Irradiation Assisted Stress Corrosion Cracking (IASCC) of Nickel-Base Alloys in Light Water Reactors Environments—Part I: Microstructure Characterization
Nickel-base alloys, 625DA and 625Plus have received renewed interest as potential structural materials in nuclear reactors to replace the austenitic stainless steels, which show high susceptibility of irradiation-assisted stress corrosion cracking (IASCC). We investigated the microstructural response of both alloys after 2 MeV protons irradiated to 5dpa at 360 °C in the Michigan Ion Beam Laboratory (MIBL). Transmission electron microscopy was performed on plan-viewed samples with a depth range 9–12 μm prepared by jet-polishing. Detailed analysis included changes in phases, dislocation loops, voids swelling, and radiation induced segregation (RIS). Nano-scaled irradiation-induced precipitates and dislocation loops were pervasive. Voids were absent in these alloys. RIS occurred at random high angle grain boundaries examined. A complete characterization of the irradiated microstructure is required to understand their mechanical and IASCC behavior.
KeywordsMicrostructure Nickel-base alloy Precipitates Proton irradiation IASCC
The authors acknowledge the financial support by EPRI (contracts 10002164 and 10002154), and DOE (contract 4000136101), and gratefully acknowledge O. Toader, T. Kubley, E. Uberseder and D. Woodley for their assistance with the proton irradiations. Access to the microscopes of the Michigan Center for Materials Characterization (MC2) at University of Michigan is also acknowledged. The technical assistance on FEI Talos Microscope from Dr. C. M. Parish at Oak Ridge National Laboratory is greatly appreciated. This work was also supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment.
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