STP645

    Analysis of Fracture Morphology of Hydrogen-Assisted Cracking in Steel and Its Welds

    Published: Jan 1978


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    Abstract

    The relationships between fracture morphology of hydrogen-assisted cracking, microstructure, and crystallographic orientation were investigated using the scanning electron microscope.

    In the fracture morphology of hydrogen-assisted cracking, quasicleavage fracture, intergranular fracture, and dimple rupture were observed. In the quasicleavage fracture caused by hydrogen, subcracks often were observed along the boundary of martensite lath or ferrite lath, or both, and at the interface between the matrix and carbides.

    The unit fracture facet for hydrogen-assisted cracking, therefore, was defined as the region between subcracks. The unit fracture facet for hydrogen-assisted cracking was smaller than that for cleavage fracture of martensite, upper bainite, and bainitic ferrite. Using the etch pit method the crystallographic orientation of the fracture morphology of hydrogen-assisted cracking was found to be the {110} plane.

    The fracture morphologies of hydrogen-assisted cracking can be categorized as one of four types, each of which can be explained by the microscopic diffusion behavior of hydrogen.

    Keywords:

    hydrogen embrittlement, fractography, crystallography, orientation, three-point bending test, implant weld cold cracking test, cleavage, fractures (materials), subcrack, unit fracture facet, hydrogen cold-work-peak height


    Author Information:

    Kikuta, Y
    Professor and associate professorDrs. of Engineering, Osaka University, Osaka,

    Araki, T
    Professor and associate professorDrs. of Engineering, Osaka University, Osaka,

    Kuroda, T
    Research instructor and Dr. of Engineering, Welding Research Institute of Osaka University, Osaka,


    Paper ID: STP38088S

    Committee/Subcommittee: E08.03

    DOI: 10.1520/STP38088S


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