High-Temperature Oxidation Behavior of TiB₂-HfB₂-Ni Cermet Material

To analyze the high-temperature oxidation behavior of TiB₂-HfB₂-Ni cermet material, TiB₂-HfB₂-Ni cermets were fabricated by hot-pressing sintering technology. The oxidation resistance and the thermal fracture of TiB₂-HfB₂-Ni cermet were investigated at 1100 °C for 1, 4, 7, and 10 h, respectively. Before oxidation, TiB₂-HfB₂-Ni cermet, consisting of TiB₂, HfB₂, and Ni, had the core-rim structure. The core was TiB₂ grain and the rim was composed of Ni and solid solution (Ti, Hf)B₂. After oxidation at 1100 °C, the oxides of the TiB₂-HfB₂-Ni cermet were mainly TiO₂, HfO₂, B₂O₃, and NiO, which the oxidation process abided by the parabolic law. With the oxidation time increasing from 1 h to 10 h, the oxidation degree of the TiB₂-HfB₂-Ni cermet increased, and the oxide layer became thicker. The oxide layer was thin and dense after oxidation at 1100 °C for 1 h. An obvious boundary was discovered between the transition layer and the substrate layer after oxidation at 1100 °C for 7 h. The thermal fracture occurred in the contact regions of different layers at 1100 °C for 10 h. TiB₂-HfB₂-Ni took place in oxidation at different levels from the outer to the inner, and the components of different oxide layers were certainly distinct.