Hydrogen infrastructure requires structural materials that combine very high strength with reliable resistance to hydrogen gas embrittlement. Previous fatigue studies of quenched‑and‑tempered low‑alloy steels have established a practical design upper bound of about 900 MPa in tensile strength for high‑pressure hydrogen, because fatigue crack growth accelerates sharply and, at higher strengths, exhibits strong time dependence at low loading frequencies. In air, crack growth remains cycle‑controlled, whereas in hydrogen the transition above approximately 900 MPa undermines conventional life prediction based on pressurization cycles. These trends, observed for martensitic steels from 0.001 to 1 Hz, motivate alloy‑ and process‑design strategies that decouple high strength from hydrogen sensitivity.

This presentation reports the discovery and validation of hydrogen‑resistant high‑strength steels that surpass the long‑standing 900 MPa limit. By combining ausforming‑based thermomechanical processing with targeted composition tuning, we manufactured candidate steels that achieve an ultimate tensile strength of approximately 1200 MPa while exhibiting excellent resistance to hydrogen‑induced acceleration of fatigue crack growth. The improvement was confirmed across multiple alloy variants, indicating robustness of the processing and design concept rather than dependence on a single outlier material. These results expand the design window for hydrogen service toward significantly higher strength levels.

Emphasis will also be placed on the activation mechanisms underlying hydrogen tolerance revealed by comparative microstructural and crack‑tip analyses. The talk will discuss how controlled microstructural states obtained by the coupled process‑composition route mitigate hydrogen‑assisted damage processes at the crack tip. These insights provide a physically grounded basis for materials selection and for translating laboratory measurements into engineering allowables for hydrogen gas environments.

Finally, we introduce a suite of data‑driven fatigue crack growth prediction programs tailored for hydrogen gas. The programs integrate experimentally curated da/dN information and predict hydrogen‑environment fatigue crack growth behavior for individual materials while supporting three primary design tasks: life prediction under service loading, rational determination of required wall thickness for target reliability, and automated screening of candidate materials against performance constraints. We have developed multiple programs tuned to distinct objectives and use cases, and example workflows will be demonstrated to show how these programs shorten the iteration cycle between materials development and structural design, thereby enabling consistent, evidence‑based decisions for hydrogen infrastructure components.

Keywords: hydrogen embrittlement, high‑strength steel, ausforming, fatigue crack growth, data‑driven prediction, hydrogen infrastructure