Abstract
The mechanism for hydrogen embrittlement type stress corrosion cracking (HESCC) in a duplex stainless steel and its welded joints was studied by facet pit method. From the fractographic observation on the fracture surfaces of base and weld metals, it was found that the ferritic phase fractured in quasi-cleavage mode and the austenitic phase in ductile mode. The weld metal was more susceptible to HESCC than base metal. From the morphologies of facet pits formed in the ferritic phase on the fracture surface, it was clarified that the fracture planes in the ferritic phase were mainly along {100} plane in the lower stress intensity region but became {110} or {112} plane in the higher one. Consequently, the mechanisms for HESCC in duplex stainless steel contain lattice decohesion at lower stress intensity and slip-off at high stress intensity.
