Mechanical polishing method for polycrystalline diamond-like cutting tools

Abstract

The present invention provides a mechanical polishing method for a polycrystalline diamond tool, and the specific steps are: polishing the back face of the polycrystalline diamond tool with an arc edge polishing machine to obtain a polycrystalline diamond tool with a back face surface roughness of 1nm and a tool back angle of 10°; selecting a metal protective layer with high compressive strength according to a prediction formula for the edge radius of the polycrystalline diamond tool; sintering a layer of metal protective layer on the back face of the polycrystalline diamond tool with a vacuum welding machine; mechanically polishing the front face of the polycrystalline diamond tool with a plane polishing machine; dissolving the obtained metal protective layer on the back face of the polycrystalline diamond tool with a chemical dissolving agent according to the characteristics of the polycrystalline diamond tool until the metal protective layer completely falls off from the back face of the polycrystalline diamond tool. The present invention effectively suppresses the chipping caused by the falling of grains on the edge of the tool cutting edge, thereby reducing the cutting blunt circle radius of the polycrystalline diamond tool.

Description

Technical Field

[0001] The invention relates to the field of diamond tool manufacturing, and in particular to a mechanical polishing method for polycrystalline diamond-like tools. Background Art

[0002] Ultra-precision turning is one of the ultra-precision machining technologies. To achieve ultra-precision level in turning, not only advanced equipment and advanced detection systems are required, but cutting tools are also a very critical link.

[0003] The sharpness of the cutting edge is an important criterion for evaluating the quality of the tool and whether it is competent for ultra-precision machining. The sharper the cutting edge, that is, the smaller the blunt radius of the cutting edge, the smaller the minimum chip thickness that can be achieved in ultra-precision turning, and the higher the machining accuracy. At present, mechanical polishing is a common method for preparing diamond turning tools with sharp cutting edges. It has high machining accuracy, strong reliability and good industrialization.

[0004] For polycrystalline diamond-like materials, their microstructure has the characteristics of multi-interface coupling. Since the strength of the interface of polycrystalline diamond-like materials is lower than that of the interior of the grains, and the outer edge of the grains in the cutting edge area is suspended, the impact load during mechanical polishing can easily cause the diamond grains in this area to fall off from the connection interface in a large area, resulting in chipping, thereby reducing the sharpness of the tool. Therefore, affected by the falling of grains, the blunt radius of the cutting edge of mechanically polished polycrystalline diamond-like tools is usually relatively large.

[0005] In the field of ultra-precision machining, the grain shedding on the outer edge of the tool cutting edge has become a bottleneck problem restricting the application of polycrystalline diamond-like tool materials. The solution of related scientific problems and the proposal of process methods are urgently needed. Therefore, for the processing of polycrystalline diamond-like tools, a new process method that effectively inhibits grain shedding is needed. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a mechanical polishing method for polycrystalline diamond tools, which mainly utilizes a vacuum welding machine to sinter a metal protective layer with a thickness of 0.2mm-0.5mm on the back face of the polycrystalline diamond tool, and utilizes a flat polishing machine to perform mechanical rough polishing and fine polishing on the front face of the polycrystalline diamond tool, thereby suppressing the chipping caused by the falling of grains on the edge of the tool cutting edge due to the impact load during mechanical polishing, reducing the blunt circle radius of the cutting edge of the polycrystalline diamond material tool, and ultimately improving the sharpness of the tool.

[0007] The present invention provides a mechanical polishing method for a polycrystalline diamond-like tool, and the specific implementation steps are as follows:

[0008] S1, polishing the flank of the polycrystalline diamond-like tool by using an arc edge polishing machine to obtain a polycrystalline diamond-like tool with a flank surface roughness Sa of 1 nm and a tool back angle of 10°;

[0009] S2. According to the prediction formula of the cutting edge radius of the polycrystalline diamond-like tool, a metal protective layer with high compressive strength is selected. The prediction formula of the cutting edge radius of the polycrystalline diamond-like tool is:

[0010]

[0011] Where n is the number of abrasive particles, m is g is the mass of a single abrasive particle, v g is the abrasive velocity, b is the maximum plastic groove depth on the surface of the metal protective layer, [σ t ] is the compressive strength of the metal protective layer material, θ is the abrasive grain apex angle, R is the tool arc radius, and γ is the fracture surface energy of polycrystalline diamond;

[0012] S3. Use a vacuum welding machine to sinter a metal protective layer on the back face of the polycrystalline diamond-like tool:

[0013] S31, melting the metal protective layer at a certain sintering temperature in a vacuum welding machine and completely covering the back surface of the polycrystalline diamond-like tool;

[0014] S32, maintaining the temperature at 800°C for 5-10 minutes and then cooling down, so that the metal protective layer changes from liquid to solid and condenses on the back face of the polycrystalline diamond-like tool;

[0015] S4. Mechanically polish the front face of the polycrystalline diamond-like tool using a flat polishing machine:

[0016] S41, adjusting the rotation speed and polishing pressure of the plane polishing machine, using abrasive particles with a diameter of 5 μm to roughly polish the front cutting surface of the polycrystalline diamond-like tool, and polishing a complete plane on the front cutting surface;

[0017] S42, fine polishing the front cutting surface of the polycrystalline diamond-like tool using abrasive grains with a diameter of 0.25 μm, until the surface of the metal protective layer and the front cutting surface of the polycrystalline diamond-like tool approach the same horizontal plane and the distance between the two in the vertical direction is 0-30 nm, and then the processing is stopped;

[0018] S5, using a chemical dissolving agent to dissolve the metal protective layer on the back face of the polycrystalline diamond-like tool obtained in S3, until the metal protective layer completely falls off from the back face of the polycrystalline diamond-like tool:

[0019] S51, prepare a dissolving solution, wherein the ratio of the dissolving solution is diluted nitric acid: water: hydrogen peroxide = 1:2:1;

[0020] S52, clamping the polycrystalline diamond-like tool with the metal protective layer obtained in S4 and suspending it vertically above the liquid surface of the dissolving liquid, and then continuously approaching the liquid surface until the dissolving liquid can completely cover the back face of the polycrystalline diamond-like tool;

[0021] S53, removing the polycrystalline diamond-like tool and observing under an optical microscope whether there is still a metal protective layer on the back surface of the polycrystalline diamond-like tool. If there is, re-operating S52; if not, the dissolution is completed.

[0022] Preferably, in the polishing of step S1, when the impact energy received by the metal protective layer is equal to the fracture initiation energy of the blunt arc surface of the cutting edge in the polycrystalline diamond tool, the arc radius corresponding to the arc surface in the metal protective layer is the radius of the polycrystalline diamond tool edge.

[0023] Preferably, in step S3, the metal protective layer is a metal mixture containing Ag, Cu and Ti nanoparticles, and the Vickers hardness of the metal protective layer is 640 MPa and the compressive strength is 2.72 Gpa.

[0024] Preferably, in step S3, the thickness of the metal protective layer is 0.2 mm-0.5 mm.

[0025] Preferably, in step S31, the sintering temperature of the vacuum welding machine increases in sequence of 200°C, 400°C, 600°C and 800°C.

[0026] Preferably, in step S41, the rotation speed of the surface polishing machine is 1500 rpm and the polishing pressure is 2.7N.

[0027] Preferably, in step S51, the concentration of the dilute nitric acid solution is 0.5 mol / L.

[0028] Preferably, in step S52, the dissolution time of the polycrystalline diamond-like cutting tool back surface by the dissolving liquid is 2h-3h.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The present invention effectively suppresses the chipping caused by the falling of grains at the edge of the tool cutting edge, thereby reducing the blunt radius of the cutting edge of the polycrystalline diamond-like material tool.

[0031] 2. In the present invention, the metal mixture protective layer on the surface of the tool back face has no significant effect on the surface quality of the tool back face after being removed by the dissolving liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1The process flow chart of the mechanical polishing method for polycrystalline diamond-like cutting tools of the present invention;

[0033] Figure 2 A tool structure diagram of the mechanical polishing method for polycrystalline diamond-like tool of the present invention;

[0034] Figure 3 A schematic diagram of the grinding of the mechanical polishing method for a polycrystalline diamond-like tool of the present invention;

[0035] Figure 4 It is a schematic diagram of the protective effect of the protective mechanical grinding rake face in the mechanical polishing method for polycrystalline diamond-like cutting tools of the present invention;

[0036] Figure 5 This is a SEM 80000 times image of the cutting edge of a nano twinned diamond tool in the mechanical polishing method for a polycrystalline diamond-like tool of the present invention;

[0037] Figure 6 This is a SEM 80000 times morphology image of the protective mechanical sharpening edge of a nano twinned diamond tool in the mechanical polishing method for a polycrystalline diamond-like tool of the present invention;

[0038] Figure 7a This is a morphology image of the cutting edge of a traditional mechanically sharpened superhard polycrystalline diamond tool in the mechanical polishing method for polycrystalline diamond-like tools of the present invention at a SEM of 20000 times;

[0039] Figure 7b This is a measurement result diagram of the cutting edge radius of a superhard polycrystalline diamond tool of 112 nm in the mechanical polishing method for polycrystalline diamond-like tools of the present invention;

[0040] Figure 8a This is a 20000 times SEM morphology image of the protective mechanical sharpening edge of a superhard polycrystalline diamond tool in the mechanical polishing method for a polycrystalline diamond-like tool of the present invention;

[0041] Figure 8b This is a graph showing the measurement results of a protective mechanical grinding edge radius of 41 nm for a superhard polycrystalline diamond tool in the mechanical polishing method for a polycrystalline diamond-like tool of the present invention.

[0042] Main reference numerals:

[0043] Flank face 1, metal protective layer 2, tool tip 3, rake face 4, grinding disc 5, polycrystalline diamond-like tool 6, fixture 7. DETAILED DESCRIPTION

[0044] In order to fully describe the technical content, objectives and effects of the present invention, the following will be described in detail with reference to the accompanying drawings.

[0045] The mechanical polishing method for polycrystalline diamond tools is mainly aimed at various polycrystalline diamond materials with large grains, high hardness and extremely difficult to process. It can inhibit or even eliminate the phenomenon of grain shedding on the outer edge of the tool cutting edge during the mechanical polishing process, and obtain a polycrystalline diamond material turning tool with a small cutting edge blunt radius, and polish an extremely sharp cutting edge, such as Figure 1-Figure 8b As shown, the specific implementation steps are as follows:

[0046] S1. Polishing the flank face 1 of the polycrystalline diamond-like tool 6 by using an arc-edge polishing machine to obtain a polycrystalline diamond-like tool with a flank face 1 surface roughness Sa of 1 nm and a tool back angle of 10°.

[0047] Specifically, during the mechanical polishing process, the abrasive particles continuously impact the cutting edge of the polycrystalline diamond tool 6, and after the metal protective layer 2 is sintered on the back face 1 of the polycrystalline diamond tool 6, the abrasive particles must first contact the metal protective layer 2 and remove the plastic material of the metal protective layer 2 before contacting the cutting edge of the polycrystalline diamond tool 6, during which the impact energy carried by the abrasive particles themselves will be consumed by the metal protective layer 2. Therefore, the sintering of the metal protective layer 2 can effectively reduce the impact energy received by the cutting edge of the polycrystalline diamond tool 6. When the impact energy received by the metal protective layer 2 is equal to the fracture initiation energy of the blunt arc surface of the cutting edge in the polycrystalline diamond tool 6, the arc radius corresponding to the arc surface in the metal protective layer 2 is the radius of the cutting edge in the polycrystalline diamond tool 6.

[0048] S2. When the polycrystalline diamond tool 6 is in protective mechanical polishing, a metal protective layer 2 with high compressive strength is selected according to the prediction formula of the edge radius of the polycrystalline diamond tool 6. The prediction formula of the edge radius of the polycrystalline diamond tool 6 is:

[0049]

[0050] Where n is the number of abrasive particles, mg is the mass of a single abrasive particle, vg is the abrasive particle velocity, b is the maximum plastic groove depth on the surface of the metal protective layer 2, [σ t ] is the compressive strength of the metal protective layer 2 material, θ is the abrasive grain apex angle, R is the arc radius of the polycrystalline diamond tool 6, and γ is the fracture surface energy of polycrystalline diamond.

[0051] Specifically, according to the prediction formula of the cutting edge radius of the polycrystalline diamond tool 6, under the condition that other parameters remain unchanged, the greater the compressive strength of the metal protective layer 2, the smaller the cutting edge radius of the polycrystalline diamond tool 6 will be. Therefore, when selecting the metal protective layer 2, while ensuring that the metal protective layer 2 can be combined with the back blade 1 of the polycrystalline diamond tool 6, the higher the compressive strength of the metal protective layer 2, the better the protection effect of the cutting edge of the polycrystalline diamond tool 6.

[0052] Furthermore, in order to achieve the protective effect of the metal protective layer 2, the selection of the metal protective layer 2 should meet the following conditions:

[0053] 1. The metal protective layer 2 should be made of a material that can be firmly bonded to the polycrystalline diamond, because there will be a certain impact load and polishing force during mechanical polishing, and there will be a gap between the metal protective layer 2 and the polycrystalline diamond, which will not play a role in protecting the cutting edge.

[0054] 2. The metal protective layer 2 cannot be made of brittle materials, because brittle materials may break during the polishing process and scratch the cutting edge.

[0055] 3. The process of adding and removing the polycrystalline diamond-like protective layer is simple, low-cost, high-efficiency and will not damage the back face 1 of the polycrystalline diamond-like tool 6.

[0056] 4. The metal protective layer 2 must be directly connected to the polycrystalline diamond-like carbon, because indirect connection will render the metal protective layer 2 ineffective, and the material between the metal protective layer 2 and the polycrystalline diamond-like carbon actually plays a protective role.

[0057] 5. The radius of the blunt circle of the cutting edge is related to the compressive strength of the material. When other values ​​are constant, the higher the compressive strength of the metal protective layer 2, the smaller the radius of the blunt circle of the cutting edge in theory.

[0058] S3. In order to reduce the impact of abrasive particles on the edge of the polycrystalline diamond-like tool 6 during mechanical polishing, a metal protective layer 2 with a thickness of 0.2 mm to 0.5 mm is sintered on the back face 1 of the polycrystalline diamond-like tool 6 using a vacuum welding machine.

[0059] Specifically, the metal protective layer 2 is dense and has high hardness and shear strength, and can be tightly bonded with the back face 1 of the polycrystalline diamond tool 6. The metal protective layer 2 is a metal mixture containing Ag, Cu and Ti nanoparticles. The Vickers hardness of the metal protective layer 2 is 640 MPa and the compressive strength is 2.72 Gpa; wherein Ti can increase the bonding strength between the metal protective layer 2 and the polycrystalline diamond tool 6, Ag and Cu can well wrap the polycrystalline diamond tool 6, and the mixed material can be heated at a temperature at which the polycrystalline diamond tool 6 does not carbonize, so that the metal protective layer 2 and the polycrystalline diamond tool 6 are tightly bonded.

[0060] S4, mechanically polishing the front face 4 of the polycrystalline diamond-like tool 6 by using a plane polishing machine to remove the metal mixture on the front face 4 (a part of the metal mixture will remain on the front face during the sintering process), and then fine polishing the front face 4 until there is no separation between the surface of the metal mixture protective layer and the edge of the tool cutting edge, and the surface of the metal mixture protective layer has obvious plastic removal to form a flat surface, such as Figure 3 As shown, by adjusting the appropriate load, the rotation speed of the grinding disc 5 and the polishing direction, the metal protective layer 2 and the front cutting surface 4 of the polycrystalline diamond-like tool 6 have good bonding.

[0061] During the mechanical polishing process, the abrasive particles are given energy as the grinding disc 5 rotates, and impact the back face 1 of the polycrystalline diamond-like tool 6 fixed on the fixture 7. With the impact of the abrasive particles, the grains at the tip 3 of the polycrystalline diamond-like tool 6 also fall off. During the protective mechanical polishing process, due to the impact of the abrasive particles on the metal protective layer 2, the impact energy received by the tip 3 is effectively reduced. According to the calculation formula of the fracture surface energy of brittle solids:

[0062] E q =2γS

[0063] Where γ is the fracture surface energy of polycrystalline diamond, S is the fracture surface area of ​​polycrystalline diamond, and E q It is the impact energy received by the polycrystalline diamond tool.

[0064] Therefore, the impact energy E received by the tip 3 of the polycrystalline diamond-like tool 6 is q The smaller it is, the smaller the fracture surface area S of the polycrystalline diamond-like material will be, and the smaller the cutting edge radius of the polycrystalline diamond-like material tool 6 will be.

[0065] S5. In order to obtain a polycrystalline diamond tool 6 that can be used for ultra-precision machining, the metal protective layer 2 needs to be removed before it can be directly applied to the machine tool. Since the metal protective layer 2 is a metal mixed material, if a high-temperature melting method is used, it is very likely to reduce the welding strength between the polycrystalline diamond tool 6 and the tool handle, and polycrystalline diamond will be carbonized under high temperature conditions, so high-temperature melting is not suitable for removing the metal protective layer 2. Since the polycrystalline diamond tool 6 has a certain corrosion resistance and the metal protective layer 2 is a metal mixture, chemical reagent dissolution can effectively remove the protective layer. According to the characteristics of the polycrystalline diamond tool 6, the metal protective layer 2 on the back face 1 of the polycrystalline diamond tool 6 obtained in S3 is dissolved by a chemical dissolving agent until the metal protective layer 2 completely falls off from the back face 1 of the polycrystalline diamond tool 6, and the surface of the back face 1 of the polycrystalline diamond tool 6 is not damaged during the removal process, and the edge quality of the polycrystalline diamond tool 6 will not be affected.

[0066] Furthermore, the method for sintering the metal protective layer 2 in step S3 includes:

[0067] S31, using a vacuum welding machine at a certain sintering temperature to melt the metal protective layer 2 and completely cover the back surface 1 of the polycrystalline diamond-like tool 6.

[0068] Preferably, during the flux sintering process, the sintering temperature of the vacuum welding machine is increased in sequence of 200°C, 400°C, 600°C and 800°C, so that the material of the metal protective layer 2 melts and completely covers the back face 1 of the polycrystalline diamond-like tool 6.

[0069] S32, maintaining the temperature at 800°C for 5-10 minutes and then cooling down, so that the metal protective layer 2 changes from liquid to solid and condenses on the back face 1 of the polycrystalline diamond-like tool 6.

[0070] Specifically, the temperature is maintained at 800°C for 5-10 minutes to ensure that the metal protective layer 2 is completely melted, and then the temperature is lowered so that the metal protective layer 2 changes from liquid to solid and condenses on the surface of the back blade 1. At a temperature of 800°C, polycrystalline diamond is not easy to graphitize and will promote the reaction between the metal protective layer 2 and the polycrystalline diamond and the diffusion process of carbon atoms into the metal material, thereby forming high-strength TiC on the surface of the back blade 1 of the polycrystalline diamond tool 6 and inside the metal protective layer 2 to ensure the bonding strength between the metal protective layer 2 and the back blade 1 of the polycrystalline diamond tool 6 as well as its own compressive strength.

[0071] Furthermore, the specific steps of mechanically polishing the front cutting surface 4 of the polycrystalline diamond-like tool 6 in step S4 are as follows:

[0072] S41, adjusting the rotation speed of the plane polishing machine to 1500 rpm and the polishing pressure to 2.7 N, using abrasive grains with a diameter of 5 μm to roughly polish the front cutting surface 4 of the polycrystalline diamond-like tool 6, and polishing a complete plane on the front cutting surface 4.

[0073] S42. Use abrasive particles with a diameter of 0.25 μm to fine-polish the front cutting edge 4 of the polycrystalline diamond tool 6 until the surface of the metal protective layer 2 is smooth, without obvious falling off and tightly combined with the edge of the tip 3, and the surface of the metal protective layer 2 and the front cutting edge 4 of the polycrystalline diamond tool 6 tend to be on the same horizontal plane and the distance between the two in the vertical direction is 0-30 nm. Stop processing, that is, when there is no gap between the metal protective layer 2 and the edge of the tip 3 of the polycrystalline diamond tool 6, the protection effect of the metal protective layer 2 on the tip 3 of the polycrystalline diamond tool 6 is best.

[0074] Furthermore, in step S5, the specific steps of dissolving the metal protective layer 2 on the back face 1 of the polycrystalline diamond-like tool 6 obtained in step S3 by using a chemical dissolving agent are as follows:

[0075] S51. Prepare a dissolving solution in a glass culture dish. The proportion of the dissolving solution is 0.5 mol / L dilute nitric acid: water: hydrogen peroxide = 1:2:1. The dilute nitric acid dissolves the components of the metal protective layer 2. Water is used to reduce the concentration of the solution to avoid corrosion damage to the polycrystalline diamond-like tool 6. Hydrogen peroxide acts as a catalyst to accelerate the dissolution of the metal protective layer 2.

[0076] In a preferred embodiment of the present invention, the specific expression of the chemical equation of the configured dissolving solution is:

[0077] 2Ag+2H + +H2O2=2Ag + +2H2O

[0078] 3Ag+4HNO3=3AgNO3+2H2O+NO↑

[0079] Cu+2H + +H2O2=Cu 2+ +2H2O

[0080] 3Cu+8HNO3=3Cu(NO3)2+4H2O+2NO↑.

[0081] S52, clamp the polycrystalline diamond-like tool 6 with the metal protective layer 2 obtained in S4 and suspend it vertically above the liquid surface of the dissolving solution, and then continue to approach the liquid surface until the dissolving solution can completely cover the back blade 1 of the polycrystalline diamond-like tool 6, and the dissolving time is 2-3h.

[0082] S53, after a certain period of dissolution, the polycrystalline diamond-like tool 6 is removed and the surface of the back face 1 of the polycrystalline diamond-like tool 6 is observed under an optical microscope to see whether the metal protective layer 2 still exists. If so, S52 is repeated. If not, the dissolution is completed.

[0083] The following is a further description of a mechanical polishing method for a polycrystalline diamond-like tool of the present invention in conjunction with an embodiment:

[0084] S1. Polish the back face 1 of the polycrystalline diamond tool 6 using a polishing machine with a diamond grinding wheel of 90 mm in diameter, and adjust the process parameters of the polishing machine: adjust the speed of the polishing machine to 6000 rpm, and adjust the polishing pressure to 6N to obtain a polycrystalline diamond tool 6 with a back face 1 surface roughness Sa of 1 nm and a tool back angle of 10°.

[0085] S2. When the polycrystalline diamond-like tool 6 is in protective mechanical polishing, a metal protective layer 2 with high compressive strength and certain mechanical properties is selected according to a prediction formula for the cutting edge radius of the polycrystalline diamond-like tool.

[0086] S3. Sintering a metal protective layer 2 with a thickness of 0.2 mm to 0.5 mm on the back face 1 of the polycrystalline diamond-like tool 6 using a vacuum welding machine.

[0087] S31, such as Figure 2 As shown, a special metal mixture containing Ag, Cu and Ti elements is evenly applied on the front cutting face 4 and the back cutting face 1 in the cutting edge area of ​​the polycrystalline diamond-like tool 6, so that the back cutting face 1 of the polycrystalline diamond-like tool 6 can be completely wrapped, and then the wrapped polycrystalline diamond-like tool 6 is placed in a vacuum welding machine for sintering at a sintering temperature of 800°C, so that the metal protective layer 2 is melted and completely covers the back cutting face 1 of the polycrystalline diamond-like tool 6.

[0088] S32, maintaining the temperature at 800°C for 5-10 minutes and then cooling down, so that the metal protective layer 2 changes from liquid to solid and condenses on the back face 1 of the polycrystalline diamond-like tool 6, thereby obtaining a dense metal protective layer 2 with certain mechanical properties.

[0089] S4, mechanically polishing the front face 4 of the polycrystalline diamond-like tool 6 by using a plane polishing machine to remove the metal mixture on the front face 4, and then fine polishing the front face 4 until there is no separation between the surface of the metal mixture protective layer and the edge of the tool cutting edge, and the surface of the metal mixture protective layer has obvious plastic removal to form a flat surface, such as Figure 3 As shown, the process of mechanical polishing is as follows Figure 2 As shown, the material of the grinding disc 5 for mechanical polishing in this embodiment is a high-phosphorus cast iron disc with a diameter of about 30 cm.

[0090] S41, adjusting the rotation speed of the plane polishing machine to 1500 rpm and the polishing pressure to 2.7 N, using abrasive particles with a diameter of 5 μm to roughly polish the front cutting surface 4 of the polycrystalline diamond-like tool 6, and polishing a smooth plane on the front cutting surface 4.

[0091] S42, using abrasive grains with a diameter of 0.25 μm to finely polish the front face 4 of the polycrystalline diamond-like tool 6, and adjusting the grinding position and load during the polishing process so that the front face 4 can be polished smoothly, and finally the contact part between the metal protective layer 2 and the front face 4 of the polycrystalline diamond-like tool 6 is well bonded. The bonding effect is as follows: Figure 4 As shown, when observed under a 20,000x electron scanning microscope, there is no obvious gap between the metal protective layer 2 and the polycrystalline diamond-like tool 6 in the cutting edge area and the cutting edge is complete and uniform.

[0092] S5. Dissolve the metal protective layer 2 on the back face 1 of the polycrystalline diamond tool 6 obtained in S3 using a chemical dissolving agent until the metal protective layer 2 is completely removed from the back face 1 of the polycrystalline diamond tool 6, and the surface of the back face 1 of the polycrystalline diamond tool 6 is not damaged during the removal process, and the edge quality of the polycrystalline diamond tool 6 is not affected.

[0093] S51. Prepare a dissolving solution in a glass culture dish. The proportion of the dissolving solution is 0.5 mol / L dilute nitric acid: water: hydrogen peroxide = 1:2:1.

[0094] S52, clamp the polycrystalline diamond-like tool 6 with the metal protective layer 2 obtained in S4 and suspend it vertically above the liquid surface of the dissolving solution, and then continue to approach the liquid surface until the dissolving solution can completely cover the back blade 1 of the polycrystalline diamond-like tool 6, and the dissolving time is 2-3h.

[0095] S53, after a certain period of dissolution, the polycrystalline diamond-like tool 6 is removed and the surface of the back face 1 of the polycrystalline diamond-like tool 6 is observed under an optical microscope to see whether the metal protective layer 2 still exists. If so, S52 is repeated. If not, the dissolution is completed.

[0096] Compared with the traditional mechanical polishing process, the comparison results of the polishing effect before and after the polycrystalline diamond-like tool obtained by the mechanical polishing method of the present invention in this embodiment are as follows:

[0097] Figure 7a This is a morphology of the cutting edge of a polycrystalline diamond-like tool 6 under a scanning electron microscope (SEM) at 50,000 times magnification under traditional mechanical polishing. It can be clearly seen that there are many chippings on the cutting edge, and it is difficult to have a long and continuous cutting edge. The corresponding cutting edge radius value is as follows: Figure 7b shown.

[0098] Figure 8a The edge morphology of the polycrystalline diamond-like tool 6 under protective mechanical polishing of the present invention under a scanning electron microscope (SEM) of 50,000 times can be clearly seen that there is a long and continuous edge on the edge and there is almost no chipping. The corresponding edge radius value is as follows: Figure 8b shown.

[0099] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A mechanical polishing method for polycrystalline diamond-like cutting tools, characterized in that: The specific implementation steps are as follows: S1, polishing the flank surface of the polycrystalline diamond-like tool by using a circular arc blade polishing machine to obtain a polycrystalline diamond-like tool with a flank surface roughness Sa of 1 nm and a tool back angle of 10°; S2. According to the prediction formula of the cutting edge radius of the polycrystalline diamond-like tool, a metal protective layer with high compressive strength is selected. The prediction formula of the cutting edge radius of the polycrystalline diamond-like tool is: Where n is the number of abrasive particles, m is g is the mass of a single abrasive particle, v g is the abrasive velocity, b is the maximum plastic groove depth on the surface of the metal protective layer, [σ t ] is the compressive strength of the metal protective layer material, θ is the abrasive grain apex angle, R is the tool arc radius, and γ is the fracture surface energy of polycrystalline diamond; S3. Use a vacuum welding machine to sinter a metal protective layer on the back face of the polycrystalline diamond-like tool: S31, melting the metal protective layer at a certain sintering temperature in a vacuum welding machine and completely covering the back surface of the polycrystalline diamond-like tool; S32, maintaining the temperature at 800°C for 5-10 minutes and then cooling down, so that the metal protective layer changes from liquid to solid and condenses on the back face of the polycrystalline diamond-like tool; S4. Mechanically polish the front face of the polycrystalline diamond-like tool using a flat polishing machine: S41, adjusting the rotation speed and polishing pressure of the plane polishing machine, using abrasive particles with a diameter of 5 μm to roughly polish the front cutting surface of the polycrystalline diamond-like tool, and polishing a complete plane on the front cutting surface; S42, fine polishing the front cutting surface of the polycrystalline diamond-like tool using abrasive grains with a diameter of 0.25 μm, until the surface of the metal protective layer and the front cutting surface of the polycrystalline diamond-like tool approach the same horizontal plane and the distance between the two in the vertical direction is 0-30 nm, and then the processing is stopped; S5, using a chemical dissolving agent to dissolve the metal protective layer on the back face of the polycrystalline diamond-like tool obtained in S3, until the metal protective layer completely falls off from the back face of the polycrystalline diamond-like tool: S51, prepare a dissolving solution, wherein the ratio of the dissolving solution is diluted nitric acid: water: hydrogen peroxide = 1:2:1; S52, clamping the polycrystalline diamond-like tool with the metal protective layer obtained in S4 and suspending it vertically above the liquid surface of the dissolving liquid, and then continuously approaching the liquid surface until the dissolving liquid can completely cover the back face of the polycrystalline diamond-like tool; S53, removing the polycrystalline diamond-like tool and observing under an optical microscope whether there is still a metal protective layer on the back surface of the polycrystalline diamond-like tool. If there is, re-operating S52; if not, the dissolution is completed.

2. The mechanical polishing method for polycrystalline diamond-like cutting tools according to claim 1, characterized in that: In the polishing of step S1, when the impact energy of the metal protective layer is equal to the fracture initiation energy of the blunt arc surface of the cutting edge in the polycrystalline diamond tool, the arc radius corresponding to the arc surface in the metal protective layer is the radius of the polycrystalline diamond tool edge.

3. The mechanical polishing method for polycrystalline diamond-like cutting tools according to claim 1, characterized in that: In step S3, the metal protective layer is a metal mixture containing Ag, Cu and Ti nanoparticles, and the Vickers hardness of the metal protective layer is 640 MPa and the compressive strength is 2.72 Gpa.

4. The mechanical polishing method for a polycrystalline diamond-like tool according to claim 1 or 3, characterized in that: In step S3, the thickness of the metal protective layer is 0.2 mm-0.5 mm.

5. The mechanical polishing method for a polycrystalline diamond-like tool according to claim 1 or 3, characterized in that: In step S31, the sintering temperature of the vacuum welding machine is increased in sequence of 200°C, 400°C, 600°C and 800°C.

6. The mechanical polishing method for a polycrystalline diamond-like tool according to claim 1 or 3, characterized in that: In step S41, the rotation speed of the surface polishing machine is 1500 rpm, and the polishing pressure is 2.7N.

7. The mechanical polishing method for polycrystalline diamond-like cutting tools according to claim 1, characterized in that: In step S51, the concentration of the dilute nitric acid solution is 0.5 mol / L.

8. The mechanical polishing method for a polycrystalline diamond-like tool according to claim 1 or 7, characterized in that: In step S52, the dissolving liquid dissolves the back face of the polycrystalline diamond-like cutting tool for 2 hours to 3 hours.

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