Optimizing hydrogen resistance in fusion energy structural stainless steel via controlled uniaxial strain

Abstract

Fusion energy as a sustainable clean power shaping our future. However, the prevalent issue of hydrogen embrittlement (HE) of secondary processing structural materials in fusion energy systems has been widely concerned. This study explored the effect of secondary deformation on HE resistance of nickel-economized stainless steel (NEASS) used in tritium plant through varying degrees of uniaxial pre-strain. Unexpectedly, the high pre-strained NEASS with H-charging simultaneously exhibited high ultimate strength and low HE susceptibility. The increase in ultimate strength comes from the strain hardening effect caused by dislocation multiplication, while the improvement of HE resistance is contributed by the synergistic effect of deformation substructure, preferred orientation, and dislocation configuration. The interplay of these effects altered the hydrogen distribution inside the material, the hydrogen trapping capacity of microstructure, and the initiation behavior of hydrogen-induced cracks (HICs). Consequently, the NEASS exhibited low HE susceptibility during subsequent slow- strain rate tensile deformation, eventually resulting in shallower brittle fracture region, fewer HICs, and lower elongation loss after fracture with H-charging.