等离子喷涂-物理气相沉积Si/莫来石/Yb2SiO5环境障涂层

采用等离子喷涂-物理气相沉积技术(PS-PVD)在SiC/SiC复合材料表面依次制备了Si(底层)、3Al₂O₃-2SiO₂ (中间层)、Yb₂SiO₅(面层)环境障涂层(EBC)。利用扫描电子显微镜(SEM)观察分析EBC涂层表面与界面的微观形貌, X射线衍射仪对喷涂过程中易非晶化的莫来石涂层进行物相分析, 研究了喷涂粉末与高温等离子体的相互作用并探讨了EBC涂层的沉积机制。结果表明：通过PS-PVD技术可制备出低孔隙率、高致密界面的EBC涂层。通过观察EBC涂层表面, Si涂层表面无裂纹, 而莫来石和Yb₂SiO₅涂层表面均发现有微裂纹, 其中莫来石涂层表面的裂纹尺度大于Yb₂SiO₅涂层。三层结构的致密EBC涂层以液相沉积为主, 同时伴随有气、固沉积。在Yb₂SiO₅涂层沉积过程中, 液相沉积导致涂层为致密的层状结构, 蒸发后气相在等离子焰流中及基体表面发生均匀形核和非均匀形核导致涂层中出现大量的纳米晶粒, 而微熔粒子和溅射粒子则形成涂层中亚微米、微米晶粒。

Preparation of Si/Mullite/Yb2SiO5 Environment Barrier Coating (EBC) by Plasma Spray-Physical Vapor Deposition (PS-PVD)

Environmental barrier coating (EBC) Si/3Al₂O₃-2SiO₂/Yb₂SiO₅ was prepared by plasma spray-physical vapor deposition (PS-PVD) on SiC/SiC ceramic matrix composites. The surface and interface of tri-layered EBC were characterized by SEM. And the phase transformation of the mullite coating was analyzed by XRD. The interaction of feedstock powder and high temperature plasma jet was investigated. Furthermore, the deposition mechanism of EBC was studied. Experimental results dermonstrated that EBC with low porosity and good bonding can be obtained by PS-PVD. EBC withont micro-crack was observed on the surface of Si coating in contrast to coating mullite and Yb₂SiO₅ coating. The size of crack in mullite surface was larger than that in Yb₂SiO₅ coating. Low porous EBC was deposited by liquid droplet accompanied by gas and solid state through PS-PVD. Yb₂SiO₅ coating was dense and formed laminar structure, mainly resulting from liquid droplet deposition. Additionally, nano-grains were observed in Yb₂SiO₅ coating which resulted from both homogeneous and heterogeneous nucleation of vapor phase. And sub-micron/micron grains were obtained from semi-molten and splashed particles.