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6456 |
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Influence of bondcoat laser texturing on the microstructures and performances of suspension sprayed YSZ thermal barrier coatings |
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Filofteia-Laura Toma* / Fraunhofer IWS, Germany Julia Sagel / Fraunhofer Institute for Material and Beam Technology, Germany Maria Barbosa/ Fraunhofer Institute for Material and Beam Technology, Germany |
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Intensive R&D work for more than one decade have demonstrated many unique thermal spray coating properties, particularly for oxide ceramic coatings by using suspensions of fine powders as feedstock in APS and HVOF processes. Suspension spraying allows producing of thermal barrier coatings with columnar-like similar to those produced by electron-beam physical vapor deposition (EB-PVD) and vertically cracked morphologies with a generally lower thermal conductivity. Therefore suspension sprayed YSZ TBCs are seen as an alternative to EB-PVD coatings and those produced by conventional APS processes. Nonetheless, the morphology of the YSZ topcoat is strongly influenced by the properties of the metallic bondcoat. Laser processing is a versatile technology which allows designing the properties of thermally sprayed coatings. In this work, different laser technologies were applied to modify and tailor the surface topography of Ni-alloy based bondcoat. Water-based suspension spraying was applied to produce YSZ coatings on top of laser-treated bondcoat. The samples were characterized in terms of microstructure, phase composition and thermal cycling performance. The influence of the bondcoat laser texturing on the properties of suspension sprayed YSZ coatings, including thermally growth oxide (TGO) formation and failure mechanism will be presented. |