Page 32 - ST Sept

INNOVATIVE TECHNOLOGY INNOVATIVE TECHNOLOGY

as a result of which the electrode consumable material is transferred and deposited onto Table 1. Characteristics of the installation for plasma-spark coating.
the surface of the product. This technology is called electrospark alloying (electrospark or
plasmaspark coating) [2]. In this case, a plus is supplied to the electrode (Fig. 1) from the Power consumption, kW 0,5
source of the pulse generator, and to the product - minus from the source. Mains supply voltage, V 220
The method of coating is based on the use of a spark discharge with a short duration of its Pulse energy, J 0,11 – 10
existence 10-6≤t and≤10-3 s and the passage of powerful pulse currents during the discharge
of a capacitor with a current density of up to 106 A / mm2. The plasma temperature in the Pulse frequency, Hz 5 – 1600
interelectrode gap can reach 7000 - 11000 ° C. As a result of the thermal and gas-dynamic Electrode vibration frequency, Hz 600
effect of the spark discharge, the erosion of the electrode (anode) material and the transfer Number of modes 70
of erosion products in the liquid, solid and vapor phases to the product (cathode) occur. In
this case, a composite material is formed on the surface of the product due to the course of Overall dimensions of the generator, mm 160х320х360
metallurgical processes, which includes the materials of the electrode and the product, the Generator weight, kg 14
products of their interaction with each other and with elements of the interelectrode medium. Maximum coating thickness of T15K6 alloy on 45 steel, microns 500

Height of irregularities in the profile of the coating Ra, μm 2,0

Height of irregularities in the profile of the coating Ra, μm 15

and connecting cables. Table 1 shows the technical characteristics of this unit
Glow discharge
Glow discharge is an independent electric discharge in 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 glow intensity. Its
distinguishing 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
a b c more. The glow discharge got its name due to the presence of the so-called glow on one of the
electrodes (cathode).

Fig. 2. Installation for plasma-spark coating (a), application wear-resistant coating made of VK8 alloy (b), applying an Cooled vacuum chamber
electrically conductive silver plating (c.
Argon
An important factor in the qualitative formation of the coating is the effect of cathode Ammonia Control blockr
cleaning, which ensures the destruction and removal of surface films from the treated surface of Propane
the product (cathode) due to the high density of the released energy in the microcathode spots Air
of the spark discharge.

The main areas of application of this technology are: Plasma source
● restoration and hardening of machine parts, tools, stamps;
● application of functional (wear-resistant, electrically conductive, decorative) coatings;
● reduction of the transition resistance of electrical contacts (tin plating, pretinning, nickel Pump
plating, silver plating). Hard alloys (T15K6, T17K12, VK6, VK8, VK20, etc.), materials based on (discharge up Glow discharge Anode
metal carbides and borides (TiC, WC, Mo2B5, CrB2, TaB2, etc.), graphite and etc. are used as to 0.2 mbar)
electrodes to strengthen the tool and technological equipment. Cathode

The main advantages of this technology are: Fig. 3. Scheme of plasma nitriding.
● the possibility of local formation of coatings in strictly specified places with a radius of
fractions of a millimeter or more, without protecting the rest of the surface; One of the applications of the glow discharge is the technology of plasma chemical-thermal
● application of coatings on large and massive parts with local zones for pretinning, tin treatment of metals, which are designed to increase the hardness, wear resistance, fatigue
plating, nickel plating, silver plating, etc.; strength, scuff resistance, heat resistance and corrosion resistance due to saturation of the
● high adhesion of the coating to the substrate; surface of the processed products with nitrogen, carbon, boron, cadmium and several elements
● lack of heating and deformation of the product during processing; at the same time. During processing, the products are immersed in a glow discharge plasma
● the possibility of using various conductive materials as electrodes, both from pure that burns between the cathode (products) and the anode (walls of the vacuum chamber) and
metals and their alloys, powder materials, etc. contains the necessary saturating element. The positively charged ions of the saturating element
● comparative simplicity of the technology, which does not require special preliminary under the action of the electric field are accelerated towards the product, bombarded and
surface treatment; penetrated into their surface layer. In this case, the energy of ions is thousands of times higher
● ease of maintenance and reliability of equipment, which is small-sized and transportable; than the energy of atoms during gas chemical-thermal treatment. The heating temperature of
● low energy consumption of manual and mechanized processes (0.5 - 2.0 kW); products during processing is 300 - 600 ° C.
● high coefficient of material transfer (60 – 80 %). The most demanded process in the world is the process of plasma nitriding (nitriding in a
Fig. 2 shows the installation and process of coating. The equipment for plasma-spark glow discharge, ion-plasma nitriding, Fig. 3, 4). Ammonia, argon, propane, natural gas, etc. are
coating consists of a block of equipment combined with a pulse generator, an electric vibrator used as working gases. Regulation and control of the technological process is fully automated

32 Stanochniy park Stanochniy park 33