The full name of PCD compact is polycrystalline diamond compact (PDC), which is subdivided into two types according to its application: oil field drilling and cutting tools. In order to better distinguish between the two, polycrystalline diamond compacts for oil field drilling are usually referred to as PDC for short, and polycrystalline diamond compacts for cutting tools are referred to as PCD compacts for short. PCD composite sheet is a composite material sintered with diamond micropowder and cemented carbide substrate under ultra-high pressure and high temperature (above 5.5GPa, above 1500°C). This material not only has the high hardness and high wear resistance of diamond At the same time, it also has the characteristics of toughness and weldability of cemented carbide. It is an ideal material for manufacturing cutting tools, drilling bits and other wear-resistant tools. my country successfully synthesized PDC for the first time in 1987 on a domestic six-sided top press, and applied it in the field of drilling. With the improvement of equipment, materials, and processes, it was only in 2003 that the domestic PCD compound for cutting tools was officially launched. Since then, the quality of PCD composite sheets in my country has been continuously improved, and the output and quality have made great progress in recent years.
1. Performance characteristics of PCD composite sheets for cutting tools
(1) Compared with large single crystal diamond, PCD composite sheet as tool material has the following advantages:
①The crystal grains are arranged in disorder, isotropic, and have no cleavage plane, so it is not like the large single crystal diamond that has great differences in strength, hardness and wear resistance on different crystal planes, and because of the cleavage plane The presence of brittleness.
②It has high strength, especially the PDC material has high impact strength due to the support of the cemented carbide matrix. When the impact is large, only small grains will be broken, not as large as single crystal diamond. Block collapse, so PCD or PDC tools can not only be used for precision cutting and ordinary semi-precision machining, but also for rough machining and intermittent machining (such as milling, etc.) with a large amount of cutting, which greatly expands the diamond tool The scope of use of the material.
③ It can prepare large pieces of PDC diamond composite sheet tool blanks to meet the needs of large-scale processing tools such as milling cutters.
④ It can be made into a specific shape to meet the needs of different processing. Due to the enlargement of PDC tools and the improvement of processing technologies such as electric discharge and laser cutting technology, triangular, herringbone and other special-shaped knife blanks can be processed and formed. In order to meet the needs of special cutting tools, it can also be designed as wrap-type, sandwich-type and roll-type PDC tool blanks.
⑤The performance of the product can be designed or predicted, and the product can be given the necessary characteristics to adapt to its specific use. For example, choosing a fine-grained PDC tool material can improve the quality of the cutting edge of the tool, and a coarse-grained PDC tool material can improve the durability of the tool, and so on.
(2) The performance and cutting characteristics of PCD composite sheet as a cutting tool are as follows:
①The hardness of PCD is high, second only to natural diamond, and its hardness and wear resistance are isotropic, that is, various physical properties are consistent in all directions.
②It has extremely high wear resistance, and its wear resistance is generally 60~80 times that of cemented carbide.
③It has a low coefficient of friction. Therefore, when processing the same material with the same processing parameters, the use of PCD tools can significantly reduce the cutting force and temperature. At the same time, due to the reduction of the coefficient of friction, the surface finish of the workpiece is also greatly improved. improve.
④It has high thermal conductivity, which is 1.5~7 times that of cemented carbide, which can greatly reduce the temperature in the cutting area and improve the durability of the tool.
⑤The linear expansion coefficient of diamond is very small, so the machining accuracy is good.
2. Application fields of PCD composite sheets for cutting tools
Polycrystalline diamond composite sheet is also a new type of composite superhard material. It is a product that has been repeatedly mentioned in the "New Material Industry "14th Five-Year Plan" Development Plan", and has become the core component of high-end machine tool processing and is widely used. In aerospace industry, bearing industry, automobile processing and many other fields.
According to statistics, the current market size of polycrystalline diamond composite sheets exceeds 30 billion yuan. With rapid development, the demand for domestic PCD composite sheets will increase at an annual rate of about 20%. With the progress of research on PCD composite cutting tool materials, its application has rapidly expanded to many manufacturing industries, such as aluminum and aluminum alloys, copper and copper alloys, hard alloys, engineering ceramics, graphite, plastics, rubber, laminates, silicon Rubber, Babbitt alloy, various composite materials, FRP, etc. Especially in automobile manufacturing, aerospace, aviation, shipbuilding and engine manufacturing industries, it can be widely used. With the continuous improvement of the new generation of large-scale six-sided roof devices and the continuous expansion of the synthesis chamber, the PCD composite sheet material is developing in the direction of large-scale size and continuous optimization of quality. The increase in size and specification of PCD composite sheets is an inevitable product of the development of ultra-high pressure and high temperature technology, and the continuous expansion of the synthesis cavity has created necessary conditions for the manufacture of large-diameter PCD composite tool materials.