Low-temperature Fe–N enabled austenite stabilization in nickel-free nitrogen-alloyed stainless steels

Nickel-stabilized austenitic stainless steels are widely used but increasingly constrained by economic, environmental, and health concerns. Nitrogen offers a sustainable alternative austenite stabilizer; however, its low solubility in molten steel and high volatility complicate incorporation under ambient pressure. Here, we demonstrate a viable laser powder bed fusion (LPBF) materials-by-design approach to fabricate nickel-free, nitrogen-alloyed stainless steels using iron nitride (Fe−N) as a low-temperature nitrogen source under ambient condition. Optimized processing achieved near-full density (>99.5%) and retained up to ∼0.45 wt% nitrogen, producing predominantly γ-austenite microstructure (∼93%) with minor δ-ferrite. X-ray diffraction and electron microscopy detected no secondary nitrides within diffraction limits, while systematic lattice expansion indicated interstitial solid-solution strengthening. The resulting alloys exhibit high strength (YS ≈ 744–882 MPa, UTS ≈ 935–1062 MPa) with tunable ductility (El ≈ 10–21%), and modified corrosion behaviour relative to nitrogen-free counterparts, consistent with nitrogen-enhanced passivation. Although performance remains below that of Cr–N alloyed steels and SS316L, this approach avoids high-pressure processing and demonstrates that Fe–N precursors can effectively deliver nitrogen effectively during LPBF. These findings provide a foundation for the future optimization of sustainable, nickel-free stainless steels relevant to biomedical, energy, and structural systems.