| 摘要 |
<p><PICT:0899275/III/1> In a process for the production of a coated workpiece, an electric arc is formed between a stick electrode 10 and a second electrode, constituted by an adjacent member 11 or by the workpiece 23 itself, a stream of gas 17 is passed in contact with electrode 10, the gas stream together with the arc vapours are conducted through a constricted passage to form a collinated arc flame 22 which, together with a feed of powdered electrically conductive "refractory" metal (m. pt. above 1450 DEG C.) and electron emissive compound from hopper 21, is directed on to a surface of the workpiece 23. In a modification, the workpiece is composed of refractory metal and the feed consists of electron emissive compound. Shaped articles are made by removing the workpiece, e.g. by melting or dissolution, after it has been coated. Specified refractory metals are Cr, Mo, Ni, Nb, Ta, Ti and W. Specified emissive compounds are basia, calcia, ceria, strontia, thoria and yttria. Gas streams 17, 19 (the latter serving to introduce coating material into the apparatus) may be of argon, helium, hydrogen, nitrogen or a reactive gas. The coated workpieces may be electrodes or hot cathode emitters for vacuum tubes. Specification 869,791 is referred to.</p> |
