Effects of Sigma Phase Transformation on Corrosion Resistance in Duplex Stainless Steels

Austenitic-ferritic stainless steels have a duplex microstructure consisting of a ferritic matrix and islands of austenite, the volume fraction of which depends on the chemical composition and heat treatment. The aim of this article is to evaluate the influence of the sigma phase on the microstructure, hardness, and corrosion resistance of duplex stainless steel SEW 410 No. 1.4517 by aging heat treatment at 850  \(^\circ \) C, which favors the transformation of the sigma phase, which has a high hardness. Despite the increased wear resistance, it is important to evaluate the effects of this phase on the corrosion resistance of the material. Corrosion tests were carried out in an electronic potentiostat to observe the effects of the amount of sigma phase on the pitting potential in a salt solution containing 3.5% sodium chloride. The results show that an increase in the sigma phase led to an increase in hardness and a decrease in pitting potential.