Influence of Bondcoat Topography on the Properties of Suspension Sprayed YSZ Thermal Barrier Coatings

Intensive R&D work of more than one decade has demonstrated many unique thermal spray coating properties, particularly for oxide ceramic coatings fabricated by using suspensions of fine powders as feedstock in APS and HVOF processes. Suspension spraying allows producing thermal barrier coatings with columnar-like microstructure, similar to those produced by electron-beam physical vapor deposition (EB-PVD), and vertically cracked morphologies, with a generally low 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 microstructure of the YSZ topcoat is strongly influenced by the properties of the metallic bondcoat.

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 plasma sprayed YSZ coatings on top of as-sprayed and laser-treated bondcoat. The samples were characterized in terms of microstructure, phase composition and thermal cycling performance. The influence of the bondcoat topography on the properties of suspension sprayed YSZ coatings, including the failure mechanism, will be presented.