Formation of nanocrystalline FeAl₂O₄ matrix coating by plasma spraying

Abstract

composite powders were deposited onto steel substrate by plasma spraying. The state (temperature and velocity) of the Al-Fe 2 O 3 composite powders in plasma flame and the formation mechanism of the nanostructured coating were investigated and analysed. The maximum temperature and velocity of the composite particles in plasma flame were 3274?5uC and 179 m s 21 respectively. FeAl 2 O 4 , Fe and Al 2 O 3 multiphase composite coatings were formed, which presented a microstructure with a number of spherical Fe and Al 2 O 3 nanosized grains embedded within the equiaxed and columnar FeAl 2 O 4 nanograin matrix. The formation process of the nanocrystalline composite coating prepared by plasma spraying can be described as follows. When smaller size droplets spread on the substrate, they were quickly chilled to form nanosized equiaxed grains. Nanosized equiaxed and columnar grains were formed in the larger size spreading droplets due to the high chilling, large undercooling and non-equilibrium directional solidification of the ceramic melt.

Deposition of plasma sprayed copper slag coatings on metal substrates

“…[1][2][3][4] The advantages of plasma spraying include formation of ceramic microstructures with fine, equiaxed grains without columnar defects, deposition of graded coatings with a wide compositional variety, formation of thick coatings with only modest investment in capital equipment and design capability for free standing thick forms of monolithic and mixed ceramics in near net shape configuration. Plasma spray coating is a typical thermal spraying process that combines particle melting, quenching and consolidation in a single operation.…”