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High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes
SJR: 0.176 SNIP: 0.48 CiteScore™: 1.3

ISSN Druckformat: 1093-3611
ISSN Online: 1940-4360

High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes

DOI: 10.1615/HighTempMatProc.v1.i3.20
pages 295-313

TRANSPORT AND CHEMICAL RATE PHENOMENA IN PLASMA SPRAYS

Armelle Vardelle
ENSIL, ESTER Technopole, 87068 Limoges - France
Nickolas J. Themelis
Columbia University, Department of Earth and Environmental Engineering, New York, NY 10027, USA
B. Dussoubs
Equipe "Plasma Laser Matériaux", ESA CNRS 6015, Université de Limoges, 123 Avenue Albert Thomas, 87060 Limoges - France
Michel Vardelle
LMCTS-URA 320, University of Limoges, 123 Avenue Albert Thomas -87060 Limoges Cedex - France
Pierre Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France

ABSTRAKT

This paper is focused on the understanding of plasma-particle and particle-substrate interactions during plasma spraying. Rough estimates by using averaged values of the appropriate transport properties make it possible to determine the relative magnitudes of heat transfer, evaporation, mass transfer and chemical reaction when 30 μm iron particles are entrained in a plasma jet, operating in ambient atmosphere.
When particles impinge on the substrate, they undergo severe deformation and rapid cooling. Particle spreading and morphology changes as well as solidification rate, control the nature of the particle-substrate interactions and thus the coating microstructure. The temperature of the substrate surface plays a major role in splat formation and splat shape. It is postulated that maintaining the substrate medium above a certain "transition" temperature ensures that the splat during formation remains in the liquid phase. When the substrate is below this temperature, the droplet begins to freeze after impact, part of the liquid mass splinters away and spreading of the droplet away from the point of impact is irregular. After impact of a metal droplet with the substrate, the principal mode of oxidation is by gas-solid reaction which follows a parabolic diffusion law.


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