Development of a high-alloyed duplex stainless steel with enhanced mechanical property and corrosion resistance

Duplex stainless steels (DSSs) are attractive structural materials because of their excellent corrosion resistance and favorable strength–ductility balance. In this study, a novel high-alloyed duplex stainless steel (HA-DSS) with a nominal composition of Fe 60 Cr 18 Co 6 Ni 6 Mo 6 Cu 4 was developed. After solution treatment at 1180 °C, the alloy exhibited a balanced duplex microstructure with BCC and FCC phase fractions of approximately 54% and 46%, respectively. Under this condition, the alloy achieved a tensile strength of 763 MPa and an elongation of 24%. Compared with commercial 2205-DSS, the optimized HA-DSS showed significantly improved corrosion resistance. In 3.5 wt% NaCl solution, the HA-DSS exhibited a higher corrosion potential (−0.250 V vs. −0.354 V), a lower corrosion current density (0.299 μA cm −2 vs. 0.909 μA cm −2 ), and a higher pitting potential (1.09 V vs. 1.01 V). In 10 wt% H 2 SO 4 solution, it also showed a higher corrosion potential (−0.230 V vs. −0.269 V) and a markedly lower corrosion current density (15.33 μA cm −2 vs. 69.99 μA cm −2 ). X-ray photoelectron spectroscopy revealed that Co, Mo, and Cu contributed synergistically to the improved passive-film characteristics. Transmission electron microscopy further showed abundant dislocations in the FCC phase and nanoscale Cu-rich precipitates in the BCC phase, which contributed to the enhanced mechanical performance. These results demonstrate that the proposed HA-DSS provides an effective strategy for simultaneously improving duplex phase stability, mechanical properties, and corrosion resistance.