Diamond has poor thermal stability. The hardness is greatly reduced when the cutting temperature reaches 800 degrees Celsius. Diamond tools are not suitable for processing iron and steel materials, because diamond and iron have a strong chemical affinity, iron atoms are easy to interact with carbon atoms at high temperature to transform them into graphite structure, the tool ais very easy to damage.Diamond tools are mainly suitable for processing non-metallic materials, non-ferrous metals and their alloys. Using single crystal diamond cutter, mirror surface machining can be realized on ultra-precision lathe.
Monocrystalline diamond cutting tool is the most important tool in the field of ultra-precision cutting, its edge can be ground very sharp, blunt radius of cutting edge up to 20~30nm, machining workpiece surface roughness is very small, up to 0.01μm Ra mirror level, and the tool life is very high, grinding can be used for hundreds of hours. At present, single crystal diamond tool is widely used in processing computer disk substrate, video recorder drum, laser mirror, all kinds of astronomical telescope, microscope, optical instrument.
Polycrystalline diamond (PCD) tools are mainly used for processing wear-resistant non-ferrous metals and their alloys and non-metallic materials. Compared with cemented carbide tools, they can keep sharp edges and cutting efficiency in a long cutting process, and their service life is much higher than cemented carbide tools. PCD tool application field distribution is: turning accounted for 37.6%, boring accounted for 27.1%, face milling accounted for 20%, hinged 14.1%, drilling accounted for 1.2%. At present, PCD tool has been widely used in automobile, motorcycle, aerospace industry, national defense industry in some difficult to process non-ferrous metal and alloy parts of high-speed precision processing. According to statistics, in the use of PCD cutting tools in the field, cars, motorcycles accounted for 53%, aircraft accounted for 10%, wood and plastic processing accounted for 26%, other 11%.
PCD face milling cutter, boring cutter, turning tool, reamer, composite hole processing and other CNC tools are widely used in high strength, high hardness silicon aluminum alloy parts automatic production line, such as used for processing the skirt of automobile and motorcycle engine aluminum alloy piston, pin hole, cylinder body, gearbox, carburetor, etc.. Due to the high silicon content of these parts materials (W (Si) = more than 12%), and most of the mass production by assembly line, the tool life requirements are higher, hard alloy tool is not qualified, and the PCD tool life is much higher than the hard alloy tool, is the hard alloy tool life dozens or even hundreds of times, And the PCD cutter with large particle size has better wear resistance, can ensure the dimensional stability of parts, and can greatly improve the cutting speed, processing efficiency and workpiece processing quality. When machining aluminum alloys with high silicon content, all tools except PCD tools produce heavy wear in a very short period of time and cannot continue to cut.
CVD diamond refers to the synthesis of diamond film on heterogeneous matrix (such as hard alloy, ceramic, etc.) by chemical vapor deposition (CVD). CVD diamond has exactly the same structure and characteristics as natural diamond. CVD diamond does not contain any metal or non-metal additives, and its mechanical properties have both advantages of single crystal diamond and PCD, but also overcome their disadvantages to a certain extent. A lot of practice shows that the service life of welded CVD diamond tool is longer than that of PCD tool, and its impact resistance is better than that of single crystal diamond. The ultra-hard wear resistance and good toughness of CVD diamond tools enable it to process most non-metallic materials and a variety of non-ferrous metal materials, such as aluminum, silicon aluminum alloy, copper, copper alloy, graphite, ceramic and various reinforced glass fiber and carbon fiber structural materials. CVD diamond tools can also be used as high efficiency and high precision machining tools at a much lower cost than more expensive natural diamond tools. At present, CVD diamond tools are not only used in the processing of engine piston silicon aluminum alloy materials, but also used in the processing of cylinder block, cylinder head, high-pressure oil pump, gasoline pump, water pump, generator rotor, starter, glass fiber reinforced plastic parts in the car body, milling, drilling, boring and so on. More typical CVD diamond tool products are Kenametal KD100 blade, KDF300 CYD diamond coated carbide end milling cutter. CVD diamond cutting tools are considered as a new generation of tool materials which can be widely used in automobile engine manufacturing.
--- EDITOR：Yvonne Feng
--- POST：Yvonne Feng