◆High-temperature fracture problem
The growing needs for energy efficient operation of modern gas turbines has boosted the use of sophisticated metallic materials (so-called superalloys) for blades attached to rotators. Since blades are subjected to an extremely high temperature environment, the evaluation of their life with a correct knowledge of crack growth mechanism has been an engineering issue.
Our original site-specific observation technique successfully unveiled the microscopic features at the crack tip region in a single-crystalline nickel-based superalloy. It was found that the formation of twin bands triggered the precipitation of elements, resulting in degradation and cracking along the bands.
For more detail, see：
Y. Takahashi, D. Kobayashi, S. Fujii, M. Takuma, K. Saitoh, T. Sato, Time-dependent crack growth mechanism in Ni-based single crystal superalloys at high-temperature, Materials Science & Engineering A, Vol. 859, 2022, 144179 (https://doi.org/10.1016/j.msea.2022.144179)
Related study:
Y. Takahashi, D. Kobayashi, M. Kashihara, T. Kozawa, S. Arai, Electron-microscopic analyses on high-temperature fatigue crack growth mechanism in a Ni-based single crystal superalloy, Materials Science & Engineering A, Vol. 793, 2020, 139821 (https://doi.org/10.1016/j.msea.2020.139821)
Y. Takahashi, D. Kobayashi, S. Fujii, S. Arai, M. Takuma, K. Saitoh, T. Sato, Time-dependent subcritical crack growth and its mechanism in Ni-based single crystal superalloys at 500 °C, Materials Science & Engineering A, Vol. 889, 2024, 145869 (https://doi.org/10.1016/j.msea.2023.145869)