In-flight diagnostics of thermal treatment of powders in induction plasmas

In-flight measurements of the principal particle parameters of size, velocity, and temperature are made for nickel powders with a mean diameter of 76 mu m, processed in a 3-MHz inductively coupled RF plasma torch. The diagnostic technique is based on the real-time observation of a particle through its own emission of Planck radiation. Measurements were carried out in the plasma plume, 340-mm downstream from the point of injection of the powder for plasma powers of 10 and 20 kW and pressures of 170 and 340 torr. The mean velocity and the surface temperature increased from 44 to 60 m/s and from 2400 to 2500 K, respectively, with the increase of the plasma power from 10 to 20 kW at 170 torr. The particle velocity decreased from 44 to 27 m/s and the surface temperature increased from 2400 to 2500 K with the increase in pressure from 170 to 340 torr at 10 kW. Cross-correlation analysis showed that the particle undergoing plasma processing has a higher surface temperature when its size is small and its velocity is low.<>