It turned out that it was impossible to use ingenious development of Wenelt in cathodes of welding electric arc, because for stable work of the welding arc it is necessary that mean density of current on the surface of a non-consumable cathode of welding arc, in addition to the current density in the cathode spot, exceeded mentioned density in the tubes at least by three orders .
According to the data of , temperature of electric arc cathode spot on zirconium dioxide achieves 4000 K.
When inspecting non-etched film at high magnification of the cathode spot, one can see on screen of a scanning microscope granular structure with streaks of eutectics (Figure 5, a).
At the very first ignition of the arc active insert is subjected to the process of sintering under action of heat flow, which enters into the active insert from the cathode spot.
The generation of high power is determined by the bombardment of the zone of the cathode spot with the ions of the sputtered material.
It is well known that the method of microarc evaporation with ion bombardment is based on the initiation of a microarc discharge in vacuum on the cathode surface and the subsequent formation of cathode spots having exceptionally high density and temperature [5-7].
Thus, for commanded pulses and positive polarity, the temperature on cathode spot