Deriving SCC Initiation Times and Growth Rates from Posttest Fractrographic Analysis

This exploratory effort demonstrates the feasibility of determining crack initiation times and growth rates by posttest analysis of the fracture surfaces of stress corrosion cracking (SCC) test specimens. The fracture surface topography analysis (FRASTA) technique was applied to constant extension rate test (CERT) specimens of type 304 (UNS S30400) stainless steel fractured in several aqueous environments. Initiation times and propagation rates were determined for intergranular stress corrosion cracks in specimens tested at 288°C in clean oxygenated water containing a small amount of H2SO4. Cracking appeared to begin predominantly at the specimen's surface in clean water, but in the specimen's interior in the H2SO4-contaminated water.