Thermal Cycle And Thermal Mechanical Fatigue Properties Of Thermal Barrier Coating Deposited By Electron Spark Deposition And EB-PVD

Thermal barrier coating(TBC),as one of the key technologies to develop high performance aero-engines,is widely used in combustion and engine blades of aviation engines.It increases the inlet temperature of the engine and engine thrust-weight ratio by reducing the surface temperature of the superalloy by substrate to reduce the amount of cooling gas engine.The goal of TBCs is to prepare a coating which has a higheroperating temperature,a greater the insulating effect,and longer service life.Currently the ceramic layer is deposited by EB-PVD,and the fabriction methods of bond coat also remains unchanged,such as multi-arc ion plating.There are few study about the bond layer deposited by ESD(Electro-Spark Deposition).The study about TBCs by EB-PVD on basis of bond layer deposited by ESD is less than the former.There are few research about the thermal cycle and thermal mechanical fatigue test.The thickness,defect sensitivity,microstructure and surface roughness of the bond layer deposited by ESD have an important influents on the ceramic coating properties.Therefore,this paper systematically studied these characteristics of the NiCoCr AlYTa layer deposited by ESD under various parameters.It was found that the quality of the coating is best under 40V,420?f,530Hz.On basis of these parameter mentioned above,12 specimens with smoothNiCoCrAlYTa layer have been prepared.Subsequently,the specimens were pre-oxidatized at different times(0h,2h,5h,10h),and ceramic layer deposited by EB-PVD on the bond layer.The performance of thermal shock resistance of the thermal barrier coatings was tested,indicating that unoxidized specimens have the best performance by statistical analysis.The surface morphology,cross-sectional morphology and composition were observed and analyzed by SEM and EDS,respectively.The analysis results show that the binding force size of the ceramic layer and the bond layer and the unevenness of TGO growth result in the coating failure.Measuring weight increase of the specimen during thermal cycle test and drawing oxidation kinetics shows that the oxidatized 5h and 10h have the best oxidation resistance,oxidatized 2h is the worst.The interaction between life of ceramic coating and dense aluminum oxide film formed by pre-oxidation caused this phenomenon.Through thermal mechanical fatigue test of bare rods,NiCoCrAlYTa coating rods and thermal barrier coating rods,it was found that the thermal barrier coatings rods had the longest thermal mechanical fatigue life.The bare rods followed.The NiCoCrAlYTa coating test rod was the worst.Through the analysis of fatigue fracture,the brittle fracture of NiCoCrAlYTa coating has an adverse effect on the thermal mechanical fatigue of specimens.Thermal barrier coatings can protect the specimens well,and has an advantageous effect on the thermal mechanical fatigue life.Fatigue toughness fracture and pores connected fracture caused by high temperature creep result in the specimens breaking.