Why Tungsten Carbide Electrodes Unexpectedly Eject Particles at High Speed
Researchers discovered that tungsten carbide cathodes in industrial arc discharge systems generate and violently accelerate millimeter-sized particles through a carbon sublimation mechanism—not thermal melting as previously assumed. The finding could improve reliability and efficiency of arc discharge systems used in coating, welding, and materials processing.
Originaltitel: Macroparticle generation in DC arc discharge from a WC cathode
<p>We have studied macroparticle generation from a tungsten carbide cathode used in a dc vacuum arc discharge. Despite a relatively high decomposition/ melting point (similar to 3100 K), there is an intensive generation of visible particles with sizes in the range 20-35 mu m. Visual observations during the discharge and scanning electron microscopy of the cathode surface and of collected macroparticles indicate a new mechanism for particle formation and acceleration. Based on the W-C phase diagram, there is an intensive sublimation of carbon from the melt resulting from the cathode spot. The sublimation supports the formation of a sphere, which is accelerated upon an explosion initiated by Joule heating at the critical contact area between the sphere and the cathode body. The explosive nature of the particle acceleration is confirmed by surface features resembling the remains of a splash on the droplet surface. Published by AIP Publishing.</p>