Spinodal decomposition in lean duplex stainless steel UNS S32101

The petrochemical and pulp and paper industries rely on heavy-duty equipment operating in corrosive environments. Duplex stainless steels (DSS) are thus an ideal option, since they offer excellent mechanical properties and good corrosion resistance. The primary issue with DSS equipment operation occurs between 250 and 550 °C, where this type of material exhibits 475° C embrittlement, also known as low-temperature embrittlement. This is a high-chromium-content phenomenon, where both BCC α′ and BCC α″ phases form through the decomposition of nonstable ferrite. Owing to this phenomenon, the pitting corrosion resistance, weldability, and impact toughness of these types of steels decrease. In this work, a DSS UNS S32101 was subjected to isothermal heat treatments at 475 °C for different times up to 6 weeks. Ferrite spinodal decomposition was characterized by electrochemical techniques, microhardness tests, and scanning electron microscopy.