High temperature corrosion behavior of DS GTD-111 in oxidizing and sulfidizing environments

Recent advances in coal combustion have made coal a cleaner, more viable source for power generation. Integrated Gasification Combined Cycle (IGCC) plants pair conventional steam turbines and coal gas turbines. The overall efficiency of each system is largely dependent on the maximum operating temperature of the system, which is limited by the available materials. Superalloys have long been used as a turbine material due to their high temperature strength and general resistance to oxidation. Superalloy GTD-111 DS is currently being used as components in steam turbine engine such as turbine blades and discs and is now being introduced to the syngas environment, which consists of H-2, CO, CH4, and H2S in addition to H2O. H2S is highly corrosive and complicates the corrosion process. The high temperature corrosion behavior of a directionally solidified superalloy, GTD-111 DS has been studied using thermogravimtric analysis coupled with metallographic studies. Parabolic oxidation behavior was observed for test environments including dry and wet air. Simulated syngas environments show aggressive sulfidization that leads to massive sample damage. In the case of wet syngas environments, a protective oxide layer was observed which seem to increase the samples ability to resist further corrosion.