Oxidation behavior of Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_{0 .2}C-M_x C (M = Ti, Zr, Hf, Nb, Ta) composite ceramic at high temperature

Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2C-M-x C composite ceramic was prepared by hot press sintering, with the Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2C high-entropy carbide as the main phase. Secondary phase M-x C (M = Ti, Zr, Hf, Nb, Ta) was found to be distributed relatively uniform in the composite ceramic. The oxidation behavior of the ceramic was examined after exposure to 923 K and 1173 K. Morphology of the surface and cross sections of all oxidation samples were observed. The characteristics of the oxidation behavior of the high-entropy carbide and the secondary phase M-x C were compared and analyzed. The secondary phases (such as Ti-rich carbide or Hf-rich carbide) in the material were seriously oxidized at 923 K and 1173 K, which reflects the superior oxidation performance of the high-entropy carbide. The nano high-entropy oxides with Ti, Zr, Hf, Nb, Ta, and O elements were discovered by oxidation of the composite ceramic. This research will help deepen the understanding of the oxidation mechanism of high-entropy carbide and composite ceramic.