Elements Of X Ray Diffraction

The synergistic action and interplay of hydrogen embrittlement mechanisms in steels and iron: Localized plasticity and decohesion

Effect of pre-strain on hydrogen embrittlement of metastable austenitic stainless steel under different hydrogen conditions

The effect of prior austenite grain size on hydrogen embrittlement of Co-containing 18Ni 300 maraging steel

Combined effects of prior plastic deformation and sensitization on hydrogen embrittlement of 304 austenitic stainless steel

A sequentially coupled hydrogen diffusion-cohesive zone modeling approach was applied to the simulation of hydrogen-induced delayed intergranular (IG) fracture in high-strength low-alloy steels. The effects of multiple hydrogen trap sites and mechanical deformation on the diffusion and cohesive strength of grain boundaries (GB) were taken account, in order to reveal that the hydrogen trapped at GB play a dominant role in the degradation processes of hydrogen of high-strength low-alloy steels, which leads to the IG fracture. The approach was implemented by Abaqus software in the form of a two-steps procedure including the coupled elastoplastic-transient hydrogen diffusion analysis and cohesive stress analysis. To validate the approach, the constant load tests of hydrogen pre-charged AISI 4135 high-strength low-alloy steel notched bars in literature were analyzed. Good agreement is observed between the simulation and experimental data of time to failure. The results confirm that hydrogen-induced IG fracture of high strength low-alloy steels can be related to the hydrogen concentration trapped at GB. The critical hydrogen concentration at GB for crack initiation is independent of the initial hydrogen concentration but depends strongly on the local stress level and stress triaxiality. The critical hydrogen concentration linearly decreases with increasing normalized peak maximal principal stress normalized by the critical cohesive strength in absence of hydrogen.

Cohesive zone modeling of hydrogen-induced delayed intergranular fracture in high strength steels

Plastic pre-strains were applied to the metastable 304L austenitic stainless steel at both room temperature (20 °C) and higher temperatures (i.e., 50, 80 and 100 °C), and then the hydrogen embrittlement (HE) susceptibility of the steel was evaluated by cathodically hydrogen-charging and tensile testing. The 20 °C pre-strain greatly strengthened the steel, but simultaneously significantly increased the HE susceptibility of the steel, since α' martensite was induced by the pre-strain, causing the pre-existence of α' martensite, which provided "highways" for hydrogen to transport deep into the steel during the hydrogen-charging. Although the warm pre-strains did not strengthen the steel as significantly as the 20 °C pre-strain, they retained the HE resistance of the steel. This is because the higher temperatures, particularly 80 and 100 °C, suppressed the α' martensite transformation during the pre-straining. Pre-strain at a temperature slightly higher than room temperature has a potential to strengthen the metastable 304L austenitic stainless steel without compromising its initial HE resistance.

Weijie Wu

Papers

Combined effects of prior plastic deformation and sensitization on hydrogen embrittlement of 304 austenitic stainless steel

Cohesive zone modeling of hydrogen-induced delayed intergranular fracture in high strength steels

Warm Pre-Strain: Strengthening the Metastable 304L Austenitic Stainless Steel without Compromising Its Hydrogen Embrittlement Resistance.