In Search of Durable Sandphobic Thermal/Environmental Barrier Coatings for Rotorcraft Gas Turbine Engines

Abstract

The objective of this research is to develop new thermal/environmental barrier coatings (T/EBCs) that exhibit greater durability and CMAS (Calcia-Magnesia-Alumino-Silicates) resistance than any of the current state-of-the-art rotorcraft turbine engine coatings. Commercial/Military aircraft engines, especially helicopter engines undergo severe damage to critical components when they need to operate over sandy terrains or volcanic zones. Typical high pressure turbine vanes/blades with current coatings undergo damages that include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicates (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid engine performance loss and in severe cases ending up in loss of aircraft. Design of novel T/EBCs for high temperature operation is presented in this paper based on ongoing work in understanding the fundamental governing parameters affecting CMAS adhesion, build-up, and chemical attack. The paper intends to report specific objectives and findings obtained thus far from an ambitious T/EBC research program funded by OSD’s Strategic Environmental Research and Development Program (SERDP). Systematic sand-phobic development research efforts and methodologies from modeling to engine relevant high-temperature environmental test evaluations are described in this paper to innovate improved T/EBCs for both Ni-superalloy based substrates and emerging SiC-SiC Ceramic Matrix Composite (CMC) based substrates.