Microstructural dependency of thermal expansion and sintering shrinkage in plasma-sprayed zirconia coatings

The effect of microstructure upon thermal expansion and sintering shrinkage in plasma-sprayed zirconia coatings was investigated by an accurate dilatometry. Cut-out samples with different microstructures were prepared from 5.8-mm-thick atmospheric plasma-sprayed (APS) and water-stabilized plasma coatings (WSP). It was quantitatively determined that the samples cut out of different thickness positions had minor differences in microstructure, and these APS samples largely differed from the WSP samples. The thermal expansion behaviors of all the samples coincided after a short annealing time despite their initial structural differences. On the other hand, all the samples showed a significant difference in sintering shrinkages with annealing at 1400 °C. This result was consistent with the theoretical result calculated with Cipitria's sintering model in terms of the relationship between shrinkage and microstructure. It was therefore demonstrated that the initial microstructure, particularly the splat thickness and the inter-splat pore height, exerts a great influence on the sinterability of plasma-sprayed coatings.