等离子喷涂用纳米结构Gd_(2)Zr_(2)O_(7)喂料的制备与性能

Preparation and Characterization of Nanostructured Gd_(2)Zr_(2)O_(7)Feedstock for Plasma Spraying

目的稀土锆酸盐具有低热导率、优异的抗烧结性能和相稳定性,是下一代热障涂层和环境障涂层的理想材料。通过纳米粉体再造粒技术制备出等离子喷涂用高性能纳米结构球形喂料Gd_(2)Zr_(2)O_(7),以满足下一代热障涂层和环境障涂层的需求。方法以Gd_(2)O_(3)与ZrO_(2)粉体为原材料,采用纳米粉体再造粒技术制备出可等离子喷涂用的纳米结构Gd_(2)Zr_(2)O_(7)喂料。利用SEM、XRD研究了固相烧结温度和时间对Gd_(2)Zr_(2)O_(7)含量和晶粒尺寸的影响,分析了纳米结构Gd_(2)Zr_(2)O_(7)喂料在不同纳米粉体再造粒阶段的微观形貌和相组成。同时,测定了纳米结构Gd_(2)Zr_(2)O_(7)喂料的流动性、松装密度和振实密度。结果纳米粉体再造粒技术可以制备出等离子喷涂用纳米结构Gd_(2)Zr_(2)O_(7)喂料,喂料内部结构致密,球形度好,粒径为10~50μm。在纳米粉体再造粒过程中,晶粒尺寸会随着烧结温度的升高而增大。在1300℃烧结2 h生成的Gd_(2)Zr_(2)O_(7)含量高,且晶粒尺寸小,为最优固相烧结工艺。等离子球化处理能有效地改善喂料的流动性。等离子球化处理后的喂料松装密度为2.09 g/cm^(3),振实密度为3.26 g/cm^(3),流动性为22.3 s/(50 g)。结论采用纳米粉体再造粒技术成功制备出纳米结构Gd_(2)Zr_(2)O_(7)粉体喂料。该喂料颗粒内部结构致密,外部表面光滑,球形度好,适合等离子喷涂,有望成为下一代热障涂层和环境障涂层。

It is an advanced surface modification technology to prepared environmental barrier coating(EBC)by plasma spraying,which can improve the corrosion resistance of SiCf/SiC composite materials.However,the corrosion resistance of Calcium-Magnesiu-Alumino-Silicate(CMAS)for the EBC coating was not well solved at present.Rare earth zirconates are ideal materials for next generation thermal barrier coatings and environmental barrier coatings because of their low thermal conductivity,excellent sinterability and phase stability.This work aims to prepare high-performance nanostructured Gd_(2)Zr_(2)O_(7)feedstocks with nanopowder regranulation technology to meet the needs of the next generation of thermal and environmental barrier coatings.The Gd_(2)O_(3) and ZrO_(2) with the average particle size of 50 nm were used to prepare the Gd_(2)Zr_(2)O_(7)feedstocks.In order to make full use of nano effect,the nanoparticles must be reconstituted to the agglomerates by nanopowder regranulation technology.Nanopowder regranulation technology includes ball milling,spray drying,sintering and plasma treatment.The slurries which composed of 298 g Gd_(2)O_(3),202 g ZrO_(2),1000 g deionized water and 2.5 g PVA were ball milled for 24 h.The prepared slurries were spray dried in a YC-018 spraying dryer to obtain the agglomerates and then sintered.The agglomerates were sintered in the heat treatment furnace at 1200℃,1300℃,1400℃,1500℃for 2 h,4 h,and 6 h,respectively.In order to improve the density and mobility of the feedstocks,the agglomerates were plasma treated by Mecto 9MC spraying system.The plasma flame caused the agglomerates surface to melt rapidly and form droplets,which are then rinsed into deionized water to cool quickly and form spherical solid particles.Plasma treatment slurries were dried in a 120℃dryer and screened through a 150-mesh sieve to obtain Gd_(2)Zr_(2)O_(7)feedstocks.The microstructure,morphology,and chemical composition of the feedstocks were observed by a Quanta 200FEG scanning electron microscope(SEM)equipped with energy dispersive spectroscopy(EDS).The phases of the feedstocks were identified by X-ray diffraction analysis(XRD)with Cu Kαradiation.The results show that the nanostructure Gd_(2)Zr_(2)O_(7)feedstocks can be prepared by nanopowder regranulation technology.The feedstocks have the dense structure and good sphericity.The particle size of feedstocks is 10~50μm.In the process of nanopowder regranulation technology,the grain size increases with the increase of sintering temperature.The optimal sintering parameters for Gd_(2)Zr_(2)O_(7)feedstocks are sintered at 1300℃for 2 hours.Compared with the other sintering parameters,the content of Gd_(2)Zr_(2)O_(7)after sintering at 1300℃for 2 hours is highest and the grain size is smallest.Plasma treatment can improve the flowability of feedstocks effectively.After plasma treatment,the apparent density is 2.09 g/cm3,the tap density is 3.26 g/cm3,and the flowability is 22.3 s/(50 g).The hausner ratio is 1.19 which indicated the feedstocks is in a free flow state.The Gd_(2)Zr_(2)O_(7)feedstocks show good flowability.Nanostructured Gd_(2)Zr_(2)O_(7)powder feedstocks are successfully prepared by the nanopowder regranulation technology.The feedstocks have dense internal structure,smooth external surface and good spherical shape.It is suitable for plasma spraying and expected to become the next generation of TBC and EBC.