How to Ensure the Size of Tungsten Carbide Product

Tungsten carbide is the second hardest tool material in the world, only after diamond. Tungsten carbide is famous for its good properties, such as high hardness, wear resistance, impact resistance, and durability, so they are good to manufacture into different tungsten carbide products.

As we all know, when we are manufacturing a tungsten carbide product, we always apply powder metallurgy, which includes compacting and sintering. And as we have talked about before, tungsten carbide products will shrink after sintering. That’s because the plastic flow increases during sintering. This phenomenon is common, however, it may bring some troubles to manufacturing tungsten carbide products. That means if we need a tungsten carbide product with a length of 16mm, we can’t make a mold with a length of 16mm and compact it into that size because it will be smaller after sintering. So how do we ensure the size of tungsten carbide products?

The most important thing is the constriction coefficient.

The constriction coefficient is one of the common physical quantities in engineering. Some objects often cause volume shrinkage because of their changes, external temperature changes, structural changes, and phase transitions. The constriction coefficient refers to the ratio of the constriction rate to the amount of constriction factor.

Many factors will affect the constriction coefficient. The quality of the mixed tungsten carbide powder and cobalt powder and the compacting process will influence the constriction coefficient. The constriction coefficient can also be affected by some requirements of products, such as the composition of the mixed powder, the density of powder, the type and amount of forming agent, and the shapes and sizes of tungsten carbide products. 

When manufacturing tungsten carbide products, we will make different molds for compacting the tungsten carbide powder. It seems like when we are compacting the tungsten carbide products in the same sizes, we can use the same mold. But in fact, we can not. When we are producing the tungsten carbide products in the same size but different grades, we should not use the same mold because tungsten carbide products in different grades will be different in density, which will affect the constriction coefficient. For example, the constriction coefficient of the most common grade YG8 is between 1.17 and 1.26.

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