Fabrication Process And Property Of 8YSZ/CoCrAlY Thermal Barrier Coatings Onto K488 Superalloy

Thermal barrier coatings(TBCs),which enable engine components free of high temperature damage,have a huge effect on the service properties and life of hot-end parts such as aircraft and gas turbine blades,combustion room.In this paper,Co Cr Al Y metal bonding coating and YSZ ceramic coating were prepared on the substrate K488 by high velocity oxygen fuel spraying(HVOF)and electron beam physical vapor deposition(EB-PVD),respectively.The thermo-mechanical and chemical performance of the TBCs were investagated in detail.The HVOF bond coatings are treated at 1050±10°C with the dwell time 4±0.5 h,following subjected to shot peening and wet blowing sand.The results show that the shot peening can improve the compactness of bond coatings(BC),improve the microstructure of the YSZ ceramic topic coatings(TC),and increase the recrystallization,densification and homogenization of the Co Cr Al Y bond coatings during the heat treatment.Moreover,The high temperature oxidation resistance of the coatings can also enhanced.The wet blowing sand can effectively clear the contaminants onto the bond coatings and increase the interfacial adhesion of the TBCs.The scanning electron microstrocopy(SEM)shows a high density of the Co Cr Al Y layer and a diffusion layer in BC/substrate,a flat interface in BC/TC.The coatings that deposited in 950-1000°C have the best resistance in the thermal shock testing.Some coatings that deposited in 950°C are used to shock resistance test in different oxygen flux.As a result,the thermal shock resistance is the best when the oxygen flux is 200 m L/min.The YSZ topic coatings were prepared according to the optimized process parameters.The phase analysis indicate that the coating is tetragonal zirconia and does not contain oth er impurity phases.There is a thin equiaxed crystal zone at the interface between BC and TC layer.There is a thin equiaxed crystal region,Zr content mutation,O,Co,Cr,Al interdiffusion at the interface BC/TC.The ceramic layer has a typical columnar structure.The thermo-mechanical property test shows that the oxidation rate of the coating is 0.0567 g/(m~2h)at 1100°C,and the ceramic coating does not undergo phase change during the high temperature oxidation.The average corrosion rate of gas hot corrosion is 0.0822 g/(m~2.h)at 900°C.There is no wrinkling,cracking,peeling,spallation at temperature of 1100°C when the number of thermal shock and thermal cycling test is 100 and 2000,respectively.The thermal conductivity is less than 1.9 W/(m.K)at temperature of 25-1200°C,which meets relevant standards.The tensile strength of the coating is 67.14 MPa,which is greater than the standard of 60 MPa.The mechanical property testing of substrate deposited thermal barrier coatings shows that the tensile strength of the system is 1077 MPa and the elongation is13.0%at room temperature.The tensile strength is 608 MPa and the elongation is47.0%at high temperature.The high temperature lasting time is 566.8 h and the elongation is 24.4%.There is no fracture when the high cycle fatigue test cycle is10000000 which meets the standard requirements.The bottom of the bending test and the ceramic surface are free of delamination or peeling.A robot program is developed for the shape of the blade,and a speci al tool for shot peening and coating is designed.Using the optimized parameters and tooling to prepare the thermal barrier coating on the blade,the parts that meet the design requirements are obtained.