Correctly understand the dialectical relationship between the effective substances and impurities in the cemented carbide composition

       In short, the components in the alloy are effective when they are needed, and impurities when they are not needed. For example, the same alloy blade, when the blade is used for fine grinding, an appropriate amount of W2C is an active ingredient, while due to gravity cutting, W2C is an impurity. In the same way, the content of Ti, Ta, Nb, and Mo can also be judged. But for permanent impurity elements, the lower the content, the better, such as Fe, Si, P, Ca, etc. That is to say, no matter what kind of cemented carbide we make, these elements cannot always play an effective role in the alloy, so their content must be strictly controlled.



    However, for non-mainstream elements such as Mo, Nb, Ni, etc. in alloys, we cannot generalize. We know that Mo is associated with W, Nb is associated with Ta, Ni is associated with Co, and in cemented carbide, W, Ta and Co are the mainstream elements. However, since Mo, Nb, and Ni are associated elements, among the above mainstream elements, the content of these three associated elements will be relatively high.



    Although Mo, Nb, Ni, etc. are non-mainstream elements, in cemented carbide, they still have many useful functions that their associated mainstream elements do not have. So this requires us to correctly understand and use them.

    For example, the role of Nb in cemented carbide is basically equivalent to that of Ta, and they each have some functions that cannot be replaced by the other. Therefore, in the production of cemented carbide, it is better to use an appropriate proportion of Ta and Nb solid solutions than pure TaC and NbC. We can see through a simple performance comparison.

Performance and role	Tantalum	niobium
atomic coefficient	73	41
Number of outermost electrons	5	5
atomic weight	180.95	92.91
density	16.66	8.57
Lattice constant	a=3.296	a=3.294
Melting point (℃)	3000±50	2470±10
Inhibit alloy grain growth	weak	powerful
Improve alloy high temperature hardness (red hardness)	slightly stronger	slightly weaker
Improve the corrosion resistance of alloys	powerful	weak
Reduce alloy friction coefficient	weak	powerful
dispersibility in alloys	weak	powerful
Wettability of cobalt to it (equivalent number of molecules)	quite	quite