Carbide teeth as a industry, the main use of refractory metal compounds of high hardness, high wear resistance and good resistance to high temperature performance and good plasticity and toughness, binding phase to achieve cutting, drilling and resistance to wear and tear. These features make contradiction between some properties of cemented carbide, such as hardness and strength, toughness and wear resistance properties, mainly because it is difficult to raise the content of the hard phase and binder phase at the same time. Science and technology is the first productive force, the new structure of carbide enables the hardness and toughness were improved to some extent at the same time. Its new structure mainly has the gradient structure, nano and super fine crystal structure, coarse grain structure, as well as other special grain distribution structure.
Gradient cemented carbide structure refers to the hard phase and binder phase in the distribution of a certain spatial scales is gradient change, thus make the regulation of its performance has the greatest degree of freedom. According to the performance requirements are different, the kinds of functionally graded cemented carbide is more. Sweden in the 1980 s, drilling tools company development of functionally graded structures bipolar DP carbide generally appear similar to the sandwich structure, the most outer layer and middle layer of the alloy are WC + Co two-phase organization, inner lining for WC + Co + eta three-phase microstructure. The outermost Co phase content is lower than that of alloy materials in the name of the cobalt content, has the very high hardness and wear resistance; Intermediary Co content is higher than in the name of the cobalt content of alloy, has the very good toughness and plasticity. DP alloy wear resistance and toughness is better than standard cemented carbide. The technique is known as "cemented carbide history since 1950, the most important innovation". In the 90 s, the technology applied in the metal cutting bit, greatly improve the product's life and cutting efficiency. Another very important gradient cemented carbide is used for coating blade base structure.
The microstructure of carbide rotary file usually include the WC, Co and beta phase. Beta is a kind of brittle phase containing titanium, and can improve the hardness of the material, but is decreased toughness. Coating and coating matrix between certain physical, chemical and mechanical properties of incompatibility. By controlling the sintering atmosphere and heat treatment, can in carbide blade surface of about 50 um no beta phase layer, has good toughness, and combination of coating and high intensity, raise the collapse resistance of coating blade and cutting life. The process is simple, most of the cemented carbide coating blade base adopted the gradient structure. Research in the structure of functionally graded cemented carbide in China it has been reported in the 1990 s, but also the lack of a system in-depth description. Because of hard alloy and functionally graded material specialized structure, the more the need for the actual research.