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. TaSi2 enhanced the residual strength within the temperature range resulting from the crack-healing effect, especially at similar to 1400 degrees C. Residual fracture toughness increased with increasing TaSi2 content from 1000 degrees C to 1600 degrees C. The addition of soft phase TaSi2 positively affected the toughening mechanism. Considering the consumption of TaSi2 at 1600 degrees C, fracture toughness of the TaSi2-containing ZrB2-SiC based ceramic decreased with increasing temperature. The formation of a compressive stress zone beneath the surface oxide layer increased fracture toughness at 1600 degrees C. The cohesive structure of the TaSi2-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. (C) 2013 Elsevier Ltd. All rights reserved.