Mechanisms responsible for enhancing low‐temperature oxidation resistance of nonstoichiometric (Zr,Ti)C

Abstract

Abstract A series of (Zr,Ti)C x ( x = 0.7–1.0) samples were fabricated by a modified spark plasma sintering apparatus to investigate the effects of carbon concentration and Ti substitutions on the oxidation behavior. Crushed powders of (Zr,Ti)C x were oxidized in lab air (N 2 –20‐vol.% O 2 ) from room temperature to 900°C. The results indicated that Zr 0.8 Ti 0.2 C 0.8 , with a nominal carbon concentration x = 0.8, displayed good oxidation resistance, which was attributed to the formation of dense t ‐(Zr,Ti)O 2 oxide solid solution. During the oxidation of (Zr,Ti)C x , Ti substitutions for Zr enhanced the outward diffusion of carbon, enabling a uniform carbon layer and a Zr–Ti–C–O layer on the surface of carbides. The formed carbon layer improved the oxidation resistance of (Zr,Ti)C x below 550°C, where carbon is relatively oxidation resistant. Increasing the Ti concentration was found to enhance the oxidation resistance of (Zr,Ti)C x with an increased oxidation onset temperature (672 ± 2°C for Zr 0.8 Ti 0.2 C 0.8 ).