Effects of temperature on stress corrosion cracking behavior of stainless steel and outer oxide distribution in cracks due to exposure to high-temperature water containing hydrogen peroxide

Cracking growth tests were conducted in high-temperature water containing hydrogen peroxide (H2O2) at 561–423K to evaluate the effects of H2O2 on stress corrosion cracking (SCC) of stainless steel (SS) at temperature lower than the boiling water reactor (BWR) operating temperature. Small compact tension (CT) specimens were prepared from thermally sensitized type 304SS. Despite the observation of only a small portion intergranular SCC (IGSCC) near the side groove of the CT specimen at 561K in high-temperature water containing 100ppb H2O2, the IGSCC area expanded to the central region of the CT specimens at 423 and 453K. Effects of H2O2 on SCC appeared intensely at temperature lower than the BWR operating temperature because of a reduction in the thermal decomposition of H2O2. To estimate the environment in the cracks, outer oxide distribution on the fracture surface and the fatigue pre-crack were examined by laser Raman spectroscopy and thermal equilibrium calculation was performed.