Abstract
La2Zr2O7 (LZ) compound is a promising candidate for the new generation of thermal barrier coatings (TBCs). Despite its unique properties, this material suffers from a quite low coefficient of thermal expansion (CTE) and also brittleness which restricts its potential application. In this study, LZ was modified with ceria stabilized zirconia (CSZ), and LZ-CSZ composite powders with different compositions were prepared and applied with the air plasma spraying (APS) method. The oxidation behavior of samples was studied at 1100 °C, and the tests were continued until coatings spallation. Microstructural studies showed that the thermally grown oxide (TGO) layer in all samples consists of alumina and mixed spinel oxide layers. Due to lower oxygen diffusivity, the samples with a higher fraction of LZ contain a narrower TGO layer with a small spinel phase. The inward oxygen penetration in coatings with higher CSZ percentages was considerable, that led to the evolution of Al-depletion zone in the bond coat area, and increased the portion of spinel oxides in the TGO. The 50CSZ-50LZ coating, due to its better combination of CTE compatibility, thermal stability, and fracture toughness, showed better oxidation resistance and collapsed after 264 h with a TGO thickness of 5.4 μm.
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