7 Points You Need To Know about Tungsten Carbide

(1)Specific Gravity

The specific gravity of tungsten carbide decreases with increasement of cobalt content and it will not be affected by tungsten carbide grain size .

(2)Coefficient of Thermal Expansion

When tungsten carbide is used in different temperature ,Coefficient of thermal expansion should be a very important factor needs to be considered. When tungsten carbides are welded to other material like steel, cracks are easy to occur. This kind of cracks is generated due to the difference of coefficient of thermal expansion. The coefficient of thermal expansion of tungsten carbide should be 1/2-1/3 of steel, which increased with the increasement of cobalt content.

(3)Coefficient of Thermal Conductivity

Under the high temperature environment, the coefficient of the conductivity is also very important factor ,just like the coefficient of thermal expansion. The coefficient of thermal conductivity of the tungsten carbide which has been blended into tungsten carbide and cobalt grains is twice of the steel, and becomes smaller with the increasement of cobalt content.

(4)Magnetism

Although tungsten carbides are not magnetic, its metal bonds such as cobalt are magnetic. Therefore, it will be affected by the metal it binds. By changing the alloy composition can obtain non-magnetic alloy, when nickel is added as a binding, its magnetic conductivity is near to 1.

(5)Oxiditive Resistance

Under high temperature atmosphere (oxidizing) environment, the quality of tungsten carbide can be degraded due to oxidation. Bound metals are first oxidized at low temperatures in an oxidizing environment. When the temperature is over 700℃, tungsten carbide starts to be oxidized. Therefore under the temperature below 700℃, the binding metal composition and quantity determine the controlling factors of oxidation. Under the temperature 700℃, adding Tic and Tac carbides and adjusting the WC grain size is an effective controlling method.

(6)Corrosion Resistance

Tungsten carbides show different corrosion phenomenon under different application environment (temperature, humidity, solution, all kinds of combination of metal and energy are factors affecting corrosion). Material strength weakened by localized corrosion .Therefore, it is very necessary to know well the factors that cause corrosion under different environment .As for the corrosion resistance of tungsten carbide,metal binder is the main reason.

(7)Porosity

The porosity indicates that the micro hole is the state of the micro structure of the tungsten carbide .Tungsten carbide is produced by powder metallurgy, sometimes , the porosity can lead to the degradation of the strength of tungsten carbide and the defect of the surface. In order to restrain and eliminate the pores, usually will take measures to improve the equipment and the process, like using pressure sintering furnace, Hot Isostatic Pressing Sintering (HIP) equipment,   CIS-006B Standard Test is the classification standard for testing tungsten carbide porosity.

The following is the classification criteria:

A:the porosity ≤ 10um,divided into A02-08 four grades, the qualified range:＜A02

B:the porosity ＝10-14um, divided into B02-08 four grades, the qualified range: ＜B02

C:free carbon pore is divided into four grades C02-08,the qualified rang: ＜C02

Our company proceeds porosity standard as A02B02C00, which is more strict than CIS-006B Standard.