Novel Cu-bearing economical 21Cr duplex stainless steels

A new family of 21Cr–2 Ni–1.0Mo–0.2 N–xCu (x = 0.5, 1.0, 1.5) economical duplex stainless steels have been developed by examining the effect of Cu on the microstructure and properties of solution-treated specimens. The results have shown that these alloys have a balanced ferrite–austenite duplex structure. The ferrite content increases with the solution treatment temperature, but decreases with an increase in Cu. Some precipitates such as sigma phase, ε-Cu and Cr2N were found when solution-treated at 780 °C for 30 min. The yield strength, tensile strength and fracture elongation values of experimental alloys solution-treated at 1020 °C for 30 min were about 540 MPa, 1000 MPa, and 35%, respectively. The pitting corrosion potentials of the solution-treated alloys were all above 500 mV in 1 mol/L NaCl solution at room temperature and the pitting corrosions always occur in ferrite phase. The mechanical properties and corrosion resistance of the designed alloys with lower production cost are better than those of AISI 316L austenitic stainless steel.

► Cu-bearing DSSs had good corrosion resistance and low-temperature impact toughness.
► 21Cr-2 Ni-1.0Mo-0.2 N-1.0Cu showed excellent comprehensive properties.
► Sigma phase, ε-Cu and Cr2N were found when solution-treated at 780 °C for 30 min.