The Research Of Nano-Structured ZrO₂-Y₂O₃ And ZrO₂-Y₂O₃-CeO₂ Feedstocks And TBCs

In this paper, ZrO₂-8wt%Y₂O₃ and ZrO₂-8wt%Y₂O₃ -8wt%CeO₂ nano-structured feedstocks were prepared by using ZrO₂-8wt%Y₂O₃ and CeO₂ as raw materials, which both the average size are under 20nm, as well as a set of moves comprising of ball milling, dry spraying, heat treating and plasma treating in line. During the dry spraying, 8YSZ slurry was harder to feed but easier to attach to the wall of drying tower. Comparing to 8YSZ feedstock, 8CYSZ feedstock was easier to prepare and had a better output. It should be noted that the average grain sizes of the 8YSZ and 8CYSZ feedstocks were both much larger than the origin grain size after heat treatment and plasma processing, which, however, were both under 100 nm.The microstructures and properties of both feedstocks were researched and compared. It could be concluded that: both nano-structured feedstocks'sizes were 20μm-60μm; most of the feedstocks have great flowability and density, which means they are ideal for preparing thermal spraying coatings.TBCs were prepared by spraying 8YSZ and 8CYSZ feedstocks to different bond coatings. For compared, commercial Dida 8YSZ feedstock was sprayed at the same condition as well. Analysis results showed that different technics, different parameters of the same technic and experiment condition were all acted on the TBCs'structures and performances. Microcracks and holes can be observed in all these coatings. Phase structure was staying the same after thermal spraying for both 8YSZ and 8CYSZ feedstocks, whose phase compositions were mainly t-ZrO₂ and c-ZrO₂, separately. Dida 8YSZ coating's phase composition was t-ZrO2. The average grain sizes of 8YSZ, 8CYSZ and Dida 8YSZ coating were all smaller than 100nm.The coatings, separately prepared by these three feedstocks at the same technical conditions, had close bond strength, which was about 15MPa. Dida 8YSZ coating had the best thermal shock resistance. The thermal conductivities of 8YSZ, 8CYSZ and Dida 8YSZ coatings were 1.39W·m^-1·K^-1, 1.18 W·m^-1·K^-1 and 1.14 W·m^-1·K^-1, separately.The diffusing of metal elements such as Al, Co, Cr in the bond coating to the top coating was restrained in 8CYSZ TBCs because of the adding 8wt.%CeO₂ in the top ceramic coating. EDS analysis show that thermal diffusion ability of the metal element like Ni, Al, Cr etc from bond coating to the interface between the bond coating and top coating also decreased since 4wt.%CeO₂ was added to the bond coating, which, however, accelerating the peeling of the TGO at the interface between the top coating and the bond coating, leading to the failure of the TBCs during the thermal cycling condition.