Oxidation kinetics of Haynes 230 alloy in air at temperatures between 650 and 850 °C

Haynes 230 alloy was oxidized in air at temperatures between 650 and 850 °C. Thermogravimetry was used to measure the kinetics of oxidation. The formed oxides were identified by the thin film (small angle) X-ray diffraction technique. Cr2O3 and MnCr2O4 were found in the oxide scale. Multi-stage oxidation kinetics was observed, and each stage follows Wagnerʹs parabolic law. The first slow oxidation stage corresponded to the growth of an Cr2O3 layer, controlled by Cr ions diffusion through the dense Cr2O3 scale. The faster second stage was a result of rapid diffusion of Mn ions passing through the established Cr2O3 scale to form MnCr2O4 on top of the Cr2O3 layer. A duplex oxide scale is expected. The third stage, with a rate close to that of the first stage, only appeared for oxidation in the intermediate temperature range, i.e., 750–800 °C, which can be explained by the interruption of the Mn flux that forms MnCr2O4.