최근, 플라즈마 용사용 토치의 용사공정 신뢰도를 높이기 위한 방안으로 아크 전압의 미시적 요동을 제어하려는 시도가 이루어지고 있다. 아크 전압의 요동은 플라즈마 유 체의 항력과 로렌쯔 힘의 균형점을 찾아 성장하는 아크 기둥과 양극 아크점이 변화하 여 발생하는 것으로 알려져 있다[1].
Normally, a non-transferred plasma torch has intrinsic fluctuations in arc voltages due to the arc shunting phenomena, which result from the anodic arc root movement along the axis. Such fluctuations can make the plasma jet unstable, which may be responsible for the poor reliability and reproducibility in a process using a conventional non-transferred plasma torch. These fluctuations of the arc voltage can be controlled by limiting the anodic arc root movement along the axis. For this purpose, a slotted nozzle is adopted in this work. By locating a slot inside the cylindrical nozzle, the region for arc root movement can be limited while turbulent mixing effect can be enhanced inside the nozzle. In order to find these effects of the slot, arc voltage fluctuations were measured for a plasma torch with a slotted nozzle in this work. Then, the measured results were compared with the ones from the conventional cylindrical nozzle.
