Crystallinity degradation caused by alloying elements diffusion during creep of ni-base superalloy

Ken Suzuki, Takuya Murakoshi, Hideo Miura

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

4 Citations (Scopus)

Abstract

High temperature mechanical properties of Ni-base superalloys are improved by the fine cuboidal γ' (Ni3Al) precipitates orderly-dispersed in the γ matrix (Ni-rich matrix) because the dispersed texture in a grain inhibits dislocation motion. However, it is well known that directional coarsening of the γ' precipitates perpendicular to a principal stress occurs not only during creep loading but also during cyclic loading and, the formation of the raft causes the decreasing of high temperature strength drastically. Therefore, it is very important to evaluate the damage of the alloys caused by creep and fatigue loading based on the change of their micro texture. In this study, the change of crystallinity of the Ni-base superalloys (CM247LC) under creep loading was analyzed by applying Electron Back-Scattered Diffraction (EBSD) method. The image quality (IQ) value obtained from the EBSD analysis was used for the quantitative evaluation of the crystallinity in the area where an electron beam of 10 nm in diameter was irradiated. The quality of the atomic alignment of both γ' and γ phases was found to degrade with increasing creep damage. The degradation of crystallinity suggests that the ordered L12 structure of Ni3Al became disordered and the density of dislocations and vacancies increased. However, KAM (Kernel Average Misorientation) value did not change significantly with increasing creep damage. Therefore, the dominant factor of the creep damage of this alloy is the strain-induced diffusion of elements under loading, and the decrease of the crystallinity.

Original languageEnglish
Title of host publicationEmerging Technologies; Safety Engineering and Risk Analysis; Materials
Subtitle of host publicationGenetics to Structures
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791857571
DOIs
Publication statusPublished - 2015 Jan 1
EventASME 2015 International Mechanical Engineering Congress and Exposition, IMECE 2015 - Houston, United States
Duration: 2015 Nov 132015 Nov 19

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume14-2015

Other

OtherASME 2015 International Mechanical Engineering Congress and Exposition, IMECE 2015
CountryUnited States
CityHouston
Period15/11/1315/11/19

ASJC Scopus subject areas

  • Mechanical Engineering

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