The production of carbide involves a process the complexity of which is, in fact, extraordinary. The base materials, tungsten carbide and cobalt, are combined by applying an exceptionally wide variety of mixing ratios. By adding further materials, such as chromium, nickel, tantalum and titanium, special characteristics can be achieved, e.g. corrosion and heat and wear resistance.
In general, smaller tungsten carbide grain sizes allow for the manufacture of carbides with a finer microstructure. A prerequisite for this is the prevention of grain growth during the sintering process by adding suitable doping components in the right amount, adjusted to the cobalt content. The latter has been determined based on the required performance specifications for the carbide. Since the specific surface of a carbide depends reciprocally on its grain size, a finely-grained carbide can adsorb more binder than a coarsely-grained TC. When considering the ISO hardness curve of a carbide in a diagram as a function of the carbide grain size and its cobalt content, the curve behaves as a decreasing polynomial function (cf. Figure 1).
Illustrates this relationship by displaying the properties of the KF grades K6UF, K40UF, K44UF, and K55SF. K40UF exhibits an average grain size of .6 µm and consists of 10 weight percent cobalt. The grade K44UF is made of .5 µm tungsten carbide powder and contains 12 percent cobalt. While the toughness of both grades is approximately the same, the Vickers hardness of K44UF is 5 percent higher. Our grade K55SF with a grain size of .2 µm and a cobalt content of 9 percent offers a 24 percent higher Vickers hardness (HV = 1,920 kg/mm²), while exhibiting a reduction in toughness of only 5 percent.
Illustrates this relationship by displaying the properties and correlation of the Berlin Carbide grades.
An increase in cobalt content results in increased toughness while hardness and wear resistance are reduced. This opposite development of the two desirable parameters, hardness and toughness, can be countered by reducing the carbide grain size. The result is an increased hardness on account of the finer basic grain of the carbide which at the same time permits a high binding metal content as the grain structure offers a large specific surface, allowing for a high toughness. Consequently, superfine grain carbide grades offer increased hardness while maintaining toughness.
Premium carbide grade for special applications, preferred grade for diamond coating.
Fine grain type. Toughness and high hardness, recommended for diamond coatings.
Ultra-fine grain type. Extremely high hardness and wear resistance.
Fine grain type. High hardness and wear resistance, medium toughness.
Fine grain type. High hardness and toughness. Increased tensile strength for cutting edge stability.
Ultra-fine grain type. High toughness, hardness and wear resistance. Increased tensile strength for cutting edge stability. Universal grade.
Ultra-fine grain type. Very high hardness and high toughness.