Progress and future of high speed cutting tool materials

Abstract: This paper combines the research of high-speed cutting technology and tool materials, summarizes the progress and application of high-speed cutting tool materials, clarifies the opportunities and challenges faced by high-speed cutting tool materials in China, and points out the future of high-speed cutting tool materials.

1 Overview The general trend in the development of machining is high efficiency, high precision, high flexibility and environmental awareness. In the field of machining, cutting (grinding) is the most widely used processing method. High-speed cutting is the development direction of cutting and has become the mainstream of cutting. It is an important common key technology for advanced manufacturing technology. The promotion of high-speed cutting technology will greatly increase production efficiency and processing quality and reduce costs. The development and application of high-speed cutting technology is determined by advances in machine tools and tooling technology, where advances in tool materials play a decisive role. Studies have shown that at high speed cutting, as the cutting speed increases, the cutting force decreases, and the cutting temperature rises very high. After reaching a certain value, the rise gradually slows down. The main cause of tool damage is mechanical friction, bonding, chemical wear, chipping, crushing and plastic deformation under the action of cutting force and cutting temperature. Therefore, the most important requirement for high-speed cutting tool materials is high temperature. Mechanical properties, thermophysical properties, anti-blocking properties, chemical stability (oxidation, diffusivity, solubility, etc.) and thermal shock resistance as well as resistance to coating cracking. Based on this requirement, in the past 20 years, a number of tool materials suitable for high-speed cutting have been developed, and various workpiece materials can be machined under different cutting conditions. At present, the aluminum alloy can be cut at a high speed of 2500 to 5000 m/min (Si content ≤ 12%, more than 12% is 500 to 1500 m/min): Cutting cast iron at 500-1500 m/min: 300-1000 m/min cutting steel: 100 ~400m/min cutting hardened steel, heat resistant alloy: cutting titanium alloy from 90 to 200m/min. Of course, people are also looking forward to processing at ultra-high cutting speeds for better results.
2 Progress and application of high-speed cutting tool materials in foreign countries In high-speed cutting, the best cutting results can be obtained by selecting the tool materials and the allowable cutting conditions for different workpiece materials. Accordingly, for the high-speed cutting of aluminum alloys, cast irons, steels and alloys and heat-resistant alloys which are widely used in production at present, the developed tool materials mainly include: diamond, cubic boron nitride, ceramic cutters, coated cutters and TiC. (N) based cemented carbide tools (cermets).
Diamond Tools Diamond tools are divided into natural diamond and synthetic diamond tools. Natural diamond has the highest hardness and thermal conductivity in natural materials. However, due to the high price, processing and welding are very difficult. Except for a few special applications (such as watch precision parts, lighting parts and jewelry engraving), they are rarely used as cutting tools in the industry. With the development of high-tech and ultra-precision machining, such as micro-mechanical micro-parts, nuclear reactors and other high-tech mirrors, navigation gyros in missiles or rockets, computer hard disk chips, accelerator guns and other ultra-precision parts Processing, single crystal natural diamond can meet the above requirements. In recent years, a variety of chemical mechanisms for grinding diamond tools and a protective atmosphere brazing diamond technology have been developed, making the manufacturing process of natural diamond tools relatively simple. Therefore, in the high-tech application field of ultra-precision mirror cutting, natural diamond has played a role. Important role.
In the 1950s, after the synthesis of diamond powder by high temperature and high pressure technology, the diamond-based cutting tool, polycrystalline diamond (PCD), was fabricated in the 1970s. The PCD grains were disorderly arranged, and they were not directional, so the hardness was uniform. It has a very high hardness (8000 ~ 12000HV) and thermal conductivity, low coefficient of thermal expansion, high modulus of elasticity and low coefficient of friction, the blade is very sharp. It can process a variety of non-ferrous metals and extremely wear-resistant high-performance non-metallic materials, such as aluminum, copper, magnesium and their alloys, hard alloys, fiber plastic materials, metal matrix composites, wood composites and so on. The average size of diamond grains contained in PCD cutters is different, and the impact on performance is also different. The larger the grain size, the higher the wear resistance. Under similar cutting edge processing, the smaller the grain size, the better the cutting edge quality. For example, a PCD cutter with a grain size of 10 to 25 μm can be used to process aluminum alloys with a Si content of less than 12% at a high-speed grain size of 8 to 9 μm from 500 to 1500 m/min: PCD processed plastics and wood with a grain size of 4 to 5 μm. Wait. For ultra-precision machining, PCD tools with small grain sizes should be used. Usually the PCD tool is sintered into a diamond-hard alloy composite blade for welding on the body. Using an ultra-high pressure device, at a high temperature of 50,000 to 60,000 atmospheres and a high temperature of 1400 to 1600 °C, single crystal diamonds with neat shapes and very few impurities can be artificially synthesized, the quality is uniform and stable, the crystal surface is very clear, and the identification is easy. It has the highest thermal conductivity of all materials and the same strength as natural diamond. The current maximum size is up to 8mm. The uniformity of the size, shape and performance of such single crystal diamonds is not possible in natural diamond products. It has better wear resistance than PCD. The wear resistance of PCD will be weakened when it exceeds 700 °C. Because its structure contains metal Co, it promotes the "reverse reaction", that is, the conversion of diamond to graphite. However, it has good fracture toughness and can be used for interrupted cutting. For example, an aluminum alloy having a Si content of 10% can be milled at a high speed of 2500 m/min. At present, the application of synthetic single crystal diamond tool materials has been rapidly developed, and its new application field is the wood processing industry. There is a growing demand for highly wear-resistant layered wood flooring with an alumina coating on the surface. During processing, the wear-resistant layer of the wood board will cause passivation of the cutting edge, which causes the wear-resistant layer of alumina to be broken. The blade must be sharpened or replaced frequently, and the performance of the artificial single crystal diamond is significantly better than that of the PCD tool.
Chemical vapor deposition CVD diamonds are currently being researched and developed, depositing PCDs with excellent inter-growth, columnar structure and very dense. CVD diamond also exhibits different grain sizes and structures depending on the growth conditions. It does not require a metal catalyst, so its thermal stability is close to that of natural diamond. Depending on the application requirements, different CVD deposition processes can be selected to synthesize PCDs with widely different grain sizes and surface topography. CVD diamond as a tool requires a variety of different grain sizes due to its application. CVD diamond is made in two forms: one is to deposit a thin film (CVD film) having a thickness of less than 30 μm on the substrate: the other is to deposit a substrate-free thick diamond film (CVD thick film) having a thickness of 1 mm. At present, there are not many CVD thin film diamond applications.
The CVD thick film can be brazed to the substrate by special but simple and feasible techniques, but the strength of the solder joint is guaranteed. Compared with PCD, it has good thermal stability but high brittleness and is non-conductive. Cannot be used in electrical discharge machining (EDM) technology. CVD thick film diamonds are popularized in woodworking tools and dressing tools. Due to the high purity and high wear resistance and thermal stability of CVD thick film diamond, it has great potential in the field of high speed machining of high wear resistant materials. CVD thick film diamond tool materials currently available for EDM cutting have also been successfully manufactured and are still to be tested and evaluated. The current cost of CVD thick film diamond is relatively high. With the development of technology, the cost is gradually reduced, and it will be a strong competitor of PCD.
The performance characteristics of the three main diamond tool materials - PCD, CVD thick film and synthetic single crystal diamond are: PCD weldability, mechanical grinding and fracture toughness, wear resistance and cutting edge quality, corrosion resistance Worst. CVD thick film has the best corrosion resistance, mechanical grinding, edge quality, fracture toughness and wear resistance are middle, and weldability is poor. Synthetic single crystal diamond edge quality, wear resistance and corrosion resistance are the best, weldability, mechanical grinding and fracture toughness is the worst.
Diamond tool is the ideal tool material for high-speed cutting (2500～5000m/min) aluminum alloy. However, due to the affinity of carbon to iron, especially at high temperature, diamond can react with iron, so it is not suitable for cutting. Iron and its alloy workpieces.
Cubic Boron Nitride Cubic Boron Nitride (CBN) is a purely synthetic material. It is the second superhard material, CBN micropowder, synthesized in the late 1950s using a diamond-like method. Due to the poor sintering performance of CBN, it was not until the 1970s that a cubic boron nitride agglomerate (polycrystalline cubic boron nitride PCBN) was produced, which consisted of CBN fine powder and a small amount of binder phase (Co, Ni or TiC, TiN, Al2O3). ) is sintered under high temperature and high pressure. CBN is a dense phase of boron nitride, with high hardness (after diamond) and heat resistance (1300 ~ 1500 ° C), excellent chemical stability (far better than diamond) and thermal conductivity, low coefficient of friction . PCBN has a low affinity for Fe elements, so it is an ideal tool material for high-speed cutting of ferrous metals. The micro-grains in the PCBN structure are disorderly arranged, uniform in hardness, non-directional, consistent wear resistance and impact resistance, and overcome the disadvantages of CBN easy cleavage and anisotropy. The CBN content, grain size and bonding are equivalent to affect the performance of the PCBN. The CBN content is high, the hardness and thermal conductivity of PCBN are high, the CBN grain size is large, the damage resistance is weak, and the sharpness of the blade is poor. When the metal materials Co and Ni are used as the binder phase, PCBN has better toughness and conductivity. When the ceramic material is used as the binder phase, it has good thermal stability. At present, the PCBN layer of about 0.5mm is directly sintered or brazed on the cemented carbide substrate to form a PCBN composite sheet, which is advantageous for improving strength and solderability, and is convenient for manufacturing PCBN cutters.
There are roughly two types of PCBN blanks in terms of organization. One is a high content of PCBN (CBN, mass 80% to 90%), which is mainly composed of direct bonding between CBN grains, and has high hardness and high thermal conductivity. The other is PCBN with a low CBN content, which is firmly bonded with a small amount of metal or ceramic binder, and has good strength and toughness. Generally, the PCBN tool with lower CBN content (50%~65%) is suitable for finishing 45~65HRC hardened steel, high content (80%~90%) suitable for processing nickel-chromium cast iron, coarse and semi-coarse intermittent Cutting hardened steel, cutting cast iron at high speed, machining hard alloys, sintered metals and heavy alloys. A PCBN tool with a suitable CBN content can be used to process cast iron at a high speed of 500 to 1500 m/min, a hardened steel of 45 to 65 HRC at 100 to 400 m/min, and a heat resistant alloy at 100 to 200 m/min. However, it is not suitable to process steel and alloy steels, alloy cast irons and heat-resistant alloys with ferrite and below 45HRC, and it is not suitable for processing workpieces below 35HRC. Coated CBN tools are still under investigation.
Ceramic Tools Ceramic tools are one of the most important tool materials for high speed cutting. At present, the proportion of ceramic inserts in the world accounts for about 3% to 5% of the indexable blades, 5% to 7% in Russia, 7% to 9% in Japan, and 9% to 12% in Germany. Britain, France, Sweden, etc. It is also vigorously promoting its application. Due to the great progress in the raw materials, components and preparation processes of modern ceramic tools, the sales growth of ceramic knives has reached 20% in the past five years. The ceramic tools that have been developed internationally are mainly two series of alumina-based (Al2O3) and silicon nitride-based (Si3N4), which are added with various oxides, nitrides, carbides and borides to form different varieties. Alumina based and silicon nitride based ceramic tools. There are more than 40 varieties and more than 200 grades, of which there are more than 25 kinds of alumina base and nearly 15 kinds of silicon nitride base.
Ceramic knives have high hardness and wear resistance, hardness of 93 ~ 95HRA, good wear resistance, suitable for processing high hardness materials of 50 ~ 65HRC, such as chilled cast iron and hardened steel. High temperature performance, cutting at 1200 ° C. It has good anti-blocking property. Al2O3 has low affinity with metal. Its mutual reaction ability with various metals is lower than that of many carbides, nitrides and borides. It is not easy to bond with metals and has good chemical stability. The dissolution rate of Al2O3 in iron is about 1/5 of that of WC, and the diffusion wear is small. The oxidation resistance of Al2O3 is particularly good. Even if the blade is in a hot state, it can be used continuously for a long time, and is suitable for high-speed cutting. Ceramic tools also have a lower coefficient of friction than cemented carbide. The main disadvantages of Al2O3 based ceramic tools are low strength and fracture toughness, high brittleness, poor thermal conductivity and low thermal shock resistance. However, for decades, a lot of fruitful research work has been done on improving the mechanical properties of ceramic tools, such as hot pressing and hot isostatic pressing processes, adding various toughening and reinforcing phases, such as adding metal carbides to Al2O3. Nitride, boride and pure metals and whiskers, such as Al2O3 + TiC, Al2O3 + ZrO2, Al2O3 + SiCw (whiskers), Al2O3 + TiN, Al2O3 + TiCN, etc., some add a small amount of Mo in these composite ceramic tools Metals such as Ni and rare earth elements improve the performance of ceramic tools. Alumina-based ceramic tools can cut steel, cast iron and alloys at high speed, and Al2O3+SiCw is suitable for processing nickel-based alloys.
Compared with Al2O3 based ceramics, silicon nitride (Si3N4) based ceramics have the most remarkable characteristics of high strength and fracture toughness, low thermal expansion coefficient and low elastic modulus, so they have high thermal shock resistance. Si3N4 based ceramic tools are suitable for processing cast iron. Both continuous and interrupted cutting are superior to Al2O3 based ceramic tools. They can also be used for finishing and semi-finishing of high hardness materials such as chilled cast iron and high hardness rolls. However, because its chemical affinity with iron is significantly higher than that of Al2O3-based ceramics, the low melting point compound formed by chemical reaction will cause the blade to break in a short time. Therefore, the Si3N4-based ceramic tool is much worse than the Al2O3 base. The Si3N4 based ceramic tool also incorporates various toughening and reinforcing phases into the Si3N4 to form a variety of ceramic tools.
The Si3N4-Al2O3 (Sialon) ceramic tool is a new type of ceramic tool. It is developed on the basis of Si3N4 by replacing the nitrogen in Si3N4 with oxygen and replacing the silicon with aluminum. It is developed by Si-Al. -ON A general term for a variety of compound groups of various compositions. Sialon ceramic cutters have high strength and fracture toughness, good chemical stability, oxidation resistance and high temperature creep resistance. They have high thermal conductivity and small thermal expansion coefficient, so they have high thermal shock resistance. Due to its high creep strength, it is not subjected to repeated high stress and heat at the tip of the tool, and there is no obvious increase in damage due to plastic deformation. It is excellent for high speed roughing cast iron and nickel based alloy. Tool material. Whisker toughened ceramic knives are superior in difficult-to-machine materials such as fine cars and semi-finished nickel-based alloys. Sialon ceramic tools are more adaptable for roughing and milling, but their dissolution wear rate is much higher than that of Al2O3 based ceramic tools, making them unsuitable for machining steel.
Choosing the right type of ceramic tool can cut the cast iron at a high speed of 500-1000 m/min, cut the steel piece at a speed of 300-800 m/min, and cut the high-hard material (50-65HRC) at a speed of 100-200 m/min. The heat resistant alloy is cut at a speed of ~300 m/min.
The main components of TiC(N)-based cemented carbide TiC(N)-based cemented carbide are TiC (titanium carbide), TiN (titanium nitride) and TiCN (titanium carbonitride), which are TiC with high wear resistance. +Ni or Mo, high toughness TiC+WC+TaC+Co, strong TiN as the main body, and high-strength TiC+NbC and other TiC(N)-based cemented carbide. Compared with WC hard alloy, hardness, strength, toughness, plastic deformation resistance and chipping resistance are significantly improved, mainly high temperature strength, high temperature hardness, thermal conductivity, oxidation resistance and thermal shock resistance. Steel has a low affinity, a low coefficient of friction, and is resistant to crater wear and adhesion. It has now evolved into an independent series of tool materials. TiC(N)-based cemented carbide with high nitrogen content and uniform fine hard structure developed in recent years, suitable for cutting general steel and high speed at 200-400m/min due to good wear resistance and chipping resistance. Alloy steel can also be used for the finishing of cast iron.
Coated tools Coated tools are growing rapidly, with over 80% currently being coated. Widely used in the coating of different nitrides, oxides and borides on cemented carbide and high speed steel knives, among which alumina (Al2O3), titanium carbonitride (TiCN), titanium aluminum nitride (TiAlN) , titanium aluminum carbonitride (TiAlCN), etc., have excellent high temperature performance. From single coating to multi-coating, the coating process includes chemical vapor deposition (CVD) and physical vapor deposition (PVD). The PVD method is mainly used for high speed steel tools, and both CVD and PVD methods can be used for cemented carbide tool coatings. The PVD method of cemented carbide knives has good resistance to breakage and is suitable for interrupted cutting, but the wear resistance is not as good as that of CVD. The coating tool has different properties depending on the coating material. The coated carbide tool has high hardness and wear resistance (2100～4200HV), high heat resistance (1000～1200°C), high resistance. Excellent bonding properties, high chemical stability and low coefficient of friction, etc., excellent WC-based, TiC (N)-based cemented carbide and ceramics can be used as the substrate of the coating tool. At present, coating materials for coated carbide tools suitable for high-speed cutting mainly include CVD TiCN+Al2O3+TiN, TiCN+Al2O3, TiCN+Al2O3+HfN, TiN+Al2O3 and TiCN and PVD composite coating TiAlN/TiN. , TiAlN, etc. Single-coated TiC or TiN is no longer needed. Coated carbide tools with different coating materials can be used to process steel, alloy steel, stainless steel, cast iron and alloy cast iron at speeds of 200 to 500 m/min. Carbon nitride (CNx), nitride (TiN/NbN, TiN/VN) developed in recent years have good thermal stability at high temperatures and are suitable for high-speed cutting. Soft-coated tools (such as MoS2, WS2 coated high-speed steel tools) are mainly used to process high-strength aluminum alloys, titanium alloys or precious metals. The nano TiN/AlN composite coated milling insert recently developed in Japan has a coating of 2000 layers and a thickness of 2.5 nm per layer, which can be cut at high speed. At present, complex tools (bits, gear tools, broaches, etc.) are mainly coated with hard coatings such as TiCN and TiN on high-performance high-speed steel substrates. Coated tools are not suitable for rough machining and large impact interrupted cutting under special heavy loads and high hardness materials (such as hardened steel and chilled cast iron). When the coated tool is cut at low speed, it is prone to peeling and chipping, etc. After the coated tool is reground, the coating effect is reduced.
Powder metallurgy high speed steel (PM HSS)
In recent years, industrial developed countries have vigorously developed powder metallurgy high-speed steel, which is a small high-speed steel powder directly obtained from high-pressure steel molten steel atomized by high-pressure argon or pure nitrogen, and then hot isostatically pressed under high temperature and high pressure. Steel ingots, which are then made into high-speed steel. Compared with the high-speed steel manufactured by the fusion method, it has the advantages of no carbide segregation, fine and uniform grain powder, up to 2~3μm, hardness after heat treatment of 67-70HRC, and bending strength 0.5~1 times. The high temperature hardness at 600 ° C is 2 to 3 HRC higher, and the tool life is increased by 0.5 to 2 times under the same cutting conditions. Due to the isotropy of physical and mechanical properties, heat treatment deformation and stress can be reduced, making it suitable for manufacturing complex tools such as drills, broaches and gear tools. The cutting speed of this type of high-speed steel tool can be multiplied. After the surface PVD coating TiN, TiCN, TiAlN, the cutting speed can reach 150-200m/min. In the field of high-speed cutting of complex tools, powder metallurgy high-speed steel coated tools will further develop and occupy an important position.
3 Challenges faced by domestic high-speed cutting tool materials Domestic high-speed cutting tool materials are far from the foreign countries. At present, the tools used in imported and domestically produced high-speed machine tools mainly rely on imports, so domestic high-speed cutting tool materials face severe challenges.
At present, the most commonly used general-purpose tools in China are mainly high-speed steel (W18Cr4V), which are mostly produced by smaller manufacturers. High-performance high-speed steel such as aluminum high-speed steel and cobalt high-speed steel are of poor quality and are rarely used. Powder metallurgy high speed steel tools are still under study, and the cutting speed is generally 25 to 40 m/min. Cars, milling, boring and end mills are commonly used for hard alloys, but most of the welding knives are mainly ordinary hard alloys (TG, YT). Although the indexable insert has WC plus TaC, NbC or Hf-Nb, and ultra-fine cemented carbide products, the application is still not common, and the cutting speed is 100-200 m/min. Hard alloys such as deep hole drills and thread cutters have also been available in recent years, but their applications are less and the processing efficiency is generally low.
The most advantageous of domestic high-speed cutting tools is ceramic knives, and the level of research and development is comparable to that of the international. At present, there are more than 30 varieties of ceramic tools, including more than 20 alumina bases and nearly 10 silicon nitride bases. The production capacity of ceramic tools with and without holes is also very large.
We have closely combined cutting science and tool material science for decades. After in-depth research, we have established a new research system for ceramic tools based on cutting reliability, fusion of ceramic tool cutting theory and tool material research and development. Now we can optimize the design and obtain the ceramic cutting tool material with excellent performance, and we are making a breakthrough in the international frontier position of the combination of computer-aided design and hot-pressing process simulation of ceramic tool materials. The traditional research and development model accelerates the research and development of ceramic tools. Based on this theory, we have successfully developed 6 varieties of 12 grades of Al2O3 based ceramic tool materials, which have been put on the market, including aluminum-titanium (LT), whisker (JX), boron-titanium (LP), special powder and Rare earth LD series, gradient function (FG) and ceramic-hard alloy composite sheet (FH) series. The mechanical properties and wear and break resistance of the FG and FH series are significantly improved, extending tool life. JX-2, LP-2, gradient function FG, ceramic-hard alloy composite sheet (FH) and LD-1 with special powder in the six varieties are synergistically toughened to fill the domestic gap. No reports have been reported abroad. The mechanical properties and cutting performance of domestic ceramic tool products are comparable to those of foreign countries, and some are better. Domestic ceramic tools can turn or mill steel, alloy steel, cast iron and alloy cast iron at high speeds of 300-1000m/min. Among these Al2O3-based varieties, SG-4, FG-2 and FH-2 are currently domestic. The ideal tool material for high-speed machining of hardened steel (55-65HRC). The silicon nitride-based ceramic insert developed in China has excellent performance and has superior advantages in processing cast iron. Sialon ceramic tools are also available. The main difference in the existence of ceramic tools is that the precision and appearance quality of high-precision ceramic blades are still not good, and some varieties are not yet available. The promotion and application are far less common in developed countries.
Cucumber Boron Nitride (PCBN) for high-speed cutting in China was successfully developed in 1980 and polycrystalline diamond (PCD) in 1980. It has developed rapidly and can be used in various fields such as car, boring and milling. PCBN tools with different CBN content and PCD tools with different grain sizes. Among them, PCBN tools are mainly used for processing hardened steel, high-hard cast iron and some difficult-to-machine materials. PCD tools are mainly used for high silicon aluminum alloy processing. At present, superhard tools (PCBN, PCD and natural diamond ND), which are mainly researched and produced by many domestic joint ventures, dominate the market. Two types of tool applications are not yet common. Synthetic single crystal diamond and coated diamond are still under investigation.
Titanium carbide (TiC(N))-based hard alloys were developed in the late 1960s. The earliest TiC-based hard alloys have been developed. In recent years, TiC-TiN containing TiN and TiC(N)-based hard TiCN have been successfully developed. Several alloy products can be used for high speed precision and semi-finished steel, alloy steel and stainless steel of 200~400m/min. Recently, TiC+TiN nano-modified Ti(C,N)-based hard alloys with TiN nanopowders have been successfully developed in China. Tests have shown that processing 45 steel at a speed of 200 m/min is twice as long as that of a tool without nano-modification. There is currently no product. The main problem with Ti(C,N)-based tool materials is that there are fewer varieties and applications.
In the early 1970s, the company began to develop coated tools, initially developed CVD TiC single-coated hard alloys, and in the early 1980s studied PCD TiN single-coated high-speed steel tools. After years of hard work. A number of coating equipments have been imported from abroad. In recent years, CVD TiC-TiN, Al2O3-TiN multi-coated carbide inserts and PVD TiN, TiCN, TiAlN, TiAlCN composite multi-coated high-speed steel complex tools have been successfully developed. Low temperature (<600 °C) external thermal DC pulse plasma enhanced chemical vapor deposition (PCVD) technology has also been developed, with simple equipment, uniform coating thickness, high bonding strength, many types of coating materials, and no deformation of the workpiece. . However, the main products of coated tools on the market today are CVD Al2O3 and TiN composite coated carbide inserts and PVD TiN coated high speed steel tools. TiCN, TiAlN and TiAlCN commercial coating products are difficult to supply in time due to technical reasons, and there is still a gap between quality and foreign countries. PVD hard coatings such as carbon nitride (CNx), Al2O3, nitride [TiN(NbN), TiN/VN, etc.] and diamond PCD film coatings and soft coatings (MoS2, WS2) and nano-coatings are yet to be developed. . Foreign domestic agent companies are selling hot-selling coating tools, which has violently impacted the domestic market.
4 The future of high-speed cutting tool materials The goal of ultra-high-speed cutting is: milling aluminum is 10000m/min, cast iron is 5000m/min, ordinary steel is 2500m/min: while drilling aluminum, cast iron and ordinary steel are 30,000, 20000 and respectively 10000r/min. Therefore, in the future, it is necessary to develop tool materials with superior high temperature mechanical properties, high chemical stability and thermal stability, and high thermal shock resistance.
PCD tools will continue to evolve and improve performance. They are widely used in the processing of aluminum alloys and high-hardness non-metallic materials, but synthetic single crystal diamond and diamond thick film coatings will develop faster and will gradually replace PCD depending on their cost. In the field of high-speed ultra-precision mirror cutting, natural diamond tools still play an important role, but some will be replaced by artificial single crystal diamond. At present, the main reason for limiting the cutting speed of aluminum alloy machining by PCD tools is the spindle speed and power of the machine tool.
Al2O3 based and Si3N4 based ceramic tools and CBN tools are the preferred tool materials for high speed cutting of steel, cast iron and their alloys, but each has its scope of use and should continue to evolve. Al2O3-based ceramic tools have a wider application prospect for high-speed machining of steel and its alloys. Compared with CBN tools, it has both cost advantages and is suitable for processing hardened and unhardened steel and ferritic materials, but heat resistant. Sexual and thermal shock resistance is not enough. The development of nano-composite Al2O3-based ceramic knives with CBN added to the high temperature strength and thermal shock resistance of 1400-1500 °C is the main direction of the future. The development of Al2O3+Si3N4-based CBN composite tool materials with higher high-temperature strength and chemical stability in the field of high-speed processing of heat-resistant alloys is an important research direction.
Coated tool materials have great potential in high-speed cutting, continuing to research new coating technologies and coating materials to improve performance and expand use. But the main development of powder coating, that is, a new generation of coated tools coated with high-performance wear-resistant materials on cemented carbide and powder metallurgy high-speed steel powder (grain), can be reground without affecting its performance, for complex tools Especially meaningful. The preliminary development of a coated blade coated with Al2O3 on cemented carbide powder demonstrates its feasibility and superiority.
For some workpiece materials that are difficult to process and apply more (such as titanium alloy), because of the high temperature during cutting, even at medium speed, study air-cooling (such as nitrogen) method that does not pollute the environment, reduce cutting Temperature to achieve efficient cutting is a viable and promising direction.
5 Conclusion High-speed cutting technology has become the mainstream of cutting processing, speeding up its promotion and application, will create huge economic benefits. High-speed cutting tool materials play a decisive role in the development and application of high-speed cutting technology. Four types of high-speed cutting tool materials, such as superhard tool materials (PCD and .CBN), ceramic tools, TiC (N)-based carbide tools (cermets) and coated tools, each have their own characteristics and application range. Competing with each other to promote the development and application of high-speed cutting technology. The country also has a certain foundation in this respect, and has made great progress. In particular, ceramic knives have a prominent advantage in China, but in general, there is a big gap with foreign countries. We seize the great opportunity of economic globalization and reform and opening up and bravely meet the severe challenges we face. In the different ways of using foreign mature technology to accelerate the development of China's high-speed cutting tool material industry, while focusing on the development of China's new generation of ceramic-based CBN composite tool materials and coating tool materials technology to promote China's high-speed and ultra-high speed The rapid development and popularization of cutting technology.