Next Generation Air Plasma Spray Porous Thermal Barrier Coatings for Gas Turbine Combustors

Abstract

Modern gas turbine combustors rely on thermal barrier coatings (TBC) in addition to sophisticated cooling strategies to survive high temperature environments. The need for lower emissions either driven by International Civil Aviation Organization (ICAO) regulations or by customer's desire for green engines often necessitates an increased air budget for improved mixing, thus resulting in less available cooling flow. Even with state-of-the-art cooling schemes to offset reduced cooling air allocation, combustors can benefit from better TBC performance to mitigate durability challenges. This paper showcases the next generation air plasma spray (APS) porous TBC developed by Honeywell as well as discusses tests performed and results gathered to assess its suitability for combustor application. A configured test specimen was utilized to evaluate suitability of a new coating system for combustor application. The configured specimen captures the material system, geometric features, manufacturing, and assembly process associated with combustor fabrication and thus provides a realistic environment for performance assessment. The configured specimen test results indicate the new APS porous TBC showed better performance than the standard 6–8% Yttria stabilized zirconia (YSZ) porous TBC. The new TBC with its lower conductivity at higher temperature increased thickness capability, and superior stability at substantially higher temperature than 6–8% YSZ TBC enables hot section components to survive hotter engine cycles.