Study On Preparation And Performance Of YSZ-based Bionic Layered Structure High Temperature Sealing Coating

With the continuous increase of the airflow temperature at the hot end of the engine,high-temperature-resistant and abradable high-temperature sealing coatings have become a research hotspot in high-performance aeroengines.At present,the most commonly used high-temperature sealing coating with service temperature above 1000℃is YSZ ceramic-based sealing coating.Under the action of thermal fatigue stress,the hard and brittle ceramic coating is prone to fatigue cracking during thermal cycling,which reduces Service life of high temperature sealed coating.Aiming at the problem of premature thermal cycle failure of YSZ ceramic-based sealing coatings,this thesis takes the optimization of the micro-morphological structure during the coating forming process as a research breakthrough.Microstructure,design and prepare the ceramic surface layer of"brick-mud"layered structure,analyze the change law of mechanical properties of coatings with different layered structures,study the effect of layered structure on crack propagation during thermal cycling and analyze its failure mechanism to improve the mechanical properties and thermal cycle life of the coating;on the basis of improving the thermal cycle performance,the influence of the layered structure on the wearability of the coating was studied,and the YSZ-based biomimetic layered structure high-temperature sealing coating was discussed to replace the traditional YSZ-based sealing coating.Feasibility of high temperature sealing coatings.Conclusion as below:（1）On the basis of ensuring that the sealing coating has a high deposition efficiency,the"brick"layer material and the"mud"layer material of the layered structure coating have been determined through abradability and mechanical performance tests,and the"brick"layer The material is YAG-YSZ（the mass ratio of yttrium aluminum garnet to YSZ is 1:20）composite coating,and the material of the"mud"layer is Si OC ceramic;（2）Compared with the traditional YSZ high-temperature sealing coating,the thermal cycle life of the YSZ-based bionic layered structure high-temperature sealing coating with layers 2,3,and 6 has increased by 61.5%,92.3%,and 10.3%,respectively.The thermal cycle failure modes of the three layered structure coatings are all the ceramic surface layer is peeled off as a whole,and longitudinal cracks appear inside the coatings.The generation of longitudinal cracks slows the initiation and propagation of transverse cracks and improves the thermal cycle performance of the coating;（3）Compared with the traditional YSZ sealing coating,the fracture toughness of the YSZ-based biomimetic laminated structure sealing coating with 3 layers has increased by85%,and the average fracture toughness is about 2.945MPa·m^0.5.Different from the traditional second-phase particle toughening,the toughening mechanism of the layered structure is mainly divided into two mechanisms:crack deflection and crack branching;（4）After 50 thermal cycles of the YSZ-based bionic layered structure high-temperature sealing coating and the traditional YSZ sealing coating,the average sliding friction coefficient of the coating increased by 20.7%and 17.2%,respectively,and the volume wear rate increased by 91.1%,116.1%,the longitudinal cracks in the layered structure coating caused a substantial increase in the volume wear rate.The abradability of the traditional YSZ sealing coating before thermal cycling is better,and the abradability of the layered structure sealing coating after 50 thermal cycles is better than that of the traditional YSZ sealing coating.