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1320 |
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Monday, June 02, 2008, Room 04 3:00 PM Wear Protection 2 Special processes for coatings against wear, improved surface roughness of as sprayed coatings, improved sliding behavior |
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CFD optimized nozzles for increased particle velocities and lowered gas consumption in the HVOF spraying process |
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Christian Rupprecht / Chemnitz University of Technology, Germany Bernhard Wielage / Chemnitz University of Technology, Germany Gerd Paczkowski*/ Chemnitz University of Technology, Germany Rolf Menzen/ IBEDA Sicherheitsgeräte und Gastechnik GmbH & Co. KG, Germany Gerd Weissenfels/ IBEDA Sicherheitsgeräte und Gastechnik GmbH & Co. KG, Germany Heinz Ulrich Bernhardt/ IBEDA Sicherheitsgeräte und Gastechnik GmbH & Co. KG, Germany Michael Runkel/ IBEDA Sicherheitsgeräte und Gastechnik GmbH & Co. KG, Germany |
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The basics for a high quality of thermal spray coatings are well adjusted processing conditions. For HVOF spraying that means super sonic particle velocities and moderate particle temperatures. To fulfil these requirements a certain speed of the gas jet is necessary. If low fuel and gas consumption is aspired, this can only be realised with adapted nozzle designs. Some efficient ways of nozzle design optimisation are shown in this paper. Novel methods and strategies in computed fluid dynamics are explained and correlated to experimental results. For this purpose, gas jet and particle velocities are investigated by means of laser optical measurements (laser optical correlation technique). Furthermore, in the presented paper some characteristic differences in spraying of wire and powder under HVOF conditions are discussed. Although both feedstock materials can be injected axial in gas powered burners, the nozzle design has to be adapted according to the smaller cross section and the higher spray jet divergence in the case of wire spraying. The feeding of wire into the fast gas jet effects a vortex detachment at the wire tip. Thereby the atomisation of the molten material is enhanced, but the jet divergence is increased. High speed camera recordings facilitate the presentation of this effect and give additional hints for nozzle optimisation. |