Evolution of the oxidation behaviors of highly oxidation-resistant (Ti(0.8)Nb(0.2))C in 1000–1200 °C steam

The evolution of the oxidation behaviors of the highly oxidation-resistant (Ti(0.8)Nb(0.2))C was investigated in a 1000–1200 °C steam environment. For the specimen oxidized below 1200 °C, a compact oxide layer less than 7 μm thick was obtained. By increasing the temperature to 1200 °C, the oxide layer grows quickly to over 30 μm. Variable distribution of Ti and Nb in the oxide scales reveals the significance of the outward diffusion of the metal elements during oxidation. Synchronized variations in Ti and Nb were observed in the specimen oxidized below 1200 °C, while the distribution trends of Ti and Nb were opposite in the specimen oxidized at 1200 °C. The incorporation of Nb effectively lowered the diffusion rate of Ti through the oxide scales and the grain growth of the oxides. Suppressed diffusion and dense oxide scales are responsible for the excellent oxidation resistance of (Ti(0.8)Nb(0.2))C below 1200 °C.