Papers by Keyword: EB-PVD

Abstract: ZrO2-4mol% Y2O3 coatings on zirconia substrate were deposited by EB-PVD. Influence of the coating thickness on thermal conductivity and thermal diffusivity of coated samples is examined. The fractured surface of the coated samples reveals a columnar microstructure consisting of feather-like structure. We have adopted a laser flash method for thermal diffusivity and specific heat capacity of coated samples. It was found that the thermal conductivity of the coating layers was strongly dependent on coating thickness. The thermal conductivity of coating layers shows increasing tendency with increasing the coating thickness.

Abstract: Effect of La2O3 addition on thermal conductivity and high temperature stability of YSZ coating produced by EB-PVD was investigated. La2O3 was selected as an additive because it had a significant effect on suppressing densification of YSZ. The developed coating showed extremely low thermal conductivity as well as high resistance to sintering. Microstructural observation revealed that the coating had fine feather-like subcolumns and nanopores, which contributed to limit thermal transport. These nanostructures were thought to be formed by suppressing densification during deposition.

Abstract: Turbine blades of airplanes and thermoelectric plants work in adverse conditions, with corrosive environment and high temperature and pressure. One way to improve the life or the working temperature of the blades is by the use of special coatings over metallic material applied by Electron Beam – Physical Vapour Deposition (EB-PVD). The most usual material for this application is zirconia doped with yttria. Addition of niobia, as a co-dopant in the Y2O3-ZrO2 system, can reduce the thermal conductivity and improve mechanical properties of the coating. The purpose of this work is to show the influence of the addition of niobia on microstructure of ceramic coating taking in to consideration X-ray diffraction and scanning electron microscopy observations. First result shows a columnar structure with only tetragonal phase in the ceramic coating in the chemical composition range studied.

Abstract: Two layer thermal barrier coatings (TBCs) were prepared by EB-PVD (Electron Beam-Physical Vapor Deposition) at different substrate temperatures in the range of 823 to 1123K, and their microstructure was investigated with SEM and AC impedance as a function of substrate temperature and thermal cycling time. YSZ layer of all TBCs samples is in column structure, but the grain size and growth orientation are different with substrate. In this research, impedance spectra (IS) was measured as a function of thermal cycling between 1323K and 298K for these thermal barrier coatings. Grain boundary and bulk can be distinguished from analysis of AC impedance spectroa to provide information about the relation between microstructure and electric properties.The change in IS until failure was found to be related with the thickness, microcracks and macrocracks of TGO and the change in the interfacial of TGO/YSZ.