STP633

    Susceptibility of Zirconium Alloys to Delayed Hydrogen Cracking

    Published: Jan 1977


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    Abstract

    Smooth and notched cantilever beams and round-notched bars were machined from pressure tubes of cold-worked Zr-2.5Nb and Zircaloy-2. They were loaded in the temperature range 290 to 520 K. After two thermal cycles and at high stress, cracks were initiated in smooth beams of cold-worked Zr-2.5Nb. Under the same test conditions, cold-worked Zircaloy-2 plastically deformed with no cracking. When notches were present, cracks propagated at the same rate in both materials by delayed hydrogen cracking. In cold-worked Zr-2.5Nb, the crack velocity followed an Arrhenius plot with an apparent activation energy of 42 kJ/mol. Below 420 K, the threshold stress intensity factor for delayed hydrogen cracking was about 5 MPa m. Therefore, cracking can be prevented by keeping tensile stresses very low.

    Keywords:

    zirconium, zirconium alloys, hydrides, crack initiation, crack propagation, stresses, temperature


    Author Information:

    Coleman, CE
    Metallurgists, Metallurgical Engineering Branch, Chalk River Nuclear Laboratories, Chalk River, Ontario,

    Ambler, JFR
    Metallurgists, Metallurgical Engineering Branch, Chalk River Nuclear Laboratories, Chalk River, Ontario,


    Paper ID: STP35593S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP35593S


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