RAPID SOLIDIFICATION OF STEEL DROPLETS IN THE PLASMA-ROTATING-ELECTRODE-PROCESS

The Plasma-Rotating-Electrode-Process (PREP) is based on the pulveriza tion by rotation of metal bars in contact with a Ar/N-2 plasma are. Du e to the high centrifugal forces of the rapidly rotating bars, high ni trogen steel powders are produced with diameters in the range of 0.02 to 0.5 mm. The low diameters and the high centrifugal forces, as well as the high particle velocities, cause the steel droplets to cool down rapidly in the reactor chamber. Mathematical calculations show that c ooling rates of up to 10(5) K/s are attained. It is demonstrated that the cooling rate of all powder particles and the structures produced c an be predicted.