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1255 |
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Wednesday, June 04, 2008, Room 08 11:20 AM Diagnostics and Sensors 1 Modern process diagnostics offer a lot of possibilities for gaining data for both quality control and process knowledge. The recorded data is the base for process models and enhances the process knowledge |
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In situ visualization of impacting phenomena of plasma sprayed zirconia: from single splat to coating formation |
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Kentaro Shinoda* / Center for Thermal Spray Research
Stony Brook University, USA Hideyuki Murakami / National Institute for Materials Science, Japan Seiji Kuroda/ National Institute for Materials Science, Japan Sachio Oki/ Kinki University, Japan Kohsei Takehara/ Kinki University, Japan |
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Understanding the impacting phenomena of yttria-stabilized zirconia (YSZ) particles and following coating formation in plasma spraying process is of importance to control and design the microstructure of coatings such as segmented thermal barrier coatings. To this aim, recently, the authors have developed a novel in situ monitoring system for particle impacts under atmospheric dc plasma spraying conditions. This system utilized a high-speed video camera coupling with a long-distance microscope and was capable of capturing the particle-impinging phenomena at one million frames per second. To understand the coating formation mechanism, two approaches were attempted, that is, observation of the single splat formation and the following coating formation. In the former case, the authors have succeeded in capturing the deformation and cooling processes of YSZ droplets impinging on substrates. For example, on a smooth quartz glass substrate kept at room temperature, the images showed that the stable liquid sheet from a droplet detached from the substrate and spread until its maximum extent. While the sheet was spreading, the center region of the flattened droplet cooled down rapidly. In the latter case, to understand the coating formation as the integration of splats, multiple-droplet-impacting phenomena were also observed as an ensemble treatment. To capture the particle-impinging phenomena under simulated plasma spraying conditions, conventional hollow YSZ powders were sprayed with a dc plasma torch at the feeding rate of 14 g/min and at the scanning speed of 50 mm/s. By using a triggering system coupling with the motion of an operating robot, multiple droplet impacts were captured at every two passes. The obtained image clearly showed the coating formation resulted by the integration of single splats. The obtained images and additional analyses of images will also be presented in this study. |