IN-SITU INVESTIGATIONS OF CALCIUM-MAGNESIUM-ALUMINOSILICATES (CMAS) INFILTRATION EFFECTS ON THERMAL BARRIER COATINGS UNDER EXTREME ENVIRONMENTS REPLICATING JET ENGINES

Abstract

Calcium-magnesium-aluminosilicate (CMAS) particulates, such as sand or volcanic ash, are ingested by gas turbine jet engines during operation. When operating within high abundance regions, these particulates negatively interact and degrade the high temperature ceramic coatings protecting underlying superalloy turbine blades vital to engine operation. These CMAS particulates melt within the engine and infiltrate into the ceramic coatings. The CMAS stiffens the coatings and causes thermo-mechanical induced high stress concentrations, risking crack formation. While molten, the CMAS thermo-chemically alters and destabilizes the coating, also risking coating failure. Premature, localized spallation failure of these ceramic thermal barrier coatings (TBCs) exposes underlying metallic components to the extreme temperatures of the hot gas streams exiting the combustor. Therefore, it is paramount to dynamically capture and characterize the evolution of CMAS infiltration and its reaction kinetics under replicated service conditions and engine environment during operation. In-situ synchrotron X-ray diffraction measurements offer high temporal and spatial resolutions, enabling the capture of complex, transient micro-mechanisms governing active CMAS infiltration processes. Capturing these phenomena elucidates CMAS infiltration wetting behaviors, crack initiation, and pore evolution in coatings exposed to CMAS during realistic flight-representative conditions. Such insights are instrumental in guiding the development of CMAS-resistant coatings and in advancing passive and active CMAS mitigation strategies. In turn, these advancements extend the service life of coating and engine operating in CMAS-rich environments