The need for higher efficiencies and performance in gas-turbine engines that propel aircraft in the air, and generate electricity on land, is pushing the operating temperatures of the engines to unprecedented levels. Replacing some of the current hot-section metallic components with ceramic-matrix composites (CMCs) is making that possible. A high-temperature ceramic coatings system, that includes environmental-barrier coatings (EBCs), are needed to protect CMCs. However, these coatings undergo degradation in the highly hostile environment of the gas-turbine engine consisting of a combination of high gas temperatures, pressures, and velocities. In addition, there is the ubiquitous presence of steam (a combustion by-product) and occasional ingestion of calcia-magnesia-aluminosilicates (CMASs) in the form of dust, sand, or ash from the environment. Steam can cause corrosion of EBCs, and the molten CMAS deposits can react with the EBCs resulting in their failure. This article provides a perspective on the understanding of these degradation mechanisms, and possible approaches, guided by that understanding, for mitigating the degradation. An outlook on the future challenges and opportunities is presented.

燃气涡轮发动机需要更高的效率和性能，以推动飞机在空中飞行并在陆地上发电，这使发动机的工作温度达到了前所未有的水平。用陶瓷基复合材料（CMC）替代一些当前的热断面金属部件使之成为可能。需要一种高温陶瓷涂层系统，其中包括环境屏障涂层（EBC），以保护CMC。然而，这些涂层在燃气涡轮发动机的高度不利环境中经历退化，该环境由高气体温度，压力和速度共同组成。此外，普遍存在蒸汽（燃烧副产物），并偶尔从环境中吸收粉尘，沙子或灰烬形式的氧化钙-镁-铝硅酸盐（CMAS）。蒸汽会导致EBC腐蚀，而熔化的CMAS沉积物会与EBC反应，从而导致EBC失效。本文提供了对这些降级机制的理解的观点，并提供了以该理解为指导的缓解降级的可能方法。提出了对未来挑战和机遇的展望。