Properties of Tungsten Carbide

Tungsten carbide is one of the most popular materials in modern industry. It can be manufactured into different types of products, like tungsten carbide rods, tungsten carbide buttons, tungsten carbide strips, tungsten carbide dies, and so on. That is because tungsten carbide has many properties, including high hardness, wear resistance, impact resistance, and so many more. In this article, we are going to talk about:

1. Thermal Expansion Coefficient

2. Temperature Conduction

3. Electrical Conductivity and Resistance

4. Magnetic Consistencies

5. Corrosion properties

Thermal Expansion Coefficient

The coefficient of thermal expansion (CTE) of cemented tungsten carbide is extremely low. When shrink fitting a carbide die into a steel case, this characteristic is quite helpful. WC-Co cemented carbides have values that are roughly half those of ferritic and martensitic steels, while the ratio for austenitic steels is closer to one to three. The value of CTE rises as the amount of binder in the mixture does, and alloying agents can also raise it.

Temperature Conduction

Although WC-Co cemented carbides have a thermal conductivity value that is around one-third that of copper, pure WC is nevertheless a very good heat conductor. Grain size has no discernible impact on this feature, but the addition of tantalum or titanium carbide will considerably reduce the heat conductivity factor.

Electrical Conductivity and Resistance

Electrical resistance in WC-Co cemented carbides is minimal, with a typical value of 20 μΩ cm. As a result, cemented carbide has an electrical conductivity of about 10% of that of copper. This characteristic is advantageous because it enables the manufacture of cemented carbide using electrical discharge machining (EDM).

Magnetic Consistencies

Because cobalt or nickel-containing metallic binder phases are present in cemented carbides, they exhibit ferromagnetic characteristics at room temperature. To detect magnetic saturation and coercivity on a piece of carbide, this property is helpful during nondestructive testing. A property of WC-Co cemented carbides with a ferromagnetic binder phase is low magnetic permeability. It rises with cobalt content, and when the standard is taken as a vacuum with a value of 1, the normal range of values is from 1.01 to roughly 12. This characteristic can be helpful in situations where magnetism would negatively impact abrasion-resistant computer or disk drive media. When pressing magnetic powders, a compacting die must have low magnetic permeability.

Corrosion properties

The individual tungsten carbide particles can withstand the majority of corrosive media. In the presence of a potent acid or alkali solution, the binder material is vulnerable to leaching. Cemented carbide's surface will experience leaching of the binder ingredient, exposing an unsupported skeletal system. Then, the carbide particles will easily wear away, exposing fresh targets for attack. The carbide skeleton is denser when the binder content is lower. When compared to grades with a larger binder concentration, low binder grades exhibit a somewhat higher combined wear and corrosion resistance.

At pH 7, which is considered neutral, straight WC-Co grades are resistant to corrosion. This also applies to WC-Co grades with additions like titanium carbide (TiC), tantalum carbide (TaC), or niobium carbide (NbC). The best corrosion resistance can be found in some alloyed titanium carbide/nickel binder based grades, which are pH1-approximate. These grades are more fragile and have poorer heat conductivity when compared to straight WC-Co grades.

They are extremely difficult to grind and braze and are only utilized in particular situations where mechanical strength and thermal shock resistance are not as crucial as corrosion and wear resistance.

The best option is to use specifically alloyed WC-Ni grades when corrosion/wear is a key design requirement. They can withstand pH levels of 2 to 3. They have demonstrated corrosion resistance in some conditions where the pH value is less than 2. Their mechanical and thermal properties are comparable to those of straight WC-Co grades since they have WC as the hard principle and nickel and cobalt are similar metals in most respects.

One of the most crucial variables in deciding how corrosive a medium will be is the pH level. The medium's electric conductivity and temperature are two additional significant contributing factors. The latter depends on the amount of dissolved salts in the solution, or the ion concentration. As a result, it is challenging to predict how corrosive a particular media would be. Although there are no universal guidelines that apply in every circumstance, it is widely agreed that WC-Co cemented carbides should not be subjected to pH levels below 7 because leaching will take place. It is advised that tests be given using the specified media for a particular grade.

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