Research On The Anti-CMAS Corrosion Performance Of YSZ Thermal Barrier Coatings Under Different Thermal Cycle Times

Thermal barrier coatings（TBCs）have very good high temperature resistance and good thermal insulation properties,they are widely used on the surface of hot end parts of aero engines,gas turbines and other turbine engines.Thermal barrier coating can effectively reduce the working temperature of turbine engine alloy substrate.The working temperature of the engine plays a very important role in improving the working efficiency and operating life of the engine.However,in the actual operating environment,aero engines will fail due to high temperature sintering and the erosion of calcium magnesium aluminum silicate（Ca O-Mg O-Al₂O₃-Si O₂,referred to as CMAS）in the air environment,which will seriously affect the working efficiency and Service life.In order to distinguish the respective destructive effects of high-temperature sintering and CMAS corrosion on YSZ coatings,and the effect of high-temperature sintering on CMAS corrosion of YSZ coatings,this paper carries out 4h,8h and 16h pure high-temperature sintering and 1300℃for YSZ coatings.Corrosion experiment of CMAS.The failure phenomenon of YSZ coating under high temperature sintering and CMAS corrosion under different time is studied,and the structure evolution and failure mechanism of YSZ coating under CMAS corrosion under different corrosion time are explored.The research results show that the YSZ coating sprayed by atmospheric plasma has a typical layered structure.The lamellae in the coating are composed of square columnar crystals with clear morphology.The gap between the lamellae and the lamellae is very obvious.The YSZ coating has more holes and microcracks.At a high temperature of 1300℃,the microcracks of the YSZ coating will disappear as the sintering time increases,the columnar crystals in the lamellae will be more completely fused with each other,and the gap between the lamellae will become smaller,The holes distributed in the YSZ coating will also become smaller.The high temperature of 1300℃will not produce phase change for YSZ coating for 4h,8h,16h.However,when YSZ coating is sintered for 8h,16h,transverse cracks and longitudinal cracks will appear.The occurrence of such cracks increases the flow of molten CMAS into YSZ.Compared with the dense YSZ coating,the path of the coating is easier for the molten CMAS to penetrate into the YSZ coating along the cracks,causing the coating to be more susceptible to corrosion by the molten CMAS.In addition,sintering will cause the pores of the YSZ coating to shrink,and because the CMAS is easy to corrode the YSZ coating along the small pores of the YSZ coating,the extension of the sintering time will accelerate the erosion rate of the CMAS on the YSZ coating.In a high temperature environment of 1300℃,the corrosion of YSZ coating by CMAS will increase in thickness with the extension of corrosion time,and the structural damage to YSZ coating will be stronger.The tetragonal zirconia produced in the coating will become monoclinic oxidation.The more the phase change of zirconium,the more complete the dissolution and precipitation reaction between CMAS and YSZ coating.When the molten CMAS corrodes the YSZ coating,it will erode the YSZ coating along the grain boundaries,pores and microcracks of the coating,and will dissolve and precipitate again with the top layer of the YSZ coating,resulting in the top layer of the YSZ coating.The area is dissolved by CMAS into many sand-like grains,and the precipitated Zr O₂is transformed into m-Zr O₂particles due to the lack of the stabilization effect of Y₂O₃.Due to the good wetting performance and low viscosity of the YSZ coating,the area outside the dissolution and precipitation zone of the YSZ coating becomes denser due to the penetration of CMAS.In addition,the thermal expansion coefficients of CMAS and YSZ coatings are not matched,and CMAS causes the YSZ coating to produce tetragonal zirconia（t-Zr O₂）to monoclinic zirconia（m-Zr O₂）caused by the phase change caused by the accumulation of volume expansion.The stress causes the YSZ coating to spall.