Berlin 2012 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 50: Topical Session Modern Atom Probe Tomography IV - Thin Films and Structural Materials
MM 50.4: Talk
Thursday, March 29, 2012, 12:30–12:45, H 0107
Atom-Probe Tomography of Grain Boundary Oxides in Stressed and Cold-Worked 304 Stainless Steel — •Karen Kruska1, David W Saxey2, George D W Smith1, Takumi Terachi3, Takuyo Yamada3, and Sergio Lozano-Perez1 — 1University of Oxford, Department of Materials, Parks Road, OX1 3PH, UK — 2School of Physics, The University of Western Australia, WA 6009, Australia — 32Institute of Nuclear Safety System (INSS), 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205, Japan
Cold-worked 304 stainless steels (SS) are known to be susceptible to stress corrosion cracking (SCC). This study employs atom-probe tomography (APT) for local chemical analysis of the oxides formed. Autoclave experiments on a set of samples with/without cold-work prior to oxidation, and with/without stress applied during oxidation, were carried out under simulated pressurised water reactor (PWR) primary conditions. APT and analytical transmission electron microscopy (ATEM) were combined to investigate chemical and structural implications of surface and grain boundary oxidation in 304 SS. Focussed ion beam (FIB) milling was used to prepare specimens containing the same grain boundary for every analysis technique. Grain boundary and deformation band oxidation were observed in all but the unstressed and non-cold worked sample. Hydrogen associated to the Nickel-rich regions and cavities was found ahead of the Cr-rich oxide in some of the samples. The implications of these findings to current SCC models will be discussed.