Diamond coating is one of the new tool coating materials. It uses low-pressure chemical vapor deposition technology to grow a layer of polycrystalline diamond film on the cemented carbide substrate, and uses it to process non-ferrous metals such as silicon aluminum alloy and copper alloy, glass fiber and other engineering materials and cemented carbide materials. The tool life is 50-100 times that of ordinary carbide tools. Diamond coating uses many diamond synthesis techniques, the most common are hot wire method, microwave plasma method and DC plasma spray method. By improving the coating method and the bonding of the coating, diamond-coated cutting tools have been produced and applied in industry. Taihao Machinery is the company's main products with rotary thimble, lead screw, machine tool spindle, shaft processing, CNC lathe processing, tool holder and chuck adapter, professional quality assurance! Because of professionalism, excellence!

 

In recent years, the United States, Japan, Sweden and other countries have successively introduced diamond-coated taps, reamers, milling cutters, as well as diamond-coated carbide drill bits for processing small holes on printed circuit boards and various indexable bits. Blades, such as CD1810 from Sandvik in Sweden and KCD25 from Kennametal in the United States. A new process for laser plasma deposition of diamonds developed by Turchan in the United States. Diamond is deposited by this method. Since the plasma field surrounds the entire tool, the coating on the tool is uniform, and its 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, which can prevent the coating from falling off, cracks and cracks.

 

 

Diamond-like coating has obvious advantages in the machining of certain materials (Al, Ti and their composite materials). Compared with natural diamond, the microstructure of diamond-like coatings deposited by low-pressure vapor phase is still quite different. In the 1990s, low-pressure vapor deposition DLC in the presence of activated hydrogen was often used, and the coating contained a large amount of hydrogen. Too much hydrogen will reduce the adhesion and hardness of the coating and increase the internal stress. The hydrogen in DLC will be slowly released at higher temperatures, causing the coating to work unstable. DLC without hydrogen has higher hardness than DLC with hydrogen, and has the advantages of uniform structure, large area deposition, low cost, and smooth surface. It has become a hot spot in the research of DLC coatings in recent years. Titanium Machinery is the company’s main products with rotary center, lead screw, machine tool spindle, shaft processing, high-precision tool holder, tool holder, elastic chuck, non-standard parts processing, and machine tool adapter. American scientist AAVoevodin proposed to deposit super hard The structure of the DLC coating is designed as Ti-TiC-DLC gradient transition coating, which gradually increases the hardness from a softer steel substrate to a super-hard DLC coating on the surface. This type of composite coating not only maintains high hardness and low friction coefficient, but also reduces brittleness and improves bearing capacity, bonding force and wear resistance. Japan's Sumitomo Corporation introduced the DL1000 coating coated with diamond DLC on hard alloy blades, which is used for cutting aluminum alloy and non-ferrous metals, anti-bonding, and can effectively reduce the roughness of the processed surface.

 

 

After years of research, it has been shown that: due to the high internal stress, poor thermal stability and catalytic effect between the diamond-like coating and ferrous metals, the SP3 structure is transformed to SP2, which determines that it can only be used to process non-ferrous metals, thus limiting It has further applications 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 also reach 20 to 40 GPa, but there is no problem of catalytic effect with ferrous metals, and its friction coefficient is very high. It is low and has good moisture resistance. It can be used with coolant during cutting and can also be used for dry cutting. Its service life is doubled compared with uncoated cutters. It can process steel materials. This has caused great demand from coating companies and tool manufacturers. Great interest. In time, this new type of diamond-like carbon coating will be widely used in the cutting field.

 

 

 

 

2. Cubic boron nitride (CBN) coating

CBN is another superhard material after synthetic diamond. In addition to having many excellent physical and chemical properties similar to diamond (such as super 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 characteristics superior to diamond. Taihao Machinery is the company's main products with rotary center, screw, machine tool spindle, shaft processing, high-precision tool holder, tool holder, elastic chuck, non-standard parts processing, and machine tool extension. CBN is chemically inert to iron, steel and oxidizing environment. It forms a thin layer of boron oxide during oxidation. This oxide provides chemical stability to the coating. Therefore, it is also heat resistant when processing hard iron and gray cast iron. Extremely good. It can also cut heat-resistant steel, hardened steel, titanium alloys, etc., at relatively high cutting temperatures, and can cut high-hardness chilled rolls, carburized and hardened materials, and silicon-aluminum alloys that are very severe to tool wear. Processing materials.

Since Inagawa et al. successfully prepared pure CBN coatings in 1987, there has been an upsurge in research on CBN hard coatings in the world. The methods of low pressure gas phase synthesis of CBN coating mainly include CVD and PVD. CVD includes chemical transport PCVD, hot wire assisted heating PCVD, ECR-CVD, etc.; PVD includes reactive ion beam plating, active reactive evaporation, laser evaporation ion beam assisted deposition, etc. The research results show that progress has been made in the synthesis of CBN phase, good adhesion to the cemented carbide matrix and appropriate hardness. At present, the maximum cubic boron nitride deposited on the cemented carbide is only 0.2-0. 5μm, if you want to achieve commercialization, you must use reliable technology to deposit a high-purity economical CBN coating, its thickness should be 3 ~ 5μm, and its effect is confirmed in the actual metal cutting process.

 

 

 

 

3. CNx coating

In the 1980s, American scientists Liu and Cohen designed a new compound β-C3N4 similar to β-Si3N4. Using solid-state physics and quantum chemistry theories, they calculated that its hardness might reach diamond, which attracted the attention of scientists from all over the world. The synthesis of carbon nitride has become a hot topic in the field of materials science in the world. FFujimoto of Okayama University in Japan used electron beam evaporation and ion beam assisted deposition to obtain a carbon nitride coating of 63.7Gpa. The hardness of carbon nitride synthesized by Wuhan University reached 50 GPa and deposited on high-speed steel twist drills to obtain very good drilling performance. The main methods for synthesizing carbon nitride include true flow and radio frequency reactive sputtering, laser evaporation and ion beam assisted deposition, ECR-CVD, and dual ion beam deposition.