Microstructure And Properties Of Plasma Sprayed Nano YSZ Coating And Changes In Diffraction Peaks During Thermal Shocks

Yttria-stabilized zirconia（YSZ）is the most commonly used thermal barrier coating material.It has the following excellent characteristics:relatively matching with the thermal expansion coefficient of superalloys,high melting point and low thermal conductivity.Nowadays,it is very common to use YSZ as a thermal barrier coating material in the fields of aerospace and energy.In order to improve the performance of all aspects of the thermal barrier coating,nanostructured YSZ coatings have gradually been researched and developed,which have better thermal insulation effects and longer thermal cycle life.In this paper,atmospheric plasma spraying was used to prepare 5YSZ and 8YSZ coatings using 5wt.%Y₂O₃-Zr O₂ and 8wt.%Y₂O₃-Zr O₂ nano-agglomerated powder.In order to compare the high temperature sintering resistance of 5YSZ and 8YSZ coatings,the two coatings were placed in an environment of 1400°C for 20 hours,and the differences in the microstructure,micro Vickers hardness and phase composition of the two coatings were compared,and the thermal shock experiment was carried out by the water quenching method.Sinter the nano 5YSZ and 8YSZ powders at 1200℃for 2h before spraying.The morphology changes before and after the powder sintering and the deposition efficiency during the spraying process were compared,and the sintered powder and unsintered powder were analyzed and compared.The microstructure and mechanical properties of the coating obtained by powder spraying.In the study,the water quenching method was used to thermally shock the nano 5YSZ and 8YSZ TBCs samples,and the X-ray diffraction method was used to analyze the shift of the coating diffraction peak position and the residual stress change of the crystal plane during the thermal shock.The peak position changes of the（111）crystal plane of the 5YSZ coating and the 8YSZ coating during the thermal shock were analyzed and compared,and the residual stress of the（111）crystal plane was calculated,and the appearance of the coating before and after the thermal shock was compared.The microstructure changes and the elastic moduli of the two coatings before and after thermal shock were measured.The experimental results show that the nano 5YSZ coating has better resistance to sintering shrinkage than the 8YSZ coating after heat treatment at 1400℃,the degree of sintering hardening of 5YSZ coating is lower than that of 8YSZ,and 5YSZ produces less t→m phase change;5YSZ has better thermal shock resistance than 8YSZ performance.After the powder is sintered,the nano-particles are tightly connected,and the deposition efficiency will be increased during spraying.The resulting coating will have a denser structure,and the micro Vickers hardness of the sintered powder coating is higher than that of the unsintered powder coating About 24%higher.Thermal shock will shift the diffraction peak of the coating’s X-ray diffraction pattern to the left,and the stress of 8YSZ coating in most crystal planes is greater than that of 5YSZ coating.When the diffraction peak of the contrast（111）crystal plane changes,as the heat As the number of shocks increases,the diffraction peak position gradually shifts to the left,reflecting the accumulation of residual stress in the coating during thermal shock.The appearance of tiny cracks on the surface of the coating will cause the release of residual stress.In the process of increasing the number of thermal shocks,the accumulated crystal plane stress of the 8YSZ coating is always greater than that of the 5YSZ coating.Thermal shock will generate a TGO layer between the bonding layer and the ceramic layer,and the elastic modulus of the coating will increase.