双硅酸镱环境障涂层的高温水氧腐蚀机理研究

High Temperature Water Oxygen Corrosion Mechanism of Ytterbium Disilicate Environmental Barrier Coatings

陶瓷基复合材料构件在航空发动机燃气环境中面临严重的水氧腐蚀退化问题,在构件表面采用环境障涂层进行热防护是提高陶瓷基复合材料部件的高温性能、延长其使用寿命的有效措施。环境障涂层的高温稳定性对部件的结构完整性具有重要影响。为了探明环境障涂层在高温下的水氧腐蚀失效行为和机理,针对大气等离子喷涂(APS)Yb_(2)Si_(2)O_(7)/莫来石/硅体系的环境障涂层系统,开展了其在1350℃、90%(体积分数)H_(2)O-10%O_(2)水/氧蒸汽环境中的静态高温水氧腐蚀试验,采用XRD、SEM、EDS等材料表征分析手段,研究涂层在高温静态水氧腐蚀环境中的失效行为,获得EBCs涂层微观结构及物相在腐蚀过程中的演变规律,揭示EBCs涂层的失效机理。结果表明:表面的Yb_(2)Si_(2)O_(7)与环境中的氧化剂(主要为水)反应生成挥发性物质Si(OH)_(4),导致Yb_(2)Si_(2)O_(7)被不断消耗,莫来石层中的Si元素与Yb_(2)Si_(2)O_(7)层中的稀土元素发生互扩散,使得高温化学反应过程和机理十分复杂;在经历500 h腐蚀后,涂层出现鼓包脱落而失效。

The composite components of ceramic matrix face serious water oxygen corrosion degradation in the aeroengine gas environment.The application of environmental barrier coatings on the surface of components for thermal protection is an effective measure to improve the high-temperature performance and extend the service life of ceramic matrix composite components.The high-temperature stability of the environmen-tal barrier coatings plays a significant role on the structural integrity of the components.For elucidating the failure behavior and mechanism of environmental barrier coatings subjected to high-temperature water oxygen corrosion,this work conducted a static high temperature water oxygen corrosion experiment on an atmospheric plasma spraying Yb_(2)Si_(2)O_(7)/mullite/silicon environmental barrier coating system at 1350℃and 90%(volume fraction)H_(2) O-10%O_(2) water/oxygen vapor environment.Meanwhile,XRD,SEM,EDS and other material characterization analysis methods were employed to study the failure behavior of coatings in high-temperature static water oxygen corrosion environments,and obtain the evolution mechanisms of the microstructure and physical phases of EBCs coatings during the corrosion process.The failure mechanism of EBCs coatings was revealed.Results showed that Yb_(2)Si_(2)O_(7) on the surface reacted with oxidants(mainly water)in the environment to generate volatile substances Si(OH)_(4),leading to the continuous consumption of Yb_(2)Si_(2)O_(7).The silicon element in the mullite layer inter-diffused with the rare earth element in the Yb_(2)Si_(2)O_(7) layer,making the process and mechanism of high-temperature chemical reactions extremely complex.After 500 h of corrosion,the coating experienced bulging and detachment,resulting in the coating failure.