Effects of nitrides precipitation in Duplex Stainless Steel

Duplex Stainless Steels (DSS) are characterized by a dual-phase ferritic-austenitic microstructure and exhibit high corrosion resistance and excellent mechanical properties. However, formation of different types of intermetallic phases and precipitated compounds as chromium nitrides may occur during fabrication processes such as welding, hot working and heat treatments; this can influence their corrosion resistance and toughness. In the framework of controversial scientific studies on this topic, the aim of this paper is to evaluate the effective influence of the content/distribution of these particles on the corrosion behaviour of two largely adopted DSS, UNS S32205 and UNS S32750. From the obtained results it is evident that corrosion resistance of the DSSs is negatively affected by the presence of chromium nitrides. In addition, the corrosion development occurs with different morphologies depending on the type of analysed DSS.