FRG: Functionally Graded High-Al Mullite Environmental Barrier Coatings

FRG：功能梯度高铝莫来石环境屏障涂料

• 批准号: 0233952
• 负责人: Soumendra Basu
• 金额: $ 64万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-15 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0233952&HistoricalAwards=false
• 关键词: FRG; Functionally; Graded; Al; Mullite

Si-based ceramics such as silicon carbide and silicon nitride require hot-corrosion and recession resistant environmental barrier coatings (EBCs) when exposed to corrosive environments containing high-pressure steam at elevated temperatures. This research will focus on developing a functionally graded Al-rich mullite (3Al2O3.2SiO2) EBC system for the protection of Si-based ceramics from such corrosive environments. These coatings will be deposited by chemical vapor deposition (CVD), which allows for the deposition of dense, uniform coatings over complex substrates. It is well established that alpha-alumina coatings, which have excellent hot-corrosion and recession resistance, can fail due to poor thermal shock resistance. In contrast, mullite coatings, which have excellent thermal shock resistance and a close CTE match with the Si-based ceramics, contains silica, which may lead to hot-corrosion and recession attack of the coatings themselves under long term exposures in corrosive environments. We propose to grow functionally graded coatings whose composition is varied from near-stoichiometric mullite at the coating/substrate interface to a highly Al-rich mullite at the coating surface. It is therefore expected that such coatings will have the oxidation, corrosion and recession resistance of alpha-alumina coatings, with the thermal shock resistance of stoichiometric mullite coatings on Si-based substrates. The proposed research will involve developing a process to grow compositionally graded CVD mullite coatings and to evaluate their oxidation, corrosion, and recession resistance. Additionally, mechanical properties of these the coatings will be evaluated, using among others, novel non-destructive evaluation (NDE) techniques. This knowledge base will be used to aid in the systematic design of functionally graded CVD mullite coatings for optimal performance in specific industrial service environments.It is projected that the successful completion of this research will lead to dense, uniform and adherent coatings on complex surfaces of Si-based ceramics, that are highly resistant to cracking, spallation, oxidation, hot-corrosion and recession. These coatings will have a critical impact by enabling gas turbines to operate at higher temperatures leading to improved fuel efficiency and reduced emissions. This research will also advance the state-of-the-art in non-destructive evaluation of coating materials including measurement of elastic properties of the graded coatings as a function of depth, monitoring coating degradation, and detection of crack growth at the coating/substrate interface during thermal cycling. The research program will train 3 graduate students to work as a team in the areas of processing, structure and property evaluations and will enable them to interact with researchers from industry, national laboratories, other academic institutions, as well as with undergraduates from Boston University.

当暴露于高温下含有高压蒸汽的腐蚀性环境时，Si基陶瓷如碳化硅和氮化硅需要抗热腐蚀和抗衰退的环境阻挡涂层（EBC）。本研究将致力于开发一种功能梯度富铝莫来石（3Al2O3.2SiO2）EBC系统，用于保护硅基陶瓷免受腐蚀环境的影响。这些涂层将通过化学气相沉积（CVD）进行沉积，其允许在复杂基底上沉积致密、均匀的涂层。众所周知，具有优异的抗热腐蚀性和抗衰退性的α-氧化铝涂层可能由于差的抗热冲击性而失效。相比之下，莫来石涂层，具有优异的抗热震性和接近的CTE匹配的Si基陶瓷，包含二氧化硅，这可能会导致热腐蚀和衰退攻击的涂层本身在长期暴露在腐蚀环境中。我们建议生长功能梯度涂层，其组成是不同的，从近化学计量的莫来石在涂层/基体界面的涂层表面的高度富铝莫来石。因此，预期这种涂层将具有α-氧化铝涂层的抗氧化性、抗腐蚀性和抗衰退性，以及Si基基材上化学计量莫来石涂层的抗热震性。 拟议的研究将涉及开发一种工艺来生长成分分级的CVD莫来石涂层，并评估其抗氧化性、抗腐蚀性和抗衰退性。此外，这些涂层的机械性能将进行评估，除其他外，使用新的非破坏性评估（NDE）技术。该知识库将用于辅助功能梯度CVD莫来石涂层的系统设计，以在特定的工业服务环境中获得最佳性能。预计该研究的成功完成将导致在Si基陶瓷的复杂表面上形成致密、均匀和粘附的涂层，该涂层具有高度的抗开裂、抗剥落、抗氧化、抗热腐蚀和抗衰退性。这些涂层将通过使燃气涡轮机在更高的温度下运行而产生关键影响，从而提高燃料效率并减少排放。这项研究还将推进涂层材料的非破坏性评估的最新技术，包括测量梯度涂层的弹性性能作为深度的函数，监测涂层降解，并检测热循环过程中涂层/基材界面处的裂纹生长。该研究计划将培养3名研究生在加工，结构和性能评估领域作为一个团队工作，并使他们能够与来自工业，国家实验室，其他学术机构的研究人员以及波士顿大学的本科生进行互动。