The effect of two raw YSZ materials with different morphology on TBCs via atmospheric plasma spraying: Microstructures and high-temperature performance

In this work, two kinds of YSZ nano powders were used as the raw materials to prepare thermal barrier coatings (TBC) via atmospheric plasma spraying. Firstly, raw materials with different original morphologies constitute feedstocks with varying internal structures. Secondly, these feedstocks, after spraying, form TBCs with different structures and porosity. Based on this, the differences in the morphologies of the raw materials may result in variations in the performance of the coatings. Therefore, the high-temperature performance of the corresponding TBCs was assessed comprehensively. Notably, the TBC prepared from flaky-YSZ (FYSZ) nano raw materials exhibited failure after only 84 thermal shock cycles, while the TBC prepared from granular-YSZ (GYSZ) nano raw materials maintained functionality even after 100 thermal shock cycles. Meanwhile, the GYSZ TBC demonstrates a better resistance to high-temperature oxidation with slower TGO growth. The failure mechanism of the TBCs was analyzed, focusing on the morphologies and structural characteristics. The findings highlight that disparities in raw materials' morphologies play a pivotal role in regulating the high-temperature service performance of the TBCs. The GYSZ raw materials are conducive to the formation of denser feedstocks, leading to decreased porosity in the coatings. In addition, their small size and uniform particle distribution facilitate the formation of columnar grains in the coating, enhancing the interlayer bonding strength of the GYSZ TBC. Consequently, during high-temperature service, the GYSZ TBC can effectively impede the growth of the thermally grown oxide (TGO) and alleviate the associated thermal mismatch stress, thereby ensuring a prolonged service life of the TBC. This work establishes a theoretical foundation for designing the performance of TBCs based on modulating the morphologies of raw materials.