Patent ID: 7569179

Claim:
A method of forming a cemented tungsten carbide material in which the tungsten carbide is embedded in a cobalt matrix having a graded composition, comprising: obtaining a sample of a cemented tungsten carbide material, the sample is a compact of powders having a first layer and a second layer, the first and second layer each containing a quantity of cobalt, wherein one of the layers is a carbon-deficient layer and the other layer is a carbon-enriched layer; and the overall carbon content including both layers is stoichiometic such that the molar amount of excess carbon in the carbon-enriched layer is substantially equal to the molar amount of deficient carbon-deficient layer such that when the material is sintered, the resulting material is neither carbon-deficient nor carbon-enriched; sintering the powder compact under conditions which fully densifies the powder compact, and allows carbon atoms to diffuse from the carbon-enriched layer to the carbon-deficient layer and cause liquid cobalt to flow in the same direction as the carbon diffusion, thereby creating a gradient of cobalt in the sample, wherein there is no eta phase in the sintered products.