Experimental Study On The Effect Mechanism Of Applied Stress Field On The Oxidation Of Thermal Barrier Coating At High Temperature

Thermal barrier coatings?TBCs?are widely used in high temperature parts of aeroengines,as a kind of high temperature resistant and corrosion resistant ceramic protective material,which are used to improve the high temperature resistance of engines and thus improve the efficiency and service life of engines.Exfoliation failure is an important bottleneck restricting the safety application of thermal barrier coatings in highperformance aeroengines.In extremely harsh service environments,the multiple effects of multiple loads such as heat,force,and chemical,and interface oxidation are likely to induce the peeling of thermal barrier coatings.Failure,interfacial oxidation is considered to be the first key factor in inducing thermal barrier coating spalling failure.Many studies have focused on the growth law of TGO in thermal barrier coating systems,but the growth behavior of TGO under external stress has not been well understood.The actual service environment of the thermal barrier coating is affected by complex external stresses.The stress caused by external loads during high-temperature oxidation is an important factor in determining the final stress state.Based on this,the purpose of this paper is to conduct an in-depth study of the effect of external stress on the growth of TGO starting from hightemperature interface oxidation.The main results achieved in this article are as follows:1.Build a thermal-mechanical-chemical coupling experimental platform.At present,we have conducted in-depth research on the theoretical study of the thermal barrier coating interface oxidation,but no effective experimental method has been established to characterize the thermal barrier coupling effect of the thermal barrier coating.Therefore,we need to understand the failure mechanism of the thermal barrier coating under the applied load by simulating the service environment of the thermal barrier coating under the applied load.Under the premise that the goals and ideas have been clarified,the thermomechanical-chemical coupling experimental characterization method is studied,and a durable thermal barrier coating experimental platform is designed to provide a platform basis for understanding the effect of the applied stress field on TGO growth.2.Taking scanning electron microscopy?SEM?as the main research method,combined with X-ray diffraction?XRD?and electron energy scattering spectroscopy?EDS?and other analytical methods,analyze the high-temperature interface oxidation and microstructure evolution of the thermal barrier coating.In the study of interfacial oxidation,the thickness of TGO is a key factor affecting the failure mechanism of TBCs.The failure mechanism of TGO is characterized by analyzing the thickness and chemical composition of TGO.Due to the selective oxidation of the bonding layer,a dense oxide composed of ?-Al₂O₃ is first formed.When the bonding layer experiences severe aluminum loss,some mixed oxides other than ?-Al₂O₃,such as spinel mixtures such as Ni O,Cr₂O₃ and NiCr?Cr,Al?₂O₄,are formed.Therefore,TGO becomes thermodynamically unstable,resulting in chemical failure of TBC.3.The larger local stress will change the diffusion constant of the oxide and the oxidation rate of the oxide at the interface.The stress caused by the external load during the high-temperature oxidation is an important factor that determines the final stress state.The stress caused by the applied load is complicated.In order to simplify the study,we divide the applied load into applied tensile stress,applied compression stress and applied bending stress.Based on the development of a thermo-mechanical-chemical coupling experimental platform,it was found that the applied stress will affect the diffusion rate of Al³⁺ in the bonding layer,and the growth rule of TGO under the high-temperature durable test machine is obtained.