Static and cyclic fatigue behaviour of crack-healed Si3N4/SiC composite ceramics

Abstract Si 3 N 4 /SiC composite ceramics were sintered in order to investigate their fatigue strength behavior after crack healing, Y 2 O 3 and Al 2 O 3 power was added as sintering additives to enhance it's sintering property. Three-point bending specimen (sized 3×4×40 mm) was hewed out according to JIS standard from sintered compact obtained. About 100 or 200 μm semi-circular surface cracks were made on the center of the tension surface of the three-point bending specimen using Vickers indenter. After the crack-healing processing of 1200 and 1300°C, 1 h, in air, cyclic and static fatigue strength behavior of these crack-healed specimen were determined systematically at room temperature and high temperature of 800, 1000, 1200 and 1300°C. The results show that Si 3 N 4 /SiC composite ceramics possess remarkable crack-healing ability, and crack-healed specimens showed similar cyclic and static fatigue strength behavior as smooth specimens at high temperature, not only at room temperature. Crack-healed zones had sufficient fatigue strength even though at high temperature environment, and most fractures occurred outside the pre-cracked zone in those crack-healed specimens.