Thermal shock behavior of ZrB₂-SiC composite ceramics with added TaSi₂

The thermal shock behavior of ZrB₂-SiC composite ceramics was remarkably enhanced by the addition of TaSi₂ particles. TaSi ₂ enhanced the residual strength within the temperature range resulting from the crack-healing effect, especially at ∼ 1400 C. Residual fracture toughness increased with increasing TaSi₂ content from 1000 C to 1600 C. The addition of soft phase TaSi₂ positively affected the toughening mechanism. Considering the consumption of TaSi₂ at ∼ 1400 C, fracture toughness of the TaSi₂-containing ZrB ₂-SiC based ceramic decreased with increasing temperature. The formation of a compressive stress zone beneath the surface oxide layer increased fracture toughness at 1600 C. The cohesive structure of the TaSi ₂-containing ZrB₂-based material inhibited crack formation and retained higher mechanical properties. Apparent surface changes were observed as a result of oxidation after severe thermal shock test. From the viewpoint of thermodynamics, thermal oxidation resistance improved with the addition of TaSi₂.