Growth of single crystals of high melting metal alloys and compounds by plasma heating

A plasma method is developed to produce single-crystals of high-melting metals, compounds, and multiphase alloys with directional structure. The growth of single-crystals of high-melting metals by means of low-temperature plasma heating results in more thorough refining due to high temperatures and plasma-chemical reactions. Several technical problems such as the production of large crystals (up to 5 mm in diameter), alloying by components of the plasma-generating gas, and simplification of the installation and servicing are solved simultaneously. The method developed provides for the growth of large single-crystals of tungsten, molybdenum, rhenium, niobium and some high-melting carbides including carbides of tantalum and hafnium whose melting points are higher than 4000°C. Eutectic alloys of the tungsten-carbon system with a directional structure are formed. The influence of some parameters of the process on the perfection of single-crystal structure and the extension of the regions having a directional eutectic structure is considered. The preferred orientation of single-crystalline filaments of tungsten and tungsten carbide and the conjunction of their crystal lattices along the planes of small indices are found to take place in tungsten-carbon alloy.