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1566 |
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Wednesday, June 04, 2008, Auditorium 2 9:40 AM Cold Spraying 1 Everything around this young thermal spraying technique, possible applications and latest developments for equipment of high pressure and low pressure cold spraying, models and simulations for a deeper process knowledge |
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How cold is cold spray? An experimental study of the heat transfer to the substrate in cold gas dynamic spraying |
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Eric Irissou* / National Research Council Canada
- Industrial Materials Institute, CANADA Jean-Gabriel Legoux / NRC-IMI, Canada Anatoly Ryabinin/ Institute of Mathematics and Mechanics, St. Petersburg University, , Russia Christian Moreau/ NRC-IMI, Canada |
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During cold gas dynamic spraying, the supersonic gas flow is directed toward a substrate where it is decelerated, compressed and deflected during its impact. This interaction produces a stagnation region in proximity of the substrate surface resulting in a rapid increase of the gas temperature up to, theoretically, the gas inlet temperature. Since the propelling gas is commonly heated up in order to reach higher velocities, the temperature of the gas in that region could be high enough to significantly increase the temperature of the substrate during cold spray deposition. It is important to assess the influence of this heat input both for applying coatings on temperature sensitive materials and for developing a fundamental understanding of the cold spray coating build-up. This study focuses on the influence of the cold spray process parameters on the heat input to the substrate surface temperature. Using spatially and time-resolved thermographic measurements by a high speed infrared camera, experiments were carried on three commercial cold spray systems (SST Centerline, CGT Kinetics 3000 and Inovati KM-CDS 2.2) spanning a wide range of gas pressures, gas temperatures, gun transverse speeds and stand-off distances. The substrate surface temperatures were measured directly beneath the cold spray gun as well as at predetermined distances from the gun giving a general evaluation of the heat input to the substrate in actual deposition conditions. It is shown that the substrate surface temperature can rise up to a value close to the inlet gas stagnation temperature in the area located beneath the cold spray gun (bow shock region). The surface temperature is a function of both, the gas temperature and the gas pressure. Besides the difference in pressure range among the three cold spray systems, significant differences were found in measured surface temperature range due to variation in nozzle configuration. |