Nickel free high nitrogen stainless steels with superior corrosion resistance and mechanical properties for coronary stents

The pitting corrosion resistance and mechanical behavior of nickel-free high nitrogen stainless steel (HNS) and its fabricated stents under varying cold deformation conditions were systematically evaluated, benchmarked against clinically deployed stent materials. Electrochemical analyses demonstrate that while aggressive cold deformation reduces the pitting resistance of HNS in physiological saline, this degradation is fully counteracted when nitrogen content reaches 0.92 wt.%. This abnormal behavior of HNS is owed to the N enrichment as SRO [CrN] in the inner layer of the passive film. Post-deformation evaluations confirm that HNS stents maintain superior pitting resistance compared to L605 and 316 L stents following compressive and over-expansion loading. Immersion tests coupled with cellular assays reveal that manganese ion release from HNS had protective effect on the activity of cellular manganese superoxide dismutase (MnSOD). The optimized strength-ductility synergy observed in cold- deformed HNS correlates with preliminary in vivo stent integrity assessments. These findings collectively suggest that HNS stents may offer enhanced clinical safety profiles through combined corrosion resistance and biomechanical compatibility advantages.