Selective Dissolution of Retained Austenite in Nanostructured Bainitic Steels

• Published in: Advanced engineering materials 2014-04, Vol.16 (4), p.442-444
• Main Authors: Kazum, Oluwole, Kannan, Mathan Bobby, Beladi, Hossein, Timokhina, Ilana, Hodgson, Peter, Khoddam, Shahin
• Format: Article
• Language: English
• Subjects: Bainitic steel; Chlorides; Corrosion; Dissolution; Localized corrosion; Nanostructure; Retained austenite; Steels
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201300287

Nanostructured bainitic steels, containing bainitic ferrite laths and retained austenite films, formed at two different isothermal temperatures were compared for corrosion behavior in chloride‐containing solution using electrochemical techniques. The potentiodynamic polarization results suggest that nanostructured bainite formed at 200 °C exhibits marginally higher corrosion resistance compared with that at 350 °C. Post‐corrosion analysis of the galvanostatically polarized samples revealed localized corrosion for both the steels, but the degree of attack was higher in the 350 °C steel than in the 200 °C steel. The localized corrosion attack was due to selective dissolution of the retained austenite phase. The higher volume fraction and larger size of retained austenite in the 350 °C steel as compared to that of the 200 °C steel contributed to the pronounced corrosion attack in the 350 °C steel. Nanostructured bainitic steels, containing bainitic ferrite laths and retained austenite films, formed at two different isothermal temperatures (i.e. 200 and 350 °C) are compared for the corrosion behavior in chloride‐containing solution. Selective dissolution of the retained austenite phase is observed for both the steels, but the corrosion attack is higher in the 350 °C steel due to the difference in the volume fraction of retained austenite.