Thermal barrier coatings (TBCs) can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of the ceramic top coat. However, the continuous pursuit of a higher operating temperature leads to degradation, delamination, and premature failure of the top coat. Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems. In this paper, the latest progress of some new ceramic materials is first reviewed. Then, a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth, ceramic sintering, erosion, and calcium-magnesium-aluminium-silicate (CMAS) molten salt corrosion. Finally, new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar, columnar, and nanostructure inclusions. The latest developments of ceramic top coat will be presented in terms of material selection, structural design, and failure mechanism, and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance, better thermal insulation, and longer lifetime.

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The thermally grown oxide (TGO) on the thermal spray bond coat surface was one of the most important factors which would influence the lifetime of thermal barrier coatings (TBCs). Pre-diffusion treatment (high temperature vacuum treatment) plays an important role in the growth of the TGO. Results show that the initial thin oxide scale, formed during deposition process, on the as-sprayed bond coating surface has broken and shrunk to discontinuous oxide particles through the elements diffusion during the pre-diffusion. Two kinds of bond coats with different initial oxide scale thicknesses were subjected to the same pre-diffusion. The two pre-diffused bond coats show different results of the average distance between the individual oxide particles. In this study, a three dimensional model with thermal grooving theory was developed to explore the essential condition for the scale breaking and explain the differences of these results. This research can provide reference for the preparation optimization and pre-treatment optimization of bond coat towards high performance TBCs.

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