Pyrometry applications in thermal plasma processing

A set of pyrometers was developed and applied for surface temperature monit oring in thermal plasma processing: a 1-spot monochromatic, a I-spot multiw avelength and a hi-dimensional monochromatic system. Measurements of solid- and liquid-phase temperature were carried out for plasma-are waste treatme nt and welding. The following characteristics are analysed versus process p arameters: temperature field, transient periods and steady-state temperatur e values. Influence of the plasma-are on temperature measurements is discus sed and identified for transferred-are processes. The dynamics of the surfa ce 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 ba sis of a heat transfer model, For plasma spraying, effect of particle injec tion (powder feeding rate) and plasma parameters variation (voltage and arg on flow) on radiative intensity radial distribution is analysed in view of process control. (C) 2000 Elsevier Science Ltd. All rights reserved.