Surface modifications of oxide layer formed in isothermal high temperature conditions of AISI 304 stainless steel

Chromia forming steels are excellent candidates to resist to high temperature oxidising atmospheres because they form protective oxide scales. To understand the oxidation mechanisms of the AISI 304 stainless steel in air at 800°C, in situ X-ray diffraction (XRD) has been used not only during high temperature oxidation, but also during and after cooling. The in situ XRD analyses carried out during high temperature AISI 304 steel oxidation in air at 800°C reveal the growth of iron containing oxides such as haematite Fe₂O₃ and iron chromite FeCr₂O₄, after 35 h of the oxidation test, whereas the initial nucleation of the oxide layer shows the single growth of chromia. Iron containing oxides develop over the initial layer and these oxides appear to be poorly adherent and spall off during cooling between 200 and 50°C. Protection against high temperature oxidation would be increased when the initial nucleation of manganese spinel compound is delayed in the oxide scale.