Material property variations in thermally sprayed coatings

Coatings of a bond coat with an yttria stabilized zirconia overlay have been examined. Microhardness tests have been performed at precisely located positions within the coating thickness. These are; within the bond coat, near the bond coat/ substrate interface and within the upper portion of the ceramic coating. At least thirty five tests were performed at each location. The present work establishes that the variability of this material property with respect to the coating thickness is statistically significant. The implications of this work are two-fold. First; the value of performing hardness tests on coatings for quality assurance purposes are of limited value since the hardness is dependent on the precise point of test within the sample. Second; the variability in material property changes across the thickness