PSI - Issue 68

Birhan Sefer et al. / Procedia Structural Integrity 68 (2025) 1121–1128 Sefer et al. / Structural Integrity Procedia 00 (2025) 000–000

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boundaries. Earlier work by Gray (1975) also reported substantial hydrogen uptake in Ni-base alloys after high temperature exposure in high pressure hydrogen environment. Interestingly the high hydrogen contents measured for both materials after SSRT at high temperature in this work has shown to be not detrimental to the mechanical performance of both materials. This is promising result for facilitating the use of AM Hastelloy X components in the combustion zone in gas turbines fuelled by H 2 . However, these results need to be cautiously interpreted since the testing conditions are not fully representative for the service conditions involving thermal cycles and dynamic loading. Hence, further research is required focusing on how and if a hydrogen uptake caused by the high temperature exposure would result in impact on the mechanical properties at lower temperatures. Moreover, a separate attention needs to be placed also on how this hydrogen would influence the thermomechanical fatigue properties of these materials combined with careful microstructural characterization. The hollow specimen test setup seems to provide a feasible way forward towards the development of testing methods for thermomechanical fatigue under the influence of hydrogen gas. 5. Conclusions This work compared the behaviour of an AM and conventionally manufactured (hot rolled) Ni-base alloy Hastelloy X material in high-pressure H 2 at room temperature and 800 ° C. The main conclusions drawn from this study are as follows: • No significant deterioration of mechanical properties occurred due to hydrogen at any of the test temperatures either for AM or hot rolled Hastelloy X material. Hence, both materials were not susceptible to hydrogen embrittlement. • No large differences in fractographic examination between hydrogen and argon tested SSRT specimens were observed. Both materials tested at room temperature and 800°C presented ductile failure with dimples, except that some small areas close to the hole surface quasi-cleavage fracture type were also seen for both materials tested at room temperature with H 2 . • Notable hydrogen uptake hydrogen was measured for the SSRT specimens tested at 800°C as compared to the ones tested at room temperature for both conventional and AM materials. • Lower creep ductility of the AM material compared to the conventionally manufactured material was also observed from the SSRT tests performed at 800 °C, in both gaseous environments, Ar and H 2 , respectively. Acknowledgements The authors acknowledge the Swedish funding agency Vinnova (Diarienr: 2022-01587 Projekttitel: Vätgasinducerade degradering av mekaniska egenskaper i nya applikationer - HYMECH II) for providing financial support of the work presented in this paper. The authors also acknowledge Oliwer Gustavsson from Swerim AB for performing all the SSRT testing. References San Marchi, C., Somerday, B.P., 2012. Technical Reference on Hydrogen Compatibility of Materials. SAND2008-1163. Behvar, A., Haghshenas, M., Djukic, M.B., 2024. Hydrogen embrittlement and hydrogen-induced crack initiation in additively manufactured metals: A critical review on mechanical and cyclic loading. International Journal of Hydrogen Energy 58, 1214-1239. Gray, H. R., 1975. Embrittlement of nickel-, cobalt-, and iron-base superalloys by exposure to hydrogen., NASA Technical Reports. Gao, M., Boodey, J.B., Wei, R.P., Wei, W.,1992, Hydrogen solubility and microstructure of Hastelloy X. Scripta Metallurgica et Materialia 26, 63-68. Hasegawa, M., Osawa, M., 1981. Hydrogen Damage of Nickel-base Heat-Resistant Alloys, Transactions of the Iron and Steel Institute of Japan 21, 25-31. ISO 7039, 2024. Metallic materials-Tensile testing-Method for evaluating the susceptibility of materials to the effects of high-pressure gas within hollow test pieces. SS-ISO 7039:2024. Kim, J.-Y., Kim, S.-G., Hwang, B., 2024. Investigation of Hydrogen Embrittlement of Haynes 617 and Hastelloy X Alloys Using Electrochemical Hydrogen Charging. Archives of metallurgy and materials 69, 141–144. Yao, J., Tan, Q., Venezuela, J., Atrens, A., Zhang, M.-X., 2023. Recent research progress in hydrogen embrittlement of additively manufactured metals – A review, Current Opinion in Solid State and Materials Science 27, 101106.