GB363236A - An improved process for coating wires, bars, bands, threads or the like - Google Patents

Abstract

363,236. Coating with metals, metalloids, and metallic compounds. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Assignees of Patent-Treuhand-Ges. fur Elektrische Gl³hlampen; 11, Ehrenbergstrasse, Berlin.) Feb. 27, 1931, No. 6243. Convention date, April 15, 1930. [Classes 72 and 82 (ii).] An electrically conducting wire, bar, band, thread or the like is coated with a metal, a metalloid, or a metallic compound by placing the wire &c. in or passing it through a reaction chamber near to but not in contact with a compound of the coating material and passing an electric current through the wire &c. to vaporize the compound and to decompose the vapour to form the coating, no external source of heat being used. A wire 4 from a roll 6 enters a glass or metal reaction vessel 1 through a lead-in tube 3 in a stopper 2 and passes through contacts 8, 9 connected through a resistance 17 to a source of current. Between the contacts 8, 9 the wire is carried through a passage 10 in a compressed body 11 which consists of the compound to be decomposed, the compressed body being spaced from the walls of the reaction vessel by asbestos, glass wool, or metallic spacing rings 12. The heat generated by the electric current passing through the wire vaporizes the compound adjacent the wire and decomposes the vapour to form a coating. Neutral or reducing washing gases may pass through the vessel by the inlet 13 and outlet 14 or the reaction may be carried out at reduced pressure preferably with mercury contacts in the wall of the reaction vessel. Several compressed bodies may be arranged in series in the vessel, each between two electrical contacts, the currents being adjusted so that the wire reaches the same temperature at the entry to each body. In the form shown in Fig. 3 the wire travels upwardly and the compound is contained in a metal vessel 32. The compound may be liquid in which case the heated wire is passed over the surface 37, Fig. 4, of the compound 39 contained in a vessel 38. The wire to be treated is preferably made of a refractory metal such as tungsten, molybdenum, tantalum, niobium, rhenium, platinum, or their alloys. Coating metals and metalloids may be tungsten deposited from the hexachloride or pentabromide, molybdenum or tantalum from their pentachlorides, rhenium from its chloride, platinum from its carbonyl, uranium or vanadium from their halides, preferably with hydrogen as washing gas, silicon from the tetrabromide, boron from the tribromide, or carbon by passing the wire across the surface of hydrocarbons, carbon tetrachloride or organic halides. The following examples of coating with compounds are given:-coating with zirconium carbide by passing the wire across the surface of zirconium tetrachloride and toluol in an atmosphere of hydrogen; with titanium nitride by using titanium tetrachloride in an atmosphere of hydrogen and nitrogen; with chromium oxide by using chromyl chloride in an atmosphere of hydrogen ; with hafnium phosphide by using hafnium tetrachloride and phosphorus trichloride in an atmosphere of hydrogen ; and with uranium sulphide by passing the wire through a passage in a compacted mass of uranium chloride in an atmosphere of sulphuretted hydrogen.