Nanostructured alumina coatings manufactured by air plasma spraying: Correlation of properties with the raw powder microstructure

摘要: Abstract High energy ball milled nanostructured Al 2 O 3 (“N”), fused/crushed conventional (“C”) and sintered (“S”) powders were air plasma sprayed on 304 stainless steel. The powder was composed of nanoparticle agglomerates, whereas the consisted solid granules. average crystal size estimated by X-ray diffraction based methods (the Scherrer equation Williamson Hall plot). Deviations between sizes calculated two indicated high lattice strain induced nanopowder production technique. Sintering did not cause any considerable grain growth; moreover, alleviated. melting degree powders, reflected γ-Al content coatings, depended their porosities. Coatings “N” presented lowest due to inherent porosity agglomerated nanoparticles composing “N”. As a result, microstructure characterized extensive microcracking. “S” coatings exhibited higher than that (similar “C” coatings), tighter attained sintering. At same time, part initial nanostructure had been preserved during sintering spraying. highest adhesion because they combined with pockets retained nanostructure; latter could act as crack arresters. Increasing spray power led an increase in and, consequently, decrease coating affected properties (adhesion hardness).