Performance And Degradation Mechanism Analysis Of Thermal Barrier Coatings Based On Real-time Synchronous Detection Of Acoustic And Infrared Testing

Thermal barrier coatings?TBCs?,a key thermal protection technology,are widely used in hot end components in aerospace engines and gas turbines,effectively extending the service life of hot end components and significantly increasing their operating temperatures.In the course of service,some atmospheric deposits CMAS?CaO-MgO-Al₂O₃-SiO₂?will melt at high temperature and penetrate into the thermal barrier coating along the defects of pores and cracks.Under the action of chemical and mechanical,the thermodynamic properties of the thermal barrier coatings are changed,and the microscopic morphology is destroyed,which eventually leads to premature failure of the coating.Therefore,the current safety application and improved design of thermal barrier coatings can be effectively carried out under the premise of understanding the failure mechanism of CMAS corrosion thermal barrier coatings.Most of the studies focus on the detection of mechanical properties,microstructure and phase structure after thermal barrier coatings failure.The research of on the detection of CMAS failure process is relatively scarce.Therefore,this paper mainly studies the failure process of CMAS corrosion thermal barrier coating under the thermal cycle in the constant temperature furnace and the rapid heating and cooling thermal cycle environment by using non-destructive testing technology,and the failure under different environments was explained by conventional testing techniques such as SEM and XRD.The main research contents include:1.Acoustic emission detection and macroscopic morphology,surface topography and characterization of phase structure during high temperature CMAS corrosion experiments in a constant temperature furnace.According to literature research,the CMAS components which can be prepared in the laboratory are determined and prepared,and then ground to the size available in the experiment.In the pre-sample preparation stage,CMAS sintering on the surface of the sample should be realized by holding the sample for 30 minutes at 950°C.Through the waveguide rod technology,acoustic emission?AE?technology is used to detect the corrosion failure of CMAS in constant temperature furnace.The signal of the whole process is analyzed based on wavelet packet technology,and the microstructure and phase structure are characterized by SEM,XRD,EDS.It is found that compared with interface oxidation,CMAS will lead to premature change of the microstructure and phase structure of the coating.The sliding interface crack obtained by acoustic emission analysis is the main crack leading to coating failure.2.The thermal cycling conditions were set in the constant temperature furnace to test the acoustic emission of the high temperature CMAS corrosion test of the thermal barrier coatings,the characterization of the macroscopic and microscopic morphology and the construction of the theoretical model of the CMAS corrosion under the thermal cycling condition of the thermal barrier coating.Establish an analytical method combined with the macroscopic and microscopic characterization of the sample to analyze the acoustic emission signals collected in this chapter.Further,establish a theoretical model and obtain the failure mechanism diagram under different cycle times.Combining the experimental results with the theoretical model,it is found that as the number of cycles increases,the critical temperature of spalling increases.3.Under the conditions of the self-developed thermal barrier coatings in service environment,acoustic emission and infrared real-time detection of high temperature CMAS corrosion process were realized.Combined with the macroscopic and microscopic morphology detection.It was found that the thermal barrier coating sample coated with CMAS corrosion had failed after 40 cycles.On the contrary,the thermal barrier coating without CMAS corrosion did not fail until 350 cycles.The failure mode with CMAS corrosion is mainly the interlayer spalling of the thermal barrier coating,while the spalling without CMAS is mainly due to the growth of oxide,which results in the spalling of coatings from the interface between bonding layer and ceramic layer.