Understanding of Spray Coating Adhesion Through the Formation of a Single Lamella
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JTTEE5 21:522–530 DOI: 10.1007/s11666-012-9763-0 1059-9630/$19.00 Ó ASM International
Understanding of Spray Coating Adhesion Through the Formation of a Single Lamella S. Goutier, M. Vardelle, and P. Fauchais (Submitted September 15, 2011; in revised form January 24, 2012) Plasma spraying involves the total or partial melting of micrometer sized particles, flattening of the particles in about one microsecond onto a substrate to build a coating by layering the resulting solidified splats. The coating adhesion is essential and depends mainly on the behaviour of first lamellae in contact with the substrate. But in the plasma spray process about 108 particles/s impact onto the substrate, and thus it is difficult to understand the role of the different spray parameters onto the coating adhesion. In order to get a better understanding of phenomena involved, it is necessary to study the formation of a single lamella. An experimental set-up has been designed to study this process and is composed of a fast (50 ns) two-colour pyrometer and an imaging system, comprising two fast (1-10 ls) CCD cameras triggered by the velocity signal of the particle in flight prior to its impact. This work is focused on alumina particles flattening onto stainless steel (304L) substrates preheated at different temperatures during different times.
Keywords
alumina, atmospheric plasma spray (APS), on-line particle behavior
1. Introduction The study of a drop impacting and flattening on a surface is the subject of many research teams, for example in the fields of the ink jet printers, painting guns, watering, fire suppression systems (Ref 1) and, among others, is the theme of this study: thermal spraying (see the two review papers (Ref 2, 3). In thermal spray, particles in a molten or semi molten state with velocities and temperatures determined by the spray process used, flatten and solidify onto a substrate or onto previously deposited layers, thus building the coating. Besides particle parameters at impact, the substrate surface physical and chemical characteristics as well as its temperature also influence the deposit characteristics (Ref 2-4). Coatings have a lamellar structure with more or less poor inter-lamellar contacts, cracks, and pores. Among the different qualities of a coating, its good adhesion,
This article is an invited paper selected from presentations at the 2011 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray 2011: Proceedings of the International Thermal Spray Conference, Hamburg, Germany, September 27-29, 2011, Basil R. Marple, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Andre´ McDonald, Ed., ASM International, Materials Park, OH, 2011. S. Goutier, M. Vardelle, and P. Fauchais, SPCTS Laboratory, University of Limoges, 12 rue Atlantis, 87068 Limoges, France. Contact e-mail: [email protected].
522—Volume 21(3-4) June 2012
closely linked to the first layer of splats, is important. The
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