Study on stress relaxation behavior of silicon carbide by BSR method

Bend stress relaxation (BSR) experiment at temperatures of 600-1400 °C for 1-100 h was performed on the two types of highly crystallized monolithic silicon carbide (SiC) produced by chemically vapor deposition (CVD) and liquid phase sintering (LPS) methods. Both materials exhibited similar time-dependent trend of stress relaxation. The BSR ratio dropped rapidly during the first hour of the tests and then decreased gradually in the higher temperature tests. The CVD-SiC and the LPS-SiC showed good thermal creep resistance at the expected operating temperature (about 600-1000 °C) of fusion blanket using SiC fiber-reinforced SiC matrix (SiC/SiC) composite. On the other hand, the BSR ratio of those two materials, especially of the LPS-SiC, dropped steeply at the temperatures of 1200-1400 °C. The activation energy of the stress relaxation calculated by a cross-cut method increased with the temperature.