Strength of hot pressed ZrB_2-SiC composite after exposure to high temperatures (1000-1700 °C)

摘要

Residual strength (room temperature strength after exposure in air at high temperatures) of hot pressed ZrB_2-SiC composites was evaluated as function of SiC contents (10-30 vol%) as well as exposure temperatures for 5 h (1000-1700 °C). Multilayer oxide scale structures were found after exposures. The composition and thickness of these multilayered oxide scale structure was dependent on exposure temperature and SiC contents in composites. After exposure to 1000 °C for 5 h, the residual strength of ZrB_2-SiC composites improved by nearly 60% compared to the as-hot pressed composites with 20 and 30 vol% SiC. On the other hand, the residual strength of these composites remained unchanged after 1500 C for 5 h. A drastic degradation in residual strength was observed in composites with 20 and 30 vol% SiC after exposure to 1700 °C for 5 h in ZrB_2-SiC. An attempt was made to correlate the microstructural changes and oxide scales with residual strength with respect to variation in SiC content and temperature of expsoure.