Study Of Preparation Of Longitudinal Structure Thermal Barrier Coating And Its Thermal Cycle Life

Increasing the inlet temperature of the engine turbine is the key to the greater thrust-to-weight ratio of the aeroengine,which requires further improvement of the high temperature capability of the aeroengine turbine blades and combustion chambers.One of the main ways to improve the aircraft engine anti-high temperature capacity is applying a thermal barrier coating(TBC)to the surface of the substrate alloy.The state of art application is double-layer thermal barrier coating system,which formed with “MCrAlY metal adhesive layer +Y2O3 stabilized ZrO2 ceramic surface layer”.However,it remains certain problem during the application,in which occurred the highest frequency and has the most significant impact is the early peeling of ceramic layer during thermal cycle.This unreliability of the life of the thermal barrier coating has become a problem to be solved in the application process of thermal barrier coating.This thesis is based on frozen casting process,using tertiary butanol as medium,and to prepare ceramic coating with the structure of the vertical hole.In this paper,the forming process of vertical hole structural ceramics was discussed,and then evaluated the coating about the porosity,compressive strength and shrinkage properties.The YSZ ceramic coating with uniform pore size distribution,large pore size and high compressive strength was prepared by adjusting the process parameters.The effects of solid content,freezing temperature and sintering temperature on the porosity,compressive strength,pore size,shrinkage and microstructure of YSZ ceramics were investigated by adjusting the solid content of the slurry,the freezing temperature and the sintering temperature.The ceramic coating has uniform pore size distribution and porosity of 30%~75%,and the corresponding compressive strength is 31~3Mpa.On the other hand,thermal barrier coatings of longitudinal structure was prepared through combing with high temperature remelting and plasma spraying technology.And then compared with thermal barrier coatings which prepared by APS method on themicro-hardness,fracture toughness,thermal insulation and thermal cycle life.The results show that the thermal barrier coating with the vertical structure has lower micro-hardness and higher fracture toughness.Due to the internal obturator existence of longitudinal thermal barrier coatings and the low conductivity of the air,the thermal resistance of the coating is far higher than that of APS coating and show better insulation performance.In addition,the longitudinal thermal barrier coatings can release stress and thermal stress during thermal cycling,so it shows a better shock resistance performance and higher thermal cycling life.