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

Abstract

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.