With the development of the materials industry and the precision machinery industry, the use of precision cutting, ultra-precision cutting and difficult-to-cut materials has increased, and the application of super-hard tool materials has become increasingly widespread.
Superhard material cutters are characterized by high work efficiency, long service life and good processing quality. They used to be used for finishing. In recent years, due to the improvement of the production process of artificial superhard tool materials, the purity and grain size of raw materials have been controlled. Composite materials and hot pressing processes, etc., the application range is expanding, in addition to general finishing and semi-finishing, it can also be used for roughing, and is internationally recognized as one of the most promising tool materials for improving productivity in the world. . Using ultra-hard materials to process steel, cast iron, non-ferrous metals and their alloys, the cutting speed can be an order of magnitude higher than that of cemented carbide, and the tool life can be tens or even hundreds of times higher than that of cemented carbide. At the same time, its appearance also changes the traditional process concept. With super-hard tools, it can often be directly milled or milled (or polished). For hardened parts processing, a single process can be used instead of multiple processes, which greatly shortens the process. .
Overview of the development of superhard tool materials
Superhard tool material refers to natural diamond and synthetic diamond and CBN (cubic boron nitride) with similar hardness and performance. Since natural diamonds are relatively expensive, artificial polycrystalline diamond (PCD), polycrystalline cubic boron nitride (PCBN), and their composites are mostly used in production.
As early as the 1950s, the United States used synthetic diamond micropowder and artificial CBN micropowder to form larger size polycrystalline blocks as tool materials under the action of high temperature, high pressure, catalyst and binder. Since then, South Africa's DeBeers, the former Soviet Union and Japan have also been successfully developed. In the early 1970s, diamond or CBN and cemented carbide composite sheets were introduced. They were sintered or pressed on a cemented carbide substrate with a layer of 0.5 mm to 1 mm of PCD or PCBN to solve the bending resistance of superhard tool materials. Problems such as low strength and difficulty in inserting welds make the application of superhard tools into practical use. At present, artificial synthetic large single crystal diamonds, as well as functional materials such as diamond thin film coatings and diamond thick films produced by CVD (Chemical Vapor Deposition), have greatly expanded the application fields of superhard tool materials.
The research and application of superhard tool materials in China began in the 1970s, and in 1970, the first professional manufacturer of superhard materials and products in China, the sixth grinding wheel factory, was built in Guiyang from 1970 to 1990. The annual production of superhard materials has increased from 460,000 carats to 35 million carats. Around the 1990s, many superhard material production professional factories imported complete sets of superhard material synthesis equipment and technology from abroad, and the output has been developed rapidly. By 1997, the annual output of artificial diamonds in China has reached 500 million carats, and the annual output of CBN has reached 8 million carats, ranking first in the world's largest producer of superhard materials.
Superhard tool material performance
Diamond has extremely high hardness and wear resistance, and its microhardness is up to 10000 HV, making it the hardest material in tool materials. At the same time, its friction coefficient is small, it has no affinity with non-ferrous metals, the chips are easy to flow out, the thermal conductivity is high, the built-up edge is not easy to be formed during cutting, and the surface quality is good. Can effectively process non-ferrous metal materials and non-metallic materials, such as copper, aluminum and other non-ferrous metals and their alloys, ceramics, sintered carbides, various fiber and particle reinforced composite materials, plastics, rubber, graphite, glass And a variety of wear-resistant wood (especially composite materials such as solid wood and plywood).
The disadvantage of diamond is poor toughness and low thermal stability. It is easy to carbonize at 700 ° C to 800 ° C, so it is not suitable for processing steel materials. Since iron atoms easily interact with carbon atoms at high temperatures, they are converted into a graphite structure. In addition, when it is used to cut a nickel-based alloy, it also wears out quickly.
The hardness of CBN is second only to diamond (up to 8000HV~9000HV), and its thermal stability is high (up to 1250°C～1350°C). It is chemically inert to iron elements and has strong anti-bonding ability. It can be ground with diamond grinding wheel. It is suitable for processing hard-to-cut materials such as hardened steel, thermal spray materials, chilled cast iron and cobalt-based and nickel-based materials above 35HRC.
Super hard tool materials have broad application prospects
Superhard tool material is an advanced tool material with broad application prospects in production. Artificial super-hard tool material, the development of single crystal in the direction of coarse particles, high strength and multi-function. GE Corporation of the United States can now produce 6 carats of synthetic diamond (about 10 mm) with a maximum particle size of 11.14 carats. PCD is developed in the direction of large diameter, fine particle size, high impact resistance and high thermal stability.
The PCD has a maximum diameter of up to 74 mm and is then laser cut to any shape desired. The commercial size of PCD particles is from 2 μm to 25 μm; the finer the particles, the better the quality of the cutting edge; the larger the particles, the longer the tool life. The PCBN product produced by DeBeers has a maximum diameter of 101.6mm and can process 70HRC high hardness materials. In addition, according to the British patent, the UK has also developed a CVD method for depositing a mixture of nickel, copper, titanium, cobalt, chromium and niobium on the outer surfaces of PCD and PCBN inserts, as well as protection of titanium nitride or titanium carbide. The coating is 4 times more wear resistant than conventional PCD and PCBN inserts.
CVD diamond film and thick film are newly developed functional materials in recent years. Although the production has not yet formed a scale, it has a wide range of applications due to its excellent performance.
There are cross-cutting applications between natural and synthetic single crystal diamonds, as well as PCD and TFD. They can complement each other to a certain extent and must be selected according to different specific conditions, especially the performance price ratio. It is expected that in the new century, super-hard tool materials CBN and diamond will be used more and more, and it may be found that a new variety of tool materials can be produced with superior performance. According to the company of Lellond, they developed a superhard composite material made of ceramic + CBN, which combines the advantages of both ceramic and CBN materials, and is an ideal material for high-speed machining of high-hard wear-resistant cast iron. For example, diamond polycrystals synthesized from graphite raw materials, and today's diamonds are C12, have been studied, and the isotopes C13 and C60 are more rigid. A few years ago, Wuhan University developed a C3N4/TiN film, which also has super-hard material properties. It can be coated on a high-speed steel drill bit to greatly improve the life of the drill bit. It can be expected that with the increase in the application of various new difficult-to-cut materials, it will certainly promote the further development and application of super-hard tool materials.
Superhard material cutters are characterized by high work efficiency, long service life and good processing quality. They used to be used for finishing. In recent years, due to the improvement of the production process of artificial superhard tool materials, the purity and grain size of raw materials have been controlled. Composite materials and hot pressing processes, etc., the application range is expanding, in addition to general finishing and semi-finishing, it can also be used for roughing, and is internationally recognized as one of the most promising tool materials for improving productivity in the world. . Using ultra-hard materials to process steel, cast iron, non-ferrous metals and their alloys, the cutting speed can be an order of magnitude higher than that of cemented carbide, and the tool life can be tens or even hundreds of times higher than that of cemented carbide. At the same time, its appearance also changes the traditional process concept. With super-hard tools, it can often be directly milled or milled (or polished). For hardened parts processing, a single process can be used instead of multiple processes, which greatly shortens the process. .
Overview of the development of superhard tool materials
Superhard tool material refers to natural diamond and synthetic diamond and CBN (cubic boron nitride) with similar hardness and performance. Since natural diamonds are relatively expensive, artificial polycrystalline diamond (PCD), polycrystalline cubic boron nitride (PCBN), and their composites are mostly used in production.
As early as the 1950s, the United States used synthetic diamond micropowder and artificial CBN micropowder to form larger size polycrystalline blocks as tool materials under the action of high temperature, high pressure, catalyst and binder. Since then, South Africa's DeBeers, the former Soviet Union and Japan have also been successfully developed. In the early 1970s, diamond or CBN and cemented carbide composite sheets were introduced. They were sintered or pressed on a cemented carbide substrate with a layer of 0.5 mm to 1 mm of PCD or PCBN to solve the bending resistance of superhard tool materials. Problems such as low strength and difficulty in inserting welds make the application of superhard tools into practical use. At present, artificial synthetic large single crystal diamonds, as well as functional materials such as diamond thin film coatings and diamond thick films produced by CVD (Chemical Vapor Deposition), have greatly expanded the application fields of superhard tool materials.
The research and application of superhard tool materials in China began in the 1970s, and in 1970, the first professional manufacturer of superhard materials and products in China, the sixth grinding wheel factory, was built in Guiyang from 1970 to 1990. The annual production of superhard materials has increased from 460,000 carats to 35 million carats. Around the 1990s, many superhard material production professional factories imported complete sets of superhard material synthesis equipment and technology from abroad, and the output has been developed rapidly. By 1997, the annual output of artificial diamonds in China has reached 500 million carats, and the annual output of CBN has reached 8 million carats, ranking first in the world's largest producer of superhard materials.
Superhard tool material performance
Diamond has extremely high hardness and wear resistance, and its microhardness is up to 10000 HV, making it the hardest material in tool materials. At the same time, its friction coefficient is small, it has no affinity with non-ferrous metals, the chips are easy to flow out, the thermal conductivity is high, the built-up edge is not easy to be formed during cutting, and the surface quality is good. Can effectively process non-ferrous metal materials and non-metallic materials, such as copper, aluminum and other non-ferrous metals and their alloys, ceramics, sintered carbides, various fiber and particle reinforced composite materials, plastics, rubber, graphite, glass And a variety of wear-resistant wood (especially composite materials such as solid wood and plywood).
The disadvantage of diamond is poor toughness and low thermal stability. It is easy to carbonize at 700 ° C to 800 ° C, so it is not suitable for processing steel materials. Since iron atoms easily interact with carbon atoms at high temperatures, they are converted into a graphite structure. In addition, when it is used to cut a nickel-based alloy, it also wears out quickly.
The hardness of CBN is second only to diamond (up to 8000HV~9000HV), and its thermal stability is high (up to 1250°C～1350°C). It is chemically inert to iron elements and has strong anti-bonding ability. It can be ground with diamond grinding wheel. It is suitable for processing hard-to-cut materials such as hardened steel, thermal spray materials, chilled cast iron and cobalt-based and nickel-based materials above 35HRC.
Super hard tool materials have broad application prospects
Superhard tool material is an advanced tool material with broad application prospects in production. Artificial super-hard tool material, the development of single crystal in the direction of coarse particles, high strength and multi-function. GE Corporation of the United States can now produce 6 carats of synthetic diamond (about 10 mm) with a maximum particle size of 11.14 carats. PCD is developed in the direction of large diameter, fine particle size, high impact resistance and high thermal stability.
The PCD has a maximum diameter of up to 74 mm and is then laser cut to any shape desired. The commercial size of PCD particles is from 2 μm to 25 μm; the finer the particles, the better the quality of the cutting edge; the larger the particles, the longer the tool life. The PCBN product produced by DeBeers has a maximum diameter of 101.6mm and can process 70HRC high hardness materials. In addition, according to the British patent, the UK has also developed a CVD method for depositing a mixture of nickel, copper, titanium, cobalt, chromium and niobium on the outer surfaces of PCD and PCBN inserts, as well as protection of titanium nitride or titanium carbide. The coating is 4 times more wear resistant than conventional PCD and PCBN inserts.
CVD diamond film and thick film are newly developed functional materials in recent years. Although the production has not yet formed a scale, it has a wide range of applications due to its excellent performance.
There are cross-cutting applications between natural and synthetic single crystal diamonds, as well as PCD and TFD. They can complement each other to a certain extent and must be selected according to different specific conditions, especially the performance price ratio. It is expected that in the new century, super-hard tool materials CBN and diamond will be used more and more, and it may be found that a new variety of tool materials can be produced with superior performance. According to the company of Lellond, they developed a superhard composite material made of ceramic + CBN, which combines the advantages of both ceramic and CBN materials, and is an ideal material for high-speed machining of high-hard wear-resistant cast iron. For example, diamond polycrystals synthesized from graphite raw materials, and today's diamonds are C12, have been studied, and the isotopes C13 and C60 are more rigid. A few years ago, Wuhan University developed a C3N4/TiN film, which also has super-hard material properties. It can be coated on a high-speed steel drill bit to greatly improve the life of the drill bit. It can be expected that with the increase in the application of various new difficult-to-cut materials, it will certainly promote the further development and application of super-hard tool materials.
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