Microstructure And Properties Of YSZ Thermal Barrier Coating Modified By CeO₂ By Supersonic Plasma Spraying

Compared with the traditional 8YSZ(8 wt%Yttria stabilized zirconia)thermal barrier coating,the rare earth oxides doped traditional yttria stabilized zirconia(Yttria stabilized zirconia,YSZ)thermal barrier coating has better performance of high temperature resistance,oxidation resistance and good heat insulation.It has been widely used in the industrial field,especially in aerospace and other high temperature service working environment.Among them,the cost of CeO₂ is relatively low and the preparation is convenient,and doping in8YSZ can improve its performance in high temperature environment.Compared with ordinary atmospheric plasma spraying(APS),the coating prepared by supersonic atmospheric plasma spraying(SAPS)has the characteristics of higher bond strength and lower porosity.In this paper,NiCoCrAlY metal bonding layer and 20 wt%CeO₂+80 wt%(8YSZ)ceramic insulation layer were prepared by high energy supersonic plasma spraying system.The microstructure,mechanical and thermal properties of the coating were analyzed and characterized,and compared with the traditional 8YSZ thermal barrier coating.The results show that:(1)During the preparation process,the particles melt and the flying particles spread well,the surface of the coating is relatively smooth,and the pores and cracks are less.On the other hand,the surface of 8YSZ coating is rough,with more and larger pores.In the coating,CeYSZ is more compact,with fewer defects,and the porosity is 2.1%.There are more 8YSZ unmelted particles,and the macropores are composed of unmelted particles and semi-melted particles,and the porosity is 3.8%.(2)The ZrO₂ phase in the original coating of the two coatings is non-equilibrium tetragonal t?-phase,in which no CeO₂ phase is found in CeYSZ,indicating that it dissolves in8YSZ to form a solid solution of Ce,Y and Zr.The thermal conductivity of CeYSZ coating is1.117-1.237 W/m K at 500?-1000?,which is lower than that of 8YSZ coating 1.287-1.375W/m K.The doping of rare earth CeO₂ makes the thermal conductivity of the coating even lower.After being held at 1300?for 100 hours,the ZrO₂ phase of CeYSZ coating is T?phase without phase transformation,which is more stable than 8YSZ coating.The100-hour oxidation gain is about 1.1×10³ g/m²,which is about 1/2 of 8YSZ.The growth of TGO is relatively slow and the TGO layer is relatively gentle.However,at high temperature for a long time,the 8YSZ coating has a phase transition inside the coating,and part of the t?-phase is transformed into c-phase and m-phase.Due to the high roughness inside the coating,there are more convex peaks in the TGO layer,so the oxidation gain is more,and there are a lot of cracks near the TGO layer.In the gas erosion experiment at 1100?,the coating did not fail when the thermal cycles of CeYSZ were 1000 times,while the coating peeling and failure occurred when the thermal cycles of 8YSZ were 230 times.(3)The bond strength of the two coatings was tested.The bond strength of the CeYSZ coating was 50 MPa,and that of the 8YSZ coating was 43.3 MPa.At room temperature and high temperature,the hardness of CeYSZ coating is 485.85 HV_0.2 and 299.90 HV₁respectively,and the hardness of 8YSZ coating is 556.15 HV_0.2 and 308.80 HV₁ respectively.In the high temperature friction and wear test,the wear resistance of CeYSZ coating is about twice that of 8YSZ coating.The wear modes of the coating are abrasive wear,fatigue wear and bonding wear.Due to the tight internal structure of CeYSZ,fewer pores,the wear resistance of CeYSZ coating is better.