PSI - Issue 79

Hiroshi Nishiguchi et al. / Procedia Structural Integrity 79 (2026) 517–523

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can be attributed to the loss of the Al-rich layer and the interface between the Al and Al/Fe intermetallic layers. These observations suggest that the high-aluminum-content layer near the surface is a major factor affecting hydrogen ingress. Future work will investigate these phenomena in detail and develop countermeasures to achieve both enhanced hydrogen ingress prevention and preservation of substrate strength.

(a)

(b)

Fig. 4. EDS and SEM images of SCM435 steel for (a) as-coated and (b) quenched specimens.

4. Conclusion In this study, the effects of an aluminum powder-coating heat treatment on the hydrogen ingress resistance of metallic substrates were investigated. The influence of subsequent quenching and tempering on both the coating structure and hydrogen ingress behavior was evaluated, with particular attention paid to the formation of Al-rich layers and the interfacial conditions. 1. The hydrogen ingress resistance was initially 100% before the additional heat treatment but decreased after quenching and tempering. The degree of reduction varied depending on the material. 2. Cavities formed in the upper part of the coated layer as a result of the heat treatment. In this region, Al diffused toward the substrate, leading to the disappearance of the high-Al-content layer. 3. The interfacial conditions and presence of a high-Al-concentration coating layer are considered the major factors contributing to the decrease in hydrogen ingress resistance. Beachem, C.D., 1972. A new model for hydrogen-assisted cracking (hydrogen ‘embrittlement’). Metallurgical and Materials Transactions B 3, 441–455. Birnbaum, H.K., Sofronis, P., 1994. Hydrogen-enhanced localized plasticity—A mechanism for hydrogen-related fracture. Materials Science and Engineering A 176, 191–202. Hirth, J.P., 1980. Effects of hydrogen on the properties of iron and steel. Metallurgical Transactions A 11, 861–890. Matsuda, Y., Nishiguchi, H., Fukuda, T., 2016. Effects of large amounts of hydrogen on the fatigue crack growth behavior of torsional prestrained carbon steel. Frattura ed Integrità Strutturale 10, 1–10. Murakami, Y., Kanezaki, T., Mine, Y., Matsuoka, S., 2008. Hydrogen embrittlement mechanism in fatigue of austenitic stainless steels. Metallurgical and Materials Transactions A 39, 1327–1339. Yamabe, J., Yoshikawa, M., Matsunaga, H., Matsuoka, S., 2017. Hydrogen trapping and fatigue crack growth property of low-carbon steel in hydrogen-gas environment. International Journal of Fatigue 102, 202–213. NASA, 1997. Safety standard for hydrogen and hydrogen systems: Guidelines for hydrogen system design, materials selection, operations, storage and transportation. NASA Technical Memorandum 112540. Nishiguchi, H., Sueyoshi, H., Sasaki, D., 2024. Al-based coatings for preventing hydrogen ingress in high-pressure systems. Proceedings of the 8th International Conference on Crack Paths (CP2024) . Oriani, R.A., Josephic, P.H., 1974. Equilibrium aspects of hydrogen-induced cracking of steels. Acta Metallurgica 22, 1065–1074. Sofronis, P., Birnbaum, H.K., 1995. Mechanics of the hydrogen-dislocation-impurity interactions—I. Increasing shear modulus. Journal of the Mechanics and Physics of Solids 43, 49–90. Takai, K., Watanuki, R., 2003. Hydrogen in trapping states innocuous to environmental degradation of high-strength steels. ISIJ International 43, 520–526. Troiano, A.R., 1960. The role of hydrogen and other interstitials in the mechanical behavior of metals. ASM Transactions 52, 54–81. References