Advanced Thermal Barrier Coating Systems for Gas Turbine Application: Microstructure, Properties, and Performance

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In the aerospace and power generation industries, demands to reduce fuel consumption, operating costs, and greenhouse gas emissions continue to push gas turbine engine (GTE) designers to find ways to improve GTE efficiency and extend operating lives. Increasing the turbine inlet temperature is a key way to increase power output without increasing fuel burn. With rising turbine inlet temperatures, demands for continuous operation under harsh environments, and a shift towards alternative fuels, hot section materials are being subjected to increased mechanical stresses and environmental attack. While state-of-the-art superalloys used to manufacture turbine blades, vanes, and combustion components can maintain strength at temperatures up to 1093°C (2000°F), most current and all next generation GTE designs require materials that can safely operate well beyond this temperature. This is only possible with the use of thermal barrier coating (TBC) systems and cooling technology. In addition, many modern superalloys have reduced environmental resistance due to lower Cr content, done to stabilize the microstructure under higher temperatures and mechanical loads. Therefore, TBCs are now required to provide both thermal barrier and environmental protection functions, and have become integral to modern GTEs. With the industry's goal to designate TBCs as a "prime reliant" in GTE design, further TBC performance improvement and reliability are needed.***Major challenges GTE designers face include: lack of understanding of substrate influence on TBC life; the existence of inward and outward diffusion of elements during GTE operation leading to early coating failure; insufficient temperature and fracture resistance of ceramic top coat materials; and lack of a universal approach to predict TBC failure mechanism(s) and life based on microstructure and service condition. Therefore, the objectives of this research program are to explore new TBC materials and structures for improved performance, to understand the microstructure evolution and failure mode(s) under different service conditions, and to enable TBC life assessment.***The outcomes of this research will include new coating material compositions and structures with enhanced durability, a coating design and selection protocol for different turbine blade substrate materials and operating conditions, and a tool to accurately predict TBC system life. This research will also enhance the understanding of coating and substrate interaction under extreme mechanical and environmental conditions and provide training to HQPs. Finding more durable coating compositions and structures will directly benefit Canadian OEMs (such as Pratt & Whitney Canada, Magellan Aerospace), gas turbine users (TransCanada Pipelines, Union Gas) and coating providers (MDS Coating Technologies, Liburdi Turbine Services, Northwest Mettech).