A new resource-saving, high manganese and nitrogen super duplex stainless steel 25Cr–2Ni–3Mo–xMn–N

A new family of resource-saving, high manganese and nitrogen super duplex stainless steels (DSSs), with a composition of 25 wt.%Cr, 2 wt.%Ni, 3 wt.%Mo, 8–12 wt.%Mn, and 0.45–0.55 wt.%N, have been developed by examining the effect of Mn and N on the microstructure, mechanical properties and corrosion properties. The results show that these alloys have a balanced ferrite–austenite relation. The ferrite content increases with the solution treatment temperature, but it decreases with an increase in Mn and N. The element Mn accelerates σ phase precipitations. The increases in manganese and nitrogen, especially nitrogen, enhance the ultimate tensile strength (UTS) and ductility of the material. The pitting corrosion potential increases first and then decreases with an increase in the amount of Mn, which is due primarily to the presence of a small amount of σ phase when the amount of Mn is 12 wt.%. Among the designed DSS alloys, 25Cr–2Ni–3Mo–10Mn–0.5N is found to be an optimum alloy with proper phase proportion, a better combination of UTS and elongation, and higher pitting corrosion resistance compared with those of the other alloys. The mechanical strength and corrosion resistance and lower production cost of the materials are better than those of SAF2507.