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 3.6. Powder Testing and Characterization: Image Analysis Image analysis method of determining powder size and shape. (a) Original image. (b) Processed image, providing shapes that are less ambiguous and easier to measure. Image analysis techniques are used to digitize an image of the powder particles and, using image enhancement, thresholding, and binary processing routines, yield a size and shape distribution. While simple in theory, this method is difficult in practice due to the need to separate touching powder particles and to accumulate a significant number of images to properly statistically represent the specimen. Provided these issues can be overcome, image analysis is a precise method of measuring particle size and shape. Source: Powder Testing and Characterization, Walter Riggs, TubalCain Co., Inc., as published in Handbook of Thermal Spray Technology, J.R. Davis (Ed.), ASM International, p 274, 2005. Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 36 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 3.7. Powder Characteristics: Morphology Micrograph of irregularly shaped water-atomized powders having high surface areas (top), and micrograph of spherical gas-atomized powder (bottom). Manufacturing process variations can effect changes in particle morphology, or shape. Morphology affects various parameters including feedability, apparent density, sprayability, unmelted particles in the coating, porosity, and vaporization. Water-atomized powders are one example of this phenomenon, where the morphology may range from almost perfect spheres to highly irregular, convoluted shapes, depending on the manufacturing process parameters. Irregularly shaped particles do not feed as easily as spherical or equiaxed (particles having the same dimension in every direction) powders, because they pack together more easily. Because a sphere has the lowest surface-to-volume ratio of any geometry, any nonspherical shape can adsorb more surface moisture than a sphere. Gas-atomized powders usually are more spherical, and, therefore, typically flow very well. Source: J.R. Davis (Ed.), Handbook of Thermal Spray Technology, ASM International, 2004, p 89 Information and data acquired from ASM International Thermal Spray Society website at http://asmcommunity.asminternational.org/portal/site/tss/SprayTips/ 37 Back to TOC Back to Overview
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Thermal Spray Tips - Swinburne University of Technology

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