1. Diamond, diamond-like (DLC) coating
Diamond coating is one of the new tool coating materials. It uses a low-pressure chemical vapor deposition technique to grow a diamond film composed of polycrystals on a cemented carbide substrate, and processes materials such as non-ferrous metals such as silicon-aluminum alloys and copper alloys, glass fibers, and hard alloys. Tool life is 50 to 100 times that of ordinary carbide tools. The diamond coating uses a number of diamond synthesis techniques, the most common being the hot wire method, the microwave plasma method and the DC plasma spray method. Diamond coated tools have been produced and improved in the industry by improving the adhesion of coating methods and coatings.
In recent years, the United States, Japan and Sweden have successively introduced diamond-coated taps, reamers, milling cutters, and small-hole diamond-coated carbide drills for processing printed circuit boards and various indexables. Blades, such as the CD1810 from Sweden's Sandvik and KCD25 from Kennametal, USA. A new process for laser plasma deposition of diamonds developed by Turchan Corporation of the United States uses this method to deposit diamond. Since the plasma field surrounds the entire tool, the coating on the tool is uniform and the deposition speed is 1000 times faster than the conventional CVD method. The diamond coating formed by this method produces a true metallurgical bond with the substrate, and the coating has high strength and can prevent defects such as peeling, cracking and cracking of the coating. CemeCon has a unique CVD diamond coating technology. In 2000, it established a production line to make the diamond coating technology reach the industrial production level. Its high technical content enables the mass production of diamond coating.
Diamond-like coatings have significant advantages in the machining of certain materials (Al, Ti and their composites). The microstructure of the diamond-like coating deposited by low pressure vapor deposition is still quite different from that of natural diamond. In the 1990s, low-pressure vapor-deposited DLC in the presence of activated hydrogen was often used, and the coating contained a large amount of hydrogen. Excessive hydrogen will reduce the adhesion and hardness of the coating and increase the internal stress. The hydrogen in the DLC will slowly release at higher temperatures, causing the coating to work unstable. The hydrogen-free DLC hardness is higher than that of hydrogen-containing DLC, and has the advantages of uniform structure, large area deposition, low cost, and smooth surface. It has become a hot spot in DLC coating research in recent years. American scientist AAVoevodin proposed that the structure of the deposited superhard DLC coating is designed as a Ti-TiC-DLC gradient-transformed coating, which gradually increases the hardness from a softer steel substrate to a super-hard DLC coating. This type of composite coating maintains high hardness and low coefficient of friction, reduces brittleness, and improves load bearing, bonding and wear resistance. Sumitomo Corporation of Japan has introduced a DL1000 coating coated with diamond DLC on a cemented carbide insert for cutting aluminum alloys and non-ferrous metals. It is resistant to sticking and can effectively reduce the roughness of the machined surface.
After years of research, it is proved that due to the high internal stress of the diamond-like coating, poor thermal stability and the catalyst effect with the ferrous metal, the SP3 structure is transformed into SP2, which determines that it can only be applied to the processing of non-ferrous metals. It is further applied in machining. However, recent studies have shown that the hardness of diamond-like coatings (also known as graphite-like coatings) based on SP2 structure can reach 20-40 GPa, but there is no problem with the catalytic effect of ferrous metals, and the friction coefficient is very high. Low and good moisture resistance, it can be used for cutting and coolant cutting. Its life is doubled compared with uncoated knives. It can process steel materials, which has caused the coating company and the tool manufacturer. Great interest. Over time, this new type of diamond-like coating will be widely used in the field of cutting.
2 cubic boron nitride (CBN) coating
CBN is another superhard material that emerges after synthetic diamond. It has many excellent physical and chemical properties similar to diamonds (such as ultra high hardness, second only to diamond, high wear resistance, low friction coefficient, low In addition to the coefficient of thermal expansion, etc., it also has some properties superior to diamond. CBN is chemically inert to iron, steel and oxidizing environments and forms a thin layer of boron oxide during oxidation. This oxide provides chemical stability to the coating, so it is heat resistant when processing hard iron and grey cast iron. It is extremely excellent, and it can cut heat-resistant steel, hardened steel, titanium alloy, etc. at a relatively high cutting temperature, and can cut high-hardness chill rolls, carburized and quenched materials, and silicon-aluminum alloys with very serious tool wear. Processing materials. Since the successful preparation of pure CBN coatings by Inagawa et al in 1987, the research boom of CBN hard coatings has been launched internationally. The methods for low pressure gas phase synthesis of CBN coatings are mainly CVD and PVD methods. CVD includes chemical transport PCVD, hot wire assisted heating PCVD, ECR-CVD, etc.; PVD has reactive ion beam plating, active reactive evaporation, laser evaporation ion beam assisted deposition, and the like. The research results show that the progress has been made in the synthesis of CBN phase, good adhesion to cemented carbide matrix and suitable hardness. At present, the maximum amount of cubic boron nitride deposited on cemented carbide is only 0.2-0.5μm. In order to achieve commercialization, reliable technology must be used to deposit high-purity and economical CBN coatings with a thickness of 3 to 5 μm, which is confirmed in actual metal cutting.
3.CNx coating
In the 1980s, American scientists Liu and Cohen designed a new β-C3N4 compound like β-Si3N4. Using solid physics and quantum chemistry theory, it was calculated that its hardness might reach diamond, which attracted the attention of scientists all over the world. Synthetic carbon nitride has become a hot topic in the world of materials science. Fujimoto of Okayama University in Japan used electron beam evaporation ion beam assisted deposition to obtain a carbon nitride coating of 63.7 Gpa. The hardness of carbon nitride synthesized by Wuhan University reached 50GPa, and it was deposited on high-speed steel twist drill to obtain very good drilling performance. The main methods for synthesizing carbon nitride include true flow and RF reactive sputtering, laser evaporation and ion beam assisted deposition ECR-CVD, and dual ion beam deposition.
Diamond coating is one of the new tool coating materials. It uses a low-pressure chemical vapor deposition technique to grow a diamond film composed of polycrystals on a cemented carbide substrate, and processes materials such as non-ferrous metals such as silicon-aluminum alloys and copper alloys, glass fibers, and hard alloys. Tool life is 50 to 100 times that of ordinary carbide tools. The diamond coating uses a number of diamond synthesis techniques, the most common being the hot wire method, the microwave plasma method and the DC plasma spray method. Diamond coated tools have been produced and improved in the industry by improving the adhesion of coating methods and coatings.
In recent years, the United States, Japan and Sweden have successively introduced diamond-coated taps, reamers, milling cutters, and small-hole diamond-coated carbide drills for processing printed circuit boards and various indexables. Blades, such as the CD1810 from Sweden's Sandvik and KCD25 from Kennametal, USA. A new process for laser plasma deposition of diamonds developed by Turchan Corporation of the United States uses this method to deposit diamond. Since the plasma field surrounds the entire tool, the coating on the tool is uniform and the deposition speed is 1000 times faster than the conventional CVD method. The diamond coating formed by this method produces a true metallurgical bond with the substrate, and the coating has high strength and can prevent defects such as peeling, cracking and cracking of the coating. CemeCon has a unique CVD diamond coating technology. In 2000, it established a production line to make the diamond coating technology reach the industrial production level. Its high technical content enables the mass production of diamond coating.
Diamond-like coatings have significant advantages in the machining of certain materials (Al, Ti and their composites). The microstructure of the diamond-like coating deposited by low pressure vapor deposition is still quite different from that of natural diamond. In the 1990s, low-pressure vapor-deposited DLC in the presence of activated hydrogen was often used, and the coating contained a large amount of hydrogen. Excessive hydrogen will reduce the adhesion and hardness of the coating and increase the internal stress. The hydrogen in the DLC will slowly release at higher temperatures, causing the coating to work unstable. The hydrogen-free DLC hardness is higher than that of hydrogen-containing DLC, and has the advantages of uniform structure, large area deposition, low cost, and smooth surface. It has become a hot spot in DLC coating research in recent years. American scientist AAVoevodin proposed that the structure of the deposited superhard DLC coating is designed as a Ti-TiC-DLC gradient-transformed coating, which gradually increases the hardness from a softer steel substrate to a super-hard DLC coating. This type of composite coating maintains high hardness and low coefficient of friction, reduces brittleness, and improves load bearing, bonding and wear resistance. Sumitomo Corporation of Japan has introduced a DL1000 coating coated with diamond DLC on a cemented carbide insert for cutting aluminum alloys and non-ferrous metals. It is resistant to sticking and can effectively reduce the roughness of the machined surface.
After years of research, it is proved that due to the high internal stress of the diamond-like coating, poor thermal stability and the catalyst effect with the ferrous metal, the SP3 structure is transformed into SP2, which determines that it can only be applied to the processing of non-ferrous metals. It is further applied in machining. However, recent studies have shown that the hardness of diamond-like coatings (also known as graphite-like coatings) based on SP2 structure can reach 20-40 GPa, but there is no problem with the catalytic effect of ferrous metals, and the friction coefficient is very high. Low and good moisture resistance, it can be used for cutting and coolant cutting. Its life is doubled compared with uncoated knives. It can process steel materials, which has caused the coating company and the tool manufacturer. Great interest. Over time, this new type of diamond-like coating will be widely used in the field of cutting.
2 cubic boron nitride (CBN) coating
CBN is another superhard material that emerges after synthetic diamond. It has many excellent physical and chemical properties similar to diamonds (such as ultra high hardness, second only to diamond, high wear resistance, low friction coefficient, low In addition to the coefficient of thermal expansion, etc., it also has some properties superior to diamond. CBN is chemically inert to iron, steel and oxidizing environments and forms a thin layer of boron oxide during oxidation. This oxide provides chemical stability to the coating, so it is heat resistant when processing hard iron and grey cast iron. It is extremely excellent, and it can cut heat-resistant steel, hardened steel, titanium alloy, etc. at a relatively high cutting temperature, and can cut high-hardness chill rolls, carburized and quenched materials, and silicon-aluminum alloys with very serious tool wear. Processing materials. Since the successful preparation of pure CBN coatings by Inagawa et al in 1987, the research boom of CBN hard coatings has been launched internationally. The methods for low pressure gas phase synthesis of CBN coatings are mainly CVD and PVD methods. CVD includes chemical transport PCVD, hot wire assisted heating PCVD, ECR-CVD, etc.; PVD has reactive ion beam plating, active reactive evaporation, laser evaporation ion beam assisted deposition, and the like. The research results show that the progress has been made in the synthesis of CBN phase, good adhesion to cemented carbide matrix and suitable hardness. At present, the maximum amount of cubic boron nitride deposited on cemented carbide is only 0.2-0.5μm. In order to achieve commercialization, reliable technology must be used to deposit high-purity and economical CBN coatings with a thickness of 3 to 5 μm, which is confirmed in actual metal cutting.
3.CNx coating
In the 1980s, American scientists Liu and Cohen designed a new β-C3N4 compound like β-Si3N4. Using solid physics and quantum chemistry theory, it was calculated that its hardness might reach diamond, which attracted the attention of scientists all over the world. Synthetic carbon nitride has become a hot topic in the world of materials science. Fujimoto of Okayama University in Japan used electron beam evaporation ion beam assisted deposition to obtain a carbon nitride coating of 63.7 Gpa. The hardness of carbon nitride synthesized by Wuhan University reached 50GPa, and it was deposited on high-speed steel twist drill to obtain very good drilling performance. The main methods for synthesizing carbon nitride include true flow and RF reactive sputtering, laser evaporation and ion beam assisted deposition ECR-CVD, and dual ion beam deposition.
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