Stress-induced acceleration of the change of microstructure of ni-base superalloy CM247LC

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

1 Citation (Scopus)

Abstract

The degradation process of Ni-base superalloy CM247LC was investigated experimentally under the creep loading at 900oC. The initial excellent high-temperature strength of this alloy is attributed to its micro texture, the fine binary phase such as cuboidal ?’ (Ni3Al) precipitates orderly dispersed in the ? matrix (Ni-rich matrix). However, it was observed that ?’ precipitates started to coarse perpendicular to the applied uniaxial load direction during high temperature creep loading. The disappearance of the strengthened micro texture caused the acceleration of the crack growth along the phase boundaries of the layered texture and seriously degrades the strength of this material. Therefore, not only the outlook of micro texture but also the changes of the atomic configuration and atomic concentration which were based on the atomic diffusion behavior was investigated for the further explication of rafting mechanism more in detail. It was found that the distribution of Image Quality (IQ) value which was obtained from EBSD analysis monotonically shifted to lower values and the full width of half maximum became wider as the creep loading time increased. This degradation of the order of atomic alignment indicated that lattice defects density increased and ordered superlattice structure (Ll2 structure) became disordered. In addition, the initial periodic distributions of component elements which corresponded to the fine periodic alignment of the ? and ?’ phases also disappeared and the concentration of each element became uniform even though both the ? and ?’ phases still remained even after rafting. The observed creep damage of CM247LC was, therefore, dominated by the degradation of the order of atomic arrangement, and this degradation was attributed to the strain-induced atomic diffusion of component elements. It is very important, therefore, to suppress this strain-induced acceleration of atomic diffusion in this alloy 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
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
Country/TerritoryUnited States
CityTampa
Period17/11/317/11/9

ASJC Scopus subject areas

  • Mechanical Engineering

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