Berlin 2015 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 15: Hydrogen in metals III: Experiments

MM 15.3: Talk

Monday, March 16, 2015, 16:30–16:45, TC 006

The impact of the carbon content on hydrogen diffusion and its influence on hydrogen embrittlement for lab-cast bainitic Fe-C steels — •Emilie Van den Eeckhout, Tom Depover, and Kim Verbeken — Department of Materials Science and Engineering, Ghent University (UGent), Technologiepark 903, B-9052 Ghent, Belgium

The present work investigates hydrogen diffusion in lab-cast alloys in which a bainitic microstructure was introduced. The high diffusivity of hydrogen is a critical factor affecting hydrogen induced cracking since hydrogen is enabled to diffuse to highly stressed regions, leading to an accelerated failure. When hydrogen diffusion is impeded by introducing hydrogen traps, fracture is delayed and the susceptibility to hydrogen embrittlement is reduced.

The hydrogen diffusion coefficient is calculated using a permeation cell based on the Devanathan - Stachurski permeability cell. Decreasing the carbon content from 0.4 to 0.2 wt. % elevates the hydrogen diffusion, which can be attributed to less hydrogen traps of the latter bainitic steel. The impact of this higher diffusivity on the degree of embrittlement was evaluated by performing tensile tests on in-situ hydrogen charged samples at various cross-head displacement speeds. A correlation with melt extraction tests is made to demonstrate the combined effect of hydrogen content and hydrogen diffusion on hydrogen embrittlement. Additionally, the role of hydrogen diffusion is evaluated by calculating and visualizing, by in-depth fractography, the distance hydrogen can diffuse during a tensile test.