Elastic constants of plasma-sprayed yttria-stabilized zirconia coatings determined via resonant ultrasound spectroscopy coupled with laser-Doppler interferometry

Plasma-sprayed yttria-stabilized zirconia (YSZ) coatings exhibit five independent elastic constants with transverse isotropy owing to splat-based layered structures, including numerous preferentially oriented defects. In this study, we measure all the elastic constants of free-standing YSZ coatings in both as-sprayed and thermally treated conditions from 800 degrees C to 1300 degrees C for 2 h. The YSZ coatings were produced via atmospheric plasma spraying under one typical processing condition. The elastic constants are determined using resonant ultrasound spectroscopy coupled with laser Doppler interfemmetry. This approach allows us to overcome the difficulty of resonant-mode identification caused by the high internal friction of plasma-sprayed YSZ coatings; hence, reliable elastic constant data are obtained. We discovered that the splat-based layered structures provide strong elastic anisotropies in both the shear and longitudinal moduli. In addition, our measurements in the as-sprayed condition suggest that the as-sprayed YSZ coatings exhibit degenerate (elliptic) transverse isotropy with inter-splat pores that tend to be perpendicular to the spraying direction. The dependence of the elastic constants on the heat-treatment temperature shows that the elastic anisotropy of the plasma-sprayed YSZ coatings increases slightly and then decreases as the heat-treatment temperature increases. This finding is supported by the different effective sintering temperatures of the inter-splat pores and intra-splat cracks.

Automated summary

This study measured the elastic constants of plasma-sprayed yttria-stabilized zirconia (YSZ) coatings under different processing conditions and found that the layered structure of the coatings influenced the elastic anisotropy. The dependence of elastic constants on heat-treatment temperature showed a slight increase followed by a decrease. This was attributed to the different effective sintering temperatures of inter-splat pores and intra-splat cracks.