A thermodynamic database for CMAS-TBC/EBC interactions

Existing TBC/EBC systems in aero-turbine engines, such as YSZ, are highly susceptible to degradation by infiltrating molten deposits formed when calcium-magnesium-aluminosilicate (CMAS) particulates such as dust, sand, or volcanic ash are ingested into the engine. There is a great opportunity for Integrated Computational Materials Engineering (ICME) tools to predict the failure of TBCs due to CMAS attack, and to utilize this ability to design novel CMAS-resistant TBCs for improved engine efficiency and material durability. This presentation reports on the development of a thermodynamic database for the CaO-MgO-FeO_x-Al₂O₃-SiO₂-Y₂O₃-Gd₂O₃-ZrO₂ (CMAS-TBCs/EBCs) system to model interactions of CMAS with TBCs and EBCs. Developed using the CALPHAD approach, this work is based on the critical evaluation of binary, ternary and important higher order systems which enables predictions to be made for multicomponent systems. All the binaries and most of the ternaries in the CMAS-TBCs are assessed, and some higher order systems as well. The phase equilibrium predictions for the CMAS-YZ interactions have been experimentally validated from a project collaborate with QuesTek Innovations LLC and the University of California Santa Barbara.