Thermal-barrier coatings are increasingly applied to hot components in gas turbines; the most prominent application processes are plasma spraying and electron-beam physical vapor deposition. Electron-beam physical vapor deposition provides distinctive coatings of a unique columnar microstructure. The main advantage of this structure is its superior tolerance against straining, erosion, and thermoshock, thus giving it a major edge in lifetime. Furthermore, cooling hole closure will be prevented and an aerodynamic design of the blades is maintained. This article outlines the interaction between chemical composition and microstructural evolution of zirconia-based thermal-barrier coatings and their respective lifetimes in cyclic burner-rig and furnace tests. Customizing the microstructure by adjusting processing parameters is emphasized. A structural-zone diagram is modified by interconnecting the influence of substrate rotation with the microstructural evolutions.

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SOURCE: Schulz, U., K. Fritscher, C. Leyens, M. Peters, and W. A. Kaysser, “The Thermocyclic Behavior of Differently Stabilized and Structured EB-PVD TBCs.”JOM-e. October 1997. TMS.