STP1175

    Helium-Induced Weld Degradation of HT-9 Steel

    Published: Jan 1994


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    Abstract

    Helium-bearing Sandvik HT-9 ferritic steel was tested for weldability to simulate the welding of structural components of a fusion reactor after irradiation. Helium was introduced into HT-9 steel to 0.3 and 1 atomic parts per million (appm) by tritium doping and decay. Autogenous single pass full penetration welds were produced using a gas tungsten arc (GTA) welding process under laterally constrained conditions. Microscopic examination showed no sign of any weld defect in HT-9 steel containing 0.3 appm helium. However, intergranular micro cracks were observed in the HAZ of HT-9 steel containing 1 appm helium. The microcracking was attributed to helium bubble growth at grain boundaries under the influence of high stresses and temperatures that were present during welding. Mechanical test results showed that both the yield strength (YS) and ultimate tensile strength (UTS) decreased with increasing temperature, while the total elongation increased with increasing temperature for all control and helium-bearing HT-9 steels.

    Keywords:

    Sandvik HT-9 steel, tritium doping and decay, GTA welding, HAZ cracking, helium bubble growth


    Author Information:

    Wang, C-A
    Research Assistant, Materials Engineering, Auburn University, AL

    Lin, HT
    Research Staff Members, Oak Ridge National Laboratory, TN

    Grossbeck, ML
    Research Staff Members, Oak Ridge National Laboratory, TN

    Chin, BA
    Professor, Materials Engineering, Auburn University, AL


    Paper ID: STP23971S

    Committee/Subcommittee: E10.02

    DOI: 10.1520/STP23971S


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