Basic knowledge of woodworking tools:

the most complete knowledge of polycrystalline diamond composite

Wood and plastic products processing                                                                                                                                                

 Woodworking and furniture industries have largely used automated machine tools to replace traditional manual operations. In addition, waste materials such as sawdust, shavings, short wood, and forestry resources have been used to cut down branches and miscellaneous wood from forestry resources. After crushing, they are then added to plastics. The binder is then processed into a "recycled material", which is more difficult to process than raw wood.（TKD CO., Ltd）

So there are two major needs:

1） the automated processing of wood and plastic products requires the use of many types of carbide or high-speed steel cutting tools. Due to the poor thermal conductivity of wood and plastic, cutting tools are easily dulled or deformed under high-speed processing. Therefore, cutting tools are frequently replaced or ground. Therefore, CBN series diamond wheels for woodworking plastic cutting tools have been produced. There are 173 specifications (including size and particle size) of 97 shapes for diamond cutting wheels for woodworking cutting tools, and 28 specifications of 20 shapes for processing plastic products. Many domestic wood and plastic industries have introduced or imitated advanced production lines, and tool manufacturers have proposed many orders for grinding wheels.

2） diamond or CBN composite polycrystalline tools used for woodworking and plastic industries have also been put on the agenda, especially PCD cutting tools for the processing of wooden floor strips, which have already been used in the world.

TKD Diamond (PCD)woodworking milling cutter is 20-100 times that of hard alloy (tungsten steel) milling cutter, and the machining accuracy can reach 0.005mm, which can reach the roughness and accuracy of polishing. There is no need to polish at all, and the processing efficiency is immediately improved by 10 times Above, it is especially suitable for various molding processing occasions and complex body processing with high cost performance!

【Diamond woodworking tools 】

【Engraving knife, milling cutter, gong knife, trimming knife, wood knife, bottom knife, arc knife, flat knife 】

【PCD Diamond woodworking tools】Mainly used in: woodworking furniture, cabinet doors, wardrobes, wooden doors, tables and chairs, photo frames, signboard trays, wooden floors, MDF, particleboard, anti-better boards, fire boards, multilayer boards, bakelite boards, fiberboards, melamine stickers Trimming, engraving, forming of panels, plexiglass, acrylic, cast aluminum, graphite, tungsten steel, ceramics, hard plastic and other materials. Diamond tools are widely used in woodworking industries such as furniture, cabinets, and wooden doors. They are durable and cost-effective. The tool life is increased by 100 times and they can be used for 12 months without grinding.

Polycrystalline diamond composite material TKD PCD is a composite material that adheres a thin layer of polycrystalline diamond to a cemented carbide substrate. Polycrystalline diamond composite sheet combines the extremely high abrasion resistance of polycrystalline diamond and the high impact resistance of cemented carbide. The cutting edge of the diamond layer is sharp and self-sharp. It can always maintain the sharpness of the cutting edge. Therefore, it is very suitable for the exploration of soft formations to medium-hard formations in petroleum and geological drilling. The diamond content in the polycrystalline diamond composite sheet is as high as 99%, so the diamond layer has extremely high hardness and excellent wear resistance. Its Knoop hardness is 6.5 × 104 ~ 7.0 × 104MPa, or even higher.

The cemented carbide matrix overcomes the lack of hardness and brittleness of polycrystalline diamond, and greatly improves the overall impact toughness of the product. The easy weldability of cemented carbides solves the problem that polycrystalline diamond is difficult to combine with other materials through welding methods, and can make the polycrystalline diamond composite sheet vertically inlaid on the drill bit. Because of its superior performance, polycrystalline diamond composites are competing for development and production at home and abroad, so that the variety and specifications are increasing, as shown in the figure below.

Main features:

1) It has extremely high hardness. The hardness of polycrystalline diamond is HV7500 ~ 9000, second only to natural diamond. Moreover, its hardness and abrasion resistance are isotropic, and no orientation is required. Its strength is supported by cemented carbide with high toughness, and its composite bending strength can reach 1500 MPa.

2) It has high wear resistance. The wear resistance of polycrystalline diamond is generally 60 to 80 times that of cemented carbide. When cutting non-metal materials with high hardness (> HV1500), the durability is extremely high.

3) Has a low friction factor. The friction factor between polycrystalline diamond and non-ferrous metals is 0.1 ~ 0.3, while the friction factor between hard alloy and non-ferrous metals is 0.3 ~ 0.6. PCD tools made of polycrystalline diamond (PCD for short) can reduce cutting force and cutting temperature by about 1/2 ~ 1/3 compared with carbide tools.

4) High thermal conductivity. The thermal conductivity of polycrystalline diamond is 1.5 to 7 times that of cemented carbide, which can greatly reduce the temperature in the cutting zone and improve the durability of the tool.

5) Has a small expansion coefficient. The coefficient of linear expansion of polycrystalline diamond is very small, about 1/10 of that of ordinary steel. In addition, because the blade is sharp, the processed surface is only about one-third of the hardened carbide tool, so the machining accuracy is good.

6) Can be made into various sizes and shapes as required.

7) It exhibits significantly superior toughness and impact resistance than single crystal diamond, and to a certain extent makes up for the shortcomings of single crystal diamond, which is brittle and easy to cleave and crack.

A brief history:                                                                                                                                                                                       
The idea of making polycrystalline diamonds probably originated from the understanding of natural "Cabnado" diamonds-this kind of diamond is composed of countless tiny diamond particles, contains a small amount of impurities, and the particles are arranged in disorder and have no cleavage surface With high hardness, strength and abrasion resistance, it is rare in nature.
Since the 1960s, scientists in the United States and the former Soviet Union have attempted to artificially synthesize the "Cabnado."
In 1964, GE's Delai filed a U.S. patent for the first time that "some metal additives can produce a direct bond between diamond and diamond."
In 1966 Blainley et al. Proposed the use of affinity metals as binders to make diamond aggregates.
In 1967, the reports of the mixed sintered body of diamond and cemented carbide and the artificial "Balas" and the artificial "Cabnado" in the Soviet Union Slavudjic were released successively.
In 1970, Hall and Stromberg completed the test of sintered diamond.
In 1971, Katzman published a report that diamond particles were agglomerated and recrystallized by cobalt.
In 1971, GE company invented a polycrystalline diamond composite sheet (referred to as PDC) supported by cemented carbide.
From 1972 to 1973, it was officially used for commercial production and was initially applied to machining tools.
In 1976, a series of products for petroleum and geological drills were officially provided to the market.
In 1981, the product won the Special Contribution Award for Offshore Technology Engineering in the United States.
In the United Kingdom, De Bees developed a PDC suitable for machining in 1977, and sold a series of PDC products for petroleum and geological drills to the market in 1983.
The US synthesis company only entered the PDC market in 1983. After fruitful R & D work and unremitting efforts, its abrasion resistance and impact resistance have been greatly improved, thus becoming the drilling PDC market share in 1997 Leader.

In addition, Mega Diamond Company, Dennis Tools and Phoenix Crystal Company in the United States also provide PDC for drill bits and other drilling tool service companies or some targeted end users, and special-shaped PDC for roller bits and PDC for bearings.
The outstanding performance of PDC in many applications over the years proves that this is undoubtedly an epoch-making invention in the field of materials science.

Main classification:                                                                                                                                                                                
The different types of binders lead to significant differences in the bonding modes and properties of diamond phases in the microstructure of polycrystalline diamond. The classification of polycrystalline diamond is of great significance for practical applications. From the perspective of synthetic technology, product macro characteristics and microstructure characteristics, polycrystalline diamond can be divided into three types.

1) Growth-sintered polycrystalline diamond.
Diamond particles are sintered together, and the interface between the grains is bonded in a diamond-diamond bonding manner. Iron group metals or alloys as sintering aids are dispersedly distributed in the skeleton in the form of islands. Commonly used binders of this type of polycrystalline diamond are Co or Co alloys, Ni or Ni alloys. During the sintering process, the growth of diamond particles and the growth of the sintering neck between the particles are mainly. This kind of polycrystalline diamond has the characteristics of good abrasion resistance and high hardness , but its thermal stability is poor, and the heat resistance temperature is generally about 700 ° C. The following figure is a schematic diagram of the microstructure of the growth-sintered polycrystalline diamond.

2) Sintered polycrystalline diamond.

The binding phase is mainly a carbide phase, which encloses and binds the diamond particles together to form the microstructure of a typical powder metallurgy liquid phase sintered material, as shown in Figure 3. Commonly used binders are Si, Ti, Si-Ti, Si-Ni, Si-Ti-B, and the like. Sintered polycrystalline diamond has good heat resistance, and the heat-resistant temperature can reach 1200 ° C. Compared with the growth-sintered polycrystalline diamond, its wear resistance is poor, but the cost is low. For some applications where the wear resistance is not high or the heat resistance is required, sintered polycrystalline diamond has its advantages. .

3) Growth type polycrystalline diamond.
Using graphite and catalyst metal as raw materials, graphite is transformed into diamond under ultra-high pressure and high temperature conditions, and diamond particles are sintered together by relying on the growth of diamond. Since graphite cannot be completely transformed, the properties of polycrystalline diamond are difficult to control. This type of polycrystalline diamond is limited to laboratory trial production, and no commercial product has been seen.

Manufacturing process:                                                                                                                                                                          
Polycrystalline diamond and diamond composite discs are generally manufactured by the static ultra-high pressure-high temperature method. The equipment used is mainly a six-sided top diamond special hydraulic press and an annual wheel-type two-side top press. These ultra-high pressure equipment are exactly the same as those used for the synthetic diamond single crystal。

At present, there are two types of static ultra-high pressure equipment for producing polycrystalline diamond and diamond composite discs: China (including a small number of foreign manufacturers) generally uses hinged six-sided top high-pressure equipment (also known as six-sided top press) as the main equipment ; Foreign countries mainly use annual wheeled double-sided top pressure ultra-high pressure equipment (also known as double-sided top pressure machine). The advantages of the six-sided top high-pressure equipment for producing polycrystalline diamond or diamond composite discs are: the pressure field generated is closer to the hydrostatic pressure, and the state of the stress field in the synthesis chamber is more reasonable; the machine has high working efficiency and the equipment is relatively inexpensive. The disadvantage is that it is difficult to enlarge the synthesis cavity. The advantages of the double-sided top ultra-high pressure equipment for the production of polycrystalline diamond or diamond composite discs are: high control accuracy of pressure and temperature; large-scale synthesis cavity is easy to realize, suitable for producing large-size products or synthesizing multiple products at a time. The disadvantage is the high cost of equipment operation.

Performance:                                                                                                                                                                                        

1) Abrasion resistance.

When polycrystalline diamond is used as a cutting or drilling tool material, its wear resistance has a direct correspondence with the tool life. Therefore, wear resistance has become the most important performance index of polycrystalline diamond. The abrasion resistance of polycrystalline diamond is usually expressed by abrasion ratio. The current method for measuring the abrasion ratio of polycrystalline diamond uses the industry standard "method for measuring abrasion ratio of artificial diamond sintered body".

2) Thermal stability.

Thermal stability is also known as heat resistance, which is generally expressed by heat-resistant temperature, which refers to the highest heat treatment temperature that polycrystalline diamond can withstand to maintain the performance basically unchanged. Thermal stability is one of the important performance indicators of polycrystalline diamond. It involves the process of making polycrystalline diamond tools and the environment in which the tool is used. It is a performance parameter that tool manufacturers must consider. Excessive temperatures used in processing and manufacturing or tools used at too high temperatures will make the use of polycrystalline diamond tools worse.

3) Impact toughness.

Impact toughness refers to the maximum ability of polycrystalline diamond or diamond composite sheet to not be damaged under the impact load. This performance index is very important for the ability of polycrystalline diamond tools to take advantage of their high hardness, good wear resistance, and long life.

4) Flexural strength.

The three-point bending test was used to determine the flexural strength of polycrystalline diamond. Polycrystalline diamond samples can be made into rods or discs.
5) Hardness.
Polycrystalline diamond has a very high hardness value, second only to single crystal diamond, and is generally measured by Knoop hardness.
6) Electrical conductivity.
Generally speaking, polycrystalline diamond is not very conductive and has a large resistance value. ordinary EDM equipment is difficult to process polycrystalline diamond. A special EDM power source is required to obtain an acceptable processing speed. Even so, the processing of polycrystalline diamond by special EDM equipment is still much slower than the processing of metal materials by ordinary EDM equipment.
7) Corrosion resistance.

After long-term heat treatment of the growth-sintering type polycrystalline diamond in acid or alkali, its mechanical properties (hardness, wear resistance, etc.) remain basically unchanged. After strong acid treatment, the growth-sintered polycrystalline diamond is leached from the polycrystalline diamond (PCD for short) after the metal phase as a binder reacts with the acid, and the conductivity of the PCD is significantly reduced.
The main phase diamond and bonded carbide of sintered polycrystalline diamond are resistant to acid and alkali corrosion. After long-term heat treatment of polycrystalline diamond in acid or alkali, its mechanical and physical properties remain basically unchanged.

Application areas:                                                                                                                                                                                  
1) Polycrystalline diamond drill.
The small-diameter polycrystalline diamond bit (Figure 6) suitable for petroleum drilling and geological exploration is very cheap compared to natural diamond and has high wear resistance.
2) Polycrystalline diamond nozzle.
At present, alumina ceramic nozzles, hard alloy nozzles and boron carbide nozzles are commonly used by the hardware and machinery industries for sand blasting. The nozzle made of polycrystalline diamond material has 10 to 200 times longer life than ordinary material nozzles, and has achieved an unprecedented long service life. The use of polycrystalline diamond nozzles can greatly reduce material consumption and significantly improve work efficiency. It can also greatly reduce the market demand for ceramic abrasives and carbides, which has obvious social benefits of energy conservation and environmental protection. Polycrystalline diamond nozzle has the characteristics of reliable performance and extremely long life. It is suitable for many occasions with high wear resistance requirements. At the same time, because of the characteristics of acid resistance, alkali resistance and corrosion resistance, polycrystalline diamond nozzles are also suitable for water cutting, acid and alkali liquid nozzles, mud nozzles and other occasions. The market and application prospects are extremely impressive.
3) Diamond composite disc thrust bearing.
Screw drilling tool is a kind of downhole power drilling tool which is driven by mud in petroleum drilling. The transmission shaft assembly of the new screw drilling tool adopts a hard alloy radial bearing and a diamond composite flat thrust bearing   to make it longer in life and higher in load capacity

4) Stone processing.

Cutting diamond composite discs for drilling into square or long strips for mining and cutting tools for soft stone can achieve higher processing efficiency.
5) Application of other wear-resistant devices.
Polycrystalline diamond is used in the suction nozzles of electronic component chip packaging and placement machines, V-groove surfaces that require high wear resistance, molds or fixture parts that require high wear resistance or low roughness, etc., and have achieved good results.

Future direction:                                                                                                                                                                                    

1) The size of polycrystalline diamond and diamond composite wafers has increased.
With the development of production technology and the continuous expansion of application fields, the requirements for the size increase of polycrystalline diamond and diamond composite sheet tools or cutting tools may become more and more intense. At present, some foreign companies can mass produce products with a diameter of 50.8 ~ 80.0 mm. There are even foreign manufacturers claiming that they have manufactured a diamond composite sheet with a diameter of 120 mm that can be commercialized.
In recent years, domestic research on the production technology of diamond composite discs for cutting tools has also made great progress. At present, the market can provide high-quality products with a maximum diameter of 40 ~ 65 mm. The larger size of polycrystalline diamond and diamond composite sheet can expand its application range and process more or more complex small cells. More importantly, for applications such as cutters and wire drawing dies, large diameter products can greatly reduce the cost of small units of polycrystalline diamond and diamond composite sheets, which will be more popular.
2) Grain refinement of polycrystalline diamond and diamond composite sheet.
Diamond grain refinement can significantly improve the bending strength of the material, and at the same time, the diamond composite sheet tool can obtain a lower machining surface roughness. The diamond grain size of the current diamond composite sheet for cutting tools and the polycrystalline diamond for drawing tools are all at the micron level. Research on sub-micron and even finer polycrystalline diamonds has been in the past 20 or 30 years, and most of them have used the explosion method. Although there are certain research results, the overall research level has not improved significantly. In addition, due to the difficulty of production and the limitation of performance, it has not yet been widely used.
Grain refinement will bring better and more special properties to polycrystalline diamond, so it will still be the development direction of polycrystalline diamond in the future. The vigorous development of nanotechnology in the past ten years has also prompted experts and scholars to pay attention to and invest in the research of nanocrystalline polycrystalline diamond. Industrial applications have also been expecting stable nano-polycrystalline diamond products from stable manufacturing processes.
3) New structural design of the internal interface between diamond composite sheets.
Non-planar bonding refers to the combination of wavy, zigzag and other curved surfaces between the cemented carbide substrate and the polycrystalline diamond layer, and then further developed into step-shaped, concentric circles, spirals, discontinuous arcs or other more complicated three-dimensional geometric forms Combined. These measures improve the mechanical bonding strength of the composite sheet to a certain extent, reduce the residual stress between the cemented carbide substrate and the polycrystalline diamond layer, improve the overall impact strength of the teeth, and have achieved good results.
Through finite element calculation, the residual stress distribution of the diamond composite sheet under the interlayer interface of different shapes can be obtained, so as to judge whether the designed interlayer internal interface structure is reasonable. Since the 1990s, the diamond composite chip has undergone revolutionary changes in non-planar combination. Therefore, how to design a more reasonable and effective interface structure is an important technology to improve and improve the performance and quality of diamond composite sheets, and it is also one of the research and development directions of diamond composite sheets in the future.

4) Study on surface modification of diamond composite sheet.
In the mid-to-late 1990s, a large number of mirror-polished diamond-composite diamond teeth were used. The polished diamond surface is considered to be more conducive to chip evacuation of the diamond composite chip, reducing the probability of mud packs in the diamond composite chip bit, which can significantly increase the drilling speed and extend the service life of the bit. The research on the removal of cobalt from diamond composites to improve heat resistance has been reported as early as the 1980s. The US NOV company re-utilized the results in recent years to launch decobalt diamond composite sheets, and obtained patent protection.
The decobalt diamond composite sheet removes the cobalt phase with a depth of about 0.3 mm from the diamond phase on the surface of the diamond composite sheet. It is said that it can increase the life of the diamond composite sheet without decobalt by three times.
5) Research on the technology of special-shaped diamond composite sheet.
The externally-shaped diamond composite sheet for drilling is used to change the diamond end face of the diamond composite sheet from a flat surface to a tooth surface. The tooth surface may be wavy, zigzag or trapezoidal. When welding a diamond composite drill bit, the special-shaped groove on the diamond end face should point to the rock surface. During the rock drilling work, a row of "teeth" is gradually formed in the working part (edge) of the grooved tooth, and the row of teeth cuts the rock. The ability and effect are much better than the flat toothless diamond composite diamond teeth, and this effect can basically be maintained until the entire teeth fail. Using this new type of teeth to make a drill bit can significantly improve the rock breaking efficiency of the diamond composite chip, especially to deal with weak rock formations, and solve the technical problem that the diamond composite chip is easy to slip.
6) Research on the technology of polycrystalline diamond with little or no binding phase.
Sintering diamonds together with little or no added binding phase is a long-term goal for experts and scholars in the field of ultra-high pressure synthetic polycrystalline diamond (PCD) research. Since the successful development of transparent polycrystalline cubic boron nitride, pure transparent PCD with a certain thickness has been expected to be born. Because pure PCD will not only make a leap in the performance of tool materials, but also welcome a wide application space in functional materials.

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