Relationships Between Characteristics Of Sm₂Zr₂O₇ Powders With Microstructures And Properties Of Coatings

With the aviation turbine developing to high-flow ratio, high thrust to weight ratio, high inlet temperature, the gas temperature and pressure of combustion chamber constantly improve. However, for hot components of aircraft engine and gas turbine, conventional ZrO2 partially stabilized with Y2O3（YSZ） coatings cannot meet the demand and new types of ceramic thermal barrier coating materials should be found. Sm₂Zr₂O₇ is one of the promising candidates due to their stable phase structure, low thermal conductivity, high melting point, etc. However, the researches about the preparation of Sm₂Zr₂O₇ nano-coating and optimization of organizational structure have not been done. To this end, the preparation process of Sm₂Zr₂O₇ powder was optimized in the thesis. The relationship of different characteristics of Sm₂Zr₂O₇ spray powders with the coating structures and mechanical properties were studied in-depth.（1）The Sm₂Zr₂O₇ original powder was synthesized by the method of co-precipitation calcination, the grain size of powders was between 60 to 100 nm under the condition of 1250℃-4h. The original powder was granulated by spray drying technology, spherical aggregates with the sizes concentrated between 40 to 50μm could be achieved after optimizing granulation processes. The aggregate grain size was between 60 to 120 nm under the condition of 1100℃-2h, the apparent density and mobility were respectively 1.51g/cm3, 42s/50 g. Using plasma injection process to densify aggregates, forming the shell aggregates with grain 100-200 nm, rim 1-3μm thick. The apparent density and mobility were respectively 2.6g/cm3, 35s/50 g.（2）Comparing the microstructure prepared by different size range of particles, it could be found that narrow range and small size aggregates were heated fuller in the plasma jet, so as the coating was molted better with a lower porosity. It could be discovered by morphology analysis.（3）The coating was prepared by micron grain with relative high density. It was found that there were many dense columnar grain structures inside the coating and the strength of coating increased from 15.1MPa to 31.5MPa.This was mainly due to the micro-grain was highly sintered, the grain was fully heated in the plasma and the grain growed up to form dense tissue. There were dense nano-micron double-state structures inside the coating, whose bond strength increased to 43.5MPa and thermal conductivity reduced by about 38% compared with YSZ. This was mainly due to the high density and spherical agglomerates were better heated in the plasma jet, coating layer was more compacted.（4）The coating was prepared by high energy plasma spray. There were extremely dense columnar grain structures inside the coating, whose bong strength increased to 57.1MPa. This was mainly due to the nature high speed and high temperature of high-energy plasma Jet, better melting aggregates impacted the matrix with high-speed to improve the adhesion of coating interface.