Incipient oxidation kinetics of alloy 617 and residual stress of the oxide scale formed in air at temperatures between 850 and 1000°C

The purpose of this study was to investigate incipient oxidation of alloy 617 in air in the temperature range of 850-1000°C. Alloy 617 exhibited a two-stage oxidation kinetics and followed Wagner's parabolic law. The activation energy for the first stage and the second stage are 271.2 and 318 kJ/mol, respectively. The transition time between the two stages decreased as the oxidation temperature increased. X-ray diffraction (XRD) revealed that the oxide phase is chromium oxide, Cr ₂O ₃, over the entire temperature range. The results of residual stress measurements showed that the grown-in stresses of the scale are tensile in nature. This may be due to the crystallite coalescence during the growth of the oxide. The measured residual stress of the substrate decreases with increasing oxidation temperature which may be attributed to the formation of pores or voids within the substrate after exposure to high temperatures.