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1552 |
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Tuesday, June 03, 2008, Room 04 2:40 PM New Equipment 3 Latest developments in thermal spray equipment, modern multiple arc plasma guns, optimized powder feeder, new vacuum processes |
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Standard HVOF process compared to the HVOF process for internal coating with fine powders |
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Goetz Matthäus* / Thermico GmbH & CO KG, Germany Waltraut Brandl / University of Applied Sciences Gelsenkirchen, Germany Gabriela Marginean/ University of Applied Sciences Gelsenkirchen, Germany Daniel Ackermann/ University of Applied Sciences Gelsenkirchen, Germany |
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To replace hardchrome coatings in landing gear applications, manufacturers require the new HVOF internal coating process with fine WCCoCr powder for tubes. The main argument against the use of the HVOF process is the high thermal stress that the substrates are subjected to during the coating process. Traditional HVOF guns operate with a flame stream energy level of 100 ? 200 kW. Rendering HVOF technology usable for the application of internal coatings requires the reduction of the energy level of the flame stream to 20 kW, while safeguarding high particle velocity and sufficient temperature despite the reduced energy level. This requires an inter-coordinated process made up of HVOF gun, powder feeder, fuel control and powder, based on the use of fine powders with particle sizes of -25+5 µm, -15+5µm and -10+3 µm. Thermico?s ID CoolFlow M HVOF internal spraying gun comes equipped with a 5mm acceleration nozzle and radial powder feed. It is suitable for internal diameters of 80mm and above and eliminates the typical overheating problem. The ID CoolFlow M HVOF gun is suitable for internal coatings with Thermico 776 WC-CoCr powder, which comes in grain sizes of 5-15µm and 15-30µm. A comparison of both processes requires a number of specimen coatings with different parameters, which have to be compared to reference coatings. These reference coatings are produced using a Thermico CJS K4.2 - 776/G in combination with WC-CoCr 86 10 4 powder with a grain size of 15-30 µm, and a CJS K5.2 - 776 gun, using a finer powder with a grain size of 5-15 µm. The base material consists of heat-treated steel rings with a hardness of 45 HRC, an internal diameter of 130 mm and a wall thickness of 10mm. Subsequently, the density, porosity and structure of the specimen is assessed, and they are checked metallographically and with a scanning electron microscope, including EDX analysis. The specimen?s wear is monitored using the prototype of an internal coating test stand, developed by the Institute for Materials Science at University of Applied Sciences Gelsenkirchen. It is essentially based on a standard pin-on-disc tribometer for rotative movements. Presenting Author: First name: Goetz Last name: Matthaeus Address: Franz-Schlueter-Strasse 10-16 44147 Dortmund Germany Phone: +49 (0)231 / 317 51 ? 10 Fax: +49 (0)231 / 317 51 ? 20 e-mail: gma@thermico.biz |