Influence of strain localization on IASCC of proton irradiated 304L stainless steel in simulated PWR primary water

Crack initiation has been correlated to crystallographic orientations and strain field measurements using SEM digital image correlation technique coupled with EBSD cartography in order to gain insight into the influence of strain localization on IASCC of proton-irradiated 304L stainless steel in simulated primary water. Type 304L specimens were irradiated with 2 MeV protons at 360°C to 5 and 10 dpa and subsequently strained in simulated primary water under monotonic and pseudo-cyclic loadings. Intergranular cracks occurring on random high angle boundaries nearly perpendicular to the tensile axis were observed. Cracking features differences between monotonic and pseudo-cyclic tests are discussed. Increasing the macroscopic strain for monotonic loading results in a higher density of cracks but does not change the crack length whereas the increase of strain for pseudo-cyclic test induces an important increase of the cracks propagation. Strain field analysis shows a strong heterogeneity, with localization in narrow lines and near some grain boundaries in the irradiated areas. On the contrary, no localization in narrow lines is observed for the non-irradiated material.