Thermal Spray Tips - Swinburne University of Technology

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Compiled by Jo Ann Gan, Edited and advised by Christopher C. Berndt Swinburne University of Technology Thermal Spray Group (SwinTS) Please contact Prof. Christopher Berndt at cberndt @swin.edu.au for further enquiries 2.10. Hypersonic Flame Spraying Cross-sectional view of a flame powder spraying system showing powder feed material being transported by the carrier gas and then melted by the oxyfuel mixture. In recent years, the field of thermal spraying has seen the introduction of hypersonic combustion flame spray (HCFS) guns. In the Jet-Kote method (the first gun of this type was commercially available in 1983), a high-velocity combustion process (chemical energy) accelerates and melts the particulates via convective heat transfer from the hot flame. The system consists basically of three parts: a main console, a pressurized powder feeder, and a portable torch. An internal combustion flame is produced in a water-cooled combustion chamber with a continuous flow of oxygen and fuel gases. This flame makes a right-angle bend and passes through four vortices that focus the hot gases into a narrow beam. This beam is accelerated through an extended-length water-cooled nozzle. The combustion process creates a high back pressure, thus requiring a pressurized powder feeder to propel particulates axially from the rear of the nozzle into the stream of hot gases. Source: Engineered Materials Handbook -> Densification and Sintering of Ceramics -> Nontraditional Densification Processes Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 18 Back to TOC Back to Overview
Compiled by Jo Ann Gan, Edited and advised by Christopher C. Berndt Swinburne University of Technology Thermal Spray Group (SwinTS) Please contact Prof. Christopher Berndt at cberndt @swin.edu.au for further enquiries 2.11. Arc and Flame Spraying Processes Electric arc spraying and flame spraying are the most suitable methods for applying coatings of zinc, aluminum, and their alloys to steel structures. These methods are simple, they can be used on-site, and they offer relatively high coverage rates compared to other thermal spray processes. Wire consumables are also more economical and easier to handle than powders. Electric arc spraying involves feeding two electrically conducting metal wires toward each other. An electric arc is produced at the wire tips, melting the metal. A highpressure air line atomizes and then sprays the fine droplets onto the steel surface. In flame spraying, a metal wire is melted in a gas flame and then air sprayed onto the steel surface. Arc and flame spray coatings usually contain numerous pores, some of which are closed and the rest connected from the coating surface to the substrate. Natural sealing can be achieved by oxidation of the metallic coating under normal environmental exposure conditions, when the resulting oxides, hydroxides, and/or basic salts are not soluble in this environment. Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 19 Back to TOC Back to Overview
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