Surface oxidation of Alloy 617 in low oxygen partial pressure He–CO–CO2 environments at 750–850 °C

Abstract

Surface Cr oxidation mechanism of Alloy 617 was investigated in He-CO-CO 2 environments with P CO / P CO 2 of either 9 or 1320 at temperatures 750-850 °C. The activation energy for surface oxidation was 169.0 ± 13.2 kJ/mol in He-P CO / P CO 2 = 9 and 234.4 ± 8.9 kJ/mol in He-P CO / P CO 2 = 1320. The ambient oxygen partial pressure dependence of the measured oxidation rates was consistent with n-type behavior of Cr 2 O 3 , in which Cr interstitials are the primary mobile species. The oxidation rates measured were greater than that can be sustained only by lattice diffusion of Cr in Cr 2 O 3 , indicating that grain boundary diffusion of Cr plays a role in the Cr 2 O 3 growth kinetics.

Oxidation behavior of GTD111 Ni-based superalloy at 900 °C in air

“…This region was not found to be associated with oxygen, as the oxygen did not extend as far into the sample as the variation in Ti concentrations. Correspondingly, the buildup of TiN [19,[23][24] particles dispersedly distributes below the Al-rich region changed with the increasing oxidation time from 192-308h, as indicated by the arrows in Fig. 2c-2f.…”

Investigation of Oxidation Performance of Co-Cr-Fe-Ni based High Entropy Alloys in Supercritical-CO2 Environment

“…Wagner's Theory relies on the diffusion of charged ions and electrons through the neutral oxide scale [54], [58], [60], [67]. The movements are dependent upon the type of defects present in the oxide layer [60]. Point defects found in the oxide phase results in bulk diffusion, also known as lattice diffusion.…”

“…The parabolic relationship is due to the solid-state diffusive transport of the charged Cr (outward) and O (inward) [60], [67] and the linear relationship corresponds to Cr2O3 decomposition into volatile species [76]. The diffusion occurs through oxide structure defects (vacancy and interstitial defects) [60]. Furthermore, the protective nature of Cr is elevated in presence of carbide forming elements, such as Mo, W, Nb.…”