Manufacturing Technology and Application of CVD Diamond Film Cutters
2021-04-14 08:03:30
As a new type of superhard tool material, chemical vapor deposition (CVD) diamond has opened up a new way for the application of diamond tools. There are two main types of CVD diamond tools: CVD diamond film coated tools and CVD diamond thick film welding tools. At present, CVD diamond thick film cutters are widely used.
First, CVD diamond film coating tool
A CVD diamond film coated tool refers to a tool that deposits diamond on a certain substrate (usually a K-type cemented carbide) blade by a CVD method at a certain temperature, and has a diamond film thickness of about 10 to 30 μm.
Due to the thin thickness of diamond, CVD diamond film coated tools are difficult to sharpen, and the front and back knives and cutting edges are of poor quality. They are only suitable for roughing, semi-finishing and complex shape knives. The roughing of the cutting is large, and when the adhesion between the diamond and the substrate is insufficient to resist the destruction of the cutting force, the diamond film will fall off. The surface roughness of the workpiece machined by this tool is generally greater than Ra 0.2 μm.
Although the application of domestic CVD thin film coating tools is still in its infancy, with the improvement of CVD diamond growth technology, the size of CVD diamond group particles has been reduced from 40 to 50 μm to a dozen or even a few nanometers, resulting in the emergence of nanometers. Diamond. For example, Dr. Gruen DM of Argonne Nat. Lab has grown a nano-diamond film of good quality with a mirror surface (the highest peak and the lowest peak spacing of 15 nm) and any thickness, and its coating The adhesion is sufficient. It is believed that its application to coated tools has been promoted.
Second, CVD diamond thick film welding tool
The CVD diamond thick film welding tool firstly welds the cut CVD diamond thick film to the substrate (usually K type hard alloy) to form a composite sheet, then polishes the composite sheet, and secondarily welds it to the cutter body, sharpening Into the shape and edge required.
Manufacturing process: preparation of high-quality CVD diamond film → laser cutting → primary welding into composite sheet → composite sheet polishing → secondary welding to the body → sharpening → inspection. Here are a few key processes such as cutting, welding, polishing and sharpening.
laser cutting
CVD diamond film is high in hardness, non-conductive (currently has conductive CVD diamond, but its electrical resistivity is very large), and its wear resistance is extremely strong. Conventional machining and wire cutting methods are not suitable for the cutting of CVD diamond thick film. An efficient method of machining is laser cutting.
One-time welding once refers to welding a CVD diamond thick film to certain substrates under vacuum to form a composite sheet. The weldability between diamond and general metal is extremely poor. At present, the welding process of diamond thick film cutters mainly adopts the method of surface metallization. The solder is a titanium-containing silver-copper alloy. The role of titanium is to react with the surface of the diamond film during the heating process to produce a TiC intermediate layer to metallize the surface of the diamond film, thereby improving the welding strength.
The base for welding is usually a K-type cemented carbide. Under high vacuum conditions, the diffusion-welding and brazing process is used, Ag-Cu-Ti alloy is used as the intermediate layer, and the diamond thick film is welded on the cemented carbide substrate, and the welding strength meets the requirements of cutting.
The purpose of polishing and polishing the composite sheet is to polish the upper surface of the blade (ie, the rake face) into a mirror surface, which is generally required to be Ra below 0.1 μm. After the flank of the tool is polished, the friction and adhesion with the chip can be reduced, and the tool life can be prolonged. At the same time, the flatness and sharpness of the blade can be improved, and the precision of the cutting process can be improved. The composite sheet is polished with a special polishing machine.
Secondary welding secondary welding refers to welding a composite sheet to a cutter body. Most of the equipment used is high frequency induction welding equipment, and the solder used is silver copper solder and flux. The soldering temperature is between 650 and 700 °C. The temperature should not be too high, and the welding surfaces should be kept clean during the welding process. Reasonable use of flux is beneficial to improve the welding strength and improve the welding performance of the composite substrate and the blade material. Generally speaking, the strength of secondary welding is 180-200 MPa, which can meet the requirements of cutting of diamond tools.
In addition, in order to improve the appearance of the tool, the excess silver and copper may be rubbed off with the oil stone strip, the surface oxide layer may be removed by sandblasting, and the surface of the Ni plating method or the passivation solution may be used to prevent oxidation and rust of the cutter body.
Sharpened CVD diamond has high hardness and wear resistance, and sharpening is extremely difficult. Sharpening methods similar to PCD tools are currently in common use.
Equipment: Specialized tool grinding machines are used. The equipment manufacturers include British COBORN Company, Taiwan KARMAM Company, Swiss EWAG Company and Beijing Dean Company. Its main functions include: straight edge grinding and arc grinding, and arc grinding includes the formation of a conical flank face and a cylindrical flank face, and a combination of a cone and a cylindrical flank face. In order to realize these functions, the main movements of the machine tool are required: the rotary motion of the machine tool spindle (grinding wheel); the reciprocating linear motion of the spindle; the rotary motion of the tool holder, and the precise alignment of the rotary center with the microscope or projector to obtain different tip rounds. Radius radius, etc.
Grinding wheel: The grinding wheel used for sharpening is a resin bonded diamond grinding wheel. The sharpening process is divided into rough grinding, semi-finishing and fine grinding. The grinding wheel has a particle size ranging from 250 to 325 to W10 to 07. In order to improve the quality of the cutting edge, it is sometimes necessary to grind, polish, etc., and the particle size used is finer, even 1 to 3 μm. In order to obtain a high quality cutting edge, sanding is usually carried out using a sanded cast iron disk.
Sharpening: During the sharpening process, it is necessary to add coolant, and should pay attention to the dressing of the grinding wheel. Normally trimming the grinding wheel with a suitable oil stone strip can improve the sharpening efficiency and improve the sharpening quality. Since the impact resistance of CVD diamond is not as good as that of PCD diamond, the blade edge after sharpening of some special requirements should be blunt, generally 0.02-0.03mm.
Inspection of the quality of the cutting edge of the tool is usually observed with a tool microscope with a magnification of 40 to 80 times. The cutting edge of the ordinary tool is ≤0.02mm. For higher precision tools, the edge serration is ≤0.005mm after grinding and polishing. In addition, the processing of different workpiece materials, the requirements for the quality of the cutting edge of the tool are also different, sharpening CVD diamond tools should be based on the actual application situation, blindly pursue high-quality cutting edge, which not only reduces production efficiency, but also increases production costs.
Third, CVD diamond film tool processing composite material cutting experiment processing metal-based SiC particle reinforced composite material (SiCp / LY12)
The CVD thick film diamond welding tool continuously cuts the SiCp/LY12 composite material (HV>3000, the weight ratio of SiCp is 30%, and the particle size is 28μm). The tool wear curve is shown in Figure 1.
v=75m/min, f=0.1mm/r, ap=0.3mm
Fig.1 VB-t curve of SiCp/LY12 composite material processed by different materials (dry cut)
Tool geometry parameters:
YS8: g0=0°, a0=12°, kr=90°, re=1.0mm, ls=0°
PCBN: g0=0°, a0=12°, kr=90°, re=0.1mm, ls=0°
PCD: g0=-4°, a0=9°, re=5.0mm
CVD thick film: g0 = 3°, a0 = 13°, kr = 75°, re = 0.6 mm.
It can be seen from Fig. 1 that the FTD value of the TFD (CVD diamond thick film) tool is about 0.05 mm when the tool is processed for 38 minutes, and the PCD tool is about 0.16 mm. The wear resistance of the thick film cutter is obviously higher than that of the PCD cutter. . The reason is that the diamond thick film is a polycrystalline material composed of pure diamond grains, and the PCD diamond is a polycrystalline material in which diamond is sintered by the metal Co and Ni as a bonding agent, and the metal Co makes the wear resistance of the PCD tool. Reduced. PCBN tools wear much faster than PCD and CVD thick film tools, while fine grained carbide YS8 tools are simply not up to the task. In production, a CVD thick film or PCD tool should be preferred.
Processed resin-based glass fiber reinforced composite (GFRP)
Figure 2 shows the wear resistance curves for PCBN, CVD diamond films, and thick film processing of GFRP.
v=80m/min, f=0.1mm/r, ap=0.3mm
Fig. 2 VB-t curve of GFRP composites processed by different materials (dry cut)
Tool geometry parameters:
PCBN: g0=0°, a0=8°, kr=45°, re=0.5mm, ls=0°
CVD film: g0=-10°, a0=8°, re=4.0mm
CVD thick film: g0=-8°, a0=8°, kr=45°, re=0.5mm, ls=0°
As can be seen from Figure 2, the CVD thick film tool has the best wear resistance, followed by the CVD film tool and the PCBN tool. The main component of GFRP is SiO2 (85HRA). The friction is large during processing and dry cutting. Therefore, the temperature during processing is high, which can lead to faster wear of the cutting edge and the flank of the tool. The GFRP material is less difficult to process than the SiCp/LY12, and the tool life is longer. The three tools used in the experiment can be applied in production.
In short, whether it is a CVD diamond film coated tool or a CVD diamond thick film welding tool, if it can make full use of its excellent performance, take its long and short to avoid it, its application prospect is very good. At the same time, on the one hand, it should continue to improve the growth technology of CVD diamond film to make its performance better; on the other hand, the manufacturing technology of CVD diamond tool should be improved to make it more widely used in various fields.
First, CVD diamond film coating tool
A CVD diamond film coated tool refers to a tool that deposits diamond on a certain substrate (usually a K-type cemented carbide) blade by a CVD method at a certain temperature, and has a diamond film thickness of about 10 to 30 μm.
Due to the thin thickness of diamond, CVD diamond film coated tools are difficult to sharpen, and the front and back knives and cutting edges are of poor quality. They are only suitable for roughing, semi-finishing and complex shape knives. The roughing of the cutting is large, and when the adhesion between the diamond and the substrate is insufficient to resist the destruction of the cutting force, the diamond film will fall off. The surface roughness of the workpiece machined by this tool is generally greater than Ra 0.2 μm.
Although the application of domestic CVD thin film coating tools is still in its infancy, with the improvement of CVD diamond growth technology, the size of CVD diamond group particles has been reduced from 40 to 50 μm to a dozen or even a few nanometers, resulting in the emergence of nanometers. Diamond. For example, Dr. Gruen DM of Argonne Nat. Lab has grown a nano-diamond film of good quality with a mirror surface (the highest peak and the lowest peak spacing of 15 nm) and any thickness, and its coating The adhesion is sufficient. It is believed that its application to coated tools has been promoted.
Second, CVD diamond thick film welding tool
The CVD diamond thick film welding tool firstly welds the cut CVD diamond thick film to the substrate (usually K type hard alloy) to form a composite sheet, then polishes the composite sheet, and secondarily welds it to the cutter body, sharpening Into the shape and edge required.
Manufacturing process: preparation of high-quality CVD diamond film → laser cutting → primary welding into composite sheet → composite sheet polishing → secondary welding to the body → sharpening → inspection. Here are a few key processes such as cutting, welding, polishing and sharpening.
laser cutting
CVD diamond film is high in hardness, non-conductive (currently has conductive CVD diamond, but its electrical resistivity is very large), and its wear resistance is extremely strong. Conventional machining and wire cutting methods are not suitable for the cutting of CVD diamond thick film. An efficient method of machining is laser cutting.
One-time welding once refers to welding a CVD diamond thick film to certain substrates under vacuum to form a composite sheet. The weldability between diamond and general metal is extremely poor. At present, the welding process of diamond thick film cutters mainly adopts the method of surface metallization. The solder is a titanium-containing silver-copper alloy. The role of titanium is to react with the surface of the diamond film during the heating process to produce a TiC intermediate layer to metallize the surface of the diamond film, thereby improving the welding strength.
The base for welding is usually a K-type cemented carbide. Under high vacuum conditions, the diffusion-welding and brazing process is used, Ag-Cu-Ti alloy is used as the intermediate layer, and the diamond thick film is welded on the cemented carbide substrate, and the welding strength meets the requirements of cutting.
The purpose of polishing and polishing the composite sheet is to polish the upper surface of the blade (ie, the rake face) into a mirror surface, which is generally required to be Ra below 0.1 μm. After the flank of the tool is polished, the friction and adhesion with the chip can be reduced, and the tool life can be prolonged. At the same time, the flatness and sharpness of the blade can be improved, and the precision of the cutting process can be improved. The composite sheet is polished with a special polishing machine.
Secondary welding secondary welding refers to welding a composite sheet to a cutter body. Most of the equipment used is high frequency induction welding equipment, and the solder used is silver copper solder and flux. The soldering temperature is between 650 and 700 °C. The temperature should not be too high, and the welding surfaces should be kept clean during the welding process. Reasonable use of flux is beneficial to improve the welding strength and improve the welding performance of the composite substrate and the blade material. Generally speaking, the strength of secondary welding is 180-200 MPa, which can meet the requirements of cutting of diamond tools.
In addition, in order to improve the appearance of the tool, the excess silver and copper may be rubbed off with the oil stone strip, the surface oxide layer may be removed by sandblasting, and the surface of the Ni plating method or the passivation solution may be used to prevent oxidation and rust of the cutter body.
Sharpened CVD diamond has high hardness and wear resistance, and sharpening is extremely difficult. Sharpening methods similar to PCD tools are currently in common use.
Equipment: Specialized tool grinding machines are used. The equipment manufacturers include British COBORN Company, Taiwan KARMAM Company, Swiss EWAG Company and Beijing Dean Company. Its main functions include: straight edge grinding and arc grinding, and arc grinding includes the formation of a conical flank face and a cylindrical flank face, and a combination of a cone and a cylindrical flank face. In order to realize these functions, the main movements of the machine tool are required: the rotary motion of the machine tool spindle (grinding wheel); the reciprocating linear motion of the spindle; the rotary motion of the tool holder, and the precise alignment of the rotary center with the microscope or projector to obtain different tip rounds. Radius radius, etc.
Grinding wheel: The grinding wheel used for sharpening is a resin bonded diamond grinding wheel. The sharpening process is divided into rough grinding, semi-finishing and fine grinding. The grinding wheel has a particle size ranging from 250 to 325 to W10 to 07. In order to improve the quality of the cutting edge, it is sometimes necessary to grind, polish, etc., and the particle size used is finer, even 1 to 3 μm. In order to obtain a high quality cutting edge, sanding is usually carried out using a sanded cast iron disk.
Sharpening: During the sharpening process, it is necessary to add coolant, and should pay attention to the dressing of the grinding wheel. Normally trimming the grinding wheel with a suitable oil stone strip can improve the sharpening efficiency and improve the sharpening quality. Since the impact resistance of CVD diamond is not as good as that of PCD diamond, the blade edge after sharpening of some special requirements should be blunt, generally 0.02-0.03mm.
Inspection of the quality of the cutting edge of the tool is usually observed with a tool microscope with a magnification of 40 to 80 times. The cutting edge of the ordinary tool is ≤0.02mm. For higher precision tools, the edge serration is ≤0.005mm after grinding and polishing. In addition, the processing of different workpiece materials, the requirements for the quality of the cutting edge of the tool are also different, sharpening CVD diamond tools should be based on the actual application situation, blindly pursue high-quality cutting edge, which not only reduces production efficiency, but also increases production costs.
Third, CVD diamond film tool processing composite material cutting experiment processing metal-based SiC particle reinforced composite material (SiCp / LY12)
The CVD thick film diamond welding tool continuously cuts the SiCp/LY12 composite material (HV>3000, the weight ratio of SiCp is 30%, and the particle size is 28μm). The tool wear curve is shown in Figure 1.
v=75m/min, f=0.1mm/r, ap=0.3mm
Fig.1 VB-t curve of SiCp/LY12 composite material processed by different materials (dry cut)
Tool geometry parameters:
YS8: g0=0°, a0=12°, kr=90°, re=1.0mm, ls=0°
PCBN: g0=0°, a0=12°, kr=90°, re=0.1mm, ls=0°
PCD: g0=-4°, a0=9°, re=5.0mm
CVD thick film: g0 = 3°, a0 = 13°, kr = 75°, re = 0.6 mm.
It can be seen from Fig. 1 that the FTD value of the TFD (CVD diamond thick film) tool is about 0.05 mm when the tool is processed for 38 minutes, and the PCD tool is about 0.16 mm. The wear resistance of the thick film cutter is obviously higher than that of the PCD cutter. . The reason is that the diamond thick film is a polycrystalline material composed of pure diamond grains, and the PCD diamond is a polycrystalline material in which diamond is sintered by the metal Co and Ni as a bonding agent, and the metal Co makes the wear resistance of the PCD tool. Reduced. PCBN tools wear much faster than PCD and CVD thick film tools, while fine grained carbide YS8 tools are simply not up to the task. In production, a CVD thick film or PCD tool should be preferred.
Processed resin-based glass fiber reinforced composite (GFRP)
Figure 2 shows the wear resistance curves for PCBN, CVD diamond films, and thick film processing of GFRP.
v=80m/min, f=0.1mm/r, ap=0.3mm
Fig. 2 VB-t curve of GFRP composites processed by different materials (dry cut)
Tool geometry parameters:
PCBN: g0=0°, a0=8°, kr=45°, re=0.5mm, ls=0°
CVD film: g0=-10°, a0=8°, re=4.0mm
CVD thick film: g0=-8°, a0=8°, kr=45°, re=0.5mm, ls=0°
As can be seen from Figure 2, the CVD thick film tool has the best wear resistance, followed by the CVD film tool and the PCBN tool. The main component of GFRP is SiO2 (85HRA). The friction is large during processing and dry cutting. Therefore, the temperature during processing is high, which can lead to faster wear of the cutting edge and the flank of the tool. The GFRP material is less difficult to process than the SiCp/LY12, and the tool life is longer. The three tools used in the experiment can be applied in production.
In short, whether it is a CVD diamond film coated tool or a CVD diamond thick film welding tool, if it can make full use of its excellent performance, take its long and short to avoid it, its application prospect is very good. At the same time, on the one hand, it should continue to improve the growth technology of CVD diamond film to make its performance better; on the other hand, the manufacturing technology of CVD diamond tool should be improved to make it more widely used in various fields.
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