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Title: Low Cycle Fatigue and Creep-Fatigue Behavior of Alloy 617 at High Temperature

Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) application of the Very High Temperature Nuclear Reactor (VHTR), expected to have an outlet temperature as high as 950 degrees C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Initial creep-fatigue work on Alloy 617 suggests a more dominant role of environment with increasing temperature and/or hold times evidenced through changes in creep-fatigue crack growth mechanism/s and failure life. Continuous cycle fatigue and creep-fatigue testing of Alloy 617 was conducted at 950 degrees C and 0.3% and 0.6% total strain in air to simulate damage modes expected in a VHTR application. Continuous cycle specimens exhibited transgranular cracking. Intergranular cracking was observed in the creep-fatigue specimens, although evidence of grain boundary cavitation was not observed. Despite the absence of grain boundary cavitation to accelerate crack propagation, the addition of a hold time at peak tensile strain was detrimental to cycle life. This suggests that creepfatigue interaction may occur by a different mechanism or that the environment may be partially responsible for accelerating failure.
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0094--9930
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Pressure Vessel Technology; Journal Volume: 135; Journal Issue: 6
Research Org:
Idaho National Laboratory (INL)
Sponsoring Org:
Country of Publication:
United States
36 MATERIALS SCIENCE; alloy 617; creep-fatigue; environment