Microstructural Characterization of Yttria-Stabilized Zirconia Plasma-Sprayed Deposits Using Multiple Small-Angle Neutron Scattering
Andrew J. Allen, J Ilavsky, Gabrielle G. Long, Jay S. Wallace, C C. Berndt, H Herman
Density, electron microscopy, elastic modulus, and small-angle neutron scattering studies are used to characterize the microstructures of yttria-stabilized zirconis plasma-sprayed deposits as a function fo both feedstock morphology and annealing. In particular, anisotropic multiple small-angle neutron scattering data are combined with anisotropic Porod scattering results to quantify each of the three main porous components in these thermal barrier coating materials intra-splat cracks, inter-splat lamellar pores and globular pores. An inverse correlation between the volume of porosity and its surface area is confirmed for the as-sprayed deposits, as is a preferential annealing of intrasplat cracks at elevated temperatures. The average elastic modulus is correlated with the total void surface area while the elastic anisotropy is related more closely to the intersplat porosity. However, depending on the feedstock morphology, globular pores are also shown to play a surprisingly significant role in post-anneal deposit microstructures and properties.