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Progress in Plasma Processing of Materials, 2001

ISBN:
1-56700-165-3 (Print)

MONITORING THE IMPACT OF LIQUID ALUMINA PARTICLES UNDER PLASMA CONDITIONS USING AN IMAGING TECHNIQUE

C. Escure
SPCTS UMR-CNRS 6638, 123 Avenue A. Thomas 87060 Limoges cedex

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

Abstract

Our work aims to study in an experimental way, including imaging, the impact of alumina droplets plasma sprayed onto dry surfaces. This study is achieved by using a complex experimental set-up including :
• A controlled atmosphere chamber allowing to study different types of substrate materials. In this chamber is set a plasma torch devoted to the alumina liquid droplets generation.
• An in-flight droplet characterization device including a PDA (droplet velocity and size measurement) and a fast (100ns) two-color pyrometer. A monochromatic pyrometer is also used in order to check the substrate surface temperature.
• An imaging device is used to observe the droplet impact. It includes a fast numerical camera equipped with a long distance microscope.
The first results obtained with all;lmina particles are in agreement with the Sommerfeld rules that predict the droplet behavior (rebound, deposition, splashing) : splashing occurs for high values of the Sommerfeld parameter K, deposition of the droplet occurs for low values of K. Yet, unexpected phenomena such as splashing at low K are also observed and explained by the important surface roughness and the low surface temperature.