Temperature-sensing diamond cutter with local boron-doped cutting edge and manufacturing method of temperature-sensing diamond cutter

Abstract

The invention belongs to the technical field of machining and cutting, and particularly relates to a temperature-sensing diamond cutter with local boron-doped cutting edges and a manufacturing method of the temperature-sensing diamond cutter. The temperature-sensing diamond cutter with the local boron-doped cutting edge comprises a diamond single crystal substrate, the diamond single crystal substrate has a certain thickness, a local boron-doped diamond single crystal layer is deposited at a corner position of the top surface of the diamond single crystal substrate, the corner position is used for arranging the cutter cutting edge, and the local boron-doped diamond single crystal layer is deposited at the corner position of the top surface of the diamond single crystal substrate. The local boron-doped diamond single crystal layer can be used as a temperature sensor to sense the temperature of an ultra-precise cutting edge micro-area by using the negative temperature coefficient thermosensitive characteristic of the local boron-doped diamond single crystal layer as a P-type semiconductor. Insulation of the outer surface of the boron-doped diamond layer is achieved, and the problem that when the tool cuts various workpieces with high conductivity, due to the fact that the thermal sensitive characteristic of the boron-doped diamond layer is affected by electric conduction between the tool and chips, the cutting temperature cannot be measured is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing and cutting, and in particular relates to a temperature-sensitive diamond tool with local boron doping on the cutting edge and a manufacturing method thereof. Background Art

[0002] Single-point diamond turning is an ultra-precision machining method that achieves high surface accuracy and nanoscale roughness through efficient mechanical material removal. As a typical thermomechanical coupling process, online monitoring of the cutting area temperature is essential for evaluating thermal deformation of the machined surface, tool wear, and analyzing tool-chip interaction. However, unlike the measurement of cutting force, accurate measurement of the temperature at the tool-chip interface is quite challenging due to the inherent limitations of the measurement principle, especially in ultra-precision cutting, where the cutting temperature is generated at the micro-nano scale near the cutting edge. Therefore, a cutting temperature measurement technology with extremely high spatial resolution and fast response is required. In addition, since the cutting depth is only at the micro-nano scale, the cutting temperature is low and changes slightly, so the accuracy and sensitivity requirements for ultra-precision cutting micro-area temperature monitoring are also more stringent. At present, the methods for measuring cutting temperature mainly include infrared thermal imagers and thermocouple technology, but since the external sensor cannot directly contact the tool edge, the resulting low spatial resolution and gap heat loss between the sensor and the tool make these methods unable to be applied to ultra-precision cutting conditions.

[0003] In order to solve this problem, the applicant has proposed a method of using boron-doped and layer-doped diamond tools for online measurement of cutting micro-area temperature (patent numbers: CN202211585437.7, CN202311083899.3). However, the above method is still limited by the following challenges in practical application: (1) The overall boron doping of diamond tools as temperature sensors will bring greater heat capacity, which means a relatively slow thermal response, affecting the dynamic performance of cutting temperature monitoring. (2) The temperature sensing mechanism of boron-doped diamond tools depends on the thermal sensitivity of boron-doped diamonds, that is, the relationship between the resistance value of the tool and the temperature. When the body-doped diamond tool is used to cut a conductive workpiece, electrical conduction will occur between the tool edge and the workpiece, interfering with the resistance change of the tool itself, so it cannot be used for cutting temperature measurement of conductive workpieces. (3) For layer-doped diamond tools, since the boron-doped diamond layer does not directly contact the cutting micro-area, this leads to a lag in the cutting temperature measurement response and a reduction in accuracy. (4) In addition, the temperature-sensing area of ​​the layer-doped diamond tool includes both the cutting area near the cutting edge and the non-cutting area away from the cutting edge. Therefore, the measured cutting temperature is greatly affected by the ambient temperature, and the temperature measurement sensitivity is affected.

[0004] Therefore, it is crucial to develop a new cutting temperature self-sensing tool for online accurate measurement of ultra-precision cutting micro-area temperature, which plays an important role in monitoring and characterizing the cutting processing state, ensuring the stability of the cutting process, and improving the quality of the processed surface. Summary of the invention

[0005] The present invention provides a temperature-sensitive diamond tool with local boron doping on the cutting edge and a manufacturing method thereof, wherein the thermal sensitivity of the local boron-doped diamond is used as a temperature sensor to realize the perception and monitoring of the temperature of a micro-region near the cutting edge of the diamond tool itself under ultra-precision cutting conditions.

[0006] To achieve the above-mentioned purpose, the present invention adopts a temperature-sensitive diamond tool with local boron doping on the cutting edge, including a diamond single crystal substrate, the diamond single crystal substrate has a certain thickness, and a local boron-doped diamond single crystal layer is deposited at a corner position on the top surface of the diamond single crystal substrate. The corner position is used to set the tool cutting edge, and the local boron-doped diamond single crystal layer is used as a P-type semiconductor. The negative temperature coefficient thermosensitive property can be used as a temperature sensor to realize the perception of the temperature of the micro-area of ​​the ultra-precision cutting edge.

[0007] A diamond tool material having a composite structure of a localized boron-doped diamond single crystal layer and a diamond single crystal substrate is formed by locally depositing a boron-doped diamond single crystal layer on the surface of a diamond single crystal substrate. The boron-doped diamond layer can be used as a temperature sensor to sense ultra-precision cutting temperature by utilizing the negative temperature coefficient thermosensitive property of a P-type semiconductor, that is, within a certain temperature range, the resistance of the boron-doped diamond layer decreases as the temperature increases. The local boron doping method makes the temperature sensing area smaller and has a lower heat capacity. At the same time, it is less affected by the ambient temperature of the non-cutting area, which helps to improve the thermal response speed and sensitivity of the boron-doped diamond layer when sensing temperature. Among them, the composite structure diamond tool material is synthesized by a microwave plasma-assisted chemical vapor deposition process. The diamond single crystal substrate and the boron-doped diamond single crystal layer are bonded by interatomic action and formed in one piece, which allows the boron-doped diamond layer as the sensing area to be sharpened into a tool edge, achieving extremely high spatial resolution for cutting micro-area temperature measurement.

[0008] Preferably, the outer surface of the local boron-doped diamond single crystal layer is provided with nitrogen impurities implanted by ion implantation technology. In order to prevent the diamond tool from forming electrical conduction between the local boron-doped cutting edge and the workpiece during the cutting of the conductive workpiece material to affect the thermal sensitivity of the boron-doped area, nitrogen impurities are implanted into the outer surface of the boron-doped diamond layer by ion implantation technology, and the outer surface of the boron-doped diamond layer is partially insulated based on the hole-electron neutralization effect between boron and nitrogen atoms.

[0009] Preferably, the thickness of the diamond single crystal substrate is 0.7-1.0 mm. More preferably, the thickness of the diamond single crystal substrate is 0.8 mm.

[0010] Preferably, the thickness of the local boron-doped diamond layer is 20-100 μm. More preferably, the thickness of the local boron-doped diamond layer is 50 μm.

[0011] Preferably, the length and width of the diamond single crystal substrate are respectively between 2-3 mm, and the length and width of the local boron-doped diamond layer are in the range of 200-400 microns.

[0012] Preferably, two opposite sides of the local boron-doped diamond single crystal layer deviating from the cutting edge are electrically connected to a conductive silver paste, and the conductive silver paste is connected to the side of the local boron-doped diamond single crystal layer by a Mo / Au stacked electrode evaporated on the side of the local boron-doped diamond single crystal layer through an electron beam evaporation process. The conductive silver paste forms an electrical path for the transmission of the terminal voltage of the boron-doped diamond layer, so as to realize the online collection of the resistance value of the boron-doped diamond layer for the characterization of the cutting temperature. The Mo thin layer and the Au thin layer are successively evaporated on the same position on the side of the boron-doped diamond layer to form electrodes, so as to ensure good ohmic contact between the conductive silver paste and the boron-doped diamond layer.

[0013] The method for manufacturing a diamond tool comprises the following sequential steps: S1. A diamond single crystal substrate is synthesized by microwave plasma assisted chemical vapor deposition process; the diamond single crystal substrate is deposited and grown in a high-purity hydrogen atmosphere, with a hydrogen flow rate of 400-600sccm, preferably 500sccm. Hydrogen, as a carrier gas and diluent gas, can promote the activation of the carbon surface of diamond, and etch a small amount of amorphous carbon produced during the diamond synthesis process, thereby improving the crystal quality of the diamond single crystal. High-purity methane is used as the carbon source, and the methane flow rate is 10-20sccm, preferably 15sccm. During the synthesis process, the substrate temperature is set to 950°C, the synthesis pressure is 21kPa, the microwave power is set to 2.5kW, and a high-quality diamond seed crystal is used as the growth substrate of the diamond single crystal. Before deposition, the substrate surface contamination is removed by plasma etching (argon or hydrogen).

[0014] S2. Depositing SiO on the diamond single crystal substrate by magnetron sputtering process 2 The film is used as a mask for the subsequent local deposition of the local boron-doped diamond layer, and the local position is shielded by a metal aluminum sheet; 2 After the deposition is completed, the metal aluminum sheet is removed to expose the diamond single crystal substrate on which the local boron-doped diamond single crystal layer is to be deposited; S3. Locally depositing a boron-doped diamond single crystal layer on the diamond single crystal substrate using a microwave plasma-assisted chemical vapor deposition process; S4. Place the composite diamond tool material obtained in step S3 in a standard solution of nitric acid and sulfuric acid to remove SiO 2 Mask.

[0015] Preferably, after step S4, the method further includes the following steps: S5. The product obtained in step S4 is subjected to an argon ion sputtering process to completely remove the denatured layer formed by amorphous carbon and graphite generated during the diamond synthesis process on the side of the boron-doped diamond layer, so as to ensure good ohmic contact between the Mo / Au electrode subsequently evaporated on the side of the boron-doped diamond layer and the boron-doped diamond layer.

[0016] S6. The product obtained in step S5 is subjected to a high temperature heat treatment at 750° C. for 1 hour in a pure oxygen environment to intensify the dispersion and uniformity of boron in the diamond lattice and enhance its semiconductor electrical properties.

[0017] Preferably, after step S6, the method further includes the following steps: S7. Grinding the product obtained in S6 at the local boron-doped layer to obtain a nano-scale defect-free cutting edge as an ultra-precision cutting tool with self-temperature sensing function; S8. Ion implantation technology is used to implant nitrogen impurities into the outer surface of the boron-doped diamond layer, and based on the hole-electron neutralization effect between boron-nitrogen atoms, the outer surface portion of the boron-doped diamond layer is insulated.

[0018] Preferably, before step S8, two opposite sides of the local boron-doped diamond single crystal layer deviating from the cutting edge each cover an area for subsequent evaporation of Mo / Au stacked electrodes, and the area is made of SiO 2 Mask or aluminum sheet or clay cover; after the nitrogen impurity injection is completed, remove the SiO covering the area 2 A mask or aluminum sheet or clay is formed, and then Mo / Au laminated electrodes are formed on both sides of the exposed boron-doped diamond single crystal layer, and then conductive silver paste is welded on the Mo / Au laminated electrodes.

[0019] In the synthesis process of composite structure diamond tool materials, before the deposition of boron-doped diamond layer on the surface of single crystal diamond substrate, a layer of SiO2 needs to be deposited on the surface of single crystal diamond substrate by magnetron sputtering process. 2 As a mask, a boron-doped diamond layer is then deposited on the surface of the single crystal diamond substrate not covered by the mask by a microwave plasma-assisted chemical vapor deposition process. 2 The mask thickness is 200 nm. After the Mo / Au boron-doped diamond layer is deposited, the composite structure diamond tool material is placed in a mixed solution of nitric acid and sulfuric acid for cleaning to remove SiO 2After pickling, the sample is ultrasonically cleaned using an organic solvent (such as acetone, isopropanol). After that, further, an argon ion sputtering process is used to completely remove the amorphous carbon and graphite generated during the diamond synthesis process on the side of the boron-doped diamond layer, and then an Au / Mo stacked electrode is deposited on the side of the boron-doped diamond layer by an electron beam evaporation process.

[0020] The diamond tool with localized boron doping at the cutting edge of the present invention plays an important role in realizing online perception of cutting micro-area temperature during ultra-precision cutting. The cutting edge of the tool is the boron-doped diamond layer, which ensures the high spatial resolution of cutting temperature measurement. The temperature-sensing area of ​​the boron-doped diamond layer at the micrometer scale significantly improves the thermal response speed of cutting temperature perception and the ability to resist ambient temperature interference. Nitrogen ion implantation on the surface of the boron-doped diamond layer achieves insulation of the outer surface of the boron-doped diamond layer, avoiding the problem that the cutting temperature cannot be measured when the tool is cutting various workpieces with high electrical conductivity due to the influence of the thermal sensitivity of the boron-doped diamond layer on the electrical conduction between the tool and the chips. The method of the present invention has extremely strong practicality and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a diamond tool with local boron doping on the cutting edge in an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of the synthesis process flow of locally boron-doped diamond single crystal in an embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram of a method for collecting resistance of a diamond tool with local boron doping at the cutting edge in an embodiment of the present invention.

[0024] Figure 4 This is a physical picture of a diamond tool with local boron doping on the cutting edge in an embodiment of the present invention.

[0025] Figure 5 This is a physical picture of a device for testing the temperature sensing performance of a diamond tool with local boron doping on the cutting edge in an embodiment of the present invention.

[0026] Figure 6 It is a calibration curve diagram of the relationship between the edge temperature of a diamond tool with local boron doping at the edge and the resistance of the boron doped diamond layer in an embodiment of the present invention.

[0027] Figure 7 This is a graph showing the temperature measurement stability results of a diamond tool with local boron doping on the cutting edge in an embodiment of the present invention.

[0028] Figure 8 This is a diagram showing the temperature measurement resolution of a diamond tool with local boron doping on the cutting edge in an embodiment of the present invention.

[0029] Fig. 9This is a diagram showing the thermal response results of temperature measurement of a diamond tool with local boron doping on the cutting edge in an embodiment of the present invention.

[0030] Fig.10 This is a graph showing the surface profile of a microstructure array cut by a diamond tool with localized boron doping on the cutting edge in an embodiment of the present invention.

[0031] Fig.11 This is a graph of the cutting micro-area temperature results when a diamond tool with locally boron doped cutting edge is used to cut a microstructure array in an embodiment of the present invention.

[0032] In the figure: 1. Diamond single crystal substrate, 2. Locally boron-doped diamond single crystal layer, 3. Zirconia ceramic knife holder, 4. SiO 2 Mask, 5. Metal aluminum sheet, 6. Boron-doped diamond deposition layer, 7. Modified layer formed by amorphous carbon and graphite on the side of the boron-doped diamond deposition layer, 8. Diamond tool with local boron doping on the cutting edge, 9. Nanoscale defect-free cutting edge of diamond tool with local boron doping on the cutting edge, 10. Constant current source, 11. Voltage measuring meter, 12. Side surface of boron-doped diamond layer, 13. Electrical path coated with conductive silver paste, 14. Mo electrode coating, 15. Au electrode coating, 16. Ceramic point heat source, 17. Temperature controller, 18. Commercial source meter. DETAILED DESCRIPTION

[0033] 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.

[0034] A temperature-sensitive diamond tool with local boron doping on the cutting edge of the present invention, such as Figure 1 As shown, the tool is a composite structure consisting of a diamond single crystal substrate 1 and a locally boron-doped diamond single crystal layer 2, which is synthesized by a microwave plasma assisted chemical vapor deposition process. The diamond single crystal substrate 1 and the locally boron-doped diamond single crystal layer 2 are bonded by interatomic action and are integrally formed. The diamond single crystal substrate 1 is brazed on a zirconia ceramic tool holder 3.

[0035] Next, combine Figure 2 , a detailed description of the synthesis method of the diamond tool material of the local boron-doped diamond single crystal layer-diamond single crystal substrate composite structure used for preparing the above-mentioned tool: (1) A diamond single crystal substrate 1 was synthesized by microwave plasma assisted chemical vapor deposition process, and the substrate thickness was 0.8 mm. The diamond single crystal was deposited and grown in a high-purity hydrogen atmosphere with a hydrogen flow rate of 500 sccm. Hydrogen, as a carrier gas and diluent gas, can promote the activation of the carbon surface of diamond and etch a small amount of amorphous carbon produced during the diamond synthesis process, thereby improving the crystal quality of the diamond single crystal. High-purity methane was used as the carbon source with a methane flow rate of 15 sccm. During the synthesis process, the substrate temperature was set to 950°C, the synthesis pressure was 21 kPa, and the microwave power was set to 2.5 kW. A high-quality (100) crystal face diamond seed crystal was used as the growth substrate for the diamond single crystal. Before deposition, the substrate surface contamination was removed by plasma etching (argon or hydrogen).

[0036] (2) Depositing SiO on the diamond single crystal substrate by magnetron sputtering process 2 The film 4 is used as a mask for the local deposition of the subsequent boron-doped diamond layer 6. The local position is shielded by the metal aluminum sheet 5. The length and width of the metal aluminum sheet are both 300 μm, which is the corresponding size of the local deposition of the boron-doped diamond layer in the subsequent process. Before magnetron sputtering, the diamond single crystal substrate is ultrasonically cleaned with an organic solvent (such as acetone, isopropanol) to remove surface contaminants. During the magnetron sputtering process, a high-purity SiO 2 As the target material, high-purity argon is used as the main sputtering gas, and the initial vacuum degree of sputtering is controlled to be less than <5×10 -6 Torr to avoid impurity contamination. The working pressure was set to 2mTorr, the RF power was set to 100W, the sputtering substrate temperature was set to 300℃, the sputtering time was 20 minutes, and the SiO 2 The mask thickness is about 200nm. 2 After the deposition is completed, the metal aluminum sheet is removed to expose the diamond single crystal substrate on which the boron-doped diamond single crystal layer is to be deposited.

[0037] (3) A local boron-doped diamond single crystal layer 6 is locally deposited on the diamond single crystal substrate using a microwave plasma assisted chemical vapor deposition process. Before deposition, surface contamination of the diamond single crystal substrate is removed by plasma etching (argon or hydrogen). 2 H 6 Borane is used as a boron source, with a concentration range of 200-400 ppm, preferably 300 ppm. During the synthesis process, the substrate temperature is set to 1050°C, the pressure in the chamber is 22 kPa, the microwave power is set to 2 kW, and the other process parameters are consistent with those when depositing the diamond single crystal substrate, and the boron-doped diamond layer has a thickness of 50 μm.

[0038] (4) The composite diamond tool material is placed in a standard solution of nitric acid and sulfuric acid (volume ratio of about 2:1) and cleaned at 120°C for 4 hours to remove SiO 2 Mask. After pickling, use an organic solvent (such as acetone, isopropanol) to ultrasonically clean the sample. After that, use an argon ion sputtering process to completely remove the denatured layer 7 formed by amorphous carbon and graphite generated during the diamond synthesis process on the side of the boron-doped diamond layer. The surface needs to be coated with a conductive silver paste to form an electrical path for the transmission of the terminal voltage of the boron-doped diamond layer, so as to realize the online collection of the resistance value of the boron-doped diamond layer for the characterization of the cutting temperature. Completely removing the amorphous carbon and graphite on the side of the boron-doped diamond layer is intended to ensure good ohmic contact between the surface and the conductive silver paste. In the argon ion sputtering process, the argon ion flow rate is 20sccm, the working gas pressure is 1mTorr, the sputtering voltage is 300V, the argon ions are vertically sputtered at an incident angle of 0°, and the sputtering time is 1 minute.

[0039] (5) After that, the samples were placed in a pure oxygen environment and subjected to a high temperature heat treatment at 750°C for 1 hour to enhance the dispersion and uniformity of boron in the diamond lattice and enhance its semiconductor electrical properties. After the above process, a diamond tool material with a composite structure of a localized boron-doped diamond single crystal layer and a diamond single crystal substrate was successfully synthesized.

[0040] like Figure 3 As shown, after the local boron-doped diamond single crystal tool material is synthesized, it is sharpened on a commercial sharpener to produce a diamond tool 8 of a local boron-doped composite structure, which has a nanoscale defect-free cutting edge 9. Among them, the reason why the boron-doped diamond part has the ability to sense temperature is that after boron doping, the diamond becomes a P-type semiconductor, which has a negative temperature coefficient thermal sensitivity, that is, within a certain temperature range, the body resistance of the boron-doped diamond decreases with increasing temperature. In this case, by accurately calibrating the temperature relationship between the body resistance of the local boron-doped diamond layer of the tool and the tool edge, and accurately collecting the body resistance of the boron-doped diamond layer of the tool online during ultra-precision cutting, real-time monitoring of the temperature of the cutting micro-area of ​​the tool edge can be achieved.

[0041] Furthermore, in order to prevent the thermal sensitivity of the boron-doped diamond layer from being disturbed by the electrical conduction between the workpiece and the cutting edge when the tool is cutting various workpieces with high electrical conductivity, the outer surface of the boron-doped diamond layer needs to be insulated. Ion implantation technology is used to inject nitrogen impurities into the outer surface of the boron-doped diamond layer, and the insulation of the outer surface of the boron-doped diamond is achieved based on the hole-electron neutralization effect between boron and nitrogen atoms. -6Torr) uses single-charged N⁺ or double-charged N²⁺ high-purity nitrogen ions as the ion source for ion implantation on the surface of the boron-doped diamond layer. The particle implantation energy is 300 keV and the ion implantation dosage is 10 15 -10 16 ions / cm 2 , the injection angle is 0°, the beam diameter is 0.5mm, in order to ensure uniform ion distribution in a large range, the ion injection depth is about 200nm, after the ion injection process is completed, the tool is placed in a 600℃ environment for heat treatment for 1 hour to intensify the diffusion of nitrogen ions and the combination with boron atoms. In addition, since the side of the subsequent boron-doped diamond layer needs to be evaporated by electron beam Mo / Au stacked electrodes, and then the conductive silver paste path is connected on the surface of the Mo / Au stacked electrodes. Therefore, before ion implanting nitrogen impurities into the surface of the boron-doped diamond single crystal layer, it is necessary to cover an area for the subsequent evaporation of Mo / Au stacked electrodes on each of the two opposite sides of the boron-doped diamond single crystal layer that deviates from the cutting edge. The size of this area is 100×100μm, and this area is made of SiO 2 Mask or aluminum sheet or clay cover; after the nitrogen impurity injection is completed, remove the SiO covering the area 2 The mask or aluminum sheet or clay exposes the two sides of the boron-doped diamond single crystal layer.

[0042] like Figure 3 As shown, the resistance of the boron-doped diamond layer is collected by a four-wire method, that is, a constant current is supplied to the boron-doped diamond layer through a constant current source 10, and its terminal voltage is collected by a voltmeter 11 at the same time, and its resistance value is calculated. The above-mentioned source and meter are connected through two paths 13 formed by conductive silver pastes drawn from the side 12 of the boron-doped diamond layer. Prior to this, a Mo thin layer 14 (length and width of about 100μm, thickness of 100nm) and an Au thin layer 15 (length and width of about 100μm, thickness of 150nm) are successively evaporated on the same position on the side of the boron-doped diamond layer to form electrodes, so as to ensure good ohmic contact between the conductive silver paste and the boron-doped diamond layer.

[0043] The performance of the above-mentioned local boron-doped diamond tool in the measurement of cutting micro-area temperature is demonstrated below through specific examples.

[0044] Among them, local boron doped diamond tools such as Figure 4 As shown, the rake angle is 0°, the back angle is 7°, and the tool tip angle is 75°. AFM measurement shows that the tool has a high-quality defect-free cutting edge with a radius of about 35nm. The conductive silver paste used to form the conductive path on the tool preferably has a transmission resistance loss of 0.02Ω.sqr -1 The conductive silver paste model is DuPont4929N.

[0045] Before conducting the cutting temperature measurement test, it is necessary to test the temperature sensing performance of the diamond tool. Due to the high-speed relative movement between the tool and the chip during the cutting process, the temperature sensing performance of the tool cannot be tested in situ. Therefore, a test device has been specially developed, such as Figure 5 As shown, a custom ceramic point heat source 16 with a tip diameter of 50 μm is used to heat the cutting edge 9 of the tool to simulate the heat generation of the cutting micro-area during ultra-precision cutting. The tip temperature of the ceramic point heat source is regulated by a temperature controller 17. The boron-doped diamond layer of the tool is connected to a commercial source meter (Keithley2400) 18 through the above-mentioned conductive silver paste path. The commercial source meter passes a constant current of 1 μm through the boron-doped diamond layer, and simultaneously collects the terminal voltage of the boron-doped diamond layer online to calculate the resistance value of the boron-doped diamond layer in real time. The surface of the ceramic point heat source is coated with graphite slurry with a thermal conductivity of 180 W / m·K to minimize the contact thermal resistance between the tool edge and the heat source, thereby improving the accuracy of the calibration result. The resistance change curve of the tool with temperature, room temperature signal stability, temperature resolution and thermal response characteristics were tested, and the results are shown below.

[0046] Figure 6 It is the calibration relationship between the tool edge temperature and the boron-doped diamond layer resistance (R) of the tool. The average value of four repeated experiments shows that the edge temperature and the boron-doped diamond layer resistance change in an approximately negative linear relationship. When the test temperature increases from 25 to 205°C, the boron-doped diamond layer resistance of the tool decreases from 2436.6 to 1077.8Ω, and the temperature sensitivity is about 7.5Ω / ℃.

[0047] As a temperature sensor, measurement stability refers to the ability to output a drift-free signal stably for a long time in a constant temperature environment. Figure 7 The resistance signal output curve of the diamond tool in an environment of 25°C for 4500s shows that the resistance signal is stable around 2439.7Ω with a random fluctuation of about 1.6Ω (about 0.2°C), and no resistance signal drift is found during the test. Therefore, it can be proved that the tool can stably monitor the temperature for a long time.

[0048] Figure 8 The temperature resolution test results of the tool are given. Figure 8 As shown, the change in resistance value of the boron-doped diamond layer of the tool when the edge temperature of the tool changes at a gradient of 0.1 and 0.2°C was tested respectively. Among them, when the edge temperature changes by 0.1 and 0.2°C respectively, the resistance of the boron-doped diamond layer changes by about 0.7 and 1.4Ω respectively. This shows that the tool can detect a temperature change of 0.1°C near the edge and has excellent temperature resolution capability.

[0049] Fig. 9 The thermal response performance test results of the tool are given. Fig. 9 As shown, the thermal response of a temperature sensor is generally quantified by the thermal time constant, which is defined as the time it takes for the resistivity of the temperature sensor to change from R to 0 Reduced to 0.632×(R 0 -R e ). Among them, the thermal time constants of bulk-doped diamond tools (patent number: CN202211585437.7), layer-doped diamond tools (patent number: CN202311083899.3) and the local boron-doped diamond tools described in this patent were compared when the tool edge temperature increased from 25°C to 55°C, which were 397, 123 and 26ms respectively. It can be seen that the diamond tools described in this patent have significantly higher thermal response capabilities.

[0050] Fig.10 The invention discloses a sinusoidal microstructure array surface which is ultra-precision cut on a polymethyl methacrylate (PMMA) substrate using the diamond tool, wherein the maximum cutting depth can reach 3 μm and the feed speed is 50 μm / s. Fig.11 The temperature variation curve measured by the diamond tool during the above-mentioned cutting process is 1.8 mm and the cutting time is 36 s. It can be seen from the figure that in the feeding direction along the surface of the microstructure array, as the cutting depth changes between 0 and 3 μm, the cutting temperature fluctuates periodically between 25.3 and 25.7 ° C synchronously. During the cutting process of the microstructure array, the material removal rate and the heat conduction and dissipation between the tool and the chips change in real time, which inevitably leads to changes in the generation and dissipation of cutting heat, thereby causing changes in the cutting temperature related to the microstructure array. The temperature measured by the diamond tool has the ability to perform online characterization of the microstructure of the machined surface, which further proves the high sensitivity and rapid thermal response of the diamond tool in ultra-precision cutting micro-area temperature measurement.

Claims

1. A temperature-sensitive diamond tool with local boron doping on the cutting edge, characterized in that: The invention comprises a diamond single crystal substrate, which has a certain thickness. A local boron-doped diamond single crystal layer is deposited at a corner position of the top surface of the diamond single crystal substrate. The corner position is used to set the cutting edge of the tool. The local boron-doped diamond single crystal layer is used as a P-type semiconductor with a negative temperature coefficient thermosensitive property to be used as a temperature sensor to realize the perception of the temperature of the micro-area of ​​the ultra-precision cutting edge.

2. The temperature-sensitive diamond tool with localized boron doping on the cutting edge according to claim 1, characterized in that: The outer surface of the local boron-doped diamond single crystal layer is provided with nitrogen impurities implanted by using ion implantation technology.

3. A temperature-sensitive diamond tool with local boron doping on the cutting edge according to claim 1 or 2, characterized in that: The thickness of the diamond single crystal substrate is 0.7-1.0 mm.

4. A temperature-sensitive diamond tool with local boron doping on the cutting edge according to claim 1 or 2, characterized in that: The thickness of the local boron-doped diamond layer is 20-100 μm.

5. A temperature-sensitive diamond tool with localized boron doping on the cutting edge according to claim 1 or 2, characterized in that: The length and width of the diamond single crystal substrate are respectively between 2-3 mm, and the length and width of the local boron-doped diamond layer are within the range of 200-400 μm.

6. A temperature-sensitive diamond tool with localized boron doping on the cutting edge according to claim 1 or 2, characterized in that: The two opposite sides of the local boron-doped diamond single crystal layer deviating from the cutting edge are respectively electrically connected to a conductive silver paste, and the conductive silver paste and the side of the local boron-doped diamond single crystal layer are connected by Mo / Au stacked electrodes evaporated on the side of the local boron-doped diamond single crystal layer through an electron beam evaporation process.

7. A method for manufacturing a temperature-sensitive diamond tool as claimed in any one of claims 1 to 6, characterized in that The following steps are involved: S1. Synthesize diamond single crystal substrate using microwave plasma assisted chemical vapor deposition process; S2. Depositing a SiO2 film as a mask on the diamond single crystal substrate by a magnetron sputtering process for the subsequent local deposition of a local boron-doped diamond layer, the local position is shielded by a metal aluminum sheet; after the SiO2 deposition is completed, the metal aluminum sheet is removed to expose the diamond single crystal substrate on which the local boron-doped diamond single crystal layer is to be deposited; S3. Locally depositing a boron-doped diamond single crystal layer on the diamond single crystal substrate using a microwave plasma-assisted chemical vapor deposition process; S4. Place the composite diamond tool material obtained in step S3 in a standard solution of nitric acid and sulfuric acid to remove the SiO2 mask.

8. The manufacturing method according to claim 7, characterized in that After step S4, the method further includes the following steps: S5. The product obtained in step S4 is subjected to an argon ion sputtering process to completely remove the denatured layer formed by amorphous carbon and graphite generated during the diamond synthesis process on the side of the boron-doped diamond layer, so as to ensure good ohmic contact between the Mo / Au electrode subsequently deposited on the side of the boron-doped diamond layer and the boron-doped diamond layer; S6. The product obtained in step S5 is subjected to a high temperature heat treatment at 750° C. for 1 hour in a pure oxygen environment to intensify the dispersion and uniformity of boron in the diamond lattice and enhance its semiconductor electrical properties.

9. The manufacturing method according to claim 8, characterized in that After step S6, the method further includes the following steps: S7. Grinding the product obtained in S6 at the local boron-doped layer to obtain a nano-scale defect-free cutting edge as an ultra-precision cutting tool with self-temperature sensing function; S8. Ion implantation technology is used to implant nitrogen impurities into the outer surface of the boron-doped diamond layer, and based on the hole-electron neutralization effect between boron-nitrogen atoms, the outer surface portion of the boron-doped diamond layer is insulated.

10. The manufacturing method according to claim 9, characterized in that: Before step S7, two opposite sides of the local boron-doped diamond single crystal layer deviating from the cutting edge each cover an area for subsequent vapor deposition of Mo / Au stacked electrodes, and the area is covered with a SiO2 mask or an aluminum sheet or clay; after the nitrogen impurity injection is completed, the SiO2 mask or the aluminum sheet or clay covering the area is removed, and then the Mo / Au stacked electrodes are vapor deposited, and then the conductive silver paste is welded on the Mo / Au stacked electrodes.

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