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 2.13. Oxyfuel Wire Spray Schematic of the oxyfuel wire spray process The oxyfuel wire spray process (also called wire flame spraying or the combustion wire process) is the oldest of the thermal spray coating methods and among the lowest in capital investment. The process utilizes an oxygen-fuel gas flame as a heating source and coating material in wire form. Any material in the form of wire and capable of being melted below 2480°C (4500°F) can be flame-sprayed. During operation, the wire is drawn into the flame by drive rolls that are powered by an adjustable air turbine or electric motor. The tip of the wire is melted as it enters the flame, atomized into particles by a surrounding jet of compressed air, and propelled to the workpiece. The diagram shows a schematic of the OFW spray process. Spray rates for this process range from 0.5 to 10 kg/h (1 to 20 lb/h) and are dictated by the melting point of the material and the choice of fuel gas. Common fuel gases are acetylene, MAPP gas, propane, propylene, and natural gas, each combined with oxygen. Source: J.R. Davis, Hardfacing, Weld Cladding, and Dissimilar Metal Joining, ASM Handbook, Vol 6, Welding, Brazing, and Soldering, ASM International, 1993, p 805. Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 22 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 2.14. Reactive Plasma Spray Forming Reactive plasma spray process for the synthesis of composite materials Controlled-atmosphere plasma spraying, adapted for reactive plasma spraying, has recently been developed to combine controlled dissociation and reactions in thermal plasma jets, for the in situ forming of new materials or to produce new phases in sprayed deposits. Reactive plasma spray forming is consequently emerging as a viable method for producing a wide range of advanced materials. The process, a logical evolution from conventional plasma spraying, allows reactive precursors to be injected into the particulate and/or hot gas streams. These reactive precursors may be liquids, gases, or mixtures of solid reactants. On contact with the high-temperature plasma jet, they decompose or dissociate to form highly reactive and ionic species that can then react with other heated materials within the plasma jet to form new compounds. The diagram illustrates the reactive plasma spray concept. Chemical reactions rely on plasma-induced dissociation of the injected precursors. These species can react with other elements to produce carbides such as TiC and WC, or under certain conditions, diamond or diamondlike carbon (DLC) films. The primary requirements are that the precursors dissociate into reactive species and that the reaction times and temperatures are sufficiently long for the desired products or phases to form. Source: R. Knight and R.W. Smith, Thermal Spray Forming of Materials, ASM Handbook, Vol 7, Powder Metal Technologies and Applications, ASM International, p 415. Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 23 Back to TOC Back to Overview
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