Thin composite wire saw with surface cutting crystals

DETAILED DESCRIPTION OF THE INVENTION The composite saw wire has a core which is of a high tensile strength metal or alloy, such as tungsten, molybdenum, tantalum, osmium, and rhenium, and alloys thereof.
The cutting surfaces are preferably boron, or borides, nitrides and/or carbides.
They are preferably selected from the group consisting of boron, and the borides, nitrides, and carbides of the transition metals and silicon.
Vapor deposition which is plating from the gaseous phase is usually used in order to provide a surface having special mechanical, chemical, electrical or optical properties.
The usual object of this technique of coating in the prior art is to give a closely adherent and smooth coating.
In order to obtain the object which is the subject of the present invention, it was necessary to modify the known vapor coating technique and carry it out in a manner counter to that taught by the prior art.
Owing to the fact that microscopic unevenness (irregularities) is always present at the surface of a metal wire which has been drawn, these surface irregularities can be used as the substrate for obtaining condensation nuclei on the wire surface.
This results because the conditions for formation of crystals on such irregular surfaces are more favorable than the conditions for the formation of crystals on the surrounding area.
Applicants have discovered that when under the aforesaid situation the above-noted condensation nuclei are subjected to slow crystalization at high temperature, they form primary crystals which increase in size without the concomitant formation of a considerable number of additional primary crystals.
This produces large crystals with irregular edges projecting from the surface.
The desired slow crystallization can be obtained by utilizing low concentrations of one or more of the reaction gas components.
This can be achieved, for instance, by dilution with inert gas; by using a large excess of a component; and by carrying out the reaction at a lower total pressure of the gaseous mixture