High temperature oxidation behavior of TBC coated Ni-based super alloys under hydrogen combustion atmospheres

Kurzfassung

Hydrogen propulsion systems in air transport have the potential to eliminate local CO2 emissions. However, they present significant challenges regarding the durability and lifespan of high-temperature components. For example, high-pressure turbine blades, which are typically made from nickel-based superalloys, must be protected against the additional water vapor generated by hydrogen combustion. Research into safe, reliable hydrogen combustion and effective handling of this energy carrier is crucial for preparing its commercial use in aircrafts. Initial combustion simulation results indicate that more than 12 wt.% water vapor is expected in the hot gas under hydrogen combustion conditions. This increased water vapor content will exacerbate oxidation and corrosion-related degradation issues of both bare alloys and their oxidation protective coatings. To investigate this, various nickel-based superalloys and MCrAlY-based bond coats with and without thermal barrier coatings (TBCs) were exposed to high-temperature water vapor conditions for varying durations up to 1000 hrs. The resulting degradation behavior will be presented, along with a discussion of the underlying mechanisms. However, these simulated experiments do not fully replicate the exact conditions of hydrogen combustion. To address this gap, a novel test stand has been developed to directly simulate hydrogen combustion atmospheres, including a temperature gradient across the cooled samples and components similar as in a real gas turbine. TBC-coated nickel-based superalloy substrates were tested under hydrogen combustion conditions, and preliminary results will be presented. These results will be compared to the water vapor oxidation experiments to better understand the specific effects of hydrogen combustion on the degradation behavior of Ni-based alloys and protective coatings.