Strength Properties of Crack-Healed Silicon-Carbide Ceramics
Sangkee LEE, Wataru ISHIDA and Kotoji ANDO
Abstract:Engineering ceramics are superior in strength than metal at high temperature. However, they are brittle and sensitive to flaws. As a result, the structural integrity of a ceramics component may be seriously affected. Whereas, some engineering ceramics have the ability of crack-healing. If this ability could be used in engineering ceramics components, their reliability will be increased and their life time will also prolonged. This study focuses on the crack-healing behavior of commercial SiC ceramics. Three point bending specimen was made from commercial SiC ceramics. A semi-elliptical surface crack of 50? To 700? In diameter (aspect ratioเ0.9) was made on each specimen. Basic crack-healing behavior as a function of crack-healing time and fracture behavior of crack-healed member were systematically studied. The main conclusions obtained were following; (1)Recommended crack-healing condition by this study was 1h at 1773K in air. (2)Maximum crack size which can be healed completely was semi-elliptical surface crack of 450? In diameter. (3)Heat resist proof temperature of crack-healed zone for bending strength was about 873K. (4)Base material is not sensitive to static fatigue, but crack-healed zone is quite sensitive to static fatigue at room temperature. Key Words:Silicon-carbide, Crack-healing, High temperature strength, Static fatigue strength, Degradation of crack-healed zone, Maximum crack size healed completely