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Keynote Lecture

Understanding the interaction between a steel microstructure and hydrogen: the key to develop more hydrogen resistant materials

Friday (28.09.2018)
09:15 - 09:45 S1/01 - A2
Part of:

Hydrogen (H) presence in metals is detrimental as unpredictable failure might occur. Though decades of research have been done, the underlying mechanism is still not fully understood. During state-of-the-art developments in material’s design, precipitates play an essential role since they can both enhance the resistance against H induced failure and strengthen the material. Well-designed H trapping sites may be a relevant strategy to enhance the H embrittlement (HE) resistance. This work studies five types of carbides in three Fe-C-X alloys with increasing carbon content: Ti, Cr, Mo, V and W-based precipitates. To evaluate the effect of these precipitates, two conditions were compared for each composition: as quenched and quenched and tempered. Carbides were introduced during tempering. The material/H interaction was fully characterized: in-situ tensile testing was performed to assess the HE sensitivity, hot/melt extraction was done to determine the H content, thermal desorption spectroscopy was performed to evaluate the H trapping capacity of the carbides and permeation experiments were executed to evaluate the H diffusivity. The HE degree was correlated with the amount of H. Three different types of H, determined by the strength by which they were trapped, were considered by combining the different H characterization techniques. It was established that H trapped at dislocations played a determinant factor. This confirmed the crucial role of an enhanced dislocation mobility in the presence of H, which is a solid experimental proof of the HELP mechanism. In contrast, H trapped by the carbides did not show a significant effect on the H induced mechanical degradation. Since all precipitates were able to deeply trap a significant amount of H, their addition was beneficial to enhance the HE resistance.

Prof. Dr. Kim Verbeken
Ghent University
Additional Authors:
  • Dr. Tom Depover
    Ghent University