Durable All-oxide Thermal-environmental Barrier Coatings (T-EBCs) Capable of High Temperature Operation

Adoption of ceramic matrix composites (CMCs) could enable significant improvements in gas turbine efficiency due to their inherently higher temperature capabilities with respect to metals. However, their utility is limited due to a vaporization or the protective oxide scale in water vapor containing combustion environments. Advanced environmental barrier coating (EBC) capable of 3100°F operation are needed protect the CMCs and enable utilization of their beneficial properties. The proposed work provides the first all-oxide EBC system which is capable of operating beyond the ~2500°F stability limit of current state-of-the-art Si bond coat EBC systems. Modified bond coat compositions will be utilized to replace Si bond coats while an outer TBC layer will be deposited to provide thermal cyclic and erosion durability while also enhancing CMAS resistance. This T-EBC system will thus enable significant increases in the operating temperature capabilities of CMCs. In Phase I, the project will deposit the oxide bond coat via the dipcasting method and subsequently deposit the remaining T-EBC via a novel plasma spray – physical vapor deposition (PS-PVD) technique. These coatings will be evaluated via thermal cycling in a flowing steam environment at temperatures of 2600°F with high temperature oxidation testing at 2900°F. In addition, the erosion resistance will be evaluated at room temperature. Three different coating architectures will be evaluated to assess the thermomechanical performance and durability. Successful demonstration of the all-oxide coatings would have significant commercial potential for both defense and commercial aviation applications as well as stationary power generation. CMCs could be utilized throughout these applications and would provide more efficient operation in terms of both cost and fuel usage. Though would ultimately result in lower emissions due to lower fuel usage as well as elevated temperature operation which natively produces fewer emissions.