Initial Intergranular Cracking of Ni-Base Superalloys Due to the Degradation of the Crystallinity of Grain Boundaries Under Creep-Fatigue Loading

Wataru Suzuki, Yifan Luo, Kenta Ishihara, Kens Suzuki, Hideo Miura

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

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.

Original languageEnglish
Title of host publicationStructural Integrity
PublisherSpringer
Pages325-331
Number of pages7
DOIs
Publication statusPublished - 2020

Publication series

NameStructural Integrity
Volume16
ISSN (Print)2522-560X
ISSN (Electronic)2522-5618

Keywords

  • Creep-fatigue damage
  • EBSD analysis
  • Intergranular cracking. EBSD analysis
  • Ni-base superalloy

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Mechanics of Materials

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