PCD tool and PCBN tool performance advantages and application industry

PCD is mainly processed non-ferrous metal and non-metal, than aluminum, copper, can be grinded very sharp edge, get better processing surface, generally can reach 0.2 smoothness, and is the first choice for processing non-metallic new materials, it is high wear resistance, friction is small, and the hardness can reach more than 10000HV, It can cut hard alloy and industrial ceramics and other high hardness products.

PCD tool performance characteristics

Diamond tools have the characteristics of high hardness, high compressive strength, good thermal conductivity and wear resistance, which can obtain high machining accuracy and efficiency in high speed cutting. The above characteristics of diamond tool are determined by the crystal state of diamond. In diamond crystal, the four valence electrons of carbon atom bond according to tetrahedral structure, and each carbon atom forms covalent bonds with four adjacent atoms, thus forming diamond structure, which has strong binding force and directivity, thus making diamond with extremely high hardness.

The hardness and wear resistance of polycrystalline diamond (PCD) are lower than that of single crystalline diamond even though the cementing agent is added, because the structure of polycrystalline diamond (PCD) is a fine crystalline sintered body with different orientations. However, because the sintered PCD is isotropic, it is difficult to crack along a single cleavage plane.

PCD tool material main performance indicators

1. The hardness of PCD can reach 8000HV, 80 -- 120 times that of cemented carbide;

2. The thermal conductivity of PCD is 700W/mK, 1.5 -- 9 times of cemented carbide, even higher than PCBN and copper, so the PCD tool heat transfer quickly;

3. The friction coefficient of PCD is generally only 0.1 -- 0.3(the friction coefficient of cemented carbide is 0.4 -- 1), so the PCD tool can significantly reduce the cutting force;

4. The thermal expansion coefficient of PCD is only 0.9×10^-6 -- 1.18×10^-6, only equivalent to 1/5 of cemented carbide, so the PCD tool thermal deformation is small, high processing accuracy;

5.PCD tool and non-ferrous metal and non-metallic materials between the affinity is very small, in the process of processing chip is not easy to bond on the tip of the chip formation.

PCD tool application

At present, the processing scope of PCD cutting tools has been expanded from traditional metal cutting to stone processing, wood processing, metal matrix composite materials, glass, engineering ceramics and other materials processing.

Through the analysis of PCD tool application in recent years, PCD tool is mainly used in the following two aspects:

(1) difficult to process non-ferrous metal materials processing: with ordinary tools to process non-ferrous metal materials, often produce tools easy to wear, low processing efficiency defects, and PCD tools can show good processing performance.

(2) Difficult to process non-metallic materials processing: PCD tool is very suitable for stone, hard carbon, carbon fiber reinforced plastic (CFRP), artificial plate and other difficult to process non-metallic materials processing. Using PCD tool to process these materials can effectively avoid the defects such as easy tool wear.

Cutting performance of PCBN tool

As both CBN crystal and diamond crystal belong to sphalerite type, with similar lattice constants and the same chemical bond type, CBN has hardness and compressive strength close to diamond, and because it is composed of N and B atoms, it has higher thermal stability and chemical inertia than diamond.

The main properties of PCBN tool materials are as follows:

It has high hardness and wear resistance

The microhardness of CBN single crystal is HV8000 -- 9000, which is the second highest known substance at present. The hardness of PCBN composite sheet is generally HV3000 -- 5000. Therefore, when it is used for processing high hardness materials, it has higher wear resistance than hard alloy and ceramics, and can reduce the size deviation or size dispersion in the processing of large parts. Especially, it is suitable for the equipment with high degree of automation, which can reduce the auxiliary time of changing and adjusting the knife and make its efficiency fully play.

It has high thermal stability and high temperature hardness

CBN heat resistance up to 1400-1500 ℃, at 800℃ hardness Al2O3/TiC ceramics at room temperature hardness, therefore, when the cutting temperature is higher, will be processed material softening, and the hardness difference between the tool increases, is conducive to cutting processing, and the tool life is not affected.

It has high chemical stability

CBN has a high oxidation resistance, at 1000℃ does not produce oxidation phenomenon, and iron material at 1200 -- 1300℃ does not occur chemical reaction, but at 1000℃ or so will produce hydrolytic effect with water, resulting in a large number of CBN wear, so with PCBN tool wet cutting need to pay attention to the selection of cutting fluid type. In general, wet cutting does not significantly improve the life of the PCBN tool, so dry cutting is often used when using the PCBN tool.

It has good thermal conductivity

The thermal conductivity of CBN material is lower than that of diamond but much higher than that of hard alloy, and with the increase of cutting temperature, the thermal conductivity of PCBN tool is increasing, so the heat at the tip can be transmitted quickly, which is conducive to the improvement of workpiece processing accuracy.

The best tool material for hard cutting technology

Finishing of quenching hardware (hardness above HRC55), usually by grinding method to finish, but with the development of cutting tool materials and lathe (especially CNC lathe) the improvement of the machining accuracy, replace the grinding with hard cutting to complete parts processing has become a new finishing way, eventually this car for grinding process method has the following advantages:

(1) It can improve machining flexibility and break through the limitation of grinding wheel. Workpiece with different geometric shapes can be machined by changing the cutting edge and cutting mode;

(2) The environmental protection problem in cutting is increasingly serious, the waste liquid and waste generated by grinding is more and more difficult to deal with and remove, and harmful to human body, and the hard cutting does not need to add coolant, which is of great significance;

(3) High cutting efficiency, short processing time, small equipment investment cost, can reduce the processing cost;

(4) The energy consumed by cutting the same volume is only 20% of that consumed by grinding, so the cutting heat generated is less, the machined surface is not easy to cause burns and small cracks, and it is easy to maintain the integrity of the surface performance of the workpiece;

(5) Under the same metal removal rate, hard cutting saves energy compared with grinding.

Ideal tool material for dry cutting processes

Due to economic and environmental reasons, dry cutting has become an important research topic in the field of machinery manufacturing in recent years. Dry cutting technology has been widely used in western industrial countries.

Suitable for dry cutting process tool materials are ceramic, cermet, coated carbide and PCBN tool materials and so on, but in terms of red hardness and thermal stability, PCBN material is the most suitable for dry cutting process tool materials.

Suitable for automatic processing and difficult processing materials processing

PCBN cutter has high hardness and wear resistance, and can process high-precision parts (small size dispersion) for a long time under high cutting speed, which greatly reduces the number of tool changes and the time spent in tool wear compensation downtime. Therefore, it is very suitable for CNC machine tools and processing equipment with a high degree of automation, and can give full play to the efficiency of the equipment.

In the application of difficult to process materials, PCBN tool also shows its excellent performance, such as surface spray welding (coating) material processing, with other materials of tool processing, tool life is very low, also can not use grinding method processing, and PCBN is the only suitable tool material; For example, the high alloy wear-resistant cast iron used in petroleum power station equipment, using PCBN tool than carbide tool to improve the cutting efficiency of more than 4 times, the cost of a single tool is reduced to the original 1/5.

In addition, the PCBN tool also shows good cutting performance in the machining of cemented carbide and other sintered materials.

PCBN tool application case

Because of PCBN has high hardness and wear resistance, do not react with iron group metals at high temperature of chemical inertness, so it is mainly used for high hardness material and machining of difficult-to-machine materials, such as hardened steel, high alloy wear resistant cast iron, high temperature alloy, high speed steel, surface spray welding materials, sintered metal materials machining difficult-to-machine materials.

(1) When machining hardened steel, the effect of turning instead of grinding can be played. Because the cutting depth is more than ten times larger than the grinding depth, the machining efficiency is high and the surface is not burned. For example, the machining efficiency of variable speed sliding gear (20CrMnTi, hardness of HRC58 -- 62) by turning instead of grinding is more than 4 times higher than the original grinding.

(2) Machining wear-resistant cast iron with high alloy (containing tungsten or chromium 18%), the cutting speed is more than 10 times higher than the hard alloy tool, and the cutting efficiency is more than 4 times higher.

(3) Processing of high cobalt chromium molybdenum corrosion and heat resistant alloy, PCBN cutting speed of 160m/min, is 8 times the carbide tool.

(4) Processing thermal spraying (spray welding) materials, surface spray welding parts can not be processed by grinding, and the cutting efficiency of the carbide tool is very low, using the PCBN tool can improve the processing efficiency, saving more than 50% of the processing cost. PCBN tool can also be used for non-ferrous metal precision cutting and sintered metal cutting and so on.