Formation of highly concentrated heterogeneous flows during plasma deposition of powder materials

Abstract

Most industrial installations for plasma spraying of powder materials are equipped by nozzles with local (radial) powder input into the thermal plasma jet generated by the plasma torch. Such a local input of the sprayed material significantly perturbs the flow of the plasma jet, and causes dispersion of temperature and velocity of the particles of the sprayed powder materials. This work presents study of high-temperature heterogeneous flows generated by the electric arc plasma torch PNK - 50 with an annular (circular) input unit of powder materials with their gas-dynamic focusing developed at ITAM SB RAS. The performed experiments proved that the annular injection of a powder material guarantees the stable formation of a highly concentrated flow of thermal plasma with particles of sprayed powder materials. The comparative analysis clearly showed the advantages of annular powder input unit with its gas-dynamic focusing. In contrast to local point injection, axisymmetric annular injection practically does not disturb the jet of thermal plasma and, thus, significantly increases the efficiency of interphase exchange.