Capturing Process Subtleties in the Processing of Thermal Barrier Coatings for Complex Geometries

The microstructural features of an air plasma sprayed (APS) ceramic thermal barrier coating (TBC) can show a wide range of variability when transitioning from model planar surfaces to complex geometries. In particular, the differences in microstructure for identical processing parameters are easily detectable when comparing the coating on a flat specimen to one on a cylindrical geometry. These differences are further exacerbated when examining microstructural trends from cylindrical substrates of varying diameter, or comparing the coating on a nearly-flat region of a turbine blade to that of its leading edge. Using in-flight particle diagnostic systems it is a possibile to develop a strategy to capture (and potentially mitigate) these microstructural differences across the aforementioned complex geometries. Results indicate a strong correlation to particle diagnostics and these differences in microstructural features (i.e. porosity, pore structure).