Rapid Synthesis of Tungsten Carbide Composite Powder

Tungsten carbide is a compound composed of tungsten and carbon. It is mainly used in the production of cemented carbide. At present, the way to produce tungsten carbide powder is the two step method, that is, first we use hydrogen to reduce tungsten oxide to tungsten powder, the tungsten powder is then carbonized and carbonized into tungsten carbide at high temperature. But this method is not easy to produce ultrafine tungsten carbide powder, not to mention the production of ultrafine particles of tungsten carbide - metal cobalt composite powder.

In this respect, Chinese scholars have done a lot of research and practice in this field. Finally, a more practical method of composite powder synthesis has been innovating. The process flow is as follows:

(1)Preparation - take a certain amount of tungsten trioxide and tricobalt oxide, the purity of 99%, and graphite powder reactive tungsten carbide - metal cobalt, 70 ~ 125% of the theoretical amount of carbon required with a carbon source, using a ball mill after 2 hours of ball milling the mixture into the graphite boat;

(2)High temperature molybdenum wire furnace graphite boat - a reaction mixture into 900~1850 ℃  or single tube furnace pusher in high temperature furnace, in reducing atmosphere reaction for 0.5 to 6 hours;

(3)Released detection of reactants in the furnace cooling with cooling 0.5 ~ 1 hours, released over 80 mesh sieve, the detection of total carbon free carbon and oxygen content to remove mechanical impurities after part of the total carbon should be 6.12 ~ 6.25 wt%, free carbon should be between 0.1 to 0.2 weight%, the oxygen content is less than or equal to 0.25 weight%;

(4)Adjustment - When the product is tungsten carbide powder and the test results do not meet the requirements, the product should be fine-tuning with carbon or tungsten oxide, when the product is tungsten carbide cobalt powder, fining is also needed to allot tungsten oxide, which is required by alloy process, cobalt oxide or cobalt alloy. The adjusted material is then mixed for 0.5 to 2 hours, and reacts for 0.5 to 6 hours in a high temperature molybdenum wire tube furnace at 900~1850 ℃ under the protection of gas.

Only in this way, tungsten oxide, cobalt and carbon can reach the precursor state of sintered cemented carbide in a single process. This method has the advantages of short process flow, good product quality, simple equipment and high efficiency. It is easy to produce ultrafine tungsten carbide powder. There are two-step method does not have the advantage.

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