Page 47 - May

NEW TECHNOLOGY

Table 2 shows certain types of products and tools, as well as surface properties after
plasma nitriding. A promising direction further increase the wear resistance of parts processed
with using plasma nitriding, is the subsequent deposition of thin-film tribological coatings using
PVD and CVD processes. At present, technologies and equipment have been developed for non-
vacuum local chemical-thermal treatment of various products using saturated plasma jets and
plasma arcs, for example, local plasma nitriding (Fig. 5), local plasma carburizing (Fig. 6).

a b
Fig. 5. The process of non-vacuum local plasma
nitriding of the ESP guide vane.
Arc discharge
It is important to note that most of the known plasma technologies
are based on the use of an arc discharge (electric arc) as an energy
source for conducting technological processes.
Arc discharges are called discharges at a current density of
102 - 103 A / mm2 and a relatively low cathode potential drop of
the order of the ionization and excitation potentials of the atoms
of the gaseous medium or the evaporated metal. The small value
of the cathodic potential drop is the result of the action of other
c mechanisms of cathodic electron emission than in a glow discharge.
They create a current density that allows
Fig. 4. Plasma nitriding unit, working chamber diameter 350 mm, the full discharge current to flow. Arc
height 500 mm, power consumption 3 kW (a), type of products in a cathodes emit electrons as a result of
glow discharge in the process plasma nitriding (b).
thermionic, autoelectronic and thermionic

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