1.Cemented Tungsten carbide Cemented Tungsten carbide is a type of sintering composition material which Is composed of cementation metal compound and metal binder, at present, the compounds used in cemented carbide are WC, TiC, TaC, NbC, Cr3C2, VC and so on. And the binders include Co, Ni. Main Characteristics of cemented tungsten carbide are: 1, High hardness and Strength. 2, High modulus of elasticity. 3, Stable chemical property. 4, Low impact toughness and thermal expansion coefficient.
2. Density The density of a material is the mass per unit volume. It’s measured per Archimedes Principles. The content of Co. in alloy is commonly determined by its density. But we cannot get porosity of cemented carbide by measuring its Density.
3. Hardness One material’s hardness means the ability of counteracting diamond indenter engender impress. Vickers-hardness ( HV) is extensive used in the world now, and this hardness testing method means using diamond to penetrate sample surface under some burthen situation, Thus to get the hardness number from testing and impress. Rockwell hardness (HRA) is another testing method frequently used in the world. Get the hardness by the penetrate deepness of brale. Both HV and HRA can be used in the hardness testing of cemented tungsten carbide, as well as they can be switched freely
4. Transverse Rupture Strength (TRS) TRS means getting the hardness from the rupture point of materials under the three-point bending experiment. TRS in the cemented tungsten carbide got through loading a sample in a normal clamp. TRS is the average number of several testing data. It will be changed along with the changes of the sample’s geometry shape, surface situation (finish), Inner stress and interior defect. Please pay attention that TRS is only an intension testing method, we cannot take it as the basis of materials selection.
5. Extent of porosity Because of incompletion sinter of impurity elements will be mixed in, micro residual porosity may exist in products’ metallurgical structure. We can use extent of porosity to measure the size &volume of the porosity in the cemented tungsten carbide products. Porosity influences products’ mechanical behavior. Porosity measurement is compared with standard illustrative map when magnified about 100 times. There are two types of porosity: A- type: less than 10um B- type: between 10um-25um
6. Grain size of WC About cemented tungsten carbide, we use grain size to show its average size. Grain size is measured by comparing with standard illustrative map when magnified about 1500 times. WC’s grain size greatly influences products’ physical and mechanical properties. Normally, the smaller of grain size, the higher strength; the bigger of grain size, the better toughness. Per international universal classification standard, the grain size of cemented tungsten carbide can be classified as following: Carbide class Nanometer Superfine Submicron Fine Middle Coarse Extra coarse Grain (ųm) ﹤ 0.2 0.2-0.5 0.5-0.8 0.8-1.3 1.3-2.5 2.5-3.0 ﹥6.0
7. Decarburization During the cemented tungsten carbide products’ manufacturer, owing to inadequate carbon content or exorbitant oxygen content, they need consume the carbon in the cemented tungsten carbide to deoxidize, decarburization phase ( u phase) will appear in the alloy structure, this time we name it as alloy decarburization. Decarburization will reduce the strength of the cemented tungsten carbide, making them more fragile. 8. Carburization When carbon content in alloys in higher than chemical value, free carbon or graphite phase will appear in the alloy, now it’s called as alloy carburization. Graphite carbon is measured by “C” type porosity. Graphite carbon will reduce cemented tungsten carbide’s strength and wear ability.