二相ステンレス鋼溶接継手部のHESCC機構に関する検討

二相ステンレス鋼溶接継手部の水素脆化型応力腐食割れの解析的評価とその機構(第4報)

抄録

In this paper, the mechanism for hydrogen embrittlement type stress corrosion cracking (HESCC) in duplex stainless steel and its weld metal was studied by using facet pit method. It was found that ferritic phase fractured in quasi-cleavage mode and austenitic phase in ductile mode. From the morphologies of facet pits formed on the fracture surfaces in ferritic phase, it was clarified that fracture planes in ferritic phase were mainly constituted of {100} plane in lower stress intensity region, and {110}, {112} plane in higher one. Consequently, the mechanism for HESCC in duplex stainless steel was explained by lattice decohesion at lower stress intensity and fracture on slip plane at higher stress intensity. From the view point of mechanism for HESCC, it was clear that the criterion for HESCC initiation mentioned in the former report (Report-3) was suitable for the lower stress intensity.