Initial Stage Oxidation of 304HCu Stainless Steel in Oxygen Environment

The early stages of oxidation and the development of transient initial oxides on 304HCu stainless steel (SS) were investigated by isothermal oxidation at 650 and 750 °C in a pure oxygen environment using thermogravimetry. At 750 °C, the formation of the continuous oxide layer occurs more rapidly, exhibiting protective parabolic kinetics, where the slow diffusion of iron through the oxide layer governs the oxidation rate. The oxide scales primarily consist of binary oxides of iron and chromium, with noticeable segregation of manganese and niobium in the early stages. Distinct morphological differences were observed in the transient initial oxide scales formed at the two temperatures, each providing additional nucleation sites for oxide formation. The GDOES depth profiles indicated the migration of Cu from the oxide/scale interface to the oxide scale. The role of the oxide composition and its morphology on the oxidation behavior of 304HCu SS are discussed in detail.