Impacts of Alternative Fuels on the Evolution and Stability of Turbine Hot-Section Materials

This talk will provide an overview of a research program focused on evaluating the potential impacts of alternative fuels (coal-derived syngas, high-hydrgen content fuels, bio-derived synthetics) on the degradation of hot-section materials through accelerated attack of protective thermally grown oxides (TGOs) and thermal barrier coating (TBC) systems.  A primary focus is the role of elevated water vapor levels, volatility, and vapor phase transport processes on the evolution of TGO and TBC systems.  Materials exposure studies will be described that demonstrate that differing simulated combustion environments affect both the growth rate and the stability of the resulting thermally grown oxides.  In systematic studies of oxide growth on MCrAlY bond coat materials in simulated combustion environments with varying pH₂O, it is shown that the extent of spinel formation during transient oxidation is highly dependent upon the water vapor content in the exposure environment, and furthermore that the evolution of surface oxides is highly dependent upon volatilization and removal of spinel phases formed during transient oxidation periods.