Keywords : Tool 1 Introduction With the rapid development of the automotive, aerospace, aerospace and other industries, the requirements for cutting tools for processing various high-performance materials are increasing, and new tools such as PCD tools and diamond tools have emerged. Although the performance of PCD cutters has been significantly improved compared with conventional carbide tools and has been widely used in machining, it still cannot fully meet the requirements for machining efficiency and surface integrity of workpieces in many machining applications. In addition, since the PCD material is composed of diamond particles and bonded phases, the edge characteristics are not ideal, which also limits the further development of PCD cutters. Since the successful development of CVD diamond in the 1980s, its application research in mechanical processing has made significant progress and has gradually entered the stage of commercial application. However, research on the wear resistance of CVD diamond tools is still insufficient. In this paper, the wear resistance of CVD diamond thick film cutter and PCD cutter cutting Al2O3 micronized reinforced resin material was compared and tested.
2 Characteristics of CVD Diamond CVD diamond is a pure diamond polycrystalline material produced by chemical vapor deposition. It can be divided into two types: diamond film coating with thickness less than 50μm and diamond thick film with thickness of 100μm or even several millimeters. . CVD diamond has excellent optical, thermal, acoustic, electrical and mechanical properties. The CVD diamond film coating can be used for surface coating of drill bits, reamer, machine clamp blades with chipbreakers, and the like. The wear layer of CVD diamond thick film is thicker. At present, the common film forming process is to deposit diamond on Si, Si3N4, WC and other transition materials, and then remove the transition material by grinding and acid etching to obtain diamond thick film. The diamond thick film is welded on the base material to make simple tools such as turning tools and boring tools. The manufacturing process is basically the same as that of the PCD tool.
Compared to PCD materials, CVD diamonds have the following characteristics:
High purity The Co contained in the PCD material has strong resistance to chipping and fracture resistance, but the presence of Co reduces the hardness of the PCD and accelerates the conversion and oxidation of diamond to graphite under high temperature conditions. CVD diamond is pure diamond, does not contain any added composite material, so it has higher hardness, thermal conductivity, compactness, sharpness, wear resistance, high temperature resistance, chemical stability, non-conductivity and better than PCD. Lower friction coefficient.
The size of diamond particles is an important factor in determining the performance of PCD materials. The coarse PCD cutter has good wear resistance, but the cutting edge is rough. The fine PCD cutter has sharp edge and easy to machine good surface texture, but wear resistance. Slightly worse. CVD diamond is a continuous material because it does not contain a binder phase, and its performance is hardly affected by the size of the inner diamond grain.
Isotropic CVD diamond is a polycrystalline material like PCD material, and its internal crystal grains have no directionality, so it can be arbitrarily oriented when making cutting tools, and is not affected by crystal characteristics, which is different from natural single crystal diamond. .
Large-area film material can be fabricated. CVD diamond is usually deposited on cemented carbide or ceramic substrates. Due to the low-pressure deposition process, a large area (f100mm or more) of diamond film is easily formed, which makes the CVD diamond in size and shape. Greater application flexibility.
3 Cutting test condition equipment The test machine tool is a J1-MA2AK460×860 type lathe. The J19 universal tool microscope was used to measure the flank wear band width of the tool.
Test pieces According to foreign data, more than 50% of PCD tools are currently used to cut silicon-aluminum alloys. Silicon-aluminum alloy (especially high-silicon aluminum alloy with Si content >12%) contains a large amount of primary Si with large particles and high hardness. When cutting, they act on the tool at the same speed as the abrasive grains of the grinding wheel. It wears out quickly and is difficult to machine with common material tools. Therefore, PCD cutters and CVD diamond cutters are currently mainly used for the cutting of such materials and hard-point-reinforced soft-based non-metal materials (such as carbon fiber reinforced plastics, various wear-resistant fiberboards, etc.). Due to the long working life of PCD cutters and CVD diamond cutters, the wear resistance test using silicon aluminum alloy or reinforced plastic takes too much time. For this reason, we have tried Al2O3 micropowder filled polyvinyl acetal resin material as a special test material. In the cutting process, the grinding, chiseling and friction of Al2O3 micropowder in this material are similar to that of silicon-aluminum alloy and reinforced plastic, and the content of Al2O3 is high, which can shorten the test period and simulate the machining of silicon-aluminum alloy and other materials.
Specimen size: outer circle f255mm, inner hole f155mm.
Tool![]()
figure 1
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figure 2
This test uses three imported PCD tools (numbered A, B, C), two domestic PCD tools (numbered D, E) and a cemented carbide tool (numbered F) for cutting with CVD diamond thick film cutters. Comparative Test. The test tools are made by the center's superhard material tool room. The tool geometry angles are: g=0°, a=6°, Kr=75°, Kr'=15°, and the tool nose radius r=0.3～0.35mm.
Cutting parameters Workpiece speed: n=240r/min
Transverse speed: f=0.205mm/r
Cutting depth: t=0.1mm
Cutting method: dry end face cutting 4. Cutting test results and analysis of wear resistance of CVD diamond tools and imported PCD tools Figure 1 shows the wear curve of CVD diamond tools and three imported PCD tools. As can be seen from the figure, the CVD diamond tool wears the least, and almost no wear is detected in the first 5 minutes of the cutting process. If the blade wear band width VB=0.15mm is the blunt standard, the working life of the CVD diamond tool is more than double that of a famous foreign brand PCD tool, which is an ideal high wear resistance tool. Although the CVD diamond tool has high wear resistance, it can be seen from the figure that the fluctuation of the wear curve is larger than that of the imported PCD tool, indicating that the flank wear is unstable. Observing with a microscope, it can be found that there is more chipping in the CVD diamond tool, which is determined by the material properties of the CVD diamond tool. Since the CVD diamond does not contain a metal bonded phase, the brittleness is large. Therefore, the CVD diamond tool More suitable for continuous cutting. To compensate for the lack of fracture toughness of CVD diamond tools, the cutting speed used should generally be higher than that of PCD tools.
Comparison of wear resistance between CVD diamond tools and domestic PCD tools Figure 2 shows the wear curve comparison between CVD diamond tools and two domestic PCD tools and carbide tools. It can be seen from the figure that the wear resistance of CVD diamond tools is significantly better than that of domestic PCD tools and carbide tools. In addition, the initial rapid wear of PCD tools is more obvious, while CVD diamond tools do not have this tendency. This is because the PCD material consists of diamond and bonded phase, and the presence of the combined phase makes it difficult for the tool to sharpen a sharp edge; Diamond is a continuous material that is easy to sharpen sharp cutting edges.
Comparison of wear resistance of tool materials It is known from the test results that CVD diamond thick film tools have higher wear resistance than various PCD tools. In order to quantitatively analyze the relative wear resistance of various tools, the tool flank wear band width VB=0.182mm is used as the blunt standard, and the above test results are processed appropriately. The calculation results are listed in the following table. As can be seen from the table, CVD diamond has a significant advantage in wear resistance.
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5. Conclusion The wear resistance of CVD diamond thick film cutters is significantly better than that of PCD cutters. Under the test conditions, the wear resistance of CVD diamond thick film cutter is 1.18 times that of a famous foreign brand PCD cutter, 4 times that of domestic PCD cutter and 236 times that of WC cutter.
CVD diamond thick film cutters have sharp cutting edges and almost no initial rapid wear and can be used for ultra-precision cutting. However, CVD diamond thick film cutters have more chipping during the cutting process and the wear curve fluctuates greatly, so it is more suitable for continuous cutting.
2 Characteristics of CVD Diamond CVD diamond is a pure diamond polycrystalline material produced by chemical vapor deposition. It can be divided into two types: diamond film coating with thickness less than 50μm and diamond thick film with thickness of 100μm or even several millimeters. . CVD diamond has excellent optical, thermal, acoustic, electrical and mechanical properties. The CVD diamond film coating can be used for surface coating of drill bits, reamer, machine clamp blades with chipbreakers, and the like. The wear layer of CVD diamond thick film is thicker. At present, the common film forming process is to deposit diamond on Si, Si3N4, WC and other transition materials, and then remove the transition material by grinding and acid etching to obtain diamond thick film. The diamond thick film is welded on the base material to make simple tools such as turning tools and boring tools. The manufacturing process is basically the same as that of the PCD tool.
Compared to PCD materials, CVD diamonds have the following characteristics:
High purity The Co contained in the PCD material has strong resistance to chipping and fracture resistance, but the presence of Co reduces the hardness of the PCD and accelerates the conversion and oxidation of diamond to graphite under high temperature conditions. CVD diamond is pure diamond, does not contain any added composite material, so it has higher hardness, thermal conductivity, compactness, sharpness, wear resistance, high temperature resistance, chemical stability, non-conductivity and better than PCD. Lower friction coefficient.
The size of diamond particles is an important factor in determining the performance of PCD materials. The coarse PCD cutter has good wear resistance, but the cutting edge is rough. The fine PCD cutter has sharp edge and easy to machine good surface texture, but wear resistance. Slightly worse. CVD diamond is a continuous material because it does not contain a binder phase, and its performance is hardly affected by the size of the inner diamond grain.
Isotropic CVD diamond is a polycrystalline material like PCD material, and its internal crystal grains have no directionality, so it can be arbitrarily oriented when making cutting tools, and is not affected by crystal characteristics, which is different from natural single crystal diamond. .
Large-area film material can be fabricated. CVD diamond is usually deposited on cemented carbide or ceramic substrates. Due to the low-pressure deposition process, a large area (f100mm or more) of diamond film is easily formed, which makes the CVD diamond in size and shape. Greater application flexibility.
3 Cutting test condition equipment The test machine tool is a J1-MA2AK460×860 type lathe. The J19 universal tool microscope was used to measure the flank wear band width of the tool.
Test pieces According to foreign data, more than 50% of PCD tools are currently used to cut silicon-aluminum alloys. Silicon-aluminum alloy (especially high-silicon aluminum alloy with Si content >12%) contains a large amount of primary Si with large particles and high hardness. When cutting, they act on the tool at the same speed as the abrasive grains of the grinding wheel. It wears out quickly and is difficult to machine with common material tools. Therefore, PCD cutters and CVD diamond cutters are currently mainly used for the cutting of such materials and hard-point-reinforced soft-based non-metal materials (such as carbon fiber reinforced plastics, various wear-resistant fiberboards, etc.). Due to the long working life of PCD cutters and CVD diamond cutters, the wear resistance test using silicon aluminum alloy or reinforced plastic takes too much time. For this reason, we have tried Al2O3 micropowder filled polyvinyl acetal resin material as a special test material. In the cutting process, the grinding, chiseling and friction of Al2O3 micropowder in this material are similar to that of silicon-aluminum alloy and reinforced plastic, and the content of Al2O3 is high, which can shorten the test period and simulate the machining of silicon-aluminum alloy and other materials.
Specimen size: outer circle f255mm, inner hole f155mm.
Tool
figure 1
figure 2
This test uses three imported PCD tools (numbered A, B, C), two domestic PCD tools (numbered D, E) and a cemented carbide tool (numbered F) for cutting with CVD diamond thick film cutters. Comparative Test. The test tools are made by the center's superhard material tool room. The tool geometry angles are: g=0°, a=6°, Kr=75°, Kr'=15°, and the tool nose radius r=0.3～0.35mm.
Cutting parameters Workpiece speed: n=240r/min
Transverse speed: f=0.205mm/r
Cutting depth: t=0.1mm
Cutting method: dry end face cutting 4. Cutting test results and analysis of wear resistance of CVD diamond tools and imported PCD tools Figure 1 shows the wear curve of CVD diamond tools and three imported PCD tools. As can be seen from the figure, the CVD diamond tool wears the least, and almost no wear is detected in the first 5 minutes of the cutting process. If the blade wear band width VB=0.15mm is the blunt standard, the working life of the CVD diamond tool is more than double that of a famous foreign brand PCD tool, which is an ideal high wear resistance tool. Although the CVD diamond tool has high wear resistance, it can be seen from the figure that the fluctuation of the wear curve is larger than that of the imported PCD tool, indicating that the flank wear is unstable. Observing with a microscope, it can be found that there is more chipping in the CVD diamond tool, which is determined by the material properties of the CVD diamond tool. Since the CVD diamond does not contain a metal bonded phase, the brittleness is large. Therefore, the CVD diamond tool More suitable for continuous cutting. To compensate for the lack of fracture toughness of CVD diamond tools, the cutting speed used should generally be higher than that of PCD tools.
Comparison of wear resistance between CVD diamond tools and domestic PCD tools Figure 2 shows the wear curve comparison between CVD diamond tools and two domestic PCD tools and carbide tools. It can be seen from the figure that the wear resistance of CVD diamond tools is significantly better than that of domestic PCD tools and carbide tools. In addition, the initial rapid wear of PCD tools is more obvious, while CVD diamond tools do not have this tendency. This is because the PCD material consists of diamond and bonded phase, and the presence of the combined phase makes it difficult for the tool to sharpen a sharp edge; Diamond is a continuous material that is easy to sharpen sharp cutting edges.
Comparison of wear resistance of tool materials It is known from the test results that CVD diamond thick film tools have higher wear resistance than various PCD tools. In order to quantitatively analyze the relative wear resistance of various tools, the tool flank wear band width VB=0.182mm is used as the blunt standard, and the above test results are processed appropriately. The calculation results are listed in the following table. As can be seen from the table, CVD diamond has a significant advantage in wear resistance.
5. Conclusion The wear resistance of CVD diamond thick film cutters is significantly better than that of PCD cutters. Under the test conditions, the wear resistance of CVD diamond thick film cutter is 1.18 times that of a famous foreign brand PCD cutter, 4 times that of domestic PCD cutter and 236 times that of WC cutter.
CVD diamond thick film cutters have sharp cutting edges and almost no initial rapid wear and can be used for ultra-precision cutting. However, CVD diamond thick film cutters have more chipping during the cutting process and the wear curve fluctuates greatly, so it is more suitable for continuous cutting.
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