Effects of alloying elements on the mechanical properties and corrosion behaviors of 2205 duplex stainless steels

The effects of alloying elements on the microstructure, mechanical properti es, and corrosion behaviors of duplex stainless steels (DSSs) have been inv estigated in this study. Experimental alloys were prepared by varying the c oncentrations of the constituent elements in DSSs, Hot ductility test, tens ile test, charpy impact test, and corrosion test were performed to evaluate the properties of the experimental alloys, The results showed that the ext ent of edge cracking of DSSs increased with the increasing value of the cra ck sensitivity index (CSI), The higher the hot ductility index (HDI) was, t he better the hot ductility of DSSs achieved, Austenite (gamma) stabilizer generally caused a decrease in the strength and an increase in the charpy i mpact absorbed energy of the stainless steel. On the contrary, ferrite (alp ha) former exerted its beneficial effect on the strength but became detrime ntal to the toughness of DSSs, The presences of sulfur and boron also cause d a decrease in the impact energy, but nitrogen and carbon hardly affected the toughness within the concentration range tested in this study. The valu e of pitting nucleation potential (E-np) of different nitrogen contents in 3.5 wt.% NaCl solution at room temperature was almost the same, but the val ue of pitting protection potential (E-pp) among these alloys was increased with increasing the content of nitrogen. The susceptibility to stress corro sion cracking (SCC) of DSSs was high when tested in boiling 45 wt.% MgCl2 s olution. On the other hand, the time to failure of the experimental steels in 40 wt.% CaCl2 solution at 100 degreesC was longer than that in MgCl2 sol ution. Nitrogen could affect the SCC behavior of DSSs in CaCl2 solution thr ough the combinative effects by varying the pitting resistance and the slip step dissolution. An optimum nitrogen (N) content of 0.15 wt.% was found w here the highest SCC resistance could be obtained. Although gamma phase exh ibited better resistance to SCC, cracks were found to penetrate through alp ha and gamma grains or to propagate along the alpha/gamma interface, As a r esult, a mixed transgranular plus intergranular mode of fracture surface wa s observed.