ON LINE CONTROL OF A FLAME SPRAY PROCESS
SPCTS UMR-CNRS 6638, 123 Avenue A. Thomas - 87060 Limoges Cedex - France
Laboratory Sciences of Ceramic and Surface Treatment Processes (SPCTS UMR-CNRS 6638) - 123, avenue Albert Thomas 87060 Limoges Cedex - France; Thermadyne Inc. 82 Benning Street, West Lebanon, NH 03784, USA
SPCTS, University of Limoges, 123, Av Albert Thomas, 87060 Limoges, France
LMCTS-URA 320, University of Limoges, 123 Avenue Albert Thomas -87060 Limoges Cedex - France
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France
Flame sprayed coatings present very often reproducibility problems due to spray parameter variations. In fact the quality of coatings is strongly linked to the temperature and velocity of particles at impact and on the substrate, and coating temperature evolution before (preheating), during (spraying) and after (cooling).
The particle temperature and velocity measurements require sophisticated devices rather expensive and not well adapted to work in the harsh environment of spray booths. Moreover with flames the particle surface temperature is generally below 2200K which make the measurements more tricky than under plasma conditions. That is why, a new system, the Spray and Deposit Control (SDC) has been developed which allows to follow continuously both the light emitted by hot particles (maximum intensity, mean trajectory and trajectory dispersion) and the substrate and coating temperature evolution during spraying. This light system (800gr), fixed on the torch has been tested for flame spraying of NiAl. This paper presents the evolutions of SDC parameters with process and coating parameters, a strategy for an on-line control, and a zone of "correct values" and acceptable variations for the process inputs.