Plasma spraying of micro-composite thermal barrier coatings

The thermal barrier coatings (TBCs) by gas tunnel-type plasma spraying exhibited ceramic-composite features consisting of a host oxide matrix ceramic with an embedded second phase material. The densities of the composite TBC were found to be higher than those sprayed with 100wt% ZrO2 or Al2O3. In the coatings produced with powder mixtures of 50wt%, the embedded splats are found to have a relatively uniform thickness between 1 and 10 mm and they exhibited clear and pore-free interfaces with the host material. The micro-composite coatings also exhibited thicknessdependent functionally gradient Vickers hardness values by the hardness measurements across the coating thickness. A one-dimensional series heat transfer model was developed to estimate upper and lower bounds of the transverse thermal resistance as a function of alumina–zirconia weight ratio. The model shows that the addition of higher thermally conducting Al2O3 can result in an increase in the transverse thermal resistivity of YSZ. r 2002 Elsevier Science Ltd. All rights reserved.