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2032 |
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Tuesday, May 04, 2010, Sophia Room 8:40 AM Nanomaterial Coatings 1 |
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Composition of alumina titania coatings manufactured by suspension plasma spraying
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Ghislain Montavon* / SPCTS - UMR CNRS 6638, Faculty of Sciences, University of Limoges, France Geoffrey Darut / SPCTS - UMR CNRS 6638, University of Limoges, France Elizaveta Klyatskina/ Instituto de Tecnología de Materiales Universidad Politécnica de Valencia, Spain Stéphane Valette/ SPCTS - UMR CNRS 6638, University of Limoges, France Alain Denoirjean/ SPCTS - UMR CNRS 6638, University of Limoges, France Hélène Ageorges/ SPCTS - UMR CNRS 6638, University of Limoges, France Pierre Fauchais/ SPCTS - UMR CNRS 6638, University of Limoges, France Francisco Segovia/ Instituto de Tecnología de Materiales Universidad Politécnica de Valencia, Spain M.D. Salvador/ Instituto de Tecnología de Materiales Universidad Politécnica de Valencia, France |
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Plasma spray technology is widely implemented for the development of protective coatings to prevent degradation of critical components working under severe conditions. In this prospect, plasma sprayed alumina-titania coatings find many industrial applications since they provide a dense and hard surface which is resistant to abrasion, corrosion, cavitation, oxidation and erosion. Moreover, thanks to the presence of the spinel Al2TiO5 phase, they show superior complaisance to low temperatures / high strains. Sub-micrometer-sized alumina-titania exhibit superior performances compared to micrometer-sized ones thanks to a higher toughness meanwhile their lower hardness. Two routes can be implemented to manufacture such finely structured coatings: i) spraying micrometer-sized agglomerates of nanometer-sized particles which results in a two-scale coating architecture and ii) spraying a suspension of sub-micrometer-sized particles (suspension plasma spraying, SPS). SPS was selected in this study and several coatings with various titania mass contents, evolving from 13 to 75%, were manufactured by spraying a suspension made of a mixture of alumina and titania particles of 300 nm average diameter. Coating architectures were studied by FESEM and their phase assessed by XRD. Results show that coatings exhibit a very fine lamellar structure with a homogeneous repartition of Al and Ti. Complex phases, made of intermediate Al, Ti, O and Fe oxides, have been identified. Their formation results from rapid solidification rates and high transient thermal fluxes imparted by the plasma flow to the substrate due to the short spray distance encountered in SPS (in the order of 30 mm) due to the small inertia and thermal inertia of sub-micrometer-sized particles. |