Research On Properties And Process Parameters Of Plasma Sprayed 8YSZ Thermal Barrier Coating

Thermal barrier coatings?TBCS?are widely used in turbine blades for gas turbine dynamic and stationary blades and aerospace engines.The ceramic material is coated on the surface of the alloy,and the metal substrate is protected by utilizing the excellent high temperature resistance,low thermal conductivity and corrosion resistance of the ceramic material,so that the hot end parts of the gas turbine and the aeroengine can be reliably operated.In this paper,NiCoCrAlY metal bonding layer and ZrO₂-8%wtY₂O₃ ceramic layer were prepared on the surface of Inconel600 nickel-base superalloy by atmospheric plasma spraying process.Through the prepared coated metallographic samples,the cross-sectional microscopic morphology of the coating was observed by optical microscope,and the surface microscopic morphology of the coating was observed by S-3400N scanning electron microscope.It was observed that the surface of the coating was beige,smooth and flat,and the structure was compact.It was formed by melt-stacking of powder particles,and the particles were well melted.The whole was flat and agglomerated and stacked,and there were a large number of cracks with a width of less than 1?m.The ceramic layer of the coating is better bonded to the interface between the bonding layer,the bonding layer and the metal substrate.There is no obvious crack,and the coating structure is relatively dense.It can be seen that the layer is formed by flattening the molten particles.The thin slices are stacked,and the pores are uniformly distributed in the ceramic layer.The Vickers microhardness tester was used to test the microhardness of the coating,the thermal shock resistance of the coating was tested by thermal shock test,the bond strength of the coating was tested by the bond strength test,and the residual stress of the coating surface was measured using an X-ray stress meter.The results show that the ZrO₂-8%wtY₂O₃ thermal barrier coating prepared by atmospheric plasma spraying has good microhardness,bonding strength and thermal shock resistance.And through the control experiment,it is found that within the test range,the microhardness of the coating decreases with the increase of the coating thickness,and the bonding strength of the coating increases with the increase of the spraying power.The residual stress on the surface of the coating is closely related to the spray current,hydrogen flow rate and argon flow rate.As the spray current,hydrogen flow rate and argon flow rate decrease,the residual stress on the coating surface increases.Design orthogonal test to study the relationship between ceramic layer thickness and porosity of thermal barrier coating and atmospheric plasma spraying process parameters.The study found that the influence of process parameters on the thickness of the ceramic layer from small to large is spray distance,argon flow,current,hydrogen flow,In the test range,as the current and hydrogen flow increase,the argon flow rate and the spray distance decrease,the thickness of the ceramic layer increases.The influence of process parameters on the porosity of the ceramic layer from small to large is argon flow,current,hydrogen flow,spray distance,During the spraying process,when the argon flow rate increases from 30 slpm/min to 40slpm/min,the porosity increases as the hydrogen flow rate increases from 5 slpm/min to 10 slpm/min.When the argon flow rate increases from 40 slpm/min to 50 slpm/min,the porosity decreases as the hydrogen flow rate increases from 10 slpm/min to 15slpm/min.When the spraying distance is increased from 5 mm to 10 mm,the porosity decreases.When the spraying distance increases from 10 mm to 15 mm,the porosity increases sharply,and as the current increases,the porosity decreases.The finite element model of thermal barrier coating was constructed by ANSYS finite element analysis software.The preparation process of the coating was simulated and the formation mechanism and distribution of residual stress in the coating were analyzed.The results show that the contact interface between the ceramic layer and the bonding layer and the contact interface stress between the bonding layer and the substrate are concentrated,and the stress concentration on the surface of the coating is the most serious.When the thickness of the 8YSZ thermal barrier coating model is100?m,the thickness of the bonding layer is 150?m,and the thickness of the ceramic layer is 200?m,the maximum residual stress on the surface of the coating reaches248 MPa.And by comparison,it is found that the residual stress of the coating increases as the thickness of the coating increases.