Deposition of Alumina Coatings from Nanopowders by Plasma Spraying

Abstract

Aluminum oxide coatings were prepared by the atmospheric plasma spraying from the Al2O3 nanopowders. The
powders were injected into the anode zone at high temperature region. Scanning electron microscopy (SEM) and X-ray
diffraction (XRD) were applied to analyze the granulated nanopowder feedstocks and coatings. The results demonstrated
that the higher the plasma torch power was the lower surface roughness. The XRD results showed that δ-Al2O3 was the
main phase for granules dried for 12 h at 473 K. Meanwhile the as-sprayed coatings are composed of γ-Al2O3 and
α-Al2O3. The increase of the plasma torch power leads to the production of the alumina coatings with a higher amount of
the γ-Al2O3 phase. The crystallite size of γ-Al2O3 (400) phase decreases from 97 nm down to 49 nm with the increase of
the torch power.