Diamond, as an ultra-hard cutting tool material, has been used in cutting processes for hundreds of years. The evolution of cutting tools spans from the late 19th century to the 20th century, with high-speed steel dominating the material landscape. In 1927, Germany first developed carbide tool materials, which saw widespread use. In the 1950s, Sweden and the United States respectively synthesized artificial diamonds, marking the beginning of a new era for cutting tools dominated by ultra-hard materials. In the 1970s, polycrystalline diamond (PCD) was synthesized using high-pressure technology, solving the issues of natural diamond scarcity and high cost, thereby expanding the application range of diamond tools to fields such as aviation, aerospace, automotive, electronics, and stone industries.
Polycrystalline Diamond cutters are characterized by high hardness, high compressive strength, excellent thermal conductivity, and wear resistance, enabling high-speed cutting with superior machining precision and efficiency. These characteristics are determined by the crystalline structure of diamond. In a diamond crystal, each carbon atom forms covalent bonds with four adjacent atoms in a tetrahedral arrangement, resulting in a very robust structure that imparts extreme hardness. Although the polycrystalline diamond consists of randomly oriented fine diamond grains sintered together, and even with the incorporation of a bonding agent, its hardness and wear resistance are still inferior to that of single crystal diamond. However, the isotropic nature of PCD makes it less prone to cleavage along a single plane.
PCD hardness can reach 8000HV, which is 80 to 120 times that of carbide;
PCD thermal conductivity is 700W/mK, which is 1.5 to 9 times that of carbide, and even higher than that of PCBN and copper, thus PCD tools dissipate heat rapidly;
PCD friction coefficient is generally only 0.1 to 0.3 (carbide's friction coefficient is 0.4 to 1), thus PCD tools significantly reduce cutting force;
PCD thermal expansion coefficient is only 0.9×10-6 to 1.18×10-6, which is only one-fifth that of carbide, resulting in minimal thermal deformation and high machining accuracy;
PCD tools exhibit very low affinity with non-ferrous metals and non-metallic materials, reducing the tendency for chips to adhere and form built-up edges during machining.
Developed countries have been researching PCD tools earlier, and their applications are relatively mature. Since Sweden first synthesized artificial diamonds in 1953, extensive research has been conducted on the cutting performance of PCD tools, leading to a rapid expansion in their application and usage.
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