Comparison of oxidation behaviors of Cr₇C₃ at 1173 K and 1273 K

Cr₇C₃ has properties of high strength, low density, good chemical stability, and resistance against corrosion and oxidation at high temperature. With these excellent properties, Cr₇C₃ is considered especially suitable as a high temperature material. However, little attention has been paid to the oxidation behavior of Cr₇C₃. In this work, the oxidation behavior of Cr₇C₃ at 1173 K and 1273 K, with seven durations from 10 h to 70 h, was investigated. After testing, oxide morphology and phase composition were observed, and identified by SEM and XRD respectively. The results indicate that the anti-oxidation levels of Cr₇C₃ at the oxidation times of 1173 K and 1273 K both belong to the total anti-oxidation grade; the oxidation rate constant and oxidation rate of Cr₇C₃ at 1273 K show improvement over those at 1173 K by about one order of magnitude and more than two-fold respectively. The result also indicates that Cr₂O₃ does not peel off from the surface of Cr₇C₃ at 1173 K; however, at 1273 K it does peel off. Furthermore, the calculation result indicates that the critical compressive stress value for Cr₂O₃ peeling from the surface of Cr₇C₃ lies between 1.14 GPa and 1.27 GPa.