Original paper(Vol.46 No.6 pp.602)
Stress corrosion cracking of sensitized duplex stainless steel weldment
Kuroda Toshio; Matsuda Fukuhisa; Bunno Kazusige
Abstract:The effects of s phase and the volume fraction of austenite (g) on stress corrosion cracking (SCC) were investigated in high temperature water and in boiling MgCl2 solution for the sensitized duplex stainless steel by using transmission electron microscopy and fractography. The samples were solution treated at various peak temperatures and then sensitized at 923 K for 72 ks. The volume fraction of g phase decreased with increasing peak temperature. The slow strain rate testing (SSRT) at 4.7x10-6s-1 was mainly carried out to evaluate the SCC.
In case of high temperature water at 562 K, the fracture strain depended on the volume fraction of g phase for the as solution treated sample. For the sensitized sample, the fracture strain was independent of the volume fraction of g phase, because the secondary austenite g* phase near g phase was preferentially corroded.
In case of boiling MgCl2 solution, the fracture strain depended on the volume fraction of g phase and the strain rate for the solution treated sample. However, the fracture strain was independent of the volume fraction of g phase for the sensitized sample, because the SCC showed fan shaped pattern with secondary cracks related to s phase.
Key Words:duplex stainless steel, stress corrosion cracking, high temperature water, boiling MgCl2 solution, sigma phase, volume fraction of austenite, fractography