Two common concerns in dc plasma torches are stability of plasma jet and anode erosion. The challenge is how to get a stable plasma jet with minimal anode erosion. This study tackles this question by using an external axial magnetic field applied to a cascaded plasma torch. A 3D, time-dependent model of the torch is used to predict the value of the magnetic field and its effect on heat flux to the anode as well as plasma jet stability. The model couples the gas phase and electrodes, making it possible to follow anode temperature evolution. For specific operating conditions, the model predicts an azimuthal self-magnetic field induced by electric arcing and the subsequent effect of an external field on arc attachment and anode wall temperature. This approach is expected to provide a better understanding of arc behavior in dc plasma torches and facilitate the control of anode erosion.

The purpose of this work is to study the effect of laser radiation on powder particles transported by gas during laser cladding. The temperature and velocity of particles entering the light field of a CO 2 laser were determined by measuring particle radiation as well as the scattered radiation of the diode laser, two independent methods. It is shown that under the action of laser radiation, the particles acquire additional acceleration due to the vapor pressure from the irradiated part of the particle surface. This sonic recoil vapor pressure can significantly affect the in-flight characteristics of powder particles in a gas jet. Particle velocities due to laser acceleration exceeded 100 m/s in a carrier gas with a flow rate less than 30 m/s. Particle temperature depends on several factors and was found to vary from ambient temperature to the boiling point of the powder.