Tungsten carbide composition is commonly used as a hard coating in wear-resistant ceramics and in manufacturing tools. It is also used as a material in nozzles. The cobalt-tungsten binder phase varies on a microscopic scale throughout the composition.
Typical commercially available tungsten carbide bodies have a hardness of 75 Rockwell A. However, the atomic ratio of carbon to tungsten may vary from three to four microns. Various means of adjusting the carbon:tungsten ratio in cobalt/tungsten carbide compositions are known.
Using a finely divided powder, the interdispersion of cobalt with tungsten carbide can be prepared. In order to achieve this, the tungsten carbide particles should be less than 0.1 microns in size and the cobalt powder should have an atomic ratio of less than one.
A representative dense body of this invention contains 10 to 12 percent cobalt. This density can be achieved by either hot-pressing the dense composition to a desired density or by rapid cooling the dense composition to a desired temperature.
The density of the dense body can be measured by determining the tapped density. Generally, the upper surface of the powder is oxidized more than the interior. But the oxidation process can produce variations in the tungsten carbide powder.
When the oxidation process is performed on the dense body, the resulting powder will absorb 0.1 to 1.0 percent of oxygen when it is exposed to air. Since a finely divided powder is suitable for this application, it should be free of impurities.
