Oxidation resistance of TiB₂-HfC ceramic at high temperature

Oxidation behavior of the TiB₂-HfC ceramic oxidized at 1100 ℃ for 1, 4, 7, 10 h was investigated to analyze the oxidation resistance of TiB₂-HfC ceramic at high temperature. According to the microstructure of TiB₂-HfC ceramic after oxidation, the oxidation layers were divided into the outer oxide layer, the sub-oxidation layer, and the transition layer. The results show that the TiO₂, B₂O₃, HfO₂, NiO, and CoO exist in the outer oxidation layer. With the increase of the oxidation time, the TiB₂-HfC ceramic is seriously oxidized, the oxide layer becomes thicker, and the bending strength decreases gradually. The oxidation gain and oxidation time were parabolic. After the oxidation for 1 h, a dense oxide layer with the thickness of about 12 μm is formed on the surface of the TiB₂-HfC ceramic. At this time, the TiB₂-HfC ceramic shows a better oxidation resistance and still has a relatively high bending strength, which is 823.6 MPa.