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Duplex stainless steel (DSS) has been considered as an excellent alternative for applications where high corrosion resistance and high mechanical strength are required. Therefore, microstructure and properties of DSS remain topics of much interest. For this purpose, the effect of warm-rolling was studied in a duplex stainless steel. The focus of this work was 2205 which is one of the most useful type of DSS. Although evolution of microstructure, texture and tensile properties during warm rolling of DDS have been reported, there is no study on the effect of warm rolling on corrosion resistance of 2205 DSS. In this context, the objective of this work is to evaluate microstructure, texture and mechanical and corrosion properties of UNS S32205 DSS after warm rolling. The duplex stainless steel was warm-rolled at 600°C up to 60 and 80% thickness reduction and submitted to electrochemical tests. The electrochemical behaviour of warm-rolled 2205 in the chlorine ion environment was evaluated using cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS). The samples exhibited an excellent corrosion resistance in 3.5% NaCl solution. The study showed that the thermomechanical treatment used favoured the formation of the passive film and led to a greater polarization resistance. This behaviour is consistent with the pits density observed by scanning electron microscopy (SEM) and the crystallographic microtexture of the steel.

Resumo O aço inoxidável duplex(AID) combina as propriedades mecânicas da ferrita à resistência à corrosão da austenita, sendo muito utilizado em aplicações industriais que requerem um bom desempenho quanto a essas propriedades. A classeleanduplex foi desenvolvida para minimizar as flutuações de custo, reduzindo elementos caros como Ni e Mo, sem grande efeitoem relação à corrosão e propriedades mecânicas. O objetivo deste trabalho foi avaliaro efeito da temperatura de recozimento na microestrutura, dureza e corrosão por pite de um aço inoxidável UNS S32304. Investigações microestruturais foram realizadas usando um microscópio eletrônico de varredura. A resistência à corrosão foi estudada por meio da técnica de polarizaçãopotenciodinâmica cíclica.As amostras apresentaram uma elevada resistência ao início da corrosão por pite em solução de NaCl 3,5%. Apesar da existência da similaridade entre os valores de potencial de circuito aberto, a temperatura de recozimento mostrou ter grande influência na resistência a corrosão do aço. A temperatura de recozimento afetou a estrutura e a composição dos filmes passivos na superfície do aço inoxidável duplex.O recozimento a 1000°Clevou a uma maior resistência a corrosão localizada. Palavras-chave:Aço inoxidável duplex; Recozimento; Corrosão por pite.

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

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