Towards sustainable hydrogen infrastructures: Additive manufacturing of metallic materials for enhanced resistance to hydrogen embrittlement

: Hydrogen embrittlement (HE) poses a critical challenge to the durability of metallic components in hydrogen infrastructure, threatening the global transition to sustainable and clean energy. Additive manufacturing (AM), with its unique design flexibility, material efficiency, and potential for microstructure control, offers new opportunities to mitigate HE-related degradation. This review focuses exactly on the current state of research at the intersection of AM and HE, highlighting the potential of AM-fabricated metallic materials to enhance performance in hydrogen-rich environments. Applications in aerospace, shipbuilding, and automotive sectors are discussed, emphasizing sustainability gains and production advantages. Uniquely, the review analyzes how key microstructural features of AM materials, such as grain size, dislocation density and dislocation morphology, secondary phases, and molten pool characteristics, influence HE resistance. Furthermore, it evaluates processing strategies, such as multi-material AM and heat treatments, to reduce hydrogen-induced damage. Despite promising advances, knowledge gaps remain in understanding hydrogen diffusion pathways and their interactions with AM-specific microstructures. This article outlines critical future research directions for enabling hydrogen-compatible, AM-based metallic systems, supporting the broader goal of decarbonized energy infrastructures.