Oxidation Behavior of Ternary Carbide Ceramics in Hf–Al–C System in Air

Abstract

The oxidation behavior of Hf–Al–C ceramics containing 37.5 wt% Hf 3 Al 3 C 5 , 30.5 wt% Hf 2 Al 4 C 5 , and 32.0 wt% Hf 3 Al 4 C 6 has been investigated at 900°–1300°C in air. The oxidation kinetics approximately follows a linear law with the activation energy of 194±12 kJ/mol. The oxidation resistance of Hf–Al–C ceramics at high temperature is superior to HfC. The oxide scale is porous and composed of well‐mixed t ‐HfO 2 and Al 2 O 3 as well as residual free carbon. The stabilization mechanisms of t ‐HfO 2 and free carbon have been discussed. The simultaneous oxidation of Hf and Al in Hf–Al–C ceramics can be attributed to their close oxygen affinity as well as the strong coupling between Hf–C blocks and Al–C units in the crystal structures.