Method for precisely cutting pure iron by using diamond coated cutter

Abstract

The invention discloses a method for precisely cutting pure iron by using a diamond coated cutter. The method comprises the following steps: (1) preparing the diamond coated cutter; the preparation method comprises the following steps: adding a single crystal diamond cutter into a perfluoropolyether solution, heating in a water bath for 1-2 hours at the temperature of 50-65 DEG C, heating the single crystal diamond cutter for 1-2 hours at the temperature of 100-400 DEG C, and cleaning to obtain a diamond coated cutter plated with a perfluoropolyether coating; and (2) carrying out precise cutting processing on the pure iron by adopting a diamond coating cutter under the lubrication of cutting fluid. According to the perfluoropolyether coating diamond cutter, the surface energy of the diamond cutter can be effectively reduced, the friction effect between cutters and chips is reduced, and flowing and discharging of the chips on the front cutter face are promoted. And the perfluoropolyether coating can establish a protective barrier, effectively isolate cutter-scrap interface contact, inhibit catalytic reaction of pure iron to the diamond cutter, prevent graphitization abrasion of the diamond cutter and prolong the service life of the cutter.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing and cutting, and in particular relates to a method for performing precision cutting processing on pure iron by using a diamond coated tool. Background Art

[0002] Pure iron (less than 0.02% carbon) is valuable in many industrial fields due to its high magnetic permeability and low coercivity. Relying on its excellent magnetic properties, pure iron is mainly used in electromagnetic devices, such as transformer cores and relays. In addition, pure iron, as a standard material, plays a calibration and benchmark role in experimental research in physics and materials science. It is also used as an alloying additive to change the properties of other metals, such as in the manufacture of low-alloy steel and stainless steel to improve their physical properties.

[0003] In these applications, the surface quality and machining accuracy of the material have a significant impact on the performance of the final product. Ultra-precision cutting is a high-precision machining technology that requires the machining surface roughness to be on the scale of tens of nanometers. It can achieve a sub-micron surface finish, significantly reducing the surface defects left by traditional machining, making the product more consistent and reliable. In addition, it allows precise control of complex geometries to meet the needs of modern precision manufacturing. In addition, compared with traditional machining methods, the advantage of ultra-precision cutting technology is that it exerts very little thermal influence on the material, which helps to maintain the original magnetic and other electrical properties of pure iron. Therefore, high-quality processing of pure iron parts through ultra-precision cutting is the key to improving the performance of pure iron products and expanding their application range, especially in modern high-tech fields.

[0004] The commonly used tools for ultra-precision cutting of pure iron are mainly diamond single crystal tools to ensure the accuracy and surface quality during the cutting process. However, due to the inherent mechanical and physical properties of the material, during the ultra-precision cutting of pure iron, the severe friction between the tool and the chip and the local high temperature will cause the chips to stick to the front face of the diamond tool, resulting in an unstable cutting process and poor surface quality. In addition, iron, as a black transition metal, will catalyze the graphitization reaction of the diamond tool under the action of high temperature and high pressure near the cutting micro-zone, resulting in damage to the diamond tool edge and reduced tool life.

[0005] Therefore, it is necessary to develop diamond tools that can improve the friction state between diamond tools and chips in ultra-precision cutting of pure iron materials, while inhibiting the graphitization reaction of pure iron on diamond tools. This is crucial to achieving high-quality surfaces in ultra-precision cutting of pure iron materials. Summary of the invention

[0006] The present invention provides a method for precision cutting pure iron using a diamond coated tool. The surface of the diamond tool is pretreated to reduce the friction between the diamond tool and the pure iron chips, thereby improving the cutting quality and tool life.

[0007] To achieve the above object, the present invention adopts a method for precision cutting of pure iron using a diamond coated tool, the method comprising: (1) Preparation of diamond coated cutting tools; The single crystal diamond tool is added into a perfluoropolyether solution, heated in a water bath at 50-65° C. for 1-2 hours, and then heated at 100-400° C. for 1-2 hours, and then cleaned to obtain a diamond coated tool coated with a perfluoropolyether coating; (2) Diamond-coated tools are used to perform precision cutting of pure iron under the lubrication of cutting fluid.

[0008] The thickness of the perfluoropolyether coating is 3-5 nm.

[0009] The single crystal diamond tool is artificially synthesized under high temperature and high pressure conditions and can be obtained commercially.

[0010] In the step (1), the perfluoropolyether solution is a solution of perfluoroalkylethanol dissolved in trichlorotrifluoroethane.

[0011] Furthermore, in the perfluoropolyether solution, the mass fraction of perfluoroalkylethanol is 0.5-0.7%, preferably 0.6-0.65%, and more preferably 0.65%.

[0012] In the step (1), the water bath heating temperature is preferably 55-60°C.

[0013] In the present invention, the water bath temperature is 50-65°C. Above 50°C, the perfluoropolyether solution boils. Experiments have shown that if the reaction temperature is lower than the boiling point, the perfluoropolyether cannot chemically adsorb with the surface of the diamond tool. Therefore, the reaction of the present invention is preferably carried out above the boiling point of the perfluoropolyether solution. However, if the water bath temperature is higher than 65°C, the perfluoropolyether solution continues to boil, the solvent evaporates, the solution concentration changes, and the hot-dip coating thickness is uneven.

[0014] Preferably, during the water bath heating in step (1), a reflux device is used to prevent the solvent of the perfluoropolyether solution from evaporating.

[0015] That is, the water bath heating is preferably carried out by heating the water bath to reflux.

[0016] In order to ensure the continuity and sufficiency of boiling, the preferred water bath heating temperature is 55-60°C.

[0017] The water bath heating time is 1 to 2 hours. If the water bath heating time is less than 1 hour, the bonding strength between the perfluoropolyether and the diamond tool surface is insufficient, and the perfluoropolyether coating is easy to fall off during the cutting process. If the water bath heating time is more than 2 hours, there will be excess perfluoropolyether residue on the perfluoropolyether coating that has not undergone chemical adsorption reaction with the diamond surface, which will prolong the subsequent cleaning time in the organic solution. It is preferred to heat for 1 hour.

[0018] After the water bath heating, the diamond tool is placed at 100-400°C for 1-2 hours to achieve the coating of the perfluoropolyether coating. If the heating temperature is lower than 100°C, the bonding strength between the perfluoropolyether and the surface of the diamond tool will be insufficient, and the perfluoropolyether coating will easily fall off during the cutting process. If the heating temperature is higher than 400°C, the perfluoropolyether coating will be thermally decomposed in the air and become ineffective.

[0019] Furthermore, in the step (1), the cleaning is preferably performed by ultrasonic cleaning in an organic solution for more than 15 minutes, more preferably for 15 to 30 minutes.

[0020] The organic solution is preferably one or more of acetone, ether, gasoline, ethanol, trichloroethane and trichloroethylene, and trichloroethane is more preferred. If the cleaning time is less than 15 minutes, the perfluoropolyether that has not chemically adsorbed on the diamond surface is likely to remain on the surface of the diamond tool, affecting the application effect.

[0021] In a preferred embodiment, step (1) is performed as follows: The single crystal diamond tool was added into a 0.65% by mass perfluoropolyether solution, heated in a water bath for reflux at 55°C for 1 hour, and then heated at 100°C for 1-2 hours and cleaned in trichloroethane for 15 minutes to obtain a diamond coated tool coated with perfluoropolyether coating.

[0022] In the step (2), the cutting fluid is preferably an ester-based cutting fluid, so as to improve the friction state between the tool and the chip.

[0023] The application of cutting fluid is well known to those skilled in the art. Generally speaking, the cutting fluid is sprayed into droplets through a nozzle by high-pressure gas and directed to the cutting area.

[0024] The present invention provides a method for improving the friction state between the diamond tool and the chips during the ultra-precision cutting process of pure iron by coating the surface of the diamond tool with a perfluoropolyether coating. Based on the idea of ​​functionalizing the diamond tool, a protective coating with a nanometer thickness is formed on the surface of the diamond tool through the covalent bonding between the hydroxyl groups in the perfluoropolyether coating and the suspended carbon atoms on the surface of the diamond tool. The single-oriented fluorine atom layer on the surface of the perfluoropolyether coating can effectively reduce the surface energy of the diamond tool, increase the wetting angle of the ester-based cutting fluid on the surface of the diamond tool, and help the diffusion, retention and replacement of the cutting fluid in the cutting area, thereby reducing the friction between the tool and the chips and promoting the flow and discharge of the chips on the front face. At the same time, the perfluoropolyether coating also serves to isolate the contact surface between pure iron and the diamond tool, establish a protective barrier, effectively slow down the chemical reaction between the tool and the chips, avoid the catalytic reaction of pure iron on the diamond tool, prevent the graphitization wear of the diamond tool, reduce the chemical damage of the diamond tool, and improve the tool life. The diamond-coated tool for pure iron cutting of the present invention plays an important role in ultra-precision pure iron cutting to obtain a high-quality machined surface. The method of the present invention has extremely strong practicality and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a perfluoropolyether coated diamond tool in an embodiment of the present invention.

[0026] Figure 2 This is a process flow chart of the preparation of a perfluoropolyether coated diamond tool in Example 1 of the present invention.

[0027] Figure 3 It is a schematic diagram of the variable temperature and variable pressure friction coefficient measurement test device in Example 2 of the present invention.

[0028] Figure 4 It is a curve chart of the test results of measuring the variable temperature friction coefficient in Example 2 of the present invention.

[0029] Figure 5 It is a curve chart of the variable pressure friction coefficient measurement test results in Example 2 of the present invention.

[0030] Figure 6 It is a schematic diagram of the orthogonal cutting experiment of the pure iron diamond tool in Example 4 of the present invention.

[0031] Figure 7 This is a photograph of pure iron chips cut by an uncoated diamond tool in Example 4 of the present invention.

[0032] Figure 8 This is a photograph of pure iron chips cut by a perfluoropolyether coated diamond tool in Example 4 of the present invention.

[0033] Fig. 9Graph showing the contact angle measurement results between different cutting fluids and the surface layer of a diamond tool coated or not coated with a perfluoropolyether coating in Example 3 of the present invention.

[0034] In the figure: 1-perfluoropolyether coated diamond tool, 2-single crystal diamond tool substrate, 3-perfluoropolyether coating, 4-diamond anvil, 5-pure iron disc, 6-cutting diamond tool, 7-pure iron workpiece for cutting. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] A diamond-coated tool for pure iron cutting of the present invention, such as Figure 1 As shown, the diamond coated tool 1 comprises a single crystal diamond tool substrate 2 for ultra-precision cutting and a perfluoropolyether coating 3 .

[0037] Example 1

[0038] The preparation method of diamond coated tools is as follows: like Figure 2 As shown, the single crystal diamond tool is placed in an acetone solution with a purity of 99.5%, an ethanol solution with a purity of 99%, and deionized water, and ultrasonically cleaned for 5 minutes respectively. Then, 65 mg of perfluoroalkylethanol (99% purity) is poured into 10 g of trifluorotrichloroethane solution (97% purity) to prepare a perfluoropolyether solution with a mass fraction of 0.65%. Then, the diamond tool is placed in a centrifuge tube of the perfluoropolyether solution and heated to boiling in a water bath to perform hot plating of the perfluoropolyether coating, the heating temperature is 55°C, and the heating time is 1 hour. Then, the perfluoropolyether coated diamond tool is taken out and placed in a 100°C oven for 1 hour to ensure the stability of the perfluoropolyether coating on the surface of the diamond tool. Then, the perfluoropolyether coated diamond tool is placed in a 99% purity chloroform solution for ultrasonic cleaning for 15 minutes to remove the perfluoropolyether residue that has not formed a film on the surface of the diamond tool.

[0039] Perfluoropolyether solutions of different concentrations were prepared, and different heating temperatures were used. The specific process conditions are shown in Table 1. The coating film thickness and wear resistance distance of the obtained perfluoropolyether coated diamond tool are shown in Table 1. The film thickness was measured by ellipsometer. The wear resistance distance was measured by the following method: the coated diamond tool was used in cutting processing, and the tool was considered to be worn when the surface roughness of the tool after cutting processing exceeded 20nm. At this time, the stroke that the tool had processed was defined as "wear resistance distance". Ester-based cutting fluid was used during cutting processing.

[0040] Table 1 Plating process parameters of different perfluoropolyether coatings No Solution concentration Heating temperature Heating time Film thickness Wear distance 1 0.5% 55±1℃ 1h 2 nm 1.8km 2 0.6% 55±1℃ 1h 3 nm 2.8km 3 0.7% 55±1℃ 1h 5 nm 1.0km 4 (preferred) 0.65% 55±1℃ 1h 4 nm 3.5km 5 0.65% 45±1℃ 1h 1 nm 0.2km As shown in Table 1, in the tool preparation process, the concentration of the perfluoropolyether solution and the heating temperature of the tool in the perfluoropolyether solution have an impact on the coating thickness of the perfluoropolyether coating on the diamond tool and its wear resistance during the cutting process, thereby affecting its effect in improving the friction state between the tool and the chip during the cutting process. Among them, when the concentration of the perfluoropolyether solution is lower than 0.6%, the coating will be too thin on the surface of the diamond tool, and the wear resistance will be poor. When the concentration of the perfluoropolyether solution is higher than 0.7%, the coating will be too thick on the surface of the diamond tool, the surface uniformity will deteriorate, and it will be easy to fall off due to cutting wear, resulting in poor wear resistance. In addition, when the heating temperature of the tool in the perfluoropolyether solution is lower than 55°C, the solution cannot guarantee the stability and continuity of boiling, and thus cannot ensure that the film is successfully plated on the surface. In experiment No. 5, the heating temperature was 45±1°C. At this time, the temperature did not reach the boiling point of the perfluoropolyether solution. Theoretically, the coating could not be plated. The film thickness of 1nm may be a measurement error. Judging from the wear resistance distance data, it is also very small. Therefore, it can be considered as a case of no coating.

[0041] In addition, process optimization experiments have confirmed that when the heating time is less than 1 hour, for example, when heating for about 40 minutes, the coating thickness on the surface of the diamond tool is too thin, the surface bonding strength is insufficient, the perfluoropolyether coating is easy to fall off during the cutting process, and is not resistant to cutting wear.

[0042] If the heating time is extended to more than 1 hour, for example 3 hours, more components that are not chemically bonded will remain on the surface of the coating, but the thickness of the coating will not increase. These residual raw materials need to be cleaned for a long time, which wastes time. Therefore, there is no need to extend the heating time. It is enough to ensure that the coating is plated uniformly. Longer heating time does not lead to thicker films.

[0043] Preferably, the plating process of the perfluoropolyether coated tool is as follows: the solution concentration is 0.65%, the heating temperature is 55°C, and the heating time is 1 hour. At this time, the coating thickness is about 4nm and the cutting distance can be 3.5km.

[0044] In this embodiment, the principle that the perfluoropolyether coated diamond tool can improve the friction state between the tool and the chip during the ultra-precision cutting of pure iron is that there is a covalent bonding effect between the hydroxyl group (-OH) in the perfluoropolyether coating and the carbon atoms suspended on the surface of the diamond tool, which belongs to chemical adsorption and has extremely strong stability. The fluorine ions in the perfluoropolyether coating can effectively reduce the surface energy of the diamond tool, thereby having a physical adsorption effect on the ester-based cutting fluid, reducing the wetting angle of the ester-based cutting fluid on the surface of the diamond tool, enhancing the diffusion, retention and replacement of the cutting fluid in the cutting area, reducing the friction between the tool and the chip, and promoting the flow and discharge of the chips on the front face. At the same time, the perfluoropolyether coating also plays a role in isolating the contact between pure iron and the surface of the diamond tool, effectively slowing down the chemical reaction between the tool and the chip (iron catalyzes diamond graphitization), reducing tool wear, and improving tool life.

[0045] Example 2 Two identical single crystal diamond anvils were prepared, one of which was treated according to the perfluoropolyether coating method of Example 1 (using the process of Experiment No. 4), and the other was uncoated as a control. The two diamond single crystal anvils were respectively subjected to variable temperature and variable pressure friction coefficient measurement experiments on pure iron discs. Figure 3 As shown, the pure iron disc 5 moves at a constant speed of 2 rad / s, the diamond anvil 4 applies pressure from above, and the pure iron disc is heated from below. Figure 4 As shown in the figure, under a pressure of 500 N, the friction coefficient between the perfluoropolyether coated diamond anvil and the pure iron disc is significantly lower than that of the uncoated diamond anvil in the range of 25-400°C. The working temperature of the ultra-precision cutting environment is 100-200°C. In this temperature range, the friction coefficient of the perfluoropolyether coated diamond is less than 50% of that of the uncoated diamond.

[0046] In addition, if Figure 5 As shown in the figure, at 25°C, in the pressure range of 400-1000 N, the friction coefficient between the perfluoropolyether coated diamond anvil and the pure iron disc is also significantly lower than that of the uncoated diamond anvil. The above experimental results prove that the perfluoropolyether coating has a significant effect on improving the friction state between the diamond tool and the pure iron material.

[0047] Example 3 This example is a cutting fluid wettability experiment. In order to test the wettability of a perfluoropolyether coated diamond tool for different cutting fluids, the following experiment was conducted: (1) A clean diamond tool was placed on the sample stage of a commercial contact angle measuring instrument. (2) A microinjector was used to slowly drip a drop (about 1 μl) of cutting fluid onto the front cutting edge of the diamond tool from a certain height. (3) The camera focus was adjusted, and photos were taken immediately after the droplet was deposited and after a certain period of time, and the contact angle at the interface between the droplet and the diamond tool was calculated. (4) The contact angle data was analyzed to determine the wettability of the surface.

[0048] The contact angle results between different cutting fluids and the perfluoropolyether coating on the diamond surface are as follows: Fig. 9 As shown in the figure, the results show that after the diamond surface is coated with PFPE coating, the wetting angle of isoparaffin cutting fluid changes from 27° without coating to 9°, and the wetting angle of ester-based cutting fluid changes from 27° without coating to 1°. This experiment proves that PFPE coating can improve the wettability of diamond surface to cutting fluid, reduce the surface energy of diamond tool, enhance the surface retention, diffusion and replacement of cutting fluid, thereby improving the lubrication environment between tool and chip, slowing down the friction between tool and chip, and improving the processing quality. And ester-based cutting fluid has better wetting effect.

[0049] Therefore, the present invention preferably uses an ester-based cutting fluid for precision cutting of pure iron.

[0050] Example 4 In this embodiment, Figure 6 As shown, a diamond tool 6 was used to perform an orthogonal cutting experiment on a pure iron workpiece 7, with a cutting speed of 5 μm / s, a cutting depth of 5 μm, and an ester-based cutting fluid (Swiss Blaser-Vascomill 10, with a spray pressure of 0.2 MPa). Two single-crystal diamond tools with the same size parameters were used, with a tip arc radius of 0.4 mm, a front angle of 0°, and a back angle of 7°. One of them was treated according to the hot-dip perfluoropolyether coating method of Example 1 (using the process of Experiment No. 4), and the other was uncoated. The chip morphology of pure iron was obtained in the two experiments. Among them, as Figure 7 As shown in Figure 1, ribbon-shaped chips are formed when a perfluoropolyether coated diamond tool is used to cut a pure iron workpiece. Figure 8 As shown in the figure, when cutting pure iron workpieces with untreated diamond tools, serrated chips are formed. Among them, the serrated chips are caused by the intense friction between the pure iron and the diamond tool, which leads to adiabatic shearing during the cutting process. Therefore, the experimental results show that the perfluoropolyether coated diamond tool has a significant effect on improving the friction state between the tool and the chip during the pure iron cutting process.

Claims

1. A method for precision cutting of pure iron using a diamond coated tool, characterized in that The method is: (1) Preparation of diamond coated cutting tools; The single crystal diamond tool is added into a perfluoropolyether solution, heated in a water bath at a temperature of 50-65° C. for 1-2 hours, and then the single crystal diamond tool is heated at a temperature of 100-400° C. for 1-2 hours, and cleaned to obtain a diamond coated tool coated with a perfluoropolyether coating; (2) Use diamond-coated tools to perform precision cutting of pure iron under the lubrication of cutting fluid.

2. The method according to claim 1, characterized in that The thickness of the perfluoropolyether coating is 3-5 nm.

3. The method according to claim 1, characterized in that In the step (1), the perfluoropolyether solution is a solution of perfluoroalkylethanol dissolved in trichlorotrifluoroethane.

4. The method according to claim 3, characterized in that In the perfluoropolyether solution, the mass fraction of perfluoroalkylethanol is 0.5-0.7%.

5. The method according to claim 4, characterized in that In the perfluoropolyether solution, the mass fraction of perfluoroalkylethanol is 0.6-0.65%.

6. The method according to claim 1, characterized in that In the step (1), the water bath heating temperature is 55-60°C.

7. The method according to claim 1, characterized in that In the step (1), the cleaning is performed by ultrasonic cleaning in an organic solution for more than 15 minutes.

8. The method according to claim 7, characterized in that The organic solvent is one or more of acetone, ether, gasoline, ethanol, trichloroethane and trichloroethylene.

9. The method according to claim 1, characterized in that The step (1) is carried out according to the following steps: The single crystal diamond tool was added into a 0.65% by mass perfluoropolyether solution, heated in a water bath for reflux at 55°C for 1 hour, and then heated at 100°C for 1-2 hours and cleaned in trichloroethane for 15 minutes to obtain a diamond coated tool coated with perfluoropolyether coating.

10. The method according to claim 1, characterized in that In the step (2), the cutting fluid is an ester-based cutting fluid.

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