Berlin 2015 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Hydrogen in metals III: Experiments
MM 15.5: Vortrag
Montag, 16. März 2015, 17:15–17:30, TC 006
Investigation of Crack and Blister Formation Due to Hydrogen Loading in Iron — •Marie Tiegel1, Annegret Lehmberg1, May L. Martin1, Martin Deutges1, Christine Borchers1, and Reiner Kirchheim1,2 — 1Institut für Materialphysik, University Göttingen, Germany — 2International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Japan
Hydrogen-induced damage is a serious problem in various applications of metals and it is becoming more relevant as hydrogen is developed as a solution for energy storage. The mechanism of damage due to hydrogen is still ambiguous and requires further investigation. In this work, hydrogen- induced cracking (HIC) in high-purity iron was investigated. The samples were electrochemically loaded with hydrogen at different current densities. Hydrogen loading leads to cracks inside the bulk of iron, and the cracks near the surface create bubble-like defects on the surface above the cracks, called blisters. The microstructure of the cracks and blisters was investigated using SEM and TEM, including electron backscatter diffraction analysis. The surface curvature of the blisters consists of steps in the material, which is attributed to multiple individual crack advance events. TEM observations of the microstructure underneath the blister surfaces suggest that the formation of the blisters is due to the production of shear bands. Density measurements allow estimation of the pressure in the cracks, which is compareble to the yield stress of iron. In conclusion, the growth mechanism of blisters and cracks is due to a stress release following an increase of pressure in newly formed voids during hydrogen loading.