A mechanistic study of the effect of temperature on crack propagation in alloy 600 under pwr primary water conditions

Conference item

The stress corrosion cracking (SCC) of three Alloy 600 has been studied in the simulated primary water of pressurized water reactor at 290ºC, 320ºC, 340ºC, and 360ºC. A clear correlation between the experiment temperature and the crack growth rate was found that the crack growth rate increased monotonously with the experiment temperature used in this study. In order to understand the temperature dependence of crack growth rate, high-resolution characterization was used to study the crack tips (CTs) prepared from Alloy 600 tested at 320ºC, 340ºC, and 360ºC. After an initial observation of the SCC crack paths on the polished cross-section surfaces via optical microscopy, a plan-view site-specific sample preparation technique via a focused ion beam has been used to prepare transmission electron microscopy (TEM) samples containing active CTs. The CTs obtained from different temperatures were detailedly analyzed through high-resolution analytical TEM to reveal the CT morphology and chemistry, which enable the study of a thermally activated diffusion-based mechanism operating during the SCC propagation. A high-resolution transmission Kikuchi diffraction was used to investigate a mechanical respond-based mechanism in the SCC propagation through quantifying the size and extent of plastic deformation around the CTs. Results obtained in this study shows that the thermally activated diffusion along the grain boundary increased with the temperature while the plastic deformation around the CT was very low and nearly independent with the temperature, indicating the thermally activated diffusion-based mechanism was the adominant one during the SCC propagation, which correspond well with the temperature dependence of crack growth rate of Alloy 600.

Authors: Shen, Z; Lozano-Perez, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Host title: Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors
• Journal: 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems (EDM 2017)
• Volume: Part F9
• Pages: 439-454
• Series: The Minerals, Metals & Materials Series
• Publication date: 2017-10-07
• DOI: 10.1007/978-3-319-67244-1_28
• ISSN: 2367-1696 and 2367-1181
• ISBN: 9783319672434
• Keywords: crack growth rate; stress corrosion cracking; transmission electron microscopy; temperature dependence; Alloy 600; transmission Kikuchi diffraction