Development of polycrystalline diamond tools

Polycrystalline diamond tools
As a superhard diamond cutting tool materials have been used for hundreds of years of history. In the tool development process, from the nineteenth century to the mid

-twentieth century, high-speed steel tool material as the main representative; 1927 Germany developed the first carbide tool material and is widely available; nineteen

fifties, Sweden and USA were synthesized diamond cutting tool with superhard materials from entering the representative period. 1970s, people were synthesized using

high pressure synthesis of polycrystalline diamond (PCD), to solve the natural diamond scarce and expensive problems, make the diamond tool applications extended to

aviation, aerospace, automotive, electronics, stone other fields.
The performance characteristics of polycrystalline diamond tools
Diamond tool with high hardness, high compressive strength, thermal conductivity and good wear resistance and other characteristics, can be obtained in a high-speed

cutting machining accuracy and processing efficiency. Above characteristics of diamond tools is determined by the state of the diamond crystal. In the diamond crystal,

the carbon atoms of the four valence electrons enter the tetrahedral bond, each carbon atom with four adjacent atoms form a covalent bond, and then form a diamond

structure, the structure is very strong binding force and direction, so that the diamond has a very high hardness. As polycrystalline diamond (PCD) of varying

orientation of the structure of fine grain diamond sintered body, although the added binding agent, the hardness and wear resistance is still lower than the single

crystal diamond. However, due to the performance of PCD sintered isotropic and therefore not split along a single cleavage plane. Polycrystalline diamond cutting tool

materials, the main performance indicators: ① polycrystalline diamond's hardness up to 8000HV, is 80 to 120 times carbide; ② thermal conductivity of polycrystalline

diamond 700W/mK, as carbide 1.5 ~ 9 times or higher than PCBN and copper, so rapid heat transfer polycrystalline diamond tools; ③ PCD friction coefficient is

typically only 0.1 to 0.3 (the friction coefficient of carbide 0.4 to 1), the polycrystalline diamond tools can significantly reduce the cutting force; ④

polycrystalline diamond thermal expansion coefficient of only 0.9 × 10 -6 ~ 1.18 × 10 -6, equivalent to only carbide 1/5, so the thermal deformation of

polycrystalline diamond tools, high precision; ⑤ poly polycrystalline diamond cutter and non-ferrous metals and non-metallic materials, the affinity between the small

chip in the process is not easy to form a bond on the tip BUE.
Application of polycrystalline diamond tools
Polycrystalline diamond tools for industrial countries study carried out earlier, its application has been more mature. The first time since 1953 in Sweden since the

synthetic diamond , polycrystalline diamond tools for cutting a lot of research to get results, polycrystalline diamond tool application and usage is expanding rapidly.

Range by turning to the initial drilling, milling expansion. Organized by the Japanese conducted a survey of about superhard cutting tool: polycrystalline diamond

tools people use the key consideration is based on the polycrystalline diamond tool machined surface accuracy, dimensional accuracy and tool life and other advantages.

PDC synthesis technology has been greatly developed. Domestic polycrystalline diamond tool market with the level of development of tool technology is also expanding.

At present, China First Automobile Group has over one hundred PCD turning point of use, and many companies are using wood-based panels polycrystalline diamond tools

for wood processing. The application of polycrystalline diamond tools for its further promote the design and manufacture technology. Domestic Tsinghua University,

Dalian University of Technology, Huazhong University of Science, Jilin University, Harbin Institute of Technology are on active research in this area. Engaged in

research and development of polycrystalline diamond tools, production of a Shanghai Shubohate, Zhengzhou New Asia, Nanjing, Leitz, Shenzhen Runxiang, Chengdu Tool

Research Institute and dozens of units. Currently, the processing of polycrystalline diamond tools range from traditional metal cutting extended to stone processing,

wood processing, metal matrix composites, glass, ceramics and other materials processing engineering. In recent years, through the analysis of the application of

polycrystalline diamond tools visible, polycrystalline diamond tools are mainly used in the following two aspects: ① difficult to machine non-ferrous materials

processing: with ordinary non-ferrous materials difficult to machine tooling, often generating tool easy to wear, processing efficiency and low defects, and

polycrystalline diamond cutting tool can exhibit good processability. Such as the use of polycrystalline diamond cutting tool can be effectively and processing of new

materials, engine pistons - hypereutectic silicon aluminum (mechanism of the materials processing has made breakthroughs). ② difficult to machine processing of non-

metallic materials: polycrystalline diamond cutting tool is very suitable for stone, hard carbon, carbon fiber reinforced plastics (CFRP), artificial board and other

difficult to machine processing of non-metallic materials. If Huazhong University in 1990 to achieve a glass with polycrystalline diamond cutting tools; currently

laminate flooring and other wood-based panels (eg MDF) is a widely used, with a polycrystalline diamond cutting tool machining these materials can effectively prevent

the tool wear and other defects .
Polycrystalline diamond tool manufacturing technology
Polycrystalline diamond tool manufacturing Guo Cheng Jujing diamond tool manufacturing process consists of two stages: ① polycrystalline diamond compact

manufacturing: Polycrystalline Diamond Compact is made from natural or synthetic diamond powder and binder (cobalt-containing , nickel and other metals) by a certain

percentage in the high temperature (1000 ~ 2000 ℃), pressure (5 to 100,000 atmospheres) for sintering. In the sintering process, due to binding agent is added,

between the diamond crystals to form TiC, SiC, Fe, Co, Ni, etc. as a main component with the bridge, the diamond crystals to form a covalent bond with the bridge

mounted on the skeleton. The composite sheet is usually made from a fixed diameter and the thickness of the disc, the need for sintering the composite sheet for

grinding and polishing and other appropriate physical and chemical treatment. ② polycrystalline diamond blade processing: the processing of polycrystalline diamond

blade includes a composite sheet cutting, welding blade, blade sharpening and other steps.
Polycrystalline diamond tools, welding process
Polycrystalline Diamond cutter body with binding mode in addition to the use of mechanical clamping and bonding methods, mostly by brazing way Polycrystalline Diamond

Compact suppressed in the cemented carbide substrate. Welding methods include laser welding, vacuum diffusion welding, vacuum brazing, high frequency induction

brazing. Currently, less investment, low cost high frequency induction heating brazed polycrystalline diamond blade welding is widely used. The blade welding process,

the welding temperature, the choice of flux and solder alloy weld will directly affect the performance of the tool. During the welding process, the welding temperature

control is very important, such as welding temperature is too low, then the weld strength is not enough; such as welding temperature, polycrystalline diamond

graphitization easy and may lead to "over-burning" effect Polycrystalline Diamond Compact with the carbide substrate combination. In the actual process, according to

the holding time and the degree of difficulty of polycrystalline diamond red controlled soldering temperature (generally should be lower than 700 ℃). Use more foreign

high-frequency welding automatic welding process, welding, high efficiency, good quality, enabling continuous production; country is to use more manual welding,

production efficiency is low, the quality is not ideal.