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5419 |
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Thursday, June 08, 2017, Hall 27 4:40 PM HVOF Spraying |
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Thermal spraying of pure nickel via HVOF: Effect of fuel and shroud gas variation on particle in-flight characteristics and final coating properties |
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Carina Hambrock* / voestalpine Stahl GmbH, Austria Carina Grill/ Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Austria Gabriela Schimo/ CEST Competence Center for Electrochemical Surface Technology, Austria Achim Walter Hassel/ Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Austria |
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Thermal spraying via HVOF is widely used for the deposition of metallic coatings because dense and less oxidized coatings can be produced in direct comparison to other thermal spraying processes, like e.g. plasma spraying. However, depending on the spraying parameters and on the choice of the thermal spraying gases, the particle in-flight characteristics as well as the coating properties widely differ. Pure nickel coatings were deposited on steel substrates by using the standard DJ 2700 equipment for HVOF thermal spraying at varying spraying distances. Different fuel gases (propane, methane and ethylene) were used for the deposition of the coatings which are well known to strongly influence the particle in-flight characteristics and therewith the coating properties. In addition, the shroud gas was varied without changing the geometry of the standard DJ nozzle or combustion chamber. With this investigation it was tried to produce even better coatings (dense and less oxidized) than during the usual HVOF thermal spray process. In the course of this investigation it could be revealed that not only the choice of the fuel gas but also the choice of the shroud gas had a strong effect on the particle in-flight characteristics as well on the coating properties. All thermal spray coatings were characterized concerning the content of pores and oxygen which was strongly depending on the individual in-flight particle characteristics (either temperature or velocity). Additionally, the samples were investigated in terms of their electrochemical corrosion behavior. In this case, a specific combination of both particle in-flight characteristics, temperature and velocity, is important for obtaining the best corrosion behavior. It was possible to determine thermal spraying parameters that were optimum concerning economy and application. |