| Thermal barrier coatings(TBCs)play an important role in reducing the surface temperature of turbine blades alloy and prolonging the service life of the vane,which were listed as one of the three key issues in the turbine engine together with high temperature structure material,and cooling technology.At present,conventional process of TBC preparation consist of APS(atmospheric plasma spray)and EB-PVD(electron beam-physical vapor deposition).APS TBC has low thermal conductivity,high deposition rate,but low thermal cyclic life.And EB-PVD TBC has good strain tolerance,but high thermal conductivity and low deposition rate.With the rapid development of aerospace technology,the traditional thermal barrier coating has been unable to meet the demand of the future development of gas turbine engine,high performance of thermal barrier coatings and its preparation technology are in urgent needed.Plasma spray-physical vapor deposition(PS-PVD)technology is a new type of thermal barrier coating preparation technology,which is based on the low pressure plasma spray.It combines the merits of APS and EB-PVD,the coating prepared by PS-PVD has a low thermal conductivity,good thermal shock resistance,and so on.PS-PVD are greatly influenced by the process parameters,which can realize gas,liquid and solid multiphase deposits,to obtain the columnar,layered,mix structure thermal barrier coating.It is possible for the preparation of a new type of-high-performance thermal barrier coating.In this paper,7YSZ ceramic coating is prepared on the K417G superalloy with LPPS NiCoCrAlYTa bond coating by PS-PVD in three different process parameters(surface roughness,powder feed rate,sample temperature).The effects of different process parameters on the structure and properties of PS-PVD 7YSZ ceramic layer were studied,and the optimum process parameters were optimized.The structure,chemical composition and phase composition of the 7YSZ thermal barrier coating were analyzed by SEM,EDS and XRD.The bond strength,anti-particle erosion performance,high temperature oxidation resistance and thermal conductivity were studied.The main results are as follows:(1)The PS-PVD 7YSZ thermal barrier coating on the surface with different roughness shows that the surface roughness mainly affects the PS-PVD coating through the shadow effect.The as-sprayed PS-PVD coating was the most affected by the shadowing effect.The cauliflower head of the as-sprayed coating and the gap between the columns were the largest,bond strength and the anti-particle erosion performance were the worst.And the effect of different roughness on the growth of TGO is not significant,which affects the existence of TGO mainly through the pores.(2)The powder feed rate mainly affects the gasification degree of the powder particles in the plasma flame flow.The coating is mainly vapor deposition with low powder feed rate,and the columnar grain is dense.The coating is mainly gas,liquid and solid three-phase deposition with the high powder feed rate,and the coating is dense.The bond strength of PFR40(powder feed rate of 40 g/min)coating is maximum,the anti-particle erosion performance of PFR20 coating is the best,the anti-high temperature oxidation performance of PFR40 is the most excellent.The thermal conductivity(0.46-1.79 W/(m · K))of PS-PVD coating is lower than that of EB-PVD thermal barrier coating,close to APS coating,and PFR20 coating has the lowest thermal conductivity.(3)The low matrix temperature causes the gas particles to form nuclei in advance,causing the coated columnar crystals to become loose and the coating becomes denser.When the substrate temperature is high,it is beneficial to the recrystallization of the coating,so that the columnar crystal shows a certain growth orientation.The bond strength of ST850(substrate temperature is 850 ?)coating is the lowest,the anti?particle erosion performance of ST950 coating is the optimum,the ST850 coating has the best anti-oxidant properties. |
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