Spectroscopic Diagnostics of the Electric Erosion of Electrodes from the High-Entropy CrMnFeCoNi Alloy in Spark Discharge in Air. Modeling and Experiment

The spark plasma parameters with electrodes produced from the high-entropy CrMnFeCoNi alloy were studied by mathematical modeling 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. The concentrations of electrons, atoms, and ions of electrode components and molecular components of plasma were determined from conditions of local thermodynamic equilibrium at the discharge axis (quasi-equilibrium conditions), and temperature was calculated from the energy balance equations. The system of nonlinear equations is solved in iterative cycles until self-consistent values of concentrations and temperatures are received. Elements with a 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 associated energy losses. Increase in the evaporation rate leads to temperature decrease, but electron concentration reduces by less than 20%, other parameters being equal. This effect results from decrease in the effective ionization potential with higher metal vapor concentration in the discharge plasma. There are complex nonlinear relations between the erosion rate and the intensity of spectral lines of atoms and singly charged and doubly charged ions, which are associated with the dependence of plasma temperature at the discharge axis on the evaporation rate. The calculated temperature and electron concentrations agree with the experiment within the error, taking into account the simplifications accepted in the model. The developed method can be used for spectroscopic diagnostics of electric erosion of the high-entropy CrMnFeCoNi alloy in the production of nanopowders by electrospark method and for emission spectral analysis of its composition.