Structural ceramics are superior to metallic materials in terms of their high-temperature strengths and critical heat proof temperatures. However, compared to metallic materials, ceramics exhibit lower fracture toughness, so they are more sensitive to flaws such as pores and cracks. The shortness considerably decreases the component reliability. To overcome the shortness, in this study, special attention is paid to structural ceramics with self-crack-healing ability. There are several advantages for using a material with self-crack-healing ability. (1) After an efficient machine operation, the materials are able to self-heal the cracks introduced by the machining. (2) The materials are able to self-heal the cracks introduced during service and recover the strength completely at healing temperature. However, ways of organizing the available knowledge to increase the through-life reliability of ceramics components have not been extensively studied. The authors propose a new concept and the corresponding flowchart. This new concept is a promising technique for increasing the through-life reliability of ceramics components with excellent self-crack-healing ability. 1. Introduction Structural ceramics are superior to metallic materials in terms of their high-temperature strengths and critical heat-proof temperatures. Structural ceramics are leading candidate materials for high-temperature applications such as components of gas turbines. However, compared to metallic materials, ceramics exhibit lower fracture toughness, so they are more sensitive to flaws such as pores and cracks. The reliability of structural ceramics in machinery is therefore limited by the following three problems. (1) Cracks occur during machining (e.g., grinding and polishing), considerably decreasing the component reliability. In order to prevent this, precise polishing is required in the final stage, which is time-consuming and lowers the fabrication efficiency and raises the fabrication cost. (2) In particular, cracks of depth about 10–30？μm affect the reliability. Nondestructive inspection technologies for detecting cracks of depth 10–30？μm have yet to be developed. (3) Cracks may occur for various reasons in components during their use at high temperatures. To overcome the above problems, in this study, special attention is paid to structural ceramics with self-crack-healing ability. There are several advantages to using a material that can heal its own surface cracks. First of all, if the self-healing of the surface crack is carried out after an efficient machine operation is
References
[1]
W. Nakao, K. Takahashi, and K. Ando, “Self-healing of surface cracks in structural ceramics,” in Self-Healing Materials, S. K. Ghosh, Ed., chapter 6, pp. 183–217, Wiley-VCH, Weinheim, Germany, 2009.
[2]
K. Ando, K. Takahashi, and W. Nakao, “Self-crack-healing behavior of structural ceramics,” in Handbook of Nanoceramics and Their Based Nanodevices, T. Y. Tseng and H. S. Nalwa, Eds., vol. 1, chapter 3, pp. 1–26, American Scientific Publishers, Valencia, Calif, USA, 2009.
[3]
T. Osada, W. Nakao, K. Takahashi, K. Ando, and S. Saito, “Strength recovery behavior of machined alumina/SiC whisker composite by crack-healing,” Journal of the Ceramic Society of Japan, vol. 115, no. 1340, pp. 278–284, 2007.
[4]
M. C. Chu, S. Sato, Y. Kobayashi, and K. Ando, “Damage healing and strengthening behaviour in intelligent mullite/SiC ceramics,” Fatigue & Fracture of Engineering Materials & Structures, vol. 18, no. 9, pp. 1019–1029, 1995.
[5]
K. Takahashi, K. Ando, H. Murase, S. Nakayama, and S. Saito, “Threshold stress for crack-healing of Si3N4/SiC and resultant cyclic fatigue strength at the healing temperature,” Journal of the American Ceramic Society, vol. 88, no. 3, pp. 645–651, 2005.
[6]
K. Takahashi, Y. Nishio, Y. Kimura, and K. Ando, “Improvement of strength and reliability of ceramics by shot peening and crack healing,” Journal of the European Ceramic Society, vol. 30, no. 15, pp. 3047–3052, 2010.
[7]
T. Frey and W. Pfeiffer, “Shot peening of ceramics: damage or benefit?” in Shot Peening, L. Wgner, Ed., pp. 185–190, Wiley-VCH, Weinheim, Germany, 2003.
[8]
W. Pfeiffer and T. Frey, “Strengthening of ceramics by shot peening,” Journal of the European Ceramic Society, vol. 26, no. 13, pp. 2639–2645, 2006.
[9]
K. Ando, Y. Shirai, M. Nakatani, Y. Kobayashi, and S. Sato, “(Crack-healing + proof test): a new methodology to guarantee the structural integrity of a ceramics component,” Journal of the European Ceramic Society, vol. 22, no. 1, pp. 121–128, 2002.
[10]
K. Ando, B. S. Kim, M. C. Chu, S. Saito, and K. Takahashi, “Crack-healing and mechanical behaviour of Al2O3/SiC composites at elevated temperature,” Fatigue & Fracture of Engineering Materials & Structures, vol. 27, no. 7, pp. 533–541, 2004.
[11]
W. Nakao, K. Takahashi, and K. Ando, “Threshold stress during crack-healing treatment of structural ceramics having the crack-healing ability,” Materials Letters, vol. 61, no. 13, pp. 2711–2713, 2007.
[12]
I. A. Chou, H. M. Chan, and M. P. Harmer, “Effect of annealing environment on the crack healing and mechanical behavior of silicon carbide-reinforced alumina nanocomposites,” Journal of the American Ceramic Society, vol. 81, no. 5, pp. 1203–1208, 1998.
[13]
K. Ando, T. Ikeda, S. Sato, F. Yao, and Y. Kobayasi, “A preliminary study on crack healing behaviour of Si3N4/SiC composite ceramics,” Fatigue & Fracture of Engineering Materials & Structures, vol. 21, no. 1, pp. 119–122, 1998.
[14]
Y. S. Jung, W. Nakao, K. Takahashi, K. Ando, and S. Saito, “Crack-healing behavior of Si3N4/SiC composite under low oxygen partial pressure,” Journal of the Society of Materials Science, Japan, vol. 57, no. 11, pp. 1132–1137, 2008.
[15]
K. Ando, K. Furusawa, K. Takahashi, M. C. Chu, and S. Sato, “Crack-healing behavior of structural ceramics under constant and cyclic stress at elevated temperature,” Journal of the Ceramic Society of Japan, vol. 110, no. 1284, pp. 741–747, 2002.
[16]
S. K. Lee, W. Ishida, S. Y. Lee, K. W. Nam, and K. Ando, “Crack-healing behavior and resultant strength properties of silicon carbide ceramic,” Journal of the European Ceramic Society, vol. 25, no. 5, pp. 569–576, 2005.
[17]
S. K. Lee, K. Ando, and Y. W. Kim, “Effect of heat treatments on the crack-healing and static fatigue behavior of silicon carbide sintered with Sc2O3 and AlN,” Journal of the American Ceramic Society, vol. 88, no. 12, pp. 3478–3482, 2005.
[18]
S. K. Lee, M. Ono, W. Nakao, K. Takahashi, and K. Ando, “Crack-healing behaviour of mullite/SiC/Y2O3 composites and its application to the structural integrity of machined components,” Journal of the European Ceramic Society, vol. 25, no. 15, pp. 3495–3502, 2005.
[19]
Y. S. Jung, Y. Guo, W. Nakao, K. Takahashi, K. Ando, and S. Saito, “Crack-healing behaviour and resultant high-temperature fatigue strength of machined Si3N4/SiC composite ceramic,” Fatigue & Fracture of Engineering Materials & Structures, vol. 31, no. 1, pp. 2–11, 2008.
[20]
K. Ando, K. Takahashi, S. Nakayama, and S. Saito, “Crack-healing behavior of Si3N4/SiC ceramics under cyclic stress and resultant fatigue strength at the healing temperature,” Journal of the American Ceramic Society, vol. 85, no. 9, pp. 2268–2272, 2002.
[21]
K. Ando, K. Furusawa, M. C. Chu, T. Hanagata, K. Tuji, and S. Sato, “Crack-healing behavior under stress of mullite silicon carbide ceramics and the resultant fatigue strength,” Journal of the American Ceramic Society, vol. 84, no. 9, pp. 2073–2078, 2001.
[22]
K. Takahashi, K. Uchiide, Y. Kimura, W. Nakao, K. Ando, and M. Yokouchi, “Threshold stress for crack healing of mullite reinforced by SiC whiskers and SiC particles and resultant fatigue strength at the healing temperature,” Journal of the American Ceramic Society, vol. 90, no. 7, pp. 2159–2164, 2007.
[23]
W. Nakao, M. Ono, S. K. Lee, K. Takahashi, and K. Ando, “Critical crack-healing condition for SiC whisker reinforced alumina under stress,” Journal of the European Ceramic Society, vol. 25, no. 16, pp. 3649–3655, 2005.
[24]
K. Takahashi, Y. S. Jung, Y. Nagoshi, and K. Ando, “Crack-healing behavior of Si3N4/SiC composite under stress and low oxygen pressure,” Materials Science and Engineering A, vol. 527, no. 15, pp. 3343–3348, 2010.
[25]
M. Nakatani, S. Sato, Y. Kobayashi, and K. Ando, “A study on crack-healing + proof test to guarantee the structural integrity of ceramic coil springs,” Journal of High Pressure Institute of Japan, vol. 43, no. 2, pp. 85–91, 2005.
[26]
M. Ono, W. Nakao, K. Takahashi, M. Nakatani, and K. Ando, “A new methodology to guarantee the structural integrity of Al2O3/SiC composite using crack healing and a proof test,” Fatigue & Fracture of Engineering Materials & Structures, vol. 30, no. 7, pp. 599–607, 2007.
