Abstract
Mullite/SiC composite ceramics was sintered and subjected to three-point bending on specimens made according to the appropriate JIS standard. Semi-elliptic surface crack of 100 - 200 μm in diameter was made on each specimen. By using three kinds of specimens that was smooth, cracked and crack healed, crack-healing behavior and cyclic fatigue strength were determined systematically at room temperature. Static fatigue strengths was determined systematically at room temperature,700℃ and 1000℃. A crack was healed at 1000℃. The main conclusions obtained are following: (a) Mullite/SiC composite ceramics has an ability to heal a crack, (b) Crack healed specimens showed higher cyclic and static fatigue strengths than as-received specimens, and this fact was caused by healing of small cracks caused by polishing, (c) Crack-healed zone had enough fatigue strength and most fracture occurred outside the crack-healed zone, (d) Crack-healed specimen has sufficient strengths for cyclic and static fatigue at room temperature, (e) The static fatigue strengths of crack-healed samples at 700℃ and 1000℃ were similar to the values at room temperature, (f) The specimen subjected to crack-healing at 1000℃ had a sufficient fatigue strength even at 1000℃.
