Incipient oxidation kinetics and residual stress of the oxide scale grown on Haynes 230 at high temperatures

Incipient oxidation kinetics of alloy 230 in air in the temperature range of 850-1000°C was investigated by in situ thermogravimetry. A two-stage oxidation kinetics was observed; each stage followed Wagner's parabolic law. The activation energies for the first and the second stages are 246.5 and 212.1kJ/mol, respectively. Grazing incidence X-ray diffraction showed that two types of oxide phases existed: Cr₂O₃ and MnCr₂O₄. Cr₂O₃ was the dominated phase. Structural characterization revealed that Cr₂O₃ and MnCr₂O₄ are mixed with each other and uniformly distributed throughout the scale. The results of residual stress measurements showed that the intrinsic residual stresses of the scale are highly tensile, ranging from 648.9 to 1308.4MPa. The stress state of alloy 230 near the scale/substrate was found to be tensile, which is opposite to the stress state in the oxide scale, such that the forces balanced.