Published online by Cambridge University Press: 25 February 2011
The visible and UV plasma emissions from a metal vapor arc were studied during vacuum arc remelting of 165 mm diameter Inconel 718 electrodes using emission spectroscopy. Internal energy distributions of a number of emitting species were analyzed using Boltzmann statistics. Analysis of the data yielded distribution “temperatures” ranging from 5,400 K to 8,200 K for the neutral atomic arc species, whereas values of 12,200 K to 17,500 K were obtained for singly ionized species. These values illustrate that the arc is not in a state of local thermodynamic equilibrium. The excited state densities of various arc constituents were measured and it was found that highly volatile alloy trace components, such as Mn, were present in the arc in dispro-portionately high concentrations. These data suggest that ionized evaporates play an important role in carrying current between the electrodes.
This work performed at Sandia National Laboratories supported by the U. S. Department of Energy under contract number DE-AC04-76DP00789.