Oxidation and strength retention of HfB2-SiC composite with La2O3 additives

The oxidation and its effect on room temperature flexural strength were examined in hot-pressed 3 vol.-% La2O3-doped HfB2-20 vol.-% SiC composite exposed to air at 1400 degrees C and 1500 degrees C, respectively, for up to 100 h. The major oxidation products consisted of SiO2 (alpha-cristobalite), La2Si2O7, HfO2 and HfSiO4 regardless of oxidation temperature. However, the morphology of the microstructure of the oxidised surfaces was shown to be dependent on oxidation temperature. In addition, it was found that the room temperature flexural strength of the composite degraded after oxidation and the degradation of strength depended on oxidation time at temperature and oxidation temperature. The strength retention displayed by composite after 100 h of oxidation at 1400 degrees C and 1500 degrees C was similar to 83% and similar to 74%, respectively.