Page 49 - May

NEW TECHNOLOGY

● a source of charged particles that enhance the passage of plasma-chemical reactions (process
of final plasma hardening).
Plasma torches for these purposes are shown in Fig. 7. The process of plasma deposition-
spraying (PTA-process) provides the use of a pilot (indirect) arc for melting the injected powder
and the main arc (transportable) to maintain the required temperature of the substrate and the
deposited powder particles. At the same time, an increase in the residence time of the powder
particles at high temperatures promotes maximum adhesion and compaction of the particles
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 product, 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, the automation of maintaining and regulating the modes of the technological process
is provided (Fig. 8).

a b c d
Fig. 7. Schemes of plasmatrons for welding (a), surfacing (a, b), spraying (c, d), final plasma hardening (d), microplasma
treatment (c - without P and TG); gases: PG - plasma-forming, ZG - protective, TG - transporting, DG - additional; PP - filler
wire; P - powder or hardening reagents.

Fig. 8. Complex of the main equipment (block of equipment, plasmatron, powder dispenser) for plasma deposition-spraying
and the process of coating the screw.

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