Irradiation-assisted stress corrosion cracking (IASCC) of stainless steels has been attributed in part to radiation-induced segregation (RIS) of both major alloying and impurity elements at grain boundaries. There are phenomenological similarities observed between IASCC and intergranular stress corrosion cracking (IGSCC) of thermally-sensitized stainless steels. One concern for both IGSCC and IASCC is the localized loss of corrosion resistance associated with chromium depletion at grain boundaries. In order to avoid complications related to the long-term, induced radioactivity of neutron-irradiated specimens, four type 304L alloys were irradiated to 1 dpa (displacements per atom) with 3.4 MeV protons at 400°C. Both analytical electron microscopy (AEM) in a Philips EM400T/FEG and Auger electron spectrometry (AES) in a Perkin Elmer (PHI) 660 were employed to measure composition at or near grain boundaries in unirradiated and irradiated specimens of four controlled purity alloys [ultra-high purity (UHP), UHP+S (0.03 at.%), UHP+P (0.08 at.%), and UHP+Si (0.87 at.%)]. A sufficient number of boundaries were analyzed via AEM and AES to result in the standard deviation of the mean boundary composition of less than -0.5 at.%. Further experimental details are presented elsewhere.
Radiation Hardening and Radiation-Induced Chromium Depletion Effects on Intergranular Stress Corrosion Cracking in Austenitic Stainless Steels
