以抗CMAS腐蚀为目标的稀土硅酸盐环境障涂层高熵化设计与性能提升

Rare Earth Silicate Environmental Barrier Coating Material:High-Entropy Design and Resistance to CMAS Corrosion

环境障涂层是大推力和高推重比航空发动机的关键材料,能够为碳化硅纤维增强碳化硅(SiCf/SiC)陶瓷基复合材料热端部件提供有效防护,阻挡燃气及环境腐蚀介质的侵蚀。稀土硅酸盐具有与SiC基复合材料匹配的热膨胀系数以及良好的化学相容性,是目前国际公认的优选环境障涂层体系。然而,目前已知稀土硅酸盐材料耐典型低熔点氧化物CaO-MgO-Al_(2)O_(3)-SiO_(2)(CMAS)腐蚀性能不足,难以满足新一代航空发动机1300℃及以上温度的工程应用需求。本文总结了近年来稀土硅酸盐耐CMAS腐蚀相关研究进展,重点介绍了本团队关于单一稀土主元单/双硅酸盐CMAS腐蚀机理的研究成果,以此为基础提出高熵化设计思路,旨在充分利用不同稀土元素在与CMAS反应过程中呈现的特性差异,通过合理设计多稀土主元搭配实现稀土硅酸盐材料耐CMAS腐蚀性能提升。最后对高熵稀土硅酸盐环境障涂层的发展方向进行了展望。

High thrust-to-weight ratios and high propulsion are necessary requirements for revolutionizing the aviation technology.Emerging hot-section engine components are currently focused on SiCf/SiC ceramic matrix composite materials,wherein the environmental barrier coatings(EBCs)are needed to protect the engine components from the harsh combustion environment.Due to their matched thermal expansion coefficient and good chemical compatibility with the SiCf/SiC ceramic matrix composites substrates,rare earth(RE)silicates have been identified as promising EBC materials.However,they cannot provide reliable protection for the engine components when the working temperature rises over 1300oC,mainly because of their poor resistance to the low melting point oxides CaO-MgO-Al_2O_3-SiO_2(CMAS)melts.This review discusses the current state of research on the CMAS corrosion resistance of RE silicates.First,the interaction and degradation mechanisms of single-RE-component RE_2SiO_5 and RE_2Si_2O_7are discussed,and the different roles of RE species in reacting with CMAS melts are summarized.Then,the concept of high-entropy design is introduced,enabling synergistic optimization of the effects of multiple RE species in terms of CMAS resistance,by delicately designing the multi-RE-component(n REx)compositions.Such a strategy leads to enhanced CMAS corrosion resistance in some novel(nRE_x)_2SiO_5 and(nRE_x)_2Si_2O_7 materials.Finally,potential prospects,opportunities,and challenges for high-entropy RE silicates as EBC materials are discussed.