STP633: Susceptibility of Zirconium Alloys to Delayed Hydrogen Cracking

    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,

    Pages: 19    Published: Jan 1977


    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


    Paper ID: STP35593S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP35593S


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