Evaluation of damage evolution in nickel-base heat-resistant alloy under creep-fatigue loading conditions

Ken Suzuki, Takuya Murakoshi, Hiroki Sasaki, Hideo Miura

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

4 Citations (Scopus)

Abstract

In this study, interrupted creep and creep-fatigue tests of Alloy 617, which is a candidate alloy for boiler tubes and pipes of A-USC (advanced ultra-supercritical) power plants of the 700oC-class, were conducted to investigate damage evolution process. Also, the change of the micro texture of the alloy was continuously observed at a fixed area to elucidate the mechanism of damage evolution under creep and creep-fatigue loading from the viewpoint of the change of the order of atom arrangement using EBSD (Electron Back-Scatter Diffraction) analysis. The conditions of the creep test were a temperature of 800oC and the stress of 150 MPa in inert gas (99.9999% Ar). The stress-controlled creep-fatigue tests were carried out at 800oC in Ar using stress ratio R = -1 and hold time of 10 minutes at peak tension. IQ (Image Quality) values, which are the average sharpness of the obtained diffraction pattern, were used for evaluating the change of the micro texture during the tests. In both creep and creep-fatigue test, intergranular cracks appeared. The IQ value decreased monotonically in the vicinity of grain boundaries with the decrease of fracture life, indicating that the crystallinity of grain boundaries degraded faster than that of grains. This localized damage around grain boundaries was attributed to the intergranular crack propagation in the creep and creep-fatigue test. In addition, all the grain boundaries with IQ value lower than 85% of IQ value in as-received specimen were found to be cracked during both creep and creep-fatigue test. Therefore, there was the critical IQ value around grain boundaries at which intergranular cracks occurred under creep or creep-fatigue loading condition.

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
CountryUnited States
CityTampa
Period17/11/317/11/9

ASJC Scopus subject areas

  • Mechanical Engineering

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