Degradation of the strength of grains and grain boundaries of Ni-base superalloy under creep and creep-fatigue loadings

Takuya Murakoshi, Hayato Sakamoto, Taichi Shinozaki, Ken Suzuki, Hideo Miura

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The degradation process of the micro texture of Ni-base superalloys was observed under fatigue and creep-fatigue loading conditions at elevated temperatures higher than 700°C by applying electron back-scatter diffraction (EBSD) analyses. The local distribution of the crystallinity of a grain and a grain boundary was defined quantitatively by analyzing the Kikuchi pattern obtained from each electron-beam-irradiated area with a diameter of 50 nm. The calculated image quality value was used for the analysis. It was found that the crystallinity of grain boundaries degraded seriously under creep-fatigue loading conditions due to the acceleration of anisotropic strain-induced diffusion of component elements. Since the initial finely-controlled strengthened micro texture disappeared due to the anisotropic diffusion of component elements, this degradation was found to cause the drastic decrease of the strength of grains and grain boundaries and thus, lifetime of the material. The decrease of the strength of both grains and grain boundaries was measured by micro tensile test system in a scanning electron microscope by making a small sample from bulk specimen using focused ion beam. The strength of a grain and a grain boundary varied drastically depending on their crystallinity, in other words, the image quality value.

Original languageEnglish
Title of host publicationAdvances in Fracture and Damage Mechanics XVI - 16th FDM
EditorsPaolo Maria Mariano, Sergio Baragetti, Katia Casavola, Carmine Pappalettere, Ferri M.H. Aliabadi
PublisherTrans Tech Publications Ltd
Pages31-34
Number of pages4
ISBN (Print)9783035711684
DOIs
Publication statusPublished - 2017
Event16th International Conference on Fracture and Damage Mechanics, 2017 - Florence, Italy
Duration: 2017 Jul 182017 Jul 20

Publication series

NameKey Engineering Materials
Volume754 KEM
ISSN (Print)1013-9826
ISSN (Electronic)1662-9795

Other

Other16th International Conference on Fracture and Damage Mechanics, 2017
CountryItaly
CityFlorence
Period17/7/1817/7/20

Keywords

  • Creep-fatigue damage
  • Micro texture
  • Ni-base superalloy
  • Order of atom arrangement
  • Strength of grain boundary

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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