2007 年 2007 巻 52 号 p. 21-25
The self crack-healing behavior of the heavily machined cracks in Si3N4/ 20 wt% SiC composite was investigate. The machined cracks were introduced in the center of specimens during making a semicircular groove by the diamond ball-drill. The machined specimens were crack-healed in various temperatures and time in air. The optimized crack-healing condition was found to be temperature of 1400℃ and time of 10 h in air. The specimen crack-healed in this condition showed the almost same strength as the smooth specimen healed. Moreover, the fracture strengths and fatigue strength of machined specimen healed at optimized condition were systematically investigated at high-temperature. The high-temperature strengths and cyclic fatigue strength of the machined specimen healed showed 700 MPa up to 1400℃, 550 MPa at 1300℃, respectively. These results demonstrate that the crack-healing could be very useful method to reduce machining cost and to increase reliability on Si3N4/ SiC composite ceramic.