Role of microalloying elements in hydrogen-induced cracking and corrosion behavior of 1.5 GPa-Grade martensitic steels in 0.1 N HCl solution

초록

Hydrogen embrittlement (HE) in high-strength martensitic steels has been extensively analyzed through the interaction between hydrogen and microstructural defects under cathodic charging conditions. However, in service environments, where both cathodic and anodic reactions occur, metal dissolution and hydrogen generation proceed simultaneously. Since metal dissolution during corrosion impacts the localized generation of hydrogen and its uptake into the metal, corrosion behavior must also be considered to fully understand hydrogen-induced failure. In this study, the relationship between corrosion behaviors and HE susceptibility in 1.5 GPa-grade martensitic steels is investigated by varying V, Mo, Ni, and Cu compositions. Electrochemical analyses and in-situ slow strain rate tensile tests in 0.1 N HCl solution reveal that Mo plays dual roles in corrosion behavior. Mo-rich carbides in the matrix can promote the initiation of localized corrosion by providing preferential dissolution sites, thereby deteriorating corrosion resistance. In contrast, Mo-containing oxides formed within the corrosion product layer enhance the stability of the protective film, which improves corrosion resistance. The combined addition of Mo, Ni, and Cu further stabilized the corrosion product layer via Cu and Mo oxide formation, suppressing metal dissolution and hydrogen uptake. These competing effects influence HE resistance, as more stable corrosion product layers result in lower elongation loss. Our findings highlight the critical role of corrosion behavior in HE resistance, offering insights for designing high-strength steels for corrosive and hydrogen-active environments.

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