Mathieu Bruzzese, Pedro Avila, Bill Baloukas, Jolanta E. Klemberg-Sapieha, Ludvik Martinu, Polytechnique Montreal, Montreal, Quebec, Canada
The modernization of commercial aircraft engines relies on the temperature of gas entering the combustion chamber. However, current operating temperatures surpass the limits tolerated by the superalloys used in engine components. Additionally, increased temperature elevates radiative heat contribution following the Stefan-Boltzmann law. Advanced Thermal Barrier Coatings (TBCs) offer a promising solution, alongside surface engineering to enhance radiation reflectivity and minimizing thermal losses. The inherent porous microstructure of TBCs presents an ideal medium for Mie scattering of heat radiation within the desired wavelength range, but the presence of pores in TBCs increases their vulnerability to degradation, particularly from Calcium-Magnesium-Alumino-Silicate (CMAS) contaminants, altering their properties over thermal cycles. Hence, safeguarding TBCs while prolonging their lifespan is imperative.
The objective of our present research is to enhance TBC’s resistance to CMAS infiltration while maintaining performance standards. The strategy involves filling the pores with a protective coating using non-line-of-sight techniques such as Atomic Layer Deposition (ALD). The role of the additional layer is to mitigate CMAS infiltration. After deposition, TBC microstructure is examined using SEM and EDS measurements followed by image analysis using machine learning tools. FDTD simulations are also conducted to evaluate the impact of pore filling and microstructural changes on light transmittance and reflectance. Additionally, an Inverse-Adding Doubling (IAD) algorithm is utilized to solve the Radiative Transfer Equation (RTE) and to extract the absorption and scattering coefficients. Optical measurements before and after coating deposition and CMAS infiltration performed in an integrating sphere facilitate comparisons between simulated and real-life TBC performances. Ultimately, the study contributes to the design of next-generation TBCs that address major challenges in aviation technology, promoting improved sustainability, efficiency, and safety in air travel.