Characterization of crack tip damage zone formation on alloy 625 during fatigue crack growth at 750°c by transmission EBSD method

Yuji Ozawa, Tatsuya Ishikawa, Yoichi Takeda

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

Abstract

In order to clarify the mechanism of fatigue crack growth in alloy 625, which is a candidate material for use in advanced ultra supercritical power plants, the crack tip damage zone formation after a crack growth test conducted in high temperature steam was investigated. It was observed that the oxide thickness at the crack tip tended to increase with decreasing cyclic loading frequency. The crack path was a mix of transgranular and intergranular fractures. According to the grain reference orientation deviation (GROD) maps, it was revealed that the density of geometrically necessary dislocations (GNDs) in the matrix along the crack path and ahead of crack tip increased with an increase in the fatigue crack growth rate (FCGR) due to environmental effects. It was observed that (1) mobile dislocations at the crack surface were blocked due to the thick oxide layer, resulting in an increase in the density of GNDs, and (2) an increase in the density of GNDs might induce stress concentration at the crack tip, deformation twinning, and the acceleration of FCGRs.

Original languageEnglish
Title of host publicationI and C, Digital Controls, and Influence of Human Factors; Plant Construction Issues and Supply Chain Management; Plant Operations, Maintenance, Aging Management, Reliability and Performance; Renewable Energy Systems
Subtitle of host publicationSolar, Wind, Hydro and Geothermal; Risk Management, Safety and Cyber Security; Steam Turbine-Generators, Electric Generators, Transformers, Switchgear, and Electric BOP and Auxiliaries; Student Competition; Thermal Hydraulics and Computational Fluid Dynamics
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791857618
DOIs
Publication statusPublished - 2017 Jan 1
EventASME 2017 Power Conference Joint with ICOPE 2017, POWER 2017-ICOPE 2017, collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum - Charlotte, United States
Duration: 2017 Jun 262017 Jun 30

Publication series

NameAmerican Society of Mechanical Engineers, Power Division (Publication) POWER
Volume2

Other

OtherASME 2017 Power Conference Joint with ICOPE 2017, POWER 2017-ICOPE 2017, collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum
CountryUnited States
CityCharlotte
Period17/6/2617/6/30

ASJC Scopus subject areas

  • Mechanical Engineering
  • Energy Engineering and Power Technology

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    Ozawa, Y., Ishikawa, T., & Takeda, Y. (2017). Characterization of crack tip damage zone formation on alloy 625 during fatigue crack growth at 750°c by transmission EBSD method. In I and C, Digital Controls, and Influence of Human Factors; Plant Construction Issues and Supply Chain Management; Plant Operations, Maintenance, Aging Management, Reliability and Performance; Renewable Energy Systems: Solar, Wind, Hydro and Geothermal; Risk Management, Safety and Cyber Security; Steam Turbine-Generators, Electric Generators, Transformers, Switchgear, and Electric BOP and Auxiliaries; Student Competition; Thermal Hydraulics and Computational Fluid Dynamics (American Society of Mechanical Engineers, Power Division (Publication) POWER; Vol. 2). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/POWER-ICOPE2017-3458