Effect of Lead on Stress Corrosion Cracking Behavior for Scratched Alloy 690

SEM, EBSD and TEM were used to study the stress corrosion cracking (SCC) behavior of scratched alloy 690 sample in lead-contaminated caustic solution and high purity water at 330 ℃. The results showed that highly deformed zone was produced during the scratching process, and original grains around the scratch groove were refined. A bundle of SCC cracks grew along mechanical twin boundaries after immersing in lead-contaminated caustic solution and the cracks continuously extended after continuing immersion in high purity water. A trace amount of residual lead on the surface of alloy 690 or crack path could advance crack growth.