CBN Cutting Tools
Knowledge and research of diamond, carbon nitride, CBN Cutting tools coating technology Part 1 The Cutting tools coating Some kinds of a film formed on the surface of the tool by chemical or physical, making the cutting tools obtain good comprehensive cutting for meeting the requirements of high-speed machining; the advantages of super hard coated tools was in the early 1970s,chemical vapor deposition (CVD) technology and physical vapor deposition (PVD) techniques have been developed together, based for improving the tools performance. The advantages of the coated tools compared to non-coated tool: longer life of the cutting tool; higher cutting efficiency; better machining accuracy and surface quality of the work piece; effectively reduce tool material consumption, reduce processing costs; reduce the use of coolant, reduce costs and environmentally friendly. Part 2 The characteristics of the cutting tools coating 1.Greatly improve the surface hardness without reducing the strength of the tool condition, the tool , the hardness can be achieved at present is close to 100GPa; 2.With the rapid development of coating technology, chemical stability and high temperature oxidation resistance of the film is more prominent, so that make high-speed machining realized. 3.Lubricating film has good solid lubricating properties, can effectively improve processing quality, and also suitable for dry machining; 4. The coating technology is the final step of the tool manufacturing , hardly effect the accuracy of the tools, and can be repeated coating process. Part 3 The common coatings 1.Titanium nitride coating: titanium nitride (TiN) is a general-PVD coating, can increase the hardness of the tool and has a high oxidation temperature. The coating is used to high-speed steel cutting tools or has a good processing results with forming tool . 2.Chromium nitride coatings: the good anti-adhesion of CrN coating is the first choose in machining which prone BUE. After coating this material, machining performance of high-speed steel cutting tools or carbide cutting tools and forming tools will be greatly improved. 3.Diamond-coated CVD diamond coating can provide the best performance of the tools which machine the non-ferrous metal, is the best coating when processing of graphite, metal matrix composites (MMC), high silicon aluminum alloy and over many other highly abrasive material (PS : pure diamond coated tools can not be used for machining steel work piece as it will generate a lot of cutting heat when machining that, and lead to a chemical reaction, so that destroy the adhesive layer between the coating and the tool). 4.TiCN Coating: the added carbon in the TiCN (TiCN) coating can improve the tools hardness and get better surface lubricity , is ideal for high-speed steel cutting tools. 5.Titanium aluminum nitride or nitrogen titanium aluminum coating (TiAlN/AlTiN): the alumina layer in the TiAlN/AlTiN coating can improve the life of the tool when in a high temperature
CBN Cutting Tools
processing. Mainly used for Carbide tools when dry or semi-dry cutting. As the ratio of aluminum and titanium in coating was different, AlTiN coating has a higher surface hardness than TiAlN coating, so it is a viable coating option in high-speed processing field. Part 4 Technology and knowledge of the tools coating 1. Titanium carbonitride (TiCN) has a higher hardness(increased by 33%) than the titanium nitride coating (TiN) coating by increased carbon content, the hardness range is about Hv3000 ~ 4000 (depending on the manufacturer). 2. CVD diamond coating: The surface hardness can reach Hv9000 CVD diamond coating is applied to the tool has been more mature, CVD diamond coating tool life increased by 10 to 20 times than PVD coated tools. The high hardness of diamond coated tools make cutting speed more than 2 to 3 times than uncoated cutting tool. 3. Require of the coated material:high hardness, good wear resistance;â‘Ąstable chemical performance, do not react chemically with the workpiece material; thermal oxidation resistance, low friction coefficient, and the substrate attached to a solid Wait. Single coating materials are difficult to meet all the technical requirements described above. Development of coating materials, has been the first single TiN coating, TiC coating, through the development stages of a TiN TiC-A12O3 composite coating and TiCN, TiAlN and other multiple composite coating, and now the latest developments in the TiN/NbN, TiN/CN, and other multiple composite film material, the tool coating performance has been greatly improved. 4. During the coated tool manufacturing process, generally choosing based on the coatings hardness, wear resistance, high temperature oxidation resistance, lubricity and anti-adhesion power or other several aspects, while the coating oxidation and cutting temperature is the main technical conditions. 5. From the application of technology: cutting temperature, cutting depth, cutting speed and coolant are all effect the coated tools applications. Part 5 Development and technology of the coating material Tin is the one coated material which is the most mature technology and used widely. As people have a higher technical requirement, TiN coating cant meet our require as its poor oxidation resistance, While TiC has a higher hardness, wear resistance of the material and thus better. At the same time it is attached to a solid matrix and, in the manufacture of multi-layer wear-resistant coatings, often as the underlying TiC film in contact with the substrate, the coated tools it is very commonly used coating materials. TiCN coatings can reduce stress and improve the toughness of the coating, increasing the thickness of the coating, preventing the diffusion cracks, reduce tool chipping. Make the TiCN coated as the master wear layer can significantly increase tools life. TiAlN has a stability chemical property , resistance to oxidation wear, TiN coated tools improve the life of more than 3-4 times when machining high-alloy steel, stainless steel, titanium alloy, nickel alloy . If the Al
CBN Cutting Tools
concentration is high in the TiAlN coating. The coated surface will generate a thin layer which is the amorphous state A12O3 when cutting, the coating tools can be used more effectively high-speed machining. The oxygen-doped nitrogen titanium carbide TiCNO has a very high hardness and chemical stability, can produce the same effect as the composite coating TIC and Al2O3. Among those hard film materials, the hardness of HV exceed 50GPa which are three kinds: diamond films, cubic boron nitride CBN, carbon nitride. Many diamond film require temperature about 600 ℃ to 900 ℃, so the technology is commonly used in carbide cutting tools diamond film deposited on the surface. Diamond Carbide Tool commercialization is a major achievement in coating technology in recent years . The hardness of CBN is next only to diamond in terms of hardness and thermal conductivity, and has a excellent thermal stability, will not oxidized by heated to 1000 ℃ in the air. CBN has a very stable chemical properties for iron group metal, so can processing the iron and steel products finishing and grinding, but diamond can not . In addition to CBN coating has excellent wear resistance, but also can process heat-resistant steel, titanium, hardened steel , cutting high hardness can chill roll, hardened carbon-doped material and tool Si-Al alloy which wear very serious with high-speed cutting. There are mainly two low-pressure vapor-phase synthesis methods for CBN film: CVD and PVD method. More information on CBN insert ,please check http://www.halnntools.com/news/focus/129.html