Architecture of thermal barrier coatings produced by electron beam-physical vapor deposition (EB-PVD)

Extremely high temperatures and severe atmospheric conditions in the hot section of aircraft engines during operation result in degradation and structural failures of turbine components. Replacing these components is very expensive. Thermal barrier coatings (TBC) composed of ZrO2- 8wt% Y2O3( 8YSZ) applied by Electron Beam-Physical Vapor Deposition (EB-PVD) to turbine components offer excellent properties for thermal protection and resistance against oxidation - induced erosion and corrosion. However, the life of turbine components is still limited due to premature failure of the TBC. It is hypothesized that the life of the coated components can be extended by lowering the thermal conductivity of the TBC by creating multiple non-distinct or distinct interfaces and alloy additions such as Nb-oxide which will result in a reduction in the thermal conductivity and oxygen transport through the coating. This paper presents the microstructural results of standard 8YSZ, layered 8YSZ, Nb-oxide alloyed 8YSZ and functionally graded 8YSZ with Nb-oxide deposited by EB-PVD. TBC samples were examined by various methods including scanning electron microscopy (SEM), high-resolution optical microscopy (OM), X-ray diffraction (XRD), and thermal cycling tests. The preliminary results strongly suggest that multiple interfaced TBC exhibits better oxidation resistant properties as compared to standard and alloyed TBC. (C) 2002 Kluwer Academic Publishers.