From DC Time-Dependent Thermal Plasma Generation to Suspension Plasma-Spraying Interactions
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Erick Meillot, S. Vincent, C. Caruyer, J.P. Caltagirone, and D. Damiani (Submitted January 30, 2009; in revised form May 4, 2009) This paper proposes an original route for modeling the time-dependent behavior of a plasma jet issued from a DC plasma-spraying torch operating with various kinds of gas mixtures. The hydrodynamic interactions between this jet and a liquid jet for suspension plasma-spraying or a classical particle injection for the deposition of coatings are studied. In a first step, the classical plasma spraying process was explored using the FLUENT CFD code. Zirconia particles, defined as Lagrangian particles, were injected in an Ar/H2 flow and their positions, kinetic and thermal states were compared with experimental results. The trend and intensity of the values demonstrated a rather good agreement. In a second step, the suspension plasma spraying was investigated with the AQUILON CFD to simulate interactions between the plasma and aqueous jets. An Ar/H2 plasma flow was simulated with the Large Eddy Scale turbulence model assumption, in which a liquid jet had been introduced. The behavior observed during the first stage of the interactions between the two fluids corresponded to expectations.
Keywords
3D simulation, modeling, plasma jet, suspension, thermal plasma spraying, transient
1. Introduction Nanomaterials are being employed in more and more fields due to their specific properties. For industrial applications requiring significant efficiency rates, thermal spraying can be one way to deposit coatings of varying width. Several surface treatment techniques can be employed, among which atmospheric plasma spraying (APS) involves a plasma gun as a thermal source transferring the electrical energy to input gas by Joule effect. This results in a high temperature and high velocity gas flow in which powder particles or suspensions are introduced. During the interaction with the gas jet, and after the evaporation of the media, the particles are subsequently fused and accelerated toward the material to be coated, thereby contributing to building up the coating by a piling of lamellae. For thick coatings, classical plasma or flame spraying processes can be used, whereas for thinner coatings, nanopowders are prepared in suspension and injected in a thermal source constituted of, for instance, a plasma jet or a flame. Due to the plasma jet being relatively difficult to analyze (high temperature, high radiation) and because of the
Erick Meillot, C. Caruyer, and D. Damiani, CEA-DAM, Le RIPAULT, F-37 260 Monts, France; and S. Vincent and J.P. Caltagirone, E.N.S.C.P.B., TREFLE Laboratory, F-33 607 Pessac, France. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
complex behavior of the process (the main parameters all being connected), simulation has a high potential as a numerical experimentation tool for obtaining an improved understanding of the interaction mechanisms. The present paper investigates the possibility of simulating classical and suspension plasma spraying processes, a
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