Pyrometry applications in thermal plasma processing

A set of pyrometers was developed and applied for surface temperature monitoring in thermal plasma processing: a 1-spot monochromatic, a I-spot multiwavelength and a hi-dimensional monochromatic system. Measurements of solid- and liquid-phase temperature were carried out for plasma-are waste treatment and welding. The following characteristics are analysed versus process parameters: temperature field, transient periods and steady-state temperature values. Influence of the plasma-are on temperature measurements is discussed and identified for transferred-are processes. The dynamics of the surface temperature along a straight-line crossing plasma heat affected zone and a full temperature image were recorded with the help of the bi-dimensional pyrometer. The dynamics of the temperature gradients is analysed on the basis of a heat transfer model, For plasma spraying, effect of particle injection (powder feeding rate) and plasma parameters variation (voltage and argon flow) on radiative intensity radial distribution is analysed in view of process control. (C) 2000 Elsevier Science Ltd. All rights reserved.