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International Heat Transfer Conference 13
Graham de Vahl Davis (open in a new tab) School of Mechanical and Manufacturing Engineering, University of New South Wales, Kensington, NSW, Australia
Eddie Leonardi (open in a new tab) Computational Fluid Dynamics Research Laboratory, School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Australia 2052

ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

DEVELOPMENT OF EXPERIMENTAL SET-UPS ALLOWING CHARACTERIZING THE INFLUENCE OF NANO-SCALE SUBSTRATE TOPOGRAPHY ONTO THE FLATTENING AND SOLIDIFICATION OF MICROMETER AND MILLIMETER SIZED MOLTEN DROPLET

page 13
DOI: 10.1615/IHTC13.p8.300
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要約

Plasma sprayed coating thermo mechanical properties depend strongly upon the contact between the layered splats forming the coating. These contacts are linked to the flattening and the solidification of the impacting molten particles. This paper describes experiments performed on micrometer sized zirconia particles (spraying) with flattening time in the μs range and millimeter sized ones (falling drops) with flattening timein the ms range. They consist in measuring the parameters for a single particle prior to its impact (temperature, velocity, diameter), its temperature and surface time evolution during its flattening. Such measurements allow following flattening velocity links to its wettability an dits cooling rate and also evaluating the thermal contact resistance RTC between the flattening paticle and the substrate. These experiments performed on a smooth stainless steel (304 L) and plasma sprayed zirconia substrates have shown that the flattening velocity and cooling rate increase when preheating substrate over a so-called transition temperature Tt. With the ZrO2 substrate preheating allows eliminating the contaminants at the surface while with 304 L besides this elimination, the skewness parameter of the surface becomes positive improving the contact flattening particle-substrate. For preheated substrates over Tt the thermal contact resistance RTC mean value decreases significantly relatively to a room temperature substrate. At last RTC varies with time probably in connection with impacting pressure strong decrease with flattening time in the millisecond range.

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