Page 45 - May

NEW TECHNOLOGY

Glow discharge
Glow discharge is an independent electric discharge in a gas with cold electrodes at currents
of 10-5 - 1.0 A and low pressure (5 • 10-2-103 Pa), which has a characteristic structure in the
form of alternating luminous areas of different colors and different intensity of luminescence.
Its distinctive feature is the existence of a layer near the cathode with a large positive space
charge, a strong field at the surface and a significant drop in potential of 100 - 400 V and
more. The glow discharge got its name from the presence of the so-called glow on one of the
electrodes (cathode).
One of the applications of the glow discharge is the technology of plasma chemical-
thermal treatment of metals, which are designed to increase the hardness, wear resistance,
fatigue strength, scuff resistance, heat resistance and corrosion resistance due to saturation
of the surface of the processed products with nitrogen, carbon, boron, cadmium and several
elements at the same time. During processing, the products are immersed in the plasma
of a glow discharge that burns between the cathode (products) and the anode (walls of the
vacuum chamber) and contains the necessary saturating element. Positively charged ions of
the saturating element under the action of an electric field are accelerated towards the product,
bombarded and penetrated into their surface layer. In this case, the energy of ions is thousands
of times higher than the energy of atoms during gas chemical-thermal treatment. The heating
temperature of products during processing is 300 - 600 °C.
The most demanded process in the
world is the process of plasma nitriding
Cooled vacuum (nitriding in a glow discharge, ion-plasma
chamber nitriding, Fig. 3, 4). Ammonia, argon,
Argon Т propane, natural gas, etc. are used as
Ammonia working gases. Regulation and control
Propane Р Control block of the technological process is fully
Air
automated and is carried out according
to a given technological program. An
U.I observation window is mounted in
Plasma source the water-cooled chamber for visual
observation of the process.
The distinctive characteristics
Pump
(res. up to of this process in comparison with gas
-, 2 mbar) Glow Anode chemical thermal treatment are:
discharge ● reduction of the processing time by 2
Cathode
- 5 times due to the higher saturation
Fig. 3. Plasma nitriding scheme
rate;
● efficiency of the process by reducing
the consumption of working gases by 20
- 100 times;

Stanochniy park 45