Microstructure, Texture, Mechanical and Corrosion Performance of the Stainless Duplex Steel UNS S32205 Submitted to Warm Rolling

Abstract

The UNS S32205 duplex stainless steel was warm rolled at 600°C with 60 and 80% of thickness reduction. The microstructure was characterized by optical, scanning and transmission electron microscopy, X-ray diffractometry and EBSD. The corrosion resistance was evaluated by electrochemical behavior in the chlorine ion environment using potentiodynamic polarization measurements. The tensile strength reached 1185 MPa and 1328 MPa, after warm rolling with 60 and 80%, respectively. In steel as-supplied, hot rolled and annealed, the tensile strength was 774 MPa. Ferrite microtexture presented the α-fiber and the rotated cube component, while the austenite enhanced the brass, copper, and cube components to a lesser extent. The substructure was characterized by intense formation of tangles and forests of dislocations and discrete subgrains in the ferritic phase and by planar gliding of dislocations and formation of dense dislocations walls in the austenite. Despite the existence of a certain similarity among the values of pitting potentials obtained for all samples, the number of pits observed was higher in the as-received sample, followed by the samples with 60 and 80% reduction. These results draw attention to innovative routes in the industrial production of duplex stainless steel of this class, even considering ductility lost. Keywords: Warm rolling; Mechanical strength; Texture; Substructure; Corrosion resistance