Application and prospect of diamond and superhard materials
Due to its superior performance and superb application, superhard materials have evolved from metal processing to areas where traditional processing such as optical glass processing, stone processing, ceramic processing, hard and brittle materials processing is difficult.
Natural single crystal diamonds have anisotropy, so the hardness of each crystal plane is very different. When the tool is sharpened, the soft side is selected as the grinding surface, and the hard surface is used as the rake face or the flank face. This brings favorable conditions for grinding. Because of its anisotropy, in the use, reasonable choice of crystal plane must be considered. For example, the anvil of the hardness tester, in use, uses the pressure or bounce to measure The hardness of the material is measured, but the results vary depending on the hardness of the working surface. Of course, the hard surface is advantageous for prolonging the life. For example, the wire drawing die made of natural diamond, because the working face of the hole is composed of crystal faces, The hardness is inconsistent, the wear will be uneven, and the stress difference will be caused to the circular section of the wire. The hardness will be uneven, which will affect the use. The diamond sintered body and the thick film diamond will become very useful in this kind of products due to isotropy. favorable.
PCD and PCBN have different properties due to their different crystal grains, and they must be reasonably selected.
Thick-film diamond is pure diamond, its hardness is close to that of natural diamond, and PCD and PCDN are sintered by mixing diamond powder and binder. Therefore, the hardness is affected by the binder, and its hardness is not as good as the former.
It is well known that diamond has an affinity for iron and can only be used on non-ferrous metals and non-metallic materials, and CBN is fully capable of cutting ferrous metals even at a high temperature of 1000 °C. It has become the main cutting tool material for difficult materials in the future. Generally superhard materials refer to synthetic diamond, artificial CBN. The simultaneous existence of these two materials plays a complementary role, covering the current and future development of various new materials, which is extremely beneficial to the entire cutting process.
The high-precision sharpening of diamond cutting tools requires a high level of skill. In order to obtain a more precise cutting edge arc radius, especially the accuracy of less than 0.05um, the grinding machine is put into strict requirements and must have a very high rotation. The precision of the spindle shaft system, the old-fashioned grinding machine has not adapted, more of the air bearing is used as the support, the grinding disc must be able to be flattened on the machine tool, so that the end face runout is controlled below 0.5um. The sharpening of PCD and PCBN is relatively easy, because the hardness is relatively low, diamond grinding wheel can be used, and thick film diamond is different, its hardness is close to natural diamond, and it is isotropic, so it is difficult to sharpen. .
Recently, the sharpening of diamond cutting tools has attracted people's attention. New sharpening solutions have been proposed one after another, among which thermochemical methods have been introduced. For example, Professor Yoshikawa Yoshikawa of Tokyo Institute of Technology in Japan used a cast iron plate heated to 800 °C. In the concept of accelerated grinding, it is believed that 70% of the grinding work is coarsely ground, so most of the retention can be removed by thermochemical methods, and then refined, which can greatly improve the work efficiency of diamond sharpening.
3 Precautions in the application of diamond and super-hard materials Natural single crystal diamond In the current ultra-precision machining, natural single crystal diamond cutting tools are essential. It achieves an extremely sharp cutting edge with a radius of the edge of the cutting edge that is not detectable by scanning electron microscopy (SEM). According to Prof. Igawa, Professor of Osaka University, Japan, the minimum is 2~4nm, which is the highest level at present, which is calculated from the chip with a thickness of 1nm obtained by cutting. In 1986, a diamond edge evaluation committee was set up in Japan to solve the measurement problem of the tool tip. It has not been solved very well today, but it has been raised from 0.05um to 2~4nm. In 1992, Toshiba Shoji of Toshiba Machinery also proposed the use of scanning tunneling microscopy (STM) or atomic force microscopy (AFM) for testing. However, it has not been reported. The Chinese Academy of Technology in China reported the use of AFM in 1996. Progress has been made, which is a gratifying achievement.
Natural single crystal diamonds have anisotropy, so the hardness of each crystal plane is very different. When the tool is sharpened, the soft side is selected as the grinding surface, and the hard surface is used as the rake face or the flank face. This brings favorable conditions for grinding. Because of its anisotropy, in the use, reasonable choice of crystal plane must be considered. For example, the anvil of the hardness tester, in use, uses the pressure or bounce to measure The hardness of the material is measured, but the results vary depending on the hardness of the working surface. Of course, the hard surface is advantageous for prolonging the life. For example, the wire drawing die made of natural diamond, because the working face of the hole is composed of crystal faces, The hardness is inconsistent, the wear will be uneven, and the stress difference will be caused to the circular section of the wire. The hardness will be uneven, which will affect the use. The diamond sintered body and the thick film diamond will become very useful in this kind of products due to isotropy. favorable.
PCD and PCBN have different properties due to their different crystal grains, and they must be reasonably selected.
Thick-film diamond is pure diamond, its hardness is close to that of natural diamond, and PCD and PCDN are sintered by mixing diamond powder and binder. Therefore, the hardness is affected by the binder, and its hardness is not as good as the former.
It is well known that diamond has an affinity for iron and can only be used on non-ferrous metals and non-metallic materials, and CBN is fully capable of cutting ferrous metals even at a high temperature of 1000 °C. It has become the main cutting tool material for difficult materials in the future. Generally superhard materials refer to synthetic diamond, artificial CBN. The simultaneous existence of these two materials plays a complementary role, covering the current and future development of various new materials, which is extremely beneficial to the entire cutting process.
The high-precision sharpening of diamond cutting tools requires a high level of skill. In order to obtain a more precise cutting edge arc radius, especially the accuracy of less than 0.05um, the grinding machine is put into strict requirements and must have a very high rotation. The precision of the spindle shaft system, the old-fashioned grinding machine has not adapted, more of the air bearing is used as the support, the grinding disc must be able to be flattened on the machine tool, so that the end face runout is controlled below 0.5um. The sharpening of PCD and PCBN is relatively easy, because the hardness is relatively low, diamond grinding wheel can be used, and thick film diamond is different, its hardness is close to natural diamond, and it is isotropic, so it is difficult to sharpen. .
Recently, the sharpening of diamond cutting tools has attracted people's attention. New sharpening solutions have been proposed one after another, among which thermochemical methods have been introduced. For example, Professor Yoshikawa Yoshikawa of Tokyo Institute of Technology in Japan used a cast iron plate heated to 800 °C. In the concept of accelerated grinding, it is believed that 70% of the grinding work is coarsely ground, so most of the retention can be removed by thermochemical methods, and then refined, which can greatly improve the work efficiency of diamond sharpening.
3 Precautions in the application of diamond and super-hard materials Natural single crystal diamond In the current ultra-precision machining, natural single crystal diamond cutting tools are essential. It achieves an extremely sharp cutting edge with a radius of the edge of the cutting edge that is not detectable by scanning electron microscopy (SEM). According to Prof. Igawa, Professor of Osaka University, Japan, the minimum is 2~4nm, which is the highest level at present, which is calculated from the chip with a thickness of 1nm obtained by cutting. In 1986, a diamond edge evaluation committee was set up in Japan to solve the measurement problem of the tool tip. It has not been solved very well today, but it has been raised from 0.05um to 2~4nm. In 1992, Toshiba Shoji of Toshiba Machinery also proposed the use of scanning tunneling microscopy (STM) or atomic force microscopy (AFM) for testing. However, it has not been reported. The Chinese Academy of Technology in China reported the use of AFM in 1996. Progress has been made, which is a gratifying achievement.
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