TY - CHAP
T1 - Initial Intergranular Cracking of Ni-Base Superalloys Due to the Degradation of the Crystallinity of Grain Boundaries Under Creep-Fatigue Loading
AU - Suzuki, Wataru
AU - Luo, Yifan
AU - Ishihara, Kenta
AU - Suzuki, Kens
AU - Miura, Hideo
N1 - Funding Information:
This research was supported partly by JSPS KAKENHI Grant Number JP16H06357. This research activity has been also supported partially by Japanese special coordination funds for promoting science and technology, Japanese Grants-in-aid for Scientific Research, and Tohoku University.
Publisher Copyright:
© Springer Nature Switzerland AG 2020.
PY - 2020
Y1 - 2020
N2 - The mechanism of the drastic decrease in the lifetime of Ni-base superalloy, Alloy 617 under creep-fatigue loading at elevated temperatures was clarified by using EBSD (Electron Back-Scatter Diffraction) analysis. The degradation process was monitored by using an intermittent creep-fatigue test and EBSD analysis. The change of the crystallinity of grains and grain boundaries was quantitatively analyzed by using the image quality (IQ) value obtained from the EBSD analysis. The IQ value indicated the density of defects such as vacancies, dislocations, local strain, and so on. The decrease in the IQ value corresponded to the decrease in the crystallinity of the observed area. The accumulation of fine voids was found to be accelerated under the creep-fatigue loading, and it caused the drastic decrease of not only the IQ value, but also the strength of the grain boundaries. Intergranular cracking started to occur when the crystallinity of grain boundaries decreased to the critical value due to the degradation of the crystallinity caused by the local accumulation of dislocations and voids around the grain boundaries.
AB - The mechanism of the drastic decrease in the lifetime of Ni-base superalloy, Alloy 617 under creep-fatigue loading at elevated temperatures was clarified by using EBSD (Electron Back-Scatter Diffraction) analysis. The degradation process was monitored by using an intermittent creep-fatigue test and EBSD analysis. The change of the crystallinity of grains and grain boundaries was quantitatively analyzed by using the image quality (IQ) value obtained from the EBSD analysis. The IQ value indicated the density of defects such as vacancies, dislocations, local strain, and so on. The decrease in the IQ value corresponded to the decrease in the crystallinity of the observed area. The accumulation of fine voids was found to be accelerated under the creep-fatigue loading, and it caused the drastic decrease of not only the IQ value, but also the strength of the grain boundaries. Intergranular cracking started to occur when the crystallinity of grain boundaries decreased to the critical value due to the degradation of the crystallinity caused by the local accumulation of dislocations and voids around the grain boundaries.
KW - Creep-fatigue damage
KW - EBSD analysis
KW - Intergranular cracking. EBSD analysis
KW - Ni-base superalloy
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U2 - 10.1007/978-3-030-47883-4_58
DO - 10.1007/978-3-030-47883-4_58
M3 - Chapter
AN - SCOPUS:85086135125
T3 - Structural Integrity
SP - 325
EP - 331
BT - Structural Integrity
PB - Springer
ER -