Threshold Stress for Crack-Healing of Si3N4/SiC and Resultant Cyclic Fatigue Strength at the Healing Temperature

• Published in: Journal of the American Ceramic Society Vol. 88; no. 3; pp. 645 - 651
• Main Authors: Takahashi, Koji, Ando, Kotoji, Murase, Hisashi, Nakayama, Shin, Saito, Shinji
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Inc 01.03.2005; Blackwell
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Cermets, ceramic and refractory composites; Chemical industry and chemicals; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Other materials; Physics; Specific materials; Structural ceramics; Technical ceramics; Ceramic matrix composite; Silicon nitride; Temperature effect; Mechanical properties; Experimental study; Composite material; Non oxide ceramics; Structural ceramic; Hot pressing; Silicon carbide; Fatigue strength; Manufacturing; Threshold stress; Crack
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2005.00106.x

Si3N4/SiC composite ceramics were hot‐pressed in order to investigate the crack‐healing behavior under stress. Semi‐elliptical surface cracks of 100 μm in surface length were made on each specimen. The pre‐cracked specimens were crack‐healed under cyclic or constant bending stress, and the resultant bending strength and cyclic fatigue strength were studied. The threshold stress for crack‐healing was investigated at healing temperatures of 1000° and 1200°C. The cyclic fatigue strengths of crack‐healed specimens were also investigated at healing temperatures of 900° and 1000°C. The main conclusions are as follows: (1) The threshold cyclic and constant stresses for crack‐healing, below which pre‐cracked specimens recovered their bending strength, were 300 MPa, which was 75% of the bending strength of the pre‐cracked specimens and (2) the crack‐healed specimens exhibited quite high cyclic fatigue strength at crack‐healing temperatures of 900° and 1000°C.