Atomic diffusion induced damage of Ni-base super alloy at elevated temperature

Motoki Takahashi, Ken Suzuki, Hideo Miura

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

1 Citation (Scopus)


Ni-base superalloys consisting of binary phases such as cuboidal ?' (Ni3Al) precipitates orderly dispersed in the ? matrix (Ni-rich matrix) have been generally used for rotor blades in energy power plants. However, fine dispersed ?' precipitates are coarsened perpendicularly to the applied load direction during high temperature creep loading. As this phenomenon called "Rafting" proceeds, the strengthened micro texture disappears and then, cracks starts to grow rapidly along the boundaries of the layered texture. Thus, it is very important to evaluate the change of the crystallinity of the alloy in detail for explicating the atomic scale damage process. In this study, the change of the micro-texture of the Ni-base superalloy (CM247LC) was observed by using EBSD method. The change in the crystallinity was evaluated using both Kernel Average Misorientation (KAM) and image quality (IQ) values. The KAM value indicates the dislocation density and the IQ value shows the order of atom arrangement in the observed area. As a result, KAM value showed no significant change with increasing the creep damage. On the other hand, the IQ value monotonically shifted to lower values and the average IQ value gradually decreased as the creep loading time increased. Decreasing IQ value without change in KAM value implies that the density of point defects such as vacancies mainly increased under creep loading and ordered Ll2 structure became disordered. Therefore, the creep damage of this alloy is mainly dominated by not the accumulation of dislocations, but the increase in the disorder of atom arrangement in the micro texture caused by the diffusion of component elements.

Original languageEnglish
Title of host publicationMechanics of Solids, Structures and Fluids; NDE, Diagnosis, and Prognosis
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791850633
Publication statusPublished - 2016
EventASME 2016 International Mechanical Engineering Congress and Exposition, IMECE 2016 - Phoenix, United States
Duration: 2016 Nov 112016 Nov 17


OtherASME 2016 International Mechanical Engineering Congress and Exposition, IMECE 2016
Country/TerritoryUnited States

ASJC Scopus subject areas

  • Mechanical Engineering


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