PCD (Polycrystalline Diamond) Tool
PCD tools have the characteristics of high hardness, high compressive strength, good thermal conductivity and wear resistance, etc., which 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 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 single crystal diamond. However, because the PCD sintered body is isotropic, it is not easy to crack along a single cleavage plane.
The main performance indicators of PCD tool materials:
(1) The hardness of PCD can reach 8000 HV, which is 80~120 times that of cemented carbide;
(2) The thermal conductivity of PCD is 700W/mK, which is 1.5~9 times that of cemented carbide, even higher than PCBN and copper, so the heat transfer of PCD tools is rapid;
(3) The friction coefficient of PCD is generally only 0.1 to 0.3 (the friction coefficient of cemented carbide is 0.4 to 1), so PCD tools can significantly reduce the cutting force;
(4) The coefficient of thermal expansion of PCD is only 0.9×10 -6 to 1.18×10 -6, which is only 1/5 of that of cemented carbide. Therefore, the thermal deformation of PCD tools is small and the machining accuracy is high;
(5) The affinity between PCD tools and non-ferrous metals and non-metallic materials is very small, and the chips are not easy to adhere to the tool tip during the machining process to form a built-up edge.
Main application of PCD tool
(1) Processing of non-ferrous metal materials that are difficult to process: When ordinary tools are used to process non-ferrous materials that are difficult to process, defects such as easy wear of the tools and low processing efficiency often occur, while PCD tools can show good processing performance. For example, PCD tools can be used to effectively process a new type of engine piston material-hypereutectic silicon aluminum alloy (a breakthrough has been made in the research on the processing mechanism of this material).
(2) Processing of non-metallic materials that are difficult to process: PCD tools are very suitable for the processing of non-metallic materials such as stone, hard carbon, carbon fiber reinforced plastic (CFRP), and man-made plates.
PCBN (Polycrystalline Cubic Boron Nitride) Tool
PCBN (cubic boron nitride) is a new type of artificial superhard material whose hardness is second only to diamond, the microhardness of CBN single crystal is HV8000-9000, is the second highest known hardness of the substance, PCBN hardness is generally HV2500-5000. Therefore, when used for processing high-hardness materials, it has higher wear resistance than cemented carbide and ceramics. CBN has high oxidation resistance and does not produce oxidation at 1000°C. Compared with iron-based materials at 1200-1300°C There is no chemical reaction at all times, so dry cutting is often used when using CBN tools. Therefore, CBN materials are unique in processing ferrous metal materials and have become the first choice for difficult-to-process materials.
Characteristics of PCBN tool
1. Ability to process high-quality workpieces;
2. Improve the efficiency of workpiece processing;
3. Machining flexibility is stronger;
4. Decrease in equipment investment;
5. No coolant is required;
6. Chip is easy to recycle;
7. Chips are more likely to be broken and discharged.