EFFECT OF HYDROGEN ON DEFORMATION STRUCTURE OF INCONEL-718

Effects of hydrogen on the deformation behavior and the structure of deformation bands under monotonic loading of Inconel 718 were investigated. Hydrogen significantly reduced tensile elongation of the material and susceptibility to hydrogen embrittlement was not influenced by the aging condition. In the hydrogen-free specimen the spacing between deformation bands decreased with increasing strain, reached the minimum value at a strain of about 8% and remained constant until its fracture. Although hydrogen reduced the band spacing at the early stage of deformation, the minimum spacing was not influenced by hydrogen. Hydrogen-induced cracking occurred along the deformation bands when the band spacing reached the minimum spacing, while the deformation of the hydrogen-free specimen still continued until the fracture with the constant band spacing. It is proposed that hydrogen suppressed the cross slip and caused stress concentration within the deformation bands which were consisted of dislocations trapping hydrogen, resulting in the brittle fracture along the deformation bands.