Preparation And High-temperature Stability Of Y₃Al₅O₁₂ Modified Sm₂Zr₂O₇ Thermal Barrier Coating

Thermal barrier coating(TBC)technology is one of the three core key technologies for the hot-end components of advanced gas turbine engines.With the continuous increase of the turbine inlet temperature of the engine,the traditional8YSZ(partially stabilized yttria zirconia)would undergo phase transformation and sintering when the long-term service temperature is above 1200°C,leading to premature failure.Therefore,it is an urgent to develop new TBC ceramic materials with low thermal conductivity,good high-temperature phase stability and sintering resistance.Sm₂Zr₂O₇material,which has a high melting point,low thermal conductivity and good high temperature phase stability,is one of the ideal candidates for thermal barrier coatings.However,the low fracture toughness of Sm₂Zr₂O₇material limits further applications.In this paper,Sm₂Zr₂O₇is used as the research object to study the effect of Y₃Al₅O₁₂doping on the microstructure,mechanical properties,thermophysical properties and high-temperature phase stability of Sm₂Zr₂O₇ceramic materials.The modified Sm₂Zr₂O₇TBCs was prepared by plasma spraying technology,and the preparation process,thermal cycle,high-temperature sintering resistance and CMAS corrosion behavior of the coatings were studied,in order to provide a theoretical basis for developing new TBCs with low thermal conductivity,sintering resistance and long service life.The conclusions were drawn as follows:The influence of Y₃Al₅O₁₂doping on the structure,mechanical properties,thermal conductivity and high-temperature phase stability of Sm₂Zr₂O₇were investigated and revealed.It is found that the(1-x)Sm₂Zr₂O₇-x Y₃Al₅O₁₂material is mainly composed of Sm₂Zr₂O₇,Y₃Al₅O₁₂,and Sm Al O₃phases.With the increase of Y₃Al₅O₁₂doping concentration,the grain size of Sm₂Zr₂O₇significantly decreases.When the doping concentration of Y₃Al₅O₁₂is x=0.2,the maximum fracture toughness of the composite material is 2.5 MPa·m^1/2,which is abboouutt 90%higher than that of pure Sm₂ZZrr₂O₇ceramic;Above 600?,the thermal conductivity of composite ceramics increases with the increase of Y₃Al₅O₁₂doping concentration.The0.8Sm₂Zr₂O₇-0.2Y₃Al₅O₁₂material is still dominated by Sm₂Zr₂O₇and Y₃Al₅O₁₂crystalline phases after sintering at 1400°C for 100 h,and the grains do not significantly grow.The preparation process and thermal cycle performance of plasma-sprayed0.8Sm₂Zr₂O₇-0.2Y₃Al₅O₁₂/YSZ TBCs were studied.The 0.8Sm₂Zr₂O₇-0.2Y₃Al₅O₁₂coating is composed of Sm₂Zr₂O₇and a small amount of amorphous phase.A new phase of Sm Al O₃is precipitated after heat-treatment at 1200°C for 5 h.The thermal conductivity of the prepared 0.8Sm₂Zr₂O₇-0.2Y₃Al₅O₁₂coating is about 1.5 W·m^-1·K^-1and varies little with the temperature between 25?and 800?.The modified Sm₂Zr₂O₇/YSZ TBCs failed after water quenching-thermal shock 90 cycles at1150°C.The sintering resistance performance and CMAS corrosion behavior of Sm₂Zr₂O₇-Y₃Al₅O₁₂coating have been investigated at high temperature.After the coating is heat-treated at 1400°C for different times,the main crystal phases are still(Sm,Y)₂Zr₂O₇and Sm Al O₃,and the grains have not obviously grown.With the further increase of the heat-treatment time,large cracks gradually healed and small cracks are generated,but the mechanical properties are basically unchanged.With the increase of CMAS corrosion time at 1250°C,high melting point Ca Al₂Si₂O₈and Ca₂Sm₈(Si O₄)₆O₂grains are formed at the interface between the coating and CMAS,which further prevents the penetration and erosion of molten CMAS.