The Effect of Complex Geometrical Variations within the Spray Footprint on Thermal Barrier Coating Properties

Consistent coating properties over the exposed areas of thermal barrier coated components are key to increasing their in service reliability. Geometrical attributes of substrates larger than the spray footprint can be accounted for with precise operation and programming. However, once a shape variation becomes smaller than the spray footprint, difficulties arise in maintaining consistent coating properties. In this study, substrates with three dimensional geometric complexities smaller than the spray footprint were plasma sprayed with yttria stabilised zirconia thermal barrier coatings. Detailed thickness and surface topography measurements over the entire coated area of the complex geometries were obtained. These were related to the inflight particle properties and powder injection location. Detailed maps reveal the relative spray angles created by the complex substrates influence the coating thickness and surface topography, displaying coating build-up in over a range of angles.