There are various types and designs of DC plasma torches. The most common is the so-called "spraying" torch (P≤100 kW, most widely used in the thermal spraying industry). A DC plasma torch contains three essential elements: a cathode, an anode, and a gas injection chamber. During operation, an initial discharge induces an arc column between the tip of the anode and the cathode. Gas is then injected behind the anode and sucked into the arc column, heated, ionized, and then forms the plasma. A DC torch can generate a plasma jet of very high temperature and enthalpy. It is thus a very convenient heat source to heat a precursor material. On the other hand, a high-velocity plasma jet provides residence times for the feed powders (in the case of precursor solids) that may be too short (≤1 ms) to allow for thorough treatment. Moreover, the most convenient gases used for DC torch operations are limited to argon, helium, hydrogen and nitrogen. Other "chemically active" gases tend to damage the torch electrodes unless special designs and materials are selected. Some types of chemically active "corrosive" precursors are also prohibited for the same reasons. These restraints limit the versatility of DC plasma processing.

Tekna's AS 300 DC plasma spraying torch