PSI - Issue 33

S. Schoenborn et al. / Procedia Structural Integrity 33 (2021) 757–764 S. Schoenborn, T. Melz, J. Baumgartner, C. Bleicher / Structural Integrity Procedia 00 (2019) 000–000

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4. Conclusions By means of fatigue tests in a pressurized hydrogen atmosphere, reduced lifetimes and changes in the slope and knee point of S/N curves were documented for the material 1.4521 in the LCF and HCF regime compared to the fatigue tests carried out in air. For VHCF, however, no influence on fatigue life or fatigue strength was observed, if the local stress is less than about 400 MPa. With an increasing notch factor this effect is more pronounced due to the high local stress concentration. The results are especially of importance because X2CrMoTi18-2, with a tensile strength of only R m = 523 MPa, is commonly not used for research regarding hydrogen embrittlement, which mostly focuses materials with a tensile strength >1000 MPa. This observation also applies to the material 1.4301, which was also investigated within the framework of this DFG research project [17, 18, 19]. While no influence of the hydrogen on the cyclic material behavior was observed based on the stress-strain curves, this influence is more evident for the evaluation in the form of the strain-life curve and the cyclic deformation curves. Due to the higher local stresses, the susceptibility of the investigated material to hydrogen also increases. This encourages hydrogen embrittlement, which leads to premature failure of the subjected specimens exposed to pressurized hydrogen, especially at high load horizons. However, this susceptibility to hydrogen is only evident under cyclic loading and not under quasi-static loading, as shown in the initial load curve. Acknowledgement This article contents results of the DFG research projekt “Grundlagen für die Bemessung druckwasserstoffexponierter Komponenten unter Berücksichtigung werkstoffspezifischer Eigenschaften und Schädigungsmechanismen“ (ME 3301/4-1 | OE 558/13-1). Our thanks go to the German Research Foundation (DFG) for funding this project. References [1] European Comission: https://ec.europa.eu/info/strategy/priorities-2019-2024/european-green-deal_de. [2] Statistisches Bundesamt, Umweltnutzung und Wirtschaft - Tabellen zu den Umweltökonomischen Gesamtrechnungen. Teil 2 - Energie, Ausgabe 2018, Tab. 3.3.4. [3] Lynch, S., 2012. Hydrogen embrittlement phenomena and mechanisms, Corrs. Rev., Bd. 30, 105-123. [4] Barnoush, A., Yang, B., Vehoff, H., 2008. Effect of Hydrogen and Grain Boundaries on Dislocation Nucleation and Multiplication Examined with a NI-AFM. Advances in Solid State Physics, 47, 253–269. [5] Barrera, O., Tarleton, E., Tang, H. W., Cocks, A.C.F., 2016. Modelling the coupling between hydrogen diffusion and the mechanical behaviour of metals. Computational Materials Science 122, 4710, 219–228. DOI: https://doi.org/10.1016/j.commatsci.2016.05.030. [6] Walston, W. S., Bernstein, I. M., Thompson, A. W., 1992. 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[19] Melz, T.; Baumgartner, J.; Schmiedl, T.; Oechsner, M.; Engler, C. T.; Vatter, J., 2021. Abschlussbericht Hy2Design - Grundlagen für die Bemessung druckwasserstoffexponierter Komponenten unter Berücksichtigung werkstoffspezifischer Eigenschaften und Schädigungsmechanismen. ME 3301/4-1 | OE 558/13-1, Deutsche Forschungsgemeinschaft DFG.