1.1 Development of Polycrystalline Diamond Cutters
Diamond, as a superhard cutters material, has been used for cutting and processing for hundreds of years. The developing route: From the end of the nineteenth century to the twentieth century, tool materials were mainly represented by high-speed steel; in 1927, Germany first developed carbide tool materials and gained wide application; in the 1950s, Sweden and the United States synthesized synthetic diamonds, and cutting tools stepped into the period which was represented by the superhard materials. In the 1970s, polycrystalline diamond
(PCD) was synthesized by high-pressure synthesis technology, which solved the problem of scarcity and high price of natural diamond, and extended the application of diamond tools to many fields such as aviation, aerospace, automobile, electronics, stone and so on.
1.2 Performance Characteristics of Polycrystalline Diamond Cutters
Diamond knife has the characteristics of high hardness, high compressive strength, good thermal conductivity and wear resistance, and can achieve high processing accuracy and efficiency in high-speed cutting, which are determined by the crystal state of diamond. In diamond crystals, four valence electrons of carbon atoms are bonded by tetrahedral structure. Each carbon atom forms covalent bonds with four adjacent atoms, thus forming a diamond structure that has strong directivity of binding force, which makes diamond extremely hard. The hardness and wear resistance of polycrystalline diamond (PCD) sintered body are lower than that of single crystal diamond, although the binder is added. However, the PCD sintered body is isotropic, so it is not easy to crack along a single cleavage plane.
2.1 Manufacturing Process of the Polycrystalline Diamond Cutters
①Manufacture of PCD Composite Chips ②Processing of PCD Blades
2.2 Cutting Technology of the PCD Composite Cutting
Because PCD composite has high hardness and wear resistance, so special processing technology must be adopted. At present, the main processing methods of PCD composite are WEDM, laser processing, ultrasonic processing, high-pressure water jet and so on.
2.3 Welding Technology of the Polycrystalline Diamond Cutters
In addition to the combination to the mechanical clamping bonding method, the PCD composite is mostly pressed on the cemented carbide matrix by brazing. The main welding methods are laser welding, vacuum diffusion welding, vacuum brazing, high frequency induction brazing and so on. At present, high frequency induction brazing PCD blade with low investment and low cost has been widely used.
2.4 Grinding Technology of the Polycrystalline Diamond Cutters
The high hardness of PCD makes its material removal rate very low (even only one thousandth of the removal rate of cemented carbide). At present, resin bonded diamond grinding wheel is mainly used in PCD cutters grinding process. Because of the interaction between grinding wheel abrasives and PCD materials with similar hardness, the grinding law is complex.
3.1 Selection of the Cutter Material
(1) Reasonable selection of PCD granularity
(2) Reasonable selection of PCD blade thickness