Enhancement of Wear and Corrosion Properties of OPTI N+ High-Nitrogen Stainless Steel via DC Magnetron Sputtered CrSiN and Ion Nitriding Duplex Treatments

This study investigates the enhancement of surface properties of OPTI N+ high-nitrogen stainless steel through a duplex treatment combining ion nitriding and CrSiN coating deposition via DC magnetron sputtering. Ion nitriding produced a hardened layer approximately 50 μm thick with a surface hardness of 1037.1 HV0.05, primarily composed of Fe₂N, Fe₃N and Fe₄N phases. CrSiN coatings deposited at various temperatures showed that the sample coated at 300°C exhibited the highest hardness (13.07 GPa), optimal H/E ratio (0.055), and superior tribological performance, including the lowest friction coefficient (0.5773), wear loss volume (7.67 × 10⁻⁴ mm³), and specific wear rate (3.23 × 10⁻⁷ mm³·m⁻¹·N⁻¹) under a 5 N load. Electrochemical tests confirmed enhanced corrosion resistance, with the lowest corrosion current density (1.38 × 10⁻⁶ A·cm⁻²) and highest polarization resistance (339.98 Ω·cm²). HRTEM analysis revealed a nanocomposite microstructure consisting of crystalline CrN and amorphous SiN. These results demonstrate that the CrSiN/ion nitriding duplex treatment significantly improves the mechanical, tribological, and corrosion resistance of high-nitrogen stainless steel.