An investigation into the effects of hydrogen on the fracture and deformation behavior of Alloy X-750

This study investigated the hydrogen embrittlement of a nickel-base superalloy, Alloy X-750. The effect of hydrogen was examined through tensile and fracture toughness testing incorporating observations from scanning electron microscopy and light microscopy. The elongation for tensile specimens tested at 3.33 ;The effect of hydrogen on the deformation behavior was studied to determine if there was a change in the deformation behavior, and how that would affect the fracture. The effect of hydrogen on the activation area was examined through stress relaxation testing and strain rate change tensile testing incorporating observations from transmission electron microscopy on the dislocation substructure. The activation area was slightly decreased for specimens which contain hydrogen. This change was small and would not be expected to have effected the fracture.;The embrittlement phenomenon may be explained by a reduction of the interfacial strength of the carbide-matrix interface due to hydrogen with possible secondary effects of hydrogen enhanced local plasticity and a local hydrogen pressure at the carbide-matrix interface reducing the void initiation strain.;The effect of hydrogen was also investigated through fracture toughness testing. A model based on a critical strain criterion correlated the fracture behavior as a function of hydrogen. The fracture toughness of the noncharged specimen was 147 MPa...