Creep and Environmental Effects on the High Temperature Creep-Fatigue Behavior of Alloy 617

    Volume 8, Issue 6 (June 2011)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 11 July 2011

    Page Count: 13


    Carroll, L. J.
    Idaho National Laboratory,

    Cabet, C.
    CEA, DEN, DPC, SCCME,

    Madland, R.
    Colorado School of Mines,

    Wright, R. N.
    Idaho National Laboratory,

    (Received 31 January 2011; accepted 2 May 2011)

    Abstract

    Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) of the very high temperature reactor (VHTR), expected to have an outlet temperature as high as 950°C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Strain-controlled low cycle fatigue (LCF) tests including hold times up to 1800 s at maximum tensile strain were conducted at 950°C and a total strain range of 0.3 % in air and in a simulated VHTR impure helium. For similar test conditions, the creep-fatigue behavior was globally similar in both environments. The fatigue resistance decreased when a hold time was added at peak tensile strain, consistent with the observed change in fracture mode from transgranular to intergranular. Further increases in the tensile hold time, beyond 180 s, were not detrimental to the creep-fatigue resistance. The influence of oxidation on the fatigue crack initiation and propagation is discussed. Bulk damage in the form of grain boundary cracking was present in the interior of the creep-fatigue specimens. This bulk cracking was quantified and found to be similar for hold times of up to 1800 s consistent with the saturation in failure lives.


    Paper ID: JAI103797

    DOI: 10.1520/JAI103797

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    Author
    Title Creep and Environmental Effects on the High Temperature Creep-Fatigue Behavior of Alloy 617
    Symposium Creep Fatigue Interactions: Test Methods and Models, 2010-11-17
    Committee E08