Optimisation expérimentale de la sphéroïdisation des poudres métalliques et céramiques par plasma inductif

Abstract

An experimental study of the spheroidization efficiency of powders in an induction plasma process was completed. The main objective being to develop a model which could be subsequently used for the prediction of the spheroidization efficiency for various powders under a wide range of plasma operating conditions. Throughout the study, optical microscopy, scanning electron microscopy, sedigraphy and X-ray diffraction were used to analyse the original and plasma treated powders. Silica, alumina, chromium oxide, zirconia and tungsten carbide powders were the subject of systematic experimentation using two different plasma installations. One of the installation had a maximum available power of 100 kW with an operating frequency of 0.3 MHz while the other had a maximum available power of 50 kW with an operating frequency of 3 MHz. Operating conditions were varied such to minimize reactions and evaporation of powders. The presence of internal cavities was observed in the treated particles along with a slight change in the mean particle diameter of the powders. The proposed model successfully predicts the spheroidization efficiency of the particles beyond a defined critical point known as the maximum energy efficiency point. The model parameters are shown to depend on the thermodynamic properties of the powders and on the induction plasma operating parameters.