Preparation And Characterization Of SiC Whisker Toughened Porous YSZ High Temperature Sealing Coating

At present,the problem of ceramic based high-temperature sealing coating is that in the service process,due to the complex system structure and harsh service environment of high-temperature sealing coating,the coating system will fail in the process of use.The most significant influence is the fatigue cracking of ceramic surface in the process of thermal cycle,which will cause the direct failure of high-temperature sealing coating system,leading to high-temperature sealing coating In addition,due to the high melting point and almost zero toughness of ceramic materials,the deposition rate of ceramic based high-temperature sealing coating is particularly low.After investigation,it is found that the deposition rate is about 10%,resulting in a serious waste of resources,increasing the manufacturing cost of the coating and limiting the application of the coating.In this study,the powder-making process and bonding phase were optimized to improve the deposition efficiency of the coating,and the thermal cycle failure mechanism of the coating was analyzed.The whisker toughening technology was used to obtain ceramic-based high-temperature sealing coating with high deposition efficiency and long thermal cycle life.The results show:(1)As a sacrificial coating,ceramic-based high-temperature sealing coating requires a certain amount of non-ceramic phase to reduce the hardness of the coating,so as to ensure that the coating will not fail prematurely due to low strength during service.The blade will be damaged due to excessive strength.The optimized particle size of the pore-forming phase in this study is 200 meshes,the content of the pore-forming phase is 10%,and the solid content of the slurry is 50%;(2)The low-melting-point ceramic is used as the bonding phase,and the melted droplets will wrap and adhere to the YSZ particles and the pore-forming phase,thereby improving the deposition efficiency of the coating.After analyzing the spreading morphology of the coatings with three bonding phases of alumina,magnesia-aluminum spinel and yttrium aluminum garnet,it was found that the coatings with yttrium aluminum garnet adhered and wrapped unmelted and unburned particles are the most,and the deposition efficiency is also the highest;(3)Compared with the coating without the bonding phase,the thermal cycle life of the coating with alumina,magnesia-aluminum spinel and yttrium-aluminum garnet was increased by 11.4%,2.97% and 43.7%,respectively.The thermal cycle failure locations of the four coatings are all inside the YSZ ceramic layer close to the substrate side.The addition of SiC whiskers did not adversely affect the sprayability of the agglomerated powder.After plasma spraying,SiC whiskers still retain the structural integrity in the coating and are evenly distributed.The thermal cycle toughening mechanism of the YSZ-based sealing coating containing the whisker toughening layer mainly includes the release of the porous structure of the whisker toughening layer on the thermal property mismatch residual stress,as well as the bridging and pulling-out effect of the SiC whisker.This effect ultimately improves the thermal cycle life of the YSZ-based seal coating containing the whisker toughening layer.