Research On High Temperature Corrosion Resistance Against CMAS Of Multi-element Rare Earth Doped Zirconia-based Thermal Barrier Coatings

6wt.%?8wt.%yttria stabilized zirconia?6?8YSZ?thermal barrier coatings?TBCs?are widely used on hot-end parts for aircraft/gas engines.TBCs could improve the thermal efficiency of engines and extend the service life effectively.However,under the service conditions of aircraft/gas engines,silicate mineral fragments?Ca O-Mg O-Al₂O₃-Si O₂,CMAS?will enter the engine and deposit on TBCs.CMAS will melt and penetrate into coatings rapidly along the pores and microcracks at high temperature,causing severe corrosion to the coatings and shorten the life of engines.Some literature shows zirconate coatings containing Gd/Yb and YSZ coating with high Y content have good CMAS corrosion resistance.There are few reports on the CMAS resistance of zirconia-based TBCs doped with Y,Gd,Yb and others.This topic intends to explore the role of Y,Gd and Yb in resisting CMAS corrosion of zirconia-based TBCs.The purpose is to optimize the rare earth doping modification scheme of zirconia-based TBCs,and evaluate the anti-CMAS performance of these modified coatings under simulated actual service conditions.Air plasma spraying?APS?was used to prepare 8YSZ and ZrO₂-9.5Y₂O₃-5.6Yb₂O₃-5.2Gd₂O₃?YSZ-Yb-Gd?free-substrate TBCs,which were subjected to heat treatment at 1350°C.The role of Y,Gd and Yb in the anti-corrosion performance of coatings was explored based on the CMAS corrosion behavior of coatings and provide a reference for improving the anti-CMAS properties of TBCs.Ni Co Cr Al Y bonding coating and three kinds of ZrO₂-Y₂O₃ceramic coatings with same total thickness but different compositions and structures were prepared on nickel-based superalloys by High Velocity Oxygen Fuel?HVOF?and APS,respectively.Do the burn rig test at 1350°C by adjusting the flow of C₃H₈/O₂.SEM,EDS,XRD,RS and other methods were used to investigate the erosion behavior and mechanism of CMAS on ZrO₂-Y₂O₃coatings,provide experimental data and technical support for the design of high-performance TBCs resistant to CMAS.Some conclusions can be drawn as follows:?1?The CMAS?50 mg/cm²?coated on the surface of 8YSZ/YSZ-Yb-Gd coatings gradually penetrated into coatings with the extension of the corrosion time,the densification depth of coatings gradually increased.There are Zr Si O₄and ZrO₂formed in the shallow layer of coatings.8YSZ and YSZ-Yb-Gd coatings began to diffuse and peel after 6 h and 1 h,respectively.The phase transition depth of m-ZrO₂is about 120?m after 24 h in 8YSZ and YSZ-Yb-Gd coatings.After that,the coating gradually return to the same phase composition as the sprayed state.The addition of a small amount of Yb and Gd did not improve the TBCs'resistance to CMAS corrosion.?2?Control the surface temperature?1350°C?and the area density of CMAS?7mg/cm²?to keep the same in burner rig test.The Anti-corrosion life of 8YSZ was the shortest,and the peeling failure occurred at the interface between the ceramic coating and the TGO/bonding layer.Followed by 38YSZ,and the peeling failure occurs inside the ceramic layer.8YSZ+Y₂O₃TBC was the best,and it remained intact after 3 h of test.Both 38YSZ and 8YSZ+Y₂O₃TBCs formed a new phase of Ca₄Y₆?Si O₄?₆O/Y_4.67?Si O₄?₃O.The dense structure prevents the deep penetration of CMAS.?3?After 1 h burner rig test,8YSZ coating was severely eroded.There is a certain amount of m-ZrO₂in the peeling coating,and the main phase of the remaining ceramic coatings is t'-ZrO₂.38YSZ coating was significantly eroded after 2 h,and the thickness reduction of coatings after test was 100?210?m.With the prolongation of the test time,there are Ca₄Y₆?Si O₄?₆O/Y_4.67?Si O₄?₃O formed on the surface of8YSZ+Y₂O₃TBCs,and Y₂O₃layer remain intact after 3 h.Compared with the original thickness of Y₂O₃,the thickness reduction of Y₂O₃after 3 h was 5?20?m.Y₂O₃provides a sufficient corrosion barrier for YSZ coatings.Therefore,8YSZ+Y₂O₃coating exhibited excellent corrosion resistance to CMAS.