Features of electrode erosion in high current high pressure arcs
In the report, erosion data of electrode made from steel, tungsten and copper are considered for high current arcs with current amplitude of 10 kA - 1.5 MA, discharge duration of 50-500 μs at the initial gas pressure of 1 kPa - 40 MPa. The specific erosion value achieves above 10 <sup>-2 </sup>g/C in such discharges. There are two cases of erosion: vaporization and ablation in liquid phase. Wide ranges of discharge current and discharge duration provide the heat flux to the electrode from ~ 10 <sup>4</sup> to ~ 10 <sup>9 </sup>W/cm <sup>2</sup>. Thus, it allows us to study the phenomenon of erosion associated with heat fluxes of specified values. Heat flux more than 10 <sup>6 </sup>W/cm <sup>2</sup> exposed to the electrode within about 50 microseconds exceeds the critical value corresponding to intense electrode evaporation, and it is an intense erosion jet formation condition. Erosion by symmetrical material ejections from the whole electrode butt-end surface was detected. The ejection exists in the limited range of the current and the current density and was registered in the range of a current amplitudes 100-200 kA. The bottom border is caused by occurrence of a pinch-effect, the top border is connected with a prevailing influence of vapor phase erosion. Transition from the erosion in a liquid phase to the vapors corresponds to sharp growth of the electrode voltage falls.