Cu-rich nano precipitates simultaneously enhance the tensile properties, antibacterial efficacy, and corrosion resistance of ultra-high strength steel

Abstract

Ultra-high strength steels with exceptional mechanical properties and corrosion resistance are increasingly critical in energy, aerospace, and biomedical applications. This study introduces a novel antibacterial Fe‒Ni‒Co‒Cr‒Ti‒Mo ultra-high strength steel, enhanced with Cu alloying, achieving a strength of approximately 1.8 GPa. We conducted a comprehensive investigation into the effects of Cu on tensile properties, antibacterial efficacy, and corrosion resistance at the atomic scale. Our findings reveal that Cu addition promotes the co-precipitation of Cu-rich and Ni₃Ti nano precipitates, which not only enhances the strength of the steel, but also provides heterogeneous nucleation sites for the reversion of austenite, resulting in improved uniform elongation. Moreover, the high density of Cu-rich precipitates disrupts the passive layer on the steel surface, facilitating the release of Cu²⁺ ions that penetrate and damage bacterial colonies, demonstrating effectiveness in reducing sulfate-reducing bacteria (SRB) related degradation. Additionally, the presence of Cu enhances the corrosion resistance by inhibiting the formation of (Cr,Mo)-enriched clusters, which promotes the development of a more continuous and adherent passive layer to mitigate localized pitting corrosion caused by SRB. These findings highlight the triple roles of Cu-rich nano precipitates in enhancing tensile properties, antibacterial efficacy, and corrosion resistance, presenting a promising strategy for extending the durability of steels in SRB-prone industrial environments.