Abstract
In this study, two kinds of La2Zr2O7/YSZ (LZ/YSZ) composite powders, i.e., composite powders (P1) and mechanically mixed powders (P2), were used to fabricate composite thermal barrier coating samples through supersonic air plasma sprayed technology. The microstructure and composition of as-prepared coatings were closely related to the distribution of LZ and YSZ in the powders. In the coatings fabricated with P1, the majority of LZ were consumed and a new metastable phase (cubic LaYSZ) formed due to the reaction between the molten LZ and YSZ particles during the thermal spraying process. Meanwhile, only a small amount of LZ particles was reserved in the unmelted regions of the coatings. In the coating fabricated with P2, LZ/YSZ composite coatings with random distribution of LZ-splats were successfully achieved and the formation of LaYSZ was suppressed. Because LaYSZ would easily decompose into LZ and YSZ accompanied by a large volume change after annealing at high temperatures, which would lead to the formation of monoclinic phase, the formation of LaYSZ originated from the reaction between the molten LZ and YSZ should be eliminated. In addition, the phenomena of “spot-spallation” could be observed in S1 in the first thermal cycling; whereas, S2 remained intact after 10 thermal cycling tests. These results further verified a better thermal cycling performance of the coating samples prepared by P2. Therefore, the mechanical mixed LZ/YSZ powders were more suitable for preparing LZ/YSZ composite coatings.
Published Version
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