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1185 |
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Comparative study between Ar-H2 and N2-H2 plasma gas mixtures: application to ZrO2-Y2O3 coatings
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Elise Nogues-Delbos* / SPCTS Laboratory, France Simon Goutier/ SPCTS, France Michel Vardelle/ SPCTS Laboratory, France Pierre Fauchais/ SPCTS Laboratory, France Pascal Granger/ Edwards, France |
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In plasma spray process, ceramic coatings can be sprayed by using either argon-hydrogen or nitrogen-hydrogen plasma gas mixtures. Starting from a given particle size distribution the question is what are the spray parameters allowing achieving similar coatings with these types of plasmas? The problem is made more complex because a torch working with Ar-H2 is different from that using N2-H2 as plasma forming gas. It is thus necessary to compare the gas mixture properties, the torches working conditions (mean voltage and thermal efficiency), the arc column diameter relatively to the nozzle internal diameter and the spray parameters, the arc root fluctuations, the powder injection, the particles mean temperatures and velocities as well as their fluctuations linked to those of arc root, the splat formation, the coating porosity and deposition efficiency. This comparison has been achieved for ZrO2-Y2O3 (7 vol%) powder with a size distribution between 5 and 25 µm and using the same plasma torch for the two plasma gas mixtures: a 3MB torch with a cylindrical anode nozzle and 5.5 mm in internal diameter. |