Process-structure-property relations for the erosion durability of plasma spray-physical vapor deposition (PS-PVD) thermal barrier coatings

New thermal barrier coating (TBC) materials and microstructures are under development to increase gas turbine operating temperatures beyond the similar to 1200 degrees C threshold of standard 7 wt% yttria stabilized zirconia (7YSZ). To deposit these advanced coatings, a new thermal spray deposition technique is used: Plasma Spray - Physical Vapor Deposition (PS-PVD). PS-PVD is capable of depositing from the vapor phase to yield strain tolerant columnar microstructures similar to Electron Beam - Physical Vapor Deposition (EB-PVD) or, alternatively, the traditional splat-like lamellar microstructure common to Air Plasma Spray (APS). This study investigates the process-structure relationships and resulting erosion response for plasma gas flow, amperage, and feed rate. It was found that in the selected design space, porosity and surface roughness vary from similar to 12-26% and similar to 5-10 mu m, respectively. Erosion behavior is discussed and the mechanism is identified to be heavily dependent upon the intercolumnar spacing. The lowest erosion rates are similar to EB-PVD, while the highest erosion rates were closer to APS. This is attributed to the hybrid nature of the PS-PVD process and provides an opportunity to tailor coatings with a wide range of properties, and thus performance. Published by Elsevier B.V.