Dual-phase cohesive zone modelling and experimental validation for hydrogen-assisted cracking of 2205 duplex stainless steel

Abstract

The hydrogen-assisted cracking (HAC) behavior of 2205 duplex stainless steel is investigated via experimental testing and computational modelling, with specific focus on developing a predictive methodology for the coupled effects of hydrogen diffusion and stress. The effects of duration and stress level on hydrogen-assisted fracture in the dual-phase microstructure are characterized via tensile testing of single-edge notch specimens under hydrogen diffusion conditions. Crack initiation and growth is shown to occur predominantly in the ferrite phase with the austenite phase acting to retard crack growth, leading to discontinuous crack patterns. Mixed brittle and ductile fracture characteristics were identified, due to the competitive effects of hydrogen-induced decohesion and localized plasticity. A key novelty is the development and verification of a sub-modelling finite element methodology of the dual-phase microstructure, incorporating hydrogen diffusion, coupled hydrogen-stress effects and cohesive zone cracking. The model consistently predicts observed crack length and mixed-phase induced crack morphology. Increased refinement of austenite phase is shown to increase fracture resistance of the dual-phase steel, consistent with published findings.