How To Control The Expansion of Tungsten Carbide During The Sintering of Hard Alloys?

During the sintering process of cemented carbide, several methods can be used to control the expansion of tungsten carbide:

1. Control sintering temperature and time

-Accurately set the appropriate sintering temperature curve to avoid excessive temperature or rapid heating, while controlling the insulation time reasonably. Excessive temperature or prolonged insulation time may lead to excessive expansion.

2. Adjust carbon content

-Ensure that the carbon content in the hard alloy is within an appropriate range. Excessive or insufficient carbon content can affect the expansion behavior of tungsten carbide. Control carbon content through precise batching and mixing processes.

3. Optimize powder particle size and distribution

-Use tungsten carbide powder with appropriate particle size and uniform particle size distribution. Finer powders may cause greater expansion, while appropriate particle size distribution can help reduce uneven expansion.

4. Apply pressure

-During the sintering process, methods such as hot pressing sintering or hot isostatic pressing sintering can be used to apply a certain pressure and suppress the expansion of tungsten carbide.

5. Atmosphere control

-Control the sintering atmosphere, such as using vacuum or specific protective gas atmosphere, to reduce oxidation and other adverse chemical reactions, thereby affecting expansion.

6. Add inhibitors

-Adding some inhibitors in moderation, such as vanadium carbide (VC), chromium carbide (Cr ∝ C ₂), etc., can inhibit the growth and abnormal expansion of tungsten carbide grains.

For example, in the production of a specific specification of hard alloy cutting tools, by precisely controlling the sintering temperature at around 1400 ℃, holding for 1 hour, using powder with a carbon content of 6.1%, and adding 0.5% VC inhibitor, hot isostatic pressing sintering is carried out in a vacuum environment, which can effectively control the expansion of tungsten carbide and ensure the dimensional accuracy and performance of the product.