Development Of High Temperature Vibration Simulator For Thermal Barrier Coatings And Its Failure Mechanism

Turbine blades are important hot end protective parts of aero engines and gas turbines.The working environment of turbine blades is extremely harsh.The vibration environment is an inevitable situation in the service process of turbine blades.Thermal barrier coatings(TBCs)are widely used in high temperature parts of aero-engines due to their excellent thermal insulation protection ability,which greatly improves the service life of the engine.However,TBCs are also accelerated to peel off due to vibration fatigue at high temperature,which seriously restricts the application of TBCs.Based on this,in view of the limitations of domestic and foreign simulation devices that can meet the high temperature,high frequency and high exciting force of thermal barrier coatings in service environment,this paper independently built a simulation platform for the high temperature vibration service environment of thermal barrier coatings on turbine blades,and adopted the thermal barrier coatings prepared by APS technology and EB-PVD technology as the research object.Combined with SEM,the high temperature vibration failure behavior of coatings was analyzed,and the experimental study of thermal barrier coatings failure under the synergistic action of high temperature and vibration was realized.At the same time,the finite element software ABAQUS was used to calculate the vibration characteristics and stress distribution of the sample.Based on the stress distribution and the experimental results,the failure mechanism of the thermal barrier coating under the synergistic action of high temperature and vibration was studied.The main research contents include:1.In order to simulate the service environment under the cyclic action of high and low cycle load of thermal barrier coating on aero-engine turbine blades(low cycle load is centrifugal force caused by wheel rotation and high temperature caused by gas,while high cycle load is mainly the alternating exciting force formed by air flow and working blade),In this paper,a simulation platform for high temperature vibration service environment of thermal barrier coatings on turbine blades is designed.The platform is mainly divided into high temperature loading module,vibration loading simulation module and control system module.The high temperature loading module uses silicon carbon rod heating element to heat the sample in a relatively closed insulation environment.The highest temperature is 1600?.The furnace is a left and right furnace type structure.The vibration loading module adopts the vibration table loading,which can achieve the maximum thrust of 6000 N and the maximum frequency of 5000 Hz,greatly shortening the vibration fatigue test time.The control system module adopts PC/PLC dual-zone dual-control system with stable operation and high control accuracy(error <1%).2.The thermal barrier coating samples were prepared by atmospheric plasma spraying technology.Two cycle tests of the APS thermal barrier coating under different temperatures were carried out on the turbine blade thermal barrier coating high-temperature vibration service environment simulation platform built independently.The vibration characteristics of the sample were calculated with the finite element software ABAQUS,and the stress distribution in the high temperature vibration environment was analyzed.The test results show that under the same conditions,there is no crack in the ceramic layer of the pure oxidized sample,but a large number of transverse cracks appear in the ceramic layer of the sample after vibration loading,and a large number of peeling occurs in the ceramic layer surface.The peeling area is mainly concentrated in the "waist" of the sample,which is consistent with the phenomenon of stress concentration.3.Under the same test conditions,the EB-PVD thermal barrier coating samples were subjected to high temperature vibration cycle tests.The results were similar to those of APS coating.Under the same test conditions,compared with the microstructure with and without vibration,it was found that vibration could induce the coating to spalling earlier,and the spalling area,crack density and width of the coating increased,which provided an important reference for the follow-up research on the mechanism of thermal barrier coating failure under high temperature vibration.