Page 37 - ST Sept

INNOVATIVE TECHNOLOGY INNOVATIVE TECHNOLOGY

with minimal overheating of the surface of the part. Optimization of the main characteristics of
the process (currents of the main and pilot arcs, distance to the work piece, powder feed rate
and plasma torch movement speed) revealed the minimum sensitivity to the powder feed rate
and, within certain limits, to the plasma torch movement speed. In modern equipment for the
PTA process, automation of maintaining and regulating the modes of the technological process
is provided (Fig. 8).
The microplasma spraying process
is a precision technology that requires the
application of functional coatings to local
areas. Realizable properties of coatings:
wear resistance, antifriction, heat resistance,
heat resistance, erosion resistance, fretting
resistance, cavitation resistance, corrosion
resistance, dielectricity, absorption and
reflection of radiation, etc.
For example, this process is used to Fig. 9. Complex of the main equipment for microplasma
improve the quality, reliability and durability spraying (block equipment, plasmatron, powder dispenser) and
the type of plasma jet during spraying.
of dentures and fixed crowns in dentistry.
At the same time, coatings are applied to
Fig. 5. The process of non-vacuum local plasma nitriding Fig. 6. The process of non-vacuum local plasma carburizing of stamped and cast prostheses, which increase with a power source and a cooling system, a
of the ESP guide vane the gear. the roughness parameters and, accordingly, microplasmatron with a set of hand pieces, a
remote control pedal.
The arc discharge and the atmospheric
In contrast to an arc discharge, at normal (atmospheric) pressure, an arc discharge in plasma jet formed by it are used in the technology
a vacuum occurs in metal vapors, while the discharge is localized in small areas of micron of tubeless chemical deposition of thin-film
dimensions and chaotically moving along the cathode surface. The power density in such areas, diamond-like coatings at atmospheric pressure
called cathode spots, reaches 109 W / cm2. Due to this, within 5 - 40 ns (the rest time of the using volatile liquid organoelement compounds
cathode spot during its chaotic movement), the metal vapor pressure reaches ~ 105 Pa, and and gaseous media with simultaneous
the degree of metal vapor ionization can be close to 100 %. activation of the surface by an electric arc
The electron temperature of the arc discharge plasma in vacuum has a value of 5 - 20 eV. plasma. In this case, the complex use of the
Consider the main technologies using an atmospheric pressure arc discharge, as the most arc discharge as a source of thermal energy
widely used as: for heating and decomposition of introduced
● a source of thermal energy capable of melting the substrate material and additional chemical compounds, a source of charged
filler material (plasma deposition-spraying process, PTA-process);
● a source of thermal energy particles for the effective passage of plasma-
only for heating and accelerating the Fig. 10. Installation for microplasma treatment. chemical reactions in a plasma-chemical reactor
filler powder material (the process of and their simultaneous effect on the substrate
plasma and microplasma spraying); the contact surface area with the subsequent (plasma activation) is provided. The novelty of
● a source of charged particles facing material - plastic, light-cured composite this process lies in the absence of the use of
for various processing of materials (the materials or ceramics (porcelain, sitall). At closed chambers, low heating temperatures of
process of microplasma processing of the same time, the adhesion of the facing products in the process of deposition of coatings
biological objects); materials to the base increases 3 - 5 times and the use of flexibly controlled electric arc
plasma. Due to the fact that the deposition of
a b c d ● a source of charged particles compared to traditional abrasive blasting, coatings on products occurs at the final stage
that enhance the passage of plasma- increased resistance to breaking loads.
Fig. 7. Schemes of plasma torches for welding (a), surfacing (a, b), chemical reactions (the process of final Titanium or metals and alloys similar of their manufacture or immediately before
spraying (c, d), final plasma hardening (d), microplasma treatment (c their use, this process is called final plasma
- without P and TG); gases: PG - plasma-forming, ZG - protective, TG plasma hardening). in chemical composition to the base material hardening (FPH). The main advantages of FPH
- transporting, DG - additional; PP - filler wire; P - powder or hardening Plasma torches for these purposes are are used as powder materials for microplasma
reagents shown in Fig. 7. spraying. The thickness of these coatings is are: implementation of the process without
The plasma deposition-spraying 50-100 microns. vacuum and chambers; minimum heating of
(PTA-process) process provides the In order to ensure localization of the products, not exceeding 2000 ˚С; the ability to
use of a pilot (indirect) arc to melt arc discharge plasma, a plasmatron for apply coatings locally, in hard-to-reach areas
the injected powder and the main arc microplasma treatment and equipment for its and on products of any size; use of small-sized,
(transferred) to maintain the required operation were developed (Fig. 10, Table 3). mobile and cost-effective equipment (Fig. 11).
temperature of the substrate and Its purpose is plasma activation, purification, The basic principle of applying thin-
deposited powder particles. At the bacteriostatic and bactericidal treatment, film wear-resistant coatings based on the FPH
same time, an increase in the residence dissection of biological tissues, coagulation of technology is the decomposition of vapors of
Fig. 8. A set of main equipment (a block of equipment, a plasmatron, time of the powder particles at a high blood vessels, therapeutic and non-traditional liquid organoelement preparations, which are
a powder dispenser) for plasma surfacing-spraying and the process of temperature contributes to maximum methods of treatment. The composition of the introduced into the plasma-chemical reactor of
coating a screw. adhesion and compaction of particles installation - a block of equipment combined the arc plasmatron, followed by plasma-chemical

36 Stanochniy park Stanochniy park 37