Plasma Arc Melting - Facilities

Plasma-Arc Installation for single crystal growth of the refractory compounds

The installation allows to grow (through the Plasma Arc Melting by the modified Verneuil method) large single crystals (refractory compounds of the transition metals of groups IV-VI with carbon and boron) and molded polycrystalline ingots of the refractory compounds. The raw material for Melting can be used in form of long-sized rods or powder. These raw materials can be produced by SHS or furnace synthesis. The installation is characterized by
- universality of the raw material used (rods or powder);
- process automation;
- specially developed systems for stabilization of the growth process.
The installation allows growing single crystals of the refractory metals (tungsten, molybdenum etc.)
A low-temperature plasma generator provides substance heating by the direct and indirect electric arc. The plasma generator design allows melting of the raw material in either rod or powder form. The current source of installation has the following parameters: the primary power - 50 kWt; the performane voltage - 46 V; efficiency - at least 80 %; the range of smooth current adjusting - 20-600 A.
The growth process is enlarging of a small seed (mono- or polycrystalline, 3-4 mm in diameter) into a large crystal (at least 10 mm in diameter and at least 100-150 mm in length). The speed of the ingot growth is 0.1-5 mm/min. The rate of the plasma gas (Ar) flow is 0.05-0.5 g/s. During growth process the following impacts are available:
- magnetic plasma arc stabilization;
- magnetic control over the plasma flow shape;
- spatial stabilization of the melt pool;
- melt temperature stabilization.

Device for producing long-sized uniform compacts

Device allows producing highly uniform compacts from the powder and powder mixtures pressed into long-sized shells. The method of subsequent portion-by-portion pressing is realized.
The relative density of the compacts is 0.35-0.7 of the theoretical mixture density (with deviation at most 1-2 % along the compact long axis). The high density (up to 0.6-0.7 of the theoretical density) is achieved by applying a very small specific pressing energy per single portion (<<1 Joule). The rate of the mixture pressing into the shell is 0.05-0.5 mm/s. The ratio of the compact length to its diameter is at least 10-50.
A device is designed for producing highly uniform compacts from the green mixture. The compacts are used for SHS to produce long-sized refractory samples. The typical compact sizes (for SHS application) are 3-25 mm in diameter and 100-250 mm in length.