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| Abstract No.: |
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Scheduled at:
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Wednesday, June 07, 2017, Hall 26 10:50 AM
Process Diagnostics, Sensors & Controls
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| Title: |
The arc movement as a source of process instability for single-cathode-anode systems a new method for direct investigation
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| Authors: |
Georg Thomas / Technische Universität Berlin, Germany
Sebastian Mihm* / Medicoat AG, Switzerland
Marius Limburg/ Technische Universität Berlin, IWF, FG Beschichtungstechnik, Germany
Heiko Gruner/ Medicoat AG, Switzerland
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| Abstract: |
The almost uncontrollable arc movement in a single-cathode-anode system limits the efficiency and process stability of this global used DC plasma spraying technique. A successful approach to stabilize the arc anode attachment and thus to increase process efficiency was the replacement of the convergent-cylindrical nozzle geometry by a convergent-divergent nozzle geometry with Laval contour. However, the advantages of this nozzle design were connected to an increased anode erosion caused by an excessive heat input from the anode attachment of the arc. Prerequisite for an optimization of the arc movement is its technical measurement and the dedicated correlation out of it with the plasma jet and the trajectory of injected powder particles. For this purpose Technical University of Berlin developed a new optical analysis method based on high-speed video recording to examine the arc movement, its position and intensity. The software based data together with the simultaneous measured voltage of the corresponding DC-arc clearly show for example the dependence of the arc movement from the position of the cathode tip in relation to center axis of the anode, impressively demonstrated for a new three-zone anode (convergent, conical and divergent). Thus a new tool is given to the developer of new anode geometries for increasing process efficiency and the lifetime of the single-cathode-anode system.
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