Spectroscopic diagnostics of electric erosion of electrodes from THE high-entropy CrMnFeCoNi alloy in a spark discharge in air. Modeling AND experimenT

Abstract

The parameters of spark plasma with electrodes produced from the high–entropy CrMnFeCoNi alloy were studied by mathematical modeling methods and experimentally. The model describes the dependence of the spark discharge plasma composition and the intensity of spectral lines on the electrode erosion rate and discharge power.  Concentrations of electrons, atoms, and ions of electrode components, as well as molecular components of plasma, were found under the conditions that there was local thermodynamic equilibrium at the discharge axis (quasi–equilibrium conditions), and temperature from the energy balance equations. The system of nonlinear equations is solved in iterative cycles to obtain self-consistent values  of concentrations and temperatures. Elements with high second ionization potential in electrode materials (for instance, Al, Cu, Ag, B) essentially increase temperature at the discharge axis resulting from reduction in the cross-section of inelastic processes and consequently  energy losses in such processes. Increase in the evaporation rate results in temperature decrease, but electron concentration decreases  by less than 20%, other parameters being equal. This effect results from decrease in the effective ionization potential with higher metal  vapor content in the discharge plasma. There are complex nonlinear relations between the erosion rate and the intensity of the spectral  lines of atoms and single-charged and double-charged ions, which are associated with the dependence of the plasma temperature at the  discharge axis on the evaporation rate. The results of temperature and electron concentration calculations agree with the experiment  within the experimental error, taking into account the simplifications accepted in the model. The developed method can be used for  spectroscopic diagnosis of electric erosion of the high-entropy CrMnFeCoNi alloy in the production of nanopowders  by electrospark method and emission spectral analysis of its composition.