Hot Corrosion of Superalloys in Boilers for Ultra-Supercritical Power Plants

The coal-based power plants have been plagued by twin problems—low thermal efficiency and emission of high level of pollutants into the environment. Over the last few decades, attention was paid by researchers worldwide to overcome these problems and to design, build, and operate coal-based plants with improving efficiency levels and reducing emission levels. Operating the power plants with higher levels of steam temperature and pressure was adopted as the direction toward achieving the needed improvements. The requirement to operate the plants with increasingly higher levels of temperature and pressure made it necessary to design the components with superalloys. Hot corrosion then becomes a major design consideration, particularly for superheaters and reheaters. Thus, it becomes important to study the hot corrosion behavior of candidate superalloys. The present chapter attempts to review the work done over the last two decades to understand the hot corrosion behavior of superalloys in the context of their use in advanced coal-based power plants.