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

在航空航天和发电行业，降低燃料消耗、运营成本和温室气体排放的需求继续推动燃气轮机发动机(GTE)设计者寻找提高GTE效率和延长运行寿命的方法。提高汽轮机进口温度是在不增加燃料消耗的情况下增加功率输出的关键途径。随着汽轮机进口温度的升高，对恶劣环境下连续运行的要求，以及向替代燃料的转变，热截面材料正受到更大的机械应力和环境侵蚀。虽然用于制造涡轮叶片、叶片和燃烧部件的最先进高温合金可以在高达1093°C(2000°F)的温度下保持强度，但大多数当前和所有下一代GTE设计都要求材料能够在此温度之后安全运行。只有使用热障涂层(TBC)系统和冷却技术才能做到这一点。此外，许多现代高温合金由于较低的铬含量而降低了耐环境性能，这是为了在更高的温度和机械载荷下稳定组织。因此，热障涂层现在被要求兼具隔热和环保功能，并已成为现代热障涂层不可或缺的组成部分。行业的目标是将热障涂层指定为热障涂层设计的“主要依赖因素”，因此需要进一步提高热障涂层的性能和可靠性。*热障涂层设计者面临的主要挑战包括：对热障涂层寿命的影响缺乏了解；热障涂层运行过程中元素的向内和向外扩散导致早期涂层失效；陶瓷面层材料的抗温性和抗断性不足；以及缺乏基于微观结构和使用条件预测热障涂层失效机理和寿命的通用方法(S)。因此，这项研究的目标是探索新的涂层材料和结构以提高性能，了解不同使用条件下的组织演变和失效模式(S)，并进行涂层寿命评估。*这项研究的结果将包括具有增强耐久性的新涂层材料组成和结构，不同涡轮叶片基材材料和运行条件的涂层设计和选择方案，以及准确预测涂层系统寿命的工具。这项研究还将加强对极端机械和环境条件下涂层和基材相互作用的理解，并为HQP提供培训。寻找更耐用的涂层成分和结构将直接使加拿大的原始设备制造商(如普惠加拿大公司、麦哲伦航空公司)、燃气轮机用户(如TransCanada管道公司、联合天然气公司)和涂层供应商(MDS涂层技术公司、Liburdi涡轮机服务公司、西北Mettech公司)受益。

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).