BROŽEK Vlastimil Vysoká škola chemicko-technologická v Praze

Spoluautoři CTIBOR Pavel, MATĚJÍČEK Jiří, WEISS Zdeněk

Tungsten powders, 20 - 150 µm in size, were melted in the jet of thermal plasma generated by a water-stabilized spray system WSP®. The molten tungsten was deposited on steel and graphite substrates, whereas the spray-ability itself was tested as well as cohesion with other substrates like metals Cu, Ti, Zr or ceramics Al2O3, SiC and BN. One of the goals of this experimentation was to gain skills for covering of variously shaped walls of nuclear fusion devices (Tokamaks). Also spraying of free-standing tungsten bodies was realized, by means of substrates easily machainable-out after deposition, as graphite and BN. Other variant consists of covering of a tungsten mesh or plates armored with tungsten wires. Protection of tungsten against oxidation in the plasma jet was a problem to be solved – the best result were gained with shroud gas, Ar plus 7 % hydrogen, and simultaneous placement of the substrates into graphite cells. The whole spray process was maintained to avoid temperatures over 700°C when the oxidation is inherent. Advantageous was predominantly covering of rotating substrates, when a de-lamination was prevented. The sprayed products were examined for their density, porosity, content of oxides and also chemical interactions with selected substrates.