For the more expensive ball point pens now in use the highest quality balls or spheres consist of tungsten carbide. Such tungsten carbide balls are presently fabricated by means of powder metallurgy. In this technique a suitable powder consisting, for example, of tungsten carbide and cobalt is cold pressed and then heated until the powder sinters or fuses together. In this manner a small ball may be manufactured with a cobalt binder. The resulting ball is still somewhat porous. Hence due to the porosity of the ball and the presence of cobalt in the interstices of the tungsten carbide grains making up the ball the ball can be chemically attacked by the various inks used in ball point pens.
In addition, balls produced by powder metallurgy, as explained hereinabove, are not sufficiently spherical. As a result they require a considerable amount of rough grinding so that they become sufficiently spherical for the finish grinding steps.
It is accordingly an object of the present invention to provide a ball suitable for ball point pens which is not porous and has no binder material, hence is substantially immune to chemical attack by the inks used in ball point pens.
Another object of the present invention is to provide a ball of the type discussed consisting of a core with a coating obtained by chemical vapor deposition and which can be manufactured relatively inexpensively.