Improved Surface Morphology and Corrosion Resistance Performance of 2205 Duplex Stainless Steel by Low Temperature Gas Nitriding

This paper investigates the effect of low temperature gas nitriding on surface properties of 2205 duplex stainless steel performed at 400 °C with the variation of holding times of 5 h, 10 h and 15 h. Thickness of as-deposited nitrided layer increased with time reaching a maximum value of 13.29 µm having 4.68 wt nitrogen content. Phase analysis shows the formation of expanded austenite (αN), Fe4N and Fe3N phases for all nitrided samples while un-nitrided duplex Stainless Steel (DSS) constituted only α (ferrite) and γ (austenite). X-ray photoelectron spectroscopy revealed that diffused N2 preferably bonded with Fe thereby suppressing the formation of Cr2N and CrN. Hence, absence of brittle intermetallic helps in retaining inherent ductility of DSS. Topographical analysis depicted that nitriding resulted in surface modification, increasing roughness of the treated samples. Polarization analysis under sour environment recorded 8 times improved corrosion resistance while in a combined sour and sweet environment, had 3.7 times better corrosion resistance than that of non-nitrided DSS. Graphical abstract: Figure not available: see fulltext. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.