A Study on Stress Corrosion Cracking of Austenitic Stainless Steel in Boiling Magnesium Chloride

The anodic reaction within the transgranular stress corrosion crack of 18-8 stainless steel in boiling MgCl2 was studied under the open circuit condition at constant tensile speeds. The entire crack sides were not passive during the crack propagation. Consequently, stress corrosion cracking (SCC) of 18-8 stainless steel in boiling MgCl2 is thought to propagate under conditions similar to those for SCC of this alloy in acidic chloride solution at room temperature. The crack propagation rate (v) in the tensile crosshead speed region of ∈˙=4−7.5×10−3 mm/minute is described as v=a∈˙+b, where a and b are constants. The rate is interpreted as the repetition of selective dissolution and subsequent ductile tearing at the crack tip. Crack propagation is controlled by selective anodic dissolution forming tunnels at the crack tip. In the high tensile crosshead speed region of 1 − 4 × 10−2 mm/minute, crack propagation was not greatly accelerated because excess plastic deformation resulted in multiple crack initiation and work-hardening of the specimen.