Stress-induced change of the microstructure and strength of modified 9Cr-1Mo steel under fatigue and creep loadings at elevated temperatures

Taichi Shinozaki, Ken Suzuki, Hideo Miura

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

1 Citation (Scopus)

Abstract

The change of the lath martensitic structure in modified 9Cr-1Mo steel was observed in the specimens after the fatigue and creep tests using EBSD (Electron Back-Scatter Diffraction). The Kernel Average Misorientation (KAM) value obtained from the EBSD analysis were used for the quantitative evaluation of the change in the lath martensitic texture. It was found that the average KAM values of the fractured specimens decreased clearly after 107-108 cycles of the fatigue loading at temperatures higher than 500oC when the amplitude of the applied stress exceeded a critical value. This change corresponded to the disappearance of the lath martensitic structure. The critical value decreased monotonically with the increase of the test temperature. This microstructure change decreased the strength of the alloy drastically. It was found that the change of the microstructure started at a certain time at each test temperature as a function of the amplitude of the applied stress. There was the critical stress at which the microstructure change started at each test temperature higher than 500oC, and the activation energy of the change was determined as a function of temperature and the amplitude of the applied stress. The dominant factor of the microstructure change was the stress-induced acceleration of the atomic diffusion of the component elements in the alloy. In order to improve the long-term reliability of the alloy, it is very important to increase the activation energy by modifying the microstructure of this alloy.

Original languageEnglish
Title of host publicationMechanics of Solids, Structures and Fluids; NDE, Structural Health Monitoring and Prognosis
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791858448
DOIs
Publication statusPublished - 2017 Jan 1
EventASME 2017 International Mechanical Engineering Congress and Exposition, IMECE 2017 - Tampa, United States
Duration: 2017 Nov 32017 Nov 9

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume9

Other

OtherASME 2017 International Mechanical Engineering Congress and Exposition, IMECE 2017
CountryUnited States
CityTampa
Period17/11/317/11/9

Keywords

  • Electron back-scatter diffraction
  • High cycle fatigue
  • Kernel average misorientation
  • Micro texture
  • Mod. 9Cr-1Mo steel

ASJC Scopus subject areas

  • Mechanical Engineering

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    Shinozaki, T., Suzuki, K., & Miura, H. (2017). Stress-induced change of the microstructure and strength of modified 9Cr-1Mo steel under fatigue and creep loadings at elevated temperatures. In Mechanics of Solids, Structures and Fluids; NDE, Structural Health Monitoring and Prognosis (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE); Vol. 9). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/IMECE2017-70494