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4781 |
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Thursday, May 12, 2016, Room 3C + 3D 9:40 AM New Processes II |
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An in-situ cooling solution for thermal spray coating process |
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Tim Bao* / Air Products, China Ranajit Ghosh/ Air Products and Chemicals, China Jerry Wu/ Air Products and Chemicals, China Feng Qin/ Air Products and Chemicals, China Liang He/ Air Products and Chemicals, China |
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Thermal spray is widely used to deposit protective coatings on a metal surface, by directly spraying melted or heated metal precursors. The coating materials are often heated by plasma or oxy-fuel combustion means. During spraying, the substrate temperature must be cooled down and well controlled to avoid coating quality issues related to overheating. A cryogenic nitrogen gas-based cooling solution has been developed to cool the part simultaneously while it is being spray coated, and therefore improves productivity by eliminating the inter-pass cooling breaks (wait for the parts to cool down ) associated with traditional air cooling methods. The system does not only cool but also controls the workpiece temperature within a specified range, with infrared sensors and a close-loop control scheme. The real-case experiments demonstrated thermal spray cooling resulted in 50% shorter process time, improved deposition efficiency, much tighter temperature control (±20F), smaller micro-porosity density (0.05%), higher substrate hardness, less coating oxidation or carbon loss, and minimized residual stresses in coatings. |