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Contribution à la compréhension et à la maîtrise du procédé d'atomisation de jets métalliques liquides

Abstract : The growing demand for metal alloy powders with specific properties used in thermal spray application and rapid manufacturing encourages researchers to improve and optimize their manufacturing processes. The aim of these processes is to master both morphology/particle size distribution and manufacturing cost. Today the vast majority of powders are produced by fluid atomization and mainly gas atomization process. Among them, the Nanoval process, consisting of a De Laval nozzle is one of the most outstanding process in terms of granulometric distribution and output.The main objective of this thesis is to improve the understanding of the physical phenomena occurring in the Nanoval process to optimize the way it operates. Two approaches will be developed:- A numerical study using Fluent. The two following models were studied, one monophasic concerning gas flow in the atomization unit form autoclave to atomization chamber and the other, a diphasic model concerning the finest part of the filament in the exit of the melt nozzle. This numerical study has highlighted the effect of parameters such as atomization pressure, nozzle diameter on the gas dynamics, fine filament, high-pressure and high speed areas before, during the process and after the disintegration of the metallic filament.- And an experimental study which required the implementation of the in-situ diagnosticTools to characterize the process under working conditions. Three analyses were carried out. The first concerns the dynamics of the atomization jet from Velocimetry measures by Particle Image Velocimetry (PIV) close to De Laval nozzle exit. The second deals with the characteristics obtained when particles impact the substrate in the atomization chamber. The third describes the particle properties and deals with the comparison with the matter in the autoclave after cooling process. Different operating parameters were explored (atomization pressure, melt nozzle diameter, pressure in the atomization chamber, nature of metal) and linked to their influence on the particle velocity and diameter. Narrow links between the analysis results were demonstrated as well as a good adequacy between experimental and modeling results.
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Othmane Khatim. Contribution à la compréhension et à la maîtrise du procédé d'atomisation de jets métalliques liquides. Autre. Université de Technologie de Belfort-Montbeliard, 2011. Français. ⟨NNT : 2011BELF0161⟩. ⟨tel-00703182⟩

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