High-resolution, in-situ, tomographic Observation of Stress Corrosion Cracking

This paper presents high resolution X-ray tomographic observations of intergranular stress corrosion crack nucleation and growth. In-situ experiments have been performed on beam line ID19 at the European Synchrotron Radiation Facility (ESRF). High-resolution tomography provides non-destructive, three-dimensional information of the shape and depth of damage. To the authors’ knowledge, these are the first such observations of stress corrosion, and demonstrate the potential for high resolution, synchrotron, X-ray tomography as a tool for observing pitting, intergranular corrosion and intergranular cracking.The application of high-resolution synchrotron X-ray tomography to two in-situ experiments is described. Localised corrosion and intergranular cracking in sensitised 5083 aluminium alloy has been studied. These results show the progressive development, transition, and coalescence of two forms of damage within the bulk of the sample. In-situ observations of intergranular cracks in sensitised 302 stainless steel have also been obtained. These provide evidence for crack bridging ligaments, caused by the high resistance of special grain boundaries. Further applications of high resolution X-ray tomography are described, such as in-situ studies of pitting and the transition from pitting to cracking in aluminium alloys and stainless steels, including the effects of near-surface residual stress.