The cutting tool can be made of natural single crystal diamond, artificial single crystal diamond, chemical vapor deposition (CVD) diamond thick film, artificial polycrystalline diamond compact, and the like.
1, natural single crystal diamond
Natural single crystal diamond An anisotropic single crystal. Hardness of HV9000-10000, the hardest substance in nature. This type of material has excellent wear resistance, cutting tool can be made to maintain dimensional stability for a long time, and therefore has a long tool life.
The natural diamond cutter edge can be machined extremely sharply. Can be used to make ophthalmic neurosurgical scalpels; can be used to process contact lens surface; can be used to cut light-guided glass fiber; used to process gold and platinum jewelry patterns; the most important use of high-speed ultra-finishing non-ferrous metals and their alloys. Such as aluminum, gold, babbitt, beryllium copper, copper and so on. Ultra-precision machining tools made of natural diamonds have a 400-fold circular arc at the tip of the knife and are observed under the microscope without defects. They are used for processing aluminum alloy polyhedral mirrors, oxygen-free copper laser mirrors, gyroscopes, and video recorder drums. The roughness can reach Ra (0.01-0.025) μm.
The natural diamond material has poor toughness and low bending strength, only (0.2-0.5) Gpa. The thermal stability is poor, and the hardness will be lost when the temperature reaches 700°C-800°C. When the temperature is higher, it will be carbonized. In addition, it is very strong with iron and is generally not suitable for processing steel.
2. Artificial single crystal diamond
Artificial single-crystal diamond as a tool material, the market can buy De Beers (DE-BEERS) production of industrial grade single crystal diamond material. This material is slightly less rigid than natural diamond. Other properties are comparable to natural diamonds. Due to the artificial manufacturing, the size of the cleavage direction becomes controllable and uniform. With the development of high-temperature and high-pressure technology, the maximum size of synthetic single-crystal diamond can already reach 8mm. Due to the relatively good consistency and low price of this material, it has received extensive attention. As an alternative to new natural diamond materials, artificial single crystal diamond applications will have great development.
3, artificial polycrystalline diamond
Artificial polycrystalline diamond (PCD) is a polycrystalline material obtained by solvent polymerization of diamond micropowders under high temperature and high pressure. Under normal circumstances made of carbide as a matrix of the overall round piece, called polycrystalline diamond compact. According to the different thickness of the diamond matrix, the composite sheet has different specifications of 1.6mm, 3.2mm, 4.8mm and so on. The thickness of polycrystalline diamond is generally about 0.5mm. At present, the domestic production of PCD diameter has reached 19mm, while foreign companies such as GE's largest composite sheet diameter has been 58mm, De Beers company has reached 74mm.
According to the production of tools, laser or wire cutting can be used to cut the cutter heads into different sizes to make lathes, boring cutters, and milling cutters.
The hardness of PCD is lower than that of natural diamond (about HV6000), but its bending strength is much higher than that of natural diamond. In addition, by adjusting the particle size concentration of diamond powder, the physical and mechanical properties of PCD products are changed to meet the needs of different materials and different processing environments, providing a variety of choices for tool users.
PCD cutters are much more shock resistant than natural diamonds. Compared with hard alloy, the hardness is 3-4 times higher; the wear life is 50-100 times longer; the cutting speed can be increased by 5-20 times; the roughness can reach Ra0.05μm. High cutting efficiency and stable machining accuracy.
PCD, like natural diamond, is not suitable for processing steel cast iron. This tool is mainly used to process non-ferrous metals and non-metallic materials, such as: aluminum, copper, zinc, gold, silver, platinum and its alloys, as well as ceramics, carbon fiber, rubber, plastics and so on. Another major feature of PCD is processing wood stone.
PCD tools are particularly suitable for processing high-silicon aluminum alloys, so the automotive, aerospace, electronics, and marine industries are widely used.
4, CVD diamond film
CVD Diamond Thick Film A chemical vapor deposition method for making diamond material. As a tool material its hardness is higher than PCD. Because it does not contain metal binders, it has high thermal conductivity and high temperature oxidation resistance. However, the toughness of currently produced CVD materials is relatively poor, and it cannot be cut and processed by a wire cutting method, and its use has been limited. Because there is no cutting directionality and the grinding process is poor, it is extremely difficult to grind a sharp edge like a natural diamond single crystal diamond. The use as a cutting tool is still in the experimental stage, pending further research and development.