Abstract

The cascade plasma torches should gradually replace the standard F4 type torches consisting of two electrodes without neutrodes. For industry; the advantages are a better lifespan of these electrodes but also a less expensive use of the process in terms of the type of gas to be used and of the power to be provided to the plasma; as well as a possible flowrate of injected powder increased. However; the configuration of a cascade torch is still poorly studied and notably the influence of the length of the body of the anode segmented by neutrodes. This work consists in studying the effect of the anode-cathode distance on the voltage fluctuations. The jet stability is clearly demonstrated with the cascaded torch. Indeed; the neutrodes can provide a longer and more stable jet compared to F4 plasma jet. That means that the length of the arc is much higher with the cascaded torch. The in-flight characteristics of alumina particles for different cascading lengths and operating parameters are studied. Particle velocities and temperatures are measured using diagnostic tools. Some alumina coatings are manufactured in order to address a correlation between the different configurations and the microstructure of the coating obtained. Good performances are obtained with microhardness of 1075HV0.3 for a porosity of 4.6 %but with a pure Ar plasma and a 350 A low amperage.

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