Analytical Estimation for Hydrogen Induced Stress Corrosion Cracking in Duplex Stainless Steel and Its Weld

Abstract

Hydrogen embrittlement type stress corrosion cracking of duplex stainless steel and its welded joint in acid environment has been studied. It was found that the electrode potential and ferrite content affected the susceptibility of duplex stainless steel to HESCC. At a less noble potential the time to failure decreased, while it increased at the noble side. Also, it was found that the crack growth rate decreased significantly with decreasing ferrite content. When the ferrite content was less than 40%, cracks did not propagate. The observation of the fracture surface showed the cleavage type fracture in α phase and the ductile fracture in γ phase. This means that γ phase would block the cracks propagating through α phase. According to the analysis of hydrogen diffusion, it was shown that the concentrations of hydrostatic stress and hydrogen appeared in α phase near the tip of γ phase, and this position became the most probable crack initiation site for HESCC.