Optimizing Surface Properties of AISI 409 Stainless Steel through Duplex Treatment Consisting of Plasma Nitriding and Vanadium-Based Deposition

This study proposes a surface modification methodology for AISI 409 stainless steel by combining cathodic cage plasma nitriding (CCPN) and deposition (CCPD), evaluating the benefits of this duplex treatment over individual treatments. The mechanical strength, tribological behavior, and corrosion resistance of the treated surfaces were investigated in relation to processing parameters and resulting microstructures. Analyses were performed using XRD, SEM, Vickers microhardness, ball-on-disc testing, and corrosion testing in a 3.5% NaCl solution. The duplex treatment at 400 and 450 °C, consisting of CCPN followed by CCPD, promoted significant surface modifications. Nitriding resulted in a thick layer of Fe₃N, Fe₄N, and CrN, increasing hardness and wear resistance, with final improvements of 5.7 and 33.5 times, respectively. The subsequent VN deposition enhanced corrosion resistance, shifting the potential from -396 mV to -221 mV, indicating reduced electrochemical activity. These results confirm the treatment's potential for automotive exhaust systems, requiring lightweight, durable materials in aggressive environments.