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US 7,118,635 B1Granted
Method for producing tungsten carbides by gas-phase carburization
AssigneeH. C. Starck GmbH
InventorsGerhard Gille, Benno Gries, Jörg Bredthauer
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Abstract
The invention relates to a method for producing wolfram carbides by gas-phase carburetion of wolfram powders and/or suitable wolfram precursor compounds in powder form at temperatures above 850° C. According to the method a CO2/CO mixture with a CO2 content greater than the Boudouard equilibrium content corresponding to the carburetion temperature is used as carburetion gas phase.
Claims6
A process for preparing tungsten carbide consisting of:
- (a) carburizing a material selected from the group consisting of tungsten powder, tungsten precursor compound powder and combinations thereof, at a temperature ranging from 850° to 950°, and in the presence of a carburizing gas phase,
- said carburizing gas phase comprising a mixture of CO and CO2, said carburizing gas phase having a CO2 content which is above the Boudouard equilibrium content corresponding to the carburization temperature, and
- wherein the carburizing step is carried out with a carbon activity ranging from 0.4 to less than 1;
- and
- (b) heat treating the tungsten carbide formed in step (a) at a temperature ranging from 1,150° C. to 1,800° C., and at a carburizing atmosphere sufficient for the carbon content of the tungsten carbide to approach the theoretical, thereby forming tungsten carbide.
2 more elements
A process for preparing tungsten carbide consisting of:
- (a) carburizing a material selected from the group consisting of tungsten powder, tungsten precursor compound powder and combinations thereof, at a temperature ranging from 850° to 950°, and in the presence of a carburizing gas phase,
- said carburizing gas phase comprising a mixture of CO and CO2, said carburizing gas phase having a CO2 content which is above the Boudouard equilibrium content corresponding to the carburization temperature, and
- wherein the carburizing step is carried out with a carbon activity ranging from 0.4 to less than 1;
- and
- (b) heat treating the tungsten carbide formed in step (a) at a temperature ranging from 1,150° C. to 1,800° C., thereby forming tungsten carbide, wherein said tungsten carbide is characterized by a relationship between coherence length x and lattice strain y according to Formula (I):
- y<(−4.06 10−4 nm−1x+0.113)%.
3 more elements
Dependencies are inferred from the claim text.