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 2.6. Effect of Torch Hardware on Particle Temperature and Velocity Gun Cooling, Pinch, and Flame Cooling air caps air caps were fitted onto nozzles, and the particle temperature (Tp) and particle velocity (Vp) were measured. The gun cooling air cap produced the highest Tp and lowest Vp because it minimized the interaction between the cooling air and the particulate loaded flame. The pinch air cap strongly directed the cooling air into the flame, and produced the highest Vp and lowest Tp values. The flame cooling air cap also directed air into the flame, but not as strongly as the pinch air cap, and as a result, the flame cooling air cap produced Tp and Vp values between those of the gun cooling and pinch air caps. Source: Journal of Thermal Spray Technology, Volume 19(4) June 2010, p. 824-827. Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 12 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 2.7. Flame Spray Process Powder flame spray system Conventional flame spray was the first thermal spray process developed (~1910) and is still in common use. Modern torches have changed little since the 1950s. Flame spray uses the chemical energy of combusting fuel gases to generate heat. Oxyacetylene torches are the most common, using acetylene as the main fuel in combustion with oxygen to generate the highest combustion temperatures. Powder, wire, or rod is introduced axially through the rear of the nozzle into the flame at the nozzle exit. The feedstock material is melted and the particles/droplets accelerated toward the surface by the expanding gas flow and air jets. An advantage of wire and rod over powder is that the degree of melting is significantly higher, producing denser coatings. In addition, the atomizing air produces finer droplets, which in turn produce finer, smoother coatings. In flame spray processes, fuel/oxygen ratio and total gas flow rates are adjusted to produce the desired thermal output. Optional air jets, downstream of the combustion zone, can further adjust the thermal profile of the flame. Flame spray is capable of depositing a wide range of materials, ranging from polymers to ceramics and refractory metals. Source: Thermal Spray Processes, revised by Daryl E. Crawmer, Thermal Spray Technologies Inc., as published in Handbook of Thermal Spray Technology, J.R. Davis (Ed.), ASM International, 2005, p 55. Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 13 Back to TOC Back to Overview
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