Hydrogen induced cracking (HIC) in Fe-3% Si single crystals under Mode 2 loading was investigated. The results revealed that hydrogen could promote cleavage fracture occurring on a (001) plane, regardless of what the orientation of tensile loading axis was. If it was along a [001] or [110] direction, the normalized threshold stress intensity (⁠KIIH/KIIX⁠) had a minimum value, while the maximum value was obtained when the tensile loading axis was nearly along [111]. Some hydrogen induced secondary cracks were found in which relative displacements normal and/or parallel to the cracking direction were evident on both sides of the secondary crack. This results from the unequal number of screw and/or edge dislocations slipping out or in both sides of the secondary crack; i.e., severe local plastic deformation occurs during hydrogen induced cleavage cracking. The reason that hydrogen promotes cleavage cracking was discussed.

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National Association of Corrosion Engineers
1987
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