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4 Pages

Microstructural characterisation of intergranular stress corrosion cracking of 300 series stainless steels in PWR conditions

Significant amounts of oxide in the cracks developed along grain boundaries have been reported in studies of metal components exposed to high temperature water (Andresen 1993, Robinson and Jackson 1999). The microstructure and chemistry of such products are complex but have previously been investigated using optical and SEM methods only at relatively low resolution. For example, Guttmann et al (1997) investigated the corrosion behaviour of high temperature alloys and reported a two-layer oxide structure consisting of Cr-rich internal and Fe-rich external layers under both stress-free or creep strain conditions. Here we report, by direct TEM imaging of the flanks and tips, the structure, morphology and chemistry of corrosion products at high spatial resolution, for the purpose of improving understanding of intergranular SCC mechanisms.