The Role of Silicon in the Reactive-Elements Effect on the Oxidation of Conventional Austenitic Stainless Steel

In this work we evaluate the influence of silicon on the high-temperature oxidation of austenitic stainless steels and propose a mechanism that explains the Reactive-Element Effect (REE) in terms of a synergistic action between the reactive element and the silica layer that forms in the innermost areas of the scale. To do this we have studied the oxidation at 900°C of austenitic commercial alloys (AISI-304, AISI-316 and AISI-310S) and a laboratory-designed high-silicon stainless steel (AISI-304). Lanthanum was selected as the reactive element which was surface deposited by means of ion interchange. Results obtained in this work allowed us to state that the reactive element would enhance the formation of a silica layer that shows diffusion through the scale. The reactive element also changes the expansion coefficient at the scale-alloy interface, increasing the adherence of the oxide layer to the metal.