The Effect of Thermal Treatments on Stress Corrosion Cracking of Alloy-800 in a Caustic Environment

Stress corrosion cracking (SCC) tests under controlled potentials were conducted on plastically stressed C-rings of Alloy-800 to evaluate the effect of thermal treatments (at 500 to 850 C) on SCC of Alloy-800 steam generator tubing. The tests were conducted in a caustic solution at 300 C; such alkaline environments may sometimes form in crevices in nuclear steam generators. The results are presented in the form of a time-temperature-SCC diagram. Thermal treatments generally inhibited the SCC of Alloy-800, and the improvement was substantial in a few cases. Application of anodic potential and increasing stress generally accelerated SCC.