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5455 |
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Thursday, June 08, 2017, Hall 27 10:20 AM Suspension Spraying II |
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Optimization of high-velocity suspension flame spraying (HVSFS) by PIV measurements for improving Al2O3 coatings micro-hardness |
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Simon Goutier* / University of Limoges, France Mélanie Baubias / University of Limoges / SPCTS, FRANCE Andreas Killinger/ University of Stuttgart, IFKB Institute, GERMANY Alain Denoirjean/ University of Limoges / SPCTS, FRANCE Philipp Müller/ University of Stuttgart, IFKB Institute, GERMANY Andrea Foerg/ University of Stuttgart, IFKB Institute, GERMANY Martin Plachetta/ University of Stuttgart, IFKB Institute, GERMANY Rainer Gadow/ University of Stuttgart, IFKB Institute, GERMANY |
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High Velocity Suspension Flame Spraying (HVSFS) is a very promising method for spraying very fine particle (micron, submicron and nanoparticles) with a high velocity at the impact. Indeed the suspension is introduced directly inside the combustion chamber of a modified HVOF torch for increasing particle acceleration and heat transfer. And so mechanical and chemical properties are improved for numerous application (medical, SOFC, &). Unfortunately if the evolution of the particle velocity for standard particle (Dparticle > 20 µm) is well known it is difficult to known the velocity evolution in the case of the HVSFS due to the particle sizes (Dparticle < 5 µm) and in these conditions optimize process parameters is a time consuming work. For measuring the particle velocity in the case of the smallest particles it is necessary to use specific measurements based on laser diffusion. In this paper the aim is to analyse the link between the particle velocity at the impact and the micro-hardness of Al2O3 coating. Particle velocities are measured by PIV (Particle Image Velocimetry) for different spray distance, gas composition and gas flow. The measuring system uses a laser sheet to illuminate the particles inside the plasma at two different times. The two laser pulses are triggering with two cameras to obtain two images of the particle jet. Thanks to a cross correlation process between the two cameras images a particle velocities mapping is performed and average velocity value is calculated inside a small volume. For this study several velocities evolutions along the torch axis are conducted and correlated to the micro-hardness and coating porosity. |