Effects of σ Phase on the SCC Susceptibility and the Hydrogen Embrittlement Susceptibility of Super Duplex Stainless Steel F55

Abstract

While duplex stainless steel has excellent mechanical properties and corrosion resistance, intermetallic compounds called σ phase easily precipitate. In this study, SSRT was performed using specimens with different amounts of σ phase precipitation. In corrosive solution, specimens with precipitated σ phase tended to have a more pronounced decrease in ductility. Moreover, SSRT was performed in a similar corrosive solution while continuously charging hydrogen by cathodic charging method. As a result, there was no correlation between the amounts of σ phase precipitation and mechanical properties. Therefore, the σ phase is considered to promote SCC while not promoting hydrogen embrittlement.

Fig. 13 Rate of cracks passing through σ phase on the surface of super duplex stainless steel F55 after SSRT in air and under a constant potential of −0.5 V (vs. Ag/AgCl). (online color)