Effect of Cathode Microstructure on Arc Velocity and Erosion Rate of Cold-Sprayed Copper Cathodes in a Magnetically Rotated Atmospheric Pressure Arc

Abstract

Atmospheric pressure arc velocity and erosion measurements were performed on cold-sprayed cathodes in a continuously running arc system. Ultrahigh purity (99.99% pure) argon was used as plasma forming gas. An external magnetic field of 0.10 T was used to rotate the arc, which was operated at a constant power of 6 kW (40 V). Cathodes having microstructures with mean grain sizes, ranging from 1.12 to 3.06 lm, were produced using cold spraying (CS) and annealing methods. CS cathodes were tested in their as-sprayed state and annealed state. Annealed CS coatings with near equi-axed grains of 2.29 lm average size gave 60% higher steady-state arc velocities and up to 50% lower erosion rates than massive copper cathodes having 20-23 lm average grain size. An effect of cathode microstructure on arc velocity and on arc erosion rates was observed.