Effect of ageing time on the toughness and the corrosion properties of duplex stainless steel UNS S31803

Duplex stainless steels are materials with high mechanical strength, toughness, and corrosion resistance, properties that make them rather appealing for the application on chemical and petrochemical industries. However, the exposure of such materials to high temperatures promotes the precipitation of deleterious intermetallic phases that cause significant damage to the mechanical and corrosion properties of these materials. In this study, the UNS S31803 duplex stainless steel received a thermal treatment at a temperature of 830 °C for 30, 90, and 180 minutes. After the treatment, the precipitates were characterized by backscattered electrons (BSE) and chemical composition mapping, and the properties of impact toughness were assessed by Charpy V-notch test for the different treatment conditions. The corrosion resistance properties were assessed by cyclic potentiodynamic polarization study. The thermal treatments at 830 °C resulted in a considerable reduction of impact toughness, and the corrosion resistance was also reduced in longer treatment times along with the loss of the passivation ability of the materials treated.