Application of CVD Diamond Tool in Machining and Its Prospects

Diamond materials are hailed as materials of the 21st century in this era of ultra-precision machining. Diamond tools have excellent adaptability in the processing of non-ferrous metals and wear-resistant materials. When using diamond tools, users have two options: one is polycrystalline diamond (PCD) and the other is newer chemical vapor deposition (CVD) diamond.
A new member of the family of diamond chemical vapor deposition (CVD) of diamond, a high abrasion resistance pure diamond material free of an adhesive. Diamond deposits come in two forms: a thick film of diamond, deposited as a unitary, individual sheet, and then cut to the desired size; and a thin film of diamond deposited on a carbide insert or rotary cutter.
To date, the most promising use of CVD diamonds has been in the processing of graphite. However, Norton DiamondFilm is selling CVD diamonds for a variety of applications for processing non-ferrous metals, plastics and composites. Norton's application technology manager believes that CVD diamond is suitable for almost all non-ferrous metals. Good results are being achieved in the interrupted cutting of high silicon aluminum alloys and in the processing of pre-sintered cemented carbide, brass, copper and carbon fiber materials. Norton also believes that CVD diamonds can compete with PCD when processing a wide range of aluminum alloy materials, including 6061 and others.
Norton's application technology manager also believes that the main advantage of CVD diamond compared to PCD is the quality of the cutting edge. Although CVD is also polycrystalline, it does not contain a cobalt binder and is pure diamond, so the cutting edge is continuous. This allows for a higher cutting speed and better surface roughness because the tool does not heat up. He also firmly believes that built-up edge does not pose a problem for CVD diamond.
According to Norton, the thermal conductivity of CVD diamond is 50% higher than that of PCD. The reason is that the CVD blade is a monolithic diamond that can be used to conduct heat immediately. The thermal conduction of the PCD blade passes through the cobalt-diamond composite, and the thermal conductivity is worse.
CVD diamond also has a lower coefficient of friction. Both cemented carbide and PCD bond the workpiece material, while CVD diamond is not sticky. At the same time, the low coefficient of friction also allows CVD diamond tools to withstand large cutting loads, making cutting faster and more efficient.
CVD diamond exhibits thermal and chemical stability in use. PCD and cemented carbide are affected by the inclusion of a metal component binder in this respect. Putting the CVD diamond into hydrochloric acid will not happen. However, if the PCD diamond is put in, the acid will eat the cobalt binder. This means that CVD diamond can withstand the attack of certain materials during the processing of acid, such as phenolic resin, urethane rubber, carbonate lowers and the like.
While all forms of diamond (including PCD) chemically react with some components of ferrous or superalloys at elevated temperatures, it is well known that diamond is still chemically inert to most materials. Since PCD and cemented carbide contain a cobalt binder, chemical stability is lowered when the cutting temperature is high. This phenomenon is avoided by the fact that CVD diamond does not contain a binder. In addition, CVD diamond has good lubricity and thermal conductivity, giving it a key advantage in high speed and dry cutting.
The last advantage of CVD diamond is that it maintains high hardness and wear resistance even at high cutting temperatures. Nagy, Norton's application technology manager, said: "Because there is no soft cobalt wrapped in diamond, the hardness of the blade is uniform."
Two, CVD tool in CVD applications in machining comprises a tool (mainly machining), thermal application aspects. At present, CVD products mainly have the following categories:
CVD ordinary tool, high precision tool;
CVD wheel dressing pen;
CVD drawing die and finished mold;
CVD new high pressure, water jet wear resistant nozzle;
CVD laminate flooring processing tool;
CVD precision bearing support and wear-resistant components.
CVD does not contain any metal or non-metallic additives, and its mechanical properties combine the advantages of single crystal diamond and PCD, and to some extent overcome their shortcomings. A large number of practices have shown that the service life of welded CVD tools exceeds that of PCD tools, and its impact resistance is superior to that of single crystal diamond films. Therefore, CVD is considered to be an ideal tool material in the non-ferrous material processing industry, such as aluminum, silicon aluminum alloy, copper, copper alloy, graphite, and various reinforced glass fiber and carbon fiber structural materials.
Tool for metal cutting 1.CVD CVDD used to make turning, milling, planing, times machining tool knives.
In the past two years, various types of diamond film turning tools and key knives have been used in dozens of domestic enterprises and are being promoted abroad. The application is as follows:
Instead of cemented carbide tools, the work efficiency is increased by a factor of ten to a hundred times, the labor intensity is reduced, the machining accuracy of the workpiece is significantly improved, and the surface roughness is significantly reduced.
Ideal machining tool for superhard materials and organic composites;
Compared with PCD tools, CVD tool has low surface roughness and good cutting edge;
Natural diamond tools can be replaced in some areas.
As far as the silicon-aluminum alloy materials used in the domestic automotive industry are concerned, the silicon content is about 12%. On the one hand, due to the uneven material and hard spots, PCD tools currently occupy most of the market, and the share of CVD is negligible. Yi tools, slot machining tools, etc. On the other hand, because the current CVD is not conductive, and the performance of the PCD is different, the difference between the two in the manufacturing process of the tool, PCD can be processed by electric machining, but CVDD does not work, if the CVD tool can be well solved Production process problems can compete with PCD tools in the automotive industry.
Practice has shown that CVD tools use the correct geometric angle, and can be used as precision cutting tools for non-ferrous metals and super-hard materials, such as motor knives (also called commutator knives) for turning copper. Have been tested, the conditions are as follows:
Tool: CVD turning tool, tool edge finishing edge L=1mm, front angle 8°, back angle 8°, main angle 60°, edge roughness Ra0.1μm;
Machine tool: CJ6125;
Environment: Precision Processing Laboratory;
Workpiece material: 8% silicon-aluminum alloy, copper;
Cutting parameters: n=1400r/min, f=4mm/min, ap=0.015mm/r
Under the above test conditions, the roughness Ra of the workpiece after turning machining is 0.012 μm, which is unachievable by PCD products. It can be seen that the CVD tool can achieve the effect of grinding by car, processing to mirror roughness, and its cost is much lower than that of natural diamond (single crystal diamond) tool.
2.CVD for processing of non-metallic CVD its high wear resistance, in woodworking tools also popular. As the wood flooring industry is now hot, the performance of Al2O3 laminate flooring is better than that of melamine wood flooring, the wear layer is harder, and the hard alloy tool processing Al2O3 laminate flooring is powerless. Diamond tools must be used. The market survey results in the past two years show that CVD is a quality woodworking tool material.
For the processing of hard and brittle materials such as stone, glass fiber, carbon composites and organic composite materials, CVD is an ideal tool material.
3. High-precision tools Common tool materials (such as high-speed steel) and hard alloy materials are difficult to achieve high precision due to their own properties (such as wear resistance, hardness, etc.), such as plate-making finishing knives for the plate-making industry. Jewelry knives used in the jewelry industry (commonly known as knives). These tools require high precision and low surface roughness (roughness Ra 0.05 μm), and a high-precision grinding machine (spindle jump of 0.1 μm) is used to produce a CVD precision tool with a surface roughness of Ra 0.05 μm. With a dimensional accuracy of 5μm, it has been used in plate making and anti-counterfeiting trademark processing with good results. The surface roughness of the workpiece can reach Ra0.012μm.
At present, CVD tools have been widely used in super-finishing, finishing, semi-finishing and continuous cutting. The wear resistance is 2 to 10 times higher than that of PCD tools, and its performance price ratio is superior to other diamond tools. According to a 1998 foreign journal, the market for cutting CVD blades is about $150 million.
Third, the bright future GE's Super Abrasives and Norton DiamondFilm believe that: At present, many production sites do not give full play to the advantages of diamonds. The reason is that the speed and torque of many machine tools are not enough to ensure the high efficiency of the tool.
In addition to the mechanical problems, there is a difficult problem to convince the people in the production plant not to focus on the initial price of diamond (PCD or CVD diamond), but to see the cost savings and performance improvements it brings. benefit. You can increase the throughput by allowing diamonds to run at higher speeds than conventional tools (depending on machine performance). At the same time, the number of tool changes is also small. Assuming that diamonds are 50 to 100 times longer than cemented carbides, you don't have to shut down often.

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