Y. Z. Huang and J. M. Titchmarsh, TEM investigation of intergranular stress corrosion cracking for 316 stainless steel in PWR environment, Acta. Materialia 54, 635-641 (2006).
Type 316 stainless steel foils containing stress corrosion cracks grown in high temperature aqueous environments have been examined by transmission electron microscopy. It was found that the crack tips are oxidized and have a three-layered morphology where all the layers taper towards the crack tip. The inner layer is a microcrystalline spinel sandwiched between the outer layers of a nano-crystalline oxide. The outer layers are enriched in Cr, and the inner in Fe, relative to the matrix. Cu was observed to segregate at the interface between oxide and matrix at one crack in type 316 steel. The inner oxide growth is dominated by different mechanisms before and after the grain boundary cracks.
Recent paper employing TEM. They examined steel foils with stress corrosion cracks, and examined the crack tips. They found a three-layer morphology. The outer layers are oxidized, and enriched in Cr, and is nanocrystalline. The inner layer is a spinel, enriched in Fe, and polycrystalline.
Summary by John