Multiple microelements coupling design for corrosion‑ and hydrogen‑resistant spring steel

Based on the multiple microelements coupling theory, a thermodynamic model for the Fe–M′(Ti, V)–B–N–C system in spring steel was established to analyze solid-solution and precipitation behaviors across a wide temperature range. By integrating these thermodynamic insights with a novel multi-point regional micro-feeding technique, the targeted microalloying-element contents were achieved during processing. Compared with conventional 50CrVA spring steel, the newly designed alloy shows consistently lower corrosion rates in immersion tests and a lower hydrogen-embrittlement susceptibility index in dynamic hydrogen-charging tensile tests. The enhanced corrosion and hydrogen-embrittlement resistance of 50-S2 is associated with the coupled Ti–B–N design. Within this system, B retained in solid solution and its enrichment near prior austenite grain boundaries may contribute to corrosion resistance, whereas Ti(C,N)-type precipitates may act as relatively strong hydrogen traps. The improved resistance of this spring steel to corrosion and hydrogen embrittlement demonstrates the potential of the proposed thermodynamic model for guiding alloy composition design.