Development of new electrochemical techniques to detect the depletion of alloying elements in nickel-chromium-molybdenum-tungsten alloys.

摘要

The Ni-Cr-Mo-W based Alloy 22 will be used for the outer wall of Nuclear Waste Package containers planned for use at the Yucca Mountain Nuclear Waste Reporitory. Corrosion has been identified as the most likely cause of failure of WPs. Although Alloy 22 is stable at low temperatures, it can form topologically close packed (TCP) phases like mu, P, sigma etc. and Cr rich carbides during welding and heat treatments. These microstructural changes could make it susceptible to localized corrosion, jeopardizing the projected 10,000 year service life. It is important to correlate these microstructural changes with the corrosion resistance of the alloy using non-destructive and rapid electrochemical tests. This investigation identifies a rapid, non-destructive, in-situ testing technique, to evaluate Cr and Mo depletion and intergranular corrosion susceptibility of Alloy 22.