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2138 |
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Diagnostics and coating formation in low pressure cold spray process |
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Heli Koivuluoto / Tampere University of Technology, Finland Sakari Tolvanen / Tampere University of Technology, Department of Materials Science, Finland Paavo Sirkka/ Tampere University of Technology, Department of Materials Science, Finland Petri Harkko/ Cavitar Ltd., Finland Taito Alahautala/ Cavitar Ltd., Finland Jussi Larjo/ Oseir Ltd., Finland Petri Vuoristo/ Tampere University of Technology, Department of Materials Science, Finland |
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In the cold spray process, powder properties (e.g., particle size and morphology) and spraying parameters have strong influence on the in-flight behavior of particles and coating formation. The aim of this study was to evaluate diagnostics of the low-pressure cold spray process and investigate effect of spraying parameters and different powder characteristics on particle behavior during process and coating build-up. LPCS Cu and Cu+Al2O3 coatings were sprayed with Dymet 403K spray system using compressed air as a process gas. Preheating temperature of air affected significantly coating thickness and deposition efficiency of the Cu+Al2O3 coatings. The best achieved deposition efficiency was measured using the highest temperature of 640ºC. In-flight properties, e.g., particle velocities were measured using a HiWatch system. Gas and particle behavior in the flow after nozzle exit and gas behavior near to the sprayed surface were illuminated with Schlieren photographic technique. Furthermore, gas and particle impacts on substrate were illustrated with Cavilux® system in order to analyze particle deformation and particle collisions with high velocities. In addition, coating structures were characterized using scanning electron microscope (SEM). |