As a superhard tool material, diamond has been used in cutting for hundreds of years. In the course of tool development, from the end of the nineteenth century to the middle of the twentieth century, high-speed steel was the main representative of tool materials; in 1927, Germany first developed cemented carbide tool materials and was widely used; in the 1950s, Sweden and The United States separately synthesized synthetic diamonds, and the cutting tools entered a period represented by superhard materials. In the 1970s, people synthesized polycrystalline diamond (PCD) using high-pressure synthesis technology, which solved the scarcity and high price of natural diamonds, and expanded the application range of diamond tools to aviation, aerospace, automobiles, electronics, stone,and many other fields.
Diamond cutting tools have the characteristics of high hardness, high compressive strength, good thermal conductivity and wear resistance, and can obtain high machining accuracy and machining efficiency in high-speed cutting. The above-mentioned characteristics of diamond tools are determined by the state of diamond crystals. In diamond crystals, the four valence electrons of carbon atoms form bonds according to a tetrahedral structure, and each carbon atom forms a covalent bond with four adjacent atoms to form a diamond structure. This structure has strong binding force and directionality. So that the diamond has extremely high hardness. Because the structure of polycrystalline diamond (PCD) is a fine-grained diamond sintered body with different orientations, although the binder is added, its hardness and wear resistance are still lower than that of single crystal diamond. However, because the PCD sintered body is isotropic, it is not easy to crack along a single cleavage plane.