Refractory metal coating method

Claim 1

An improved coating method to deposit a refractory metal continuously on a length of refractory metal wire which comprises: (a) continuously moving a refractory metal wire at a predetermined speed upwardly through an enclosed unheated reaction chamber in a substantially vertical direction, (b) heating said refractory metal wire during passage through said reaction chamber utilizing electrical energy supplied with mercury electrical contacts located at both bottom and top apertures in said reaction chamber, (c) continuously introducing a volatilized refractory metal compound to the bottom of said reaction chamber which undergoes thermal diffusion separation therein so that flow in the downward direction takes place and said compound undergoes substantially quantitative conversion to avoid side reactions at the top aperture in said reaction chamber, (d) maintaining a temperature gradient along the vertically moving refractory metal wire so that the lower part of the said wire in the reaction chamber is cooler where deposition first takes place and produces fine grain nucleation in the initial coating, and (e) continuously exhausting the reaction products formed in said reaction chamber while depositing a refractory metal coating of substantially even thickness around the refractory metal wire.