Influence of Anode Nozzle and External Torch Contour on the Quality of the Atmospheric DC Plasma Spray Process

By means of Schlieren photography, enthalpy probe, mass spectrometry and the particle measuring system DPV 2000 the influence of the internal and external anode nozzle and torch geometry, on plasma jet quality for atmospheric plasma spraying was investigated. It turned out that there is a strong geometrical effect of the inner contour and that with a proper expansion of the hot core of the plasma jet a considerable improvement of the melting and deposition quality can be obtained. Also the outer torch contour is of influence on the spray process because it controls the formation and the intensity of turbulence and the interaction of the plasma jet with its surrounding and hence the cold gas entrainment.