Time-resolved imaging of anodic arc root behavior during fluctuations of adc plasma spraying torch

The fluctuating behavior of a Sulzer Metco F4 de plasma gun has been invest igated by simultaneous measurement of the:time dependencies of the are volt age and of images from the nozzle interior. An end-on imaging arrangement u sing a mirror and a mask in the optical path from the are to the camera all ows visualization of the anodic are attachment by strongly attenuating the bright emission from the are column, With the torch operating in the restri ke mode, sequences of images have been acquired in synchronization with sev eral typical features of the are voltage fluctuations showing that the atta chment nature changes during a restrike cycle, Multiple attachments which c oexist at least during the 1 mus exposure time of the camera have been evid enced and are interpreted as a continuous process of creation/vanishing of successive are roots with a smooth transfer of the current from one to the other, The anode wear is shown to have a strong effect on the root position over the anode periphery, with a preference for attachment in eroded regio ns. The effects of operation parameters such as current, gas flow and injec tor type on the attachment nature and position are also presented.