₂O₃ rich scale in the early stages. However, the oxide growth process results in development of blisters in the scale, as parts of it develop out of contact with the steel surface. Mechanical failure of these features allows access of oxygen to a chromium depleted steel surface. In 310 stainless steel, there is sufficient chromium to ensure re-establishment of a Cr₂O₃ rich scale at 1000°C but, in 321 stainless steel, this is not always the case and rapid growth of iron rich oxide nodules dominates the oxidation process after periods of up to 1000 h. At 800°C, there are fewer differences in the performances of the two steels. In both cases, the more slowly growing nodules are healed by an Fe–Cr spinel oxide, although this is less effective than a Cr₂O₃ layer. Consideration is also given to the role of the minor alloying elements in the oxidation performances.

MST/953