Terminology About Tungsten Carbide

With the development of technology, people are chasing better tools, and materials for their construction and business. Under this atmosphere, tungsten carbide takes an important role in modern industry. And in this article, some terminology about tungsten carbide will be introduced.

1. Cemented carbide

Cemented carbide refers to a sintered composite composed of refractory metal carbides and metal binders. Among the metal carbides, tungsten carbide, titanium carbide, tantalum carbide, and so on are the currently commonly used carbides. And the most widely used metal binder is cobalt powder, and other metal binders like nickel, and iron, will also be used sometimes.

2. Tungsten carbide

Tungsten carbide is a kind of cemented carbide, which composited of tungsten carbide powder and metal binders. With the high melting point, tungsten carbide products can not be manufactured as other materials. Powder metallurgy is a common method for manufacturing tungsten carbide products. With tungsten atoms and carbon atoms, tungsten carbide products have many great properties, making them a popular tool material in modern industry.

3. Density

Density refers to the ratio of the mass to the volume of the material. Its volume also contains the volume of the pores in the material.

In the tungsten carbide products, cobalt or other metal particles exist. The common tungsten carbide grade YG8, which contents of 8% cobalt, has a density of 14.8g/cm3. Therefore, as the cobalt content in the tungsten-cobalt alloy increases, the overall density will decrease. 

4. Hardness

Hardness refers to the ability of a material to resist plastic deformation. Vickers hardness and Rockwell hardness are usually used for measuring the hardness of tungsten carbide products.

Vickers hardness is widely used internationally. This hardness measurement method refers to the hardness value obtained by measuring the size of the indentation by using a diamond to penetrate the surface of the sample under a certain load condition.

Rockwell hardness is another method of hardness measurement that is commonly used. It measures the hardness using the penetration depth of a standard diamond cone.

Both the Vickers hardness measurement method and the Rockwell hardness measurement method can be used for the measurement of the hardness of the cemented carbide, and the two can be mutually converted.

The hardness of tungsten carbide ranges from 85 HRA to 90 HRA. The common grade of tungsten carbide, YG8, has a hardness of 89.5 HRA. A tungsten carbide product with high hardness can endure impact and wear better, so it can work longer. As a bonder, less cobalt causes better hardness. And lower carbon can make tungsten carbide harder. But decarbonization can make tungsten carbide easier to damage. Generally, fine tungsten carbide will increase its hardness.

5. Bending strength

The sample is multiplied as a simply supported beam on two fulcrums, and a load is applied to the center line of the two fulcrums until the sample breaks. The value calculated by the winding formula is used according to the load required for the fracture and the cross-sectional area of the sample. Also known as transverse rupture strength or bending resistance.

In WC-Co tungsten carbide, the flexural strength increases with the increase of cobalt content of the tungsten-cobalt alloy, but when the cobalt content reaches about 15%, the flexural strength reaches the maximum value, then begins descending.

The bending strength is measured by the average of several measured values. This value will also change as the geometry of the specimen, surface condition, internal stress, and internal defects of the material change. Therefore, flexural strength is only a measure of strength, and the flexural strength value cannot be used as the basis for material selection.

6. Transverse rupture strength

Transverse rupture strength is the ability of tungsten carbide to resist bending. Tungsten carbide with better transverse rupture strength is more difficult to damage under impact. Fine tungsten carbide has better transverse rupture strength. And when the particles of tungsten carbide distribute evenly, the transverse is better, and the tungsten carbide is not easy to damage. The transverse rupture strength of YG8 tungsten carbide products is around 2200 MPa.

7. Coercive force

Coercive force is the residual magnetic force measured by magnetizing a magnetic material in a cemented carbide to a saturated state and then demagnetizing it.

There is a direct relationship between the average particle size of the cemented carbide phase and the coercive force. The finer the average particle size of the magnetized phase, the higher the coercive force value. In the lab, the coercive force is tested by a coercive force tester.

These are the terminology of tungsten carbide and its properties. More other terminologies will also be introduced in the following articles. 

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