Stress Corrosion Cracking of 316 SS and Alloy 625 in Supercritical Water

Abstract

The supercritical water reactor (SCWR) offers many advantages compared to current light and heavy water cooled reactor. However, one of the key challenges is the selection of materials that can withstand the corrosive conditions that will exist in the core and in downstream components. The materials used in this work were Alloy 625 and 316 SS in tube shape. Water was lost during exposure of capsule specimens at 500 degrees C and the amount of lost water increases with exposure time. No cracks were observed on Alloy 625 after 3 weeks of exposure at 500 degrees C, while cracks at the inner wall of the tube were observed on 316 SS only after 4 hour heating at 500 degrees C. The oxide layer on 316 SS is much thicker than that formed on Alloy 625.