STP782

    Irradiation Embrittlement in Some Austenitic Superalloys

    Published: Jan 1982


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    Abstract

    The nature of the irradiation embrittlement phenomenon in selected austenitic superalloys was evaluated in tubular specimens compression tested at elevated temperatures. Materials included the commercial alloys Inconel 706 and Nimonic PE-16 and two experimental alloys. All are precipitation hardenable and were irradiated from 2.8 to 7.1 × 1022 n/cm2 (E>0.1MeV). The tests revealed marked ductility losses in all alloys, the most severe embrittlement occurring at 110°C above the temperature at which the materials were irradiated. In some instances, zero ductility was recorded. The testing further revealed that short-term post-irradiation heat treatments produced moderate to high levels of ductility recovery without significant losses in strength.

    Extensive scanning and transmission electron microscopy examinations have indicated that the low ductility behavior is associated with intergranular fracture and the copious precipitation of γ′ along or adjacent to grain boundaries. Based upon these results it is concluded that the principal cause of embrittlement in these alloys is the precipitation of γ′ along grain boundaries during irradiation. The segregation of silicon in addition to titanium and aluminum is considered a major factor in the embrittlement mechanism.

    Keywords:

    radiation damage, embrittlement, superalloys, gamma prime


    Author Information:

    Vaidyanathan, S
    Manager and Senior Engineer, Advanced Reactor Systems Department, General Electric Co., Sunnyvale, California

    Lauritzen, T
    Manager and Senior Engineer, Advanced Reactor Systems Department, General Electric Co., Sunnyvale, California

    Bell, WL
    Senior Engineer, Advanced Reactor Systems Department, Vallecitos Nuclear Center, Pleasanton, California


    Paper ID: STP34369S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP34369S


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