A Comparison between Nanostructured YSZ Coatings Fabricated by LPPS and APS Method Using Unsintered Porous Agglomerates

Nanostructured YSZ coatings were deposited by plasma spraying at different pressures and plasma currents. Coatings sprayed at low pressures exhibited fine equiaxed grain structures with consolidated coarser grains and loose-packed nano granules. Especially at the low end of the current range, larger amounts of crystalline grain fell into the nanoscale, significantly reducing the average grain size in the coating. At the high end of the range, the coating exhibited a uniform fine equiaxed grain structure of around 200 nm. Mechanical properties, including average microhardness and elastic modulus, were also measured and compared. LPPS YZS coatings showed slightly higher microhardness, but half the elastic modulus of APS YSZ layers.