Oxidation behavior of AISI 321, AISI 316, and AISI 409 stainless steels: Kinetic, thermodynamic, and diffusion studies

The oxidation behavior of three types of stainless steels, namely AISI 321, AISI 316, and AISI 409, was compared. In all stainless steels, oxide layers were formed and their masses and thicknesses increased with oxidation time. Among them, AISI 409 ferritic stainless steel demonstrated higher oxidation rate. According to the kinetical oxidation behavior of them at elevated temperatures, the oxidation mechanism was determined. Among them, the AISI 409 ferritic stainless steel showed the lowest and AISI 321 austenitic stainless steel demonstrated the highest oxidation resistance. Based on the experimental results, it was suggested that the kinetic of oxide growth in stainless steels was followed by a parabolic relationship. In all cases, a well-known Cr-rich internal oxidation zone (IOZ) was observed. The formation of IOZ was suggested by the Gibbs free energy expression and confirmed by following up the formed oxide layers at different holding times. Furthermore, the formation of thicker oxide layers in ferritic stainless steel was explained by using solid-state diffusion relations and supported by quasi-steady-state approximation of Fick's first law.