PSI - Issue 77

Jan Kec et al. / Procedia Structural Integrity 77 (2026) 264–271

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4. Conclusions This study investigated FCGR and FT of electrochemically hydrogen-charged HFW welds in X52 steel. The most important findings are: - Quantitative analysis of the effect of hydrogen on FCGR revealed significant acceleration across the tested ΔK range (15-30 MPa.m 0.5 ). The maximum acceleration factor of 20.7 was observed at the lowest ΔK (15 MPa.m 0.5 ), progressively decreasing to 9.7 at ΔK = 30 MPa.m 0.5 . Fracto graphic analysis at ΔK = 20 MPa.m 0.5 showed distinct fracture mechanisms: samples tested in air exhibited ductile striations, while those tested under hydrogen charging displayed mixed fracture modes with quasi-cleavage facets and poorly defined striations. - In FT testing, a notable reduction in the J 0.2 parameter was observed. While samples tested in air consistently exceeded 200 kJ/m², hydrogen-charged samples mostly fell below this threshold, with one case even dropping under 100 kJ/m². Quantitative analysis revealed a 43% reduction in average J 0.2 values under hydrogen charging compared to air tests, confirming substantial loss of fracture resistance. The fractographic analysis revealed a transition in failure mechanisms: air-tested specimens exhibited dimpled morphology consistent with micro-void coalescence. In contrast, hydrogen-charged samples displayed predominantly quasi-cleavage fracture morphology with only isolated regions of dimples. Acknowledgements The authors would like to thank the Technology Agency of the Czech Republic (TACR) for financial support of the project TK05020150. References Alvaro, A., Wan, D., Olden, V., Barnoush, A., 2019. Hydrogen enhanced fatigue crack growth rates in a ferritic Fe- 3 wt%Si alloy and a X70 pipeline steel. Engineering Fracture Mechanics 219, 106641. António, M., Jesus, J. S., Vilhena, L., Borrego, L. P., Branco, R., Silva, E. L., Ferreira, J. A. M, 2025. Influence of hydrogen embrittlement on the fatigue behaviour of 316L stainless steel welded joints. International Journal of Hydrogen Energy 128, 534-543. Donnerbauer, K., Nickel, T., von Pavel, M., Otto, J. L., Gerdes, L., Vasquez, J. R., Lingnau, L. A., Koch, A., Walther, F., 2025. Methodology for Hydrogen-Assisted Fatigue Testing Using In Situ Cathodic Charging. Materials 18 (2), 339. Chowdhury, M. F. W., Tapia-Bastidas, C. V., Hoschke, J., Venezuela, J., Liu, T., Mcinnes, L., Roethig, M., Karimi, A., Atrens, A., 2024. Preliminary Evaluation of the Influence of Hydrogen on the Fracture Toughness of an X65 Gas-Transmission Pipeline Steel. Adv. Eng. Mater. 26, 2400352. Cauwels, M., Depraetere, R., De Waele, W., Hertelé, S., Verbeken, K., Depover, T., 2022. Effect of hydrogen charging on Charpy impact toughness of an X70 pipeline steel. Procedia Structural Integrity 42, 977-984. Tian, P., Xu, K., Lu, G., Qiao, G., Xiao, F. 2018. Low-Cycle Fatigue Properties of the X70 High-Frequency Electric-Resistant Welded Pipes. Advances in Materials Science and Engineering. 2358038.