Microstructure and stress corrosion cracking study of AISI 304 and AISI 304L stainless steel subjected to proton irradiation

The dose dependence of solute segregation and phase transformation phenomena in commercial purity AISI 304 and AISI 304L austenitic stainless steels, and the influences on their intergranular stress corrosion cracking (IGSCC) susceptibility, were investigated in this study. Miniature tensile specimens and three millimeter diameter TEM discs were irradiated at 550 degrees C with 5 MeV H+, to doses ranging from 0.01 to 1 dpa. Analytical electron microscopy and constant elongation rate tensile (CERT) test were performed to study the effects of solute segregation and phase transformation on IGSCC susceptibility of these materials. The microstructural evolution indicated irradiation enhanced chromium-rich M23C6 carbides precipitating along grain boundaries in irradiated 304 specimens. Energy dispersive X-ray (EDX) analysis indicated that significant radiation-induced solute segregation (RIS) occurred near the grain boundary areas in the irradiated 304 specimens. It was found that ferrite phase formed in the matrix as well as near grain boundary areas in all 304L SS specimens after irradiation. In addition, the size and density of ferrite increased with increasing fluence, and it was also found chromium-rich M23C6 carbides formed along the γ-α interfaces