A method of processing a diamond / silicon carbide ceramic composite

Abstract

The application discloses a processing method of diamond / silicon carbide ceramic composite material and belongs to the technical field of ceramic composite materials. The processing method is composed of the following steps: primary laser processing, primary mechanical polishing, secondary laser processing, tertiary laser processing and secondary mechanical polishing. The primary mechanical polishing is to mechanically polish the composite material after the primary laser processing, and ceramic grinding fluid is sprayed for cooling during the mechanical polishing. Each polishing time is 10-20h. The mechanical polishing is performed until the length of the composite material is the target length, the width is the target width, and the height is the target height+2.5mm. The composite material after the primary mechanical polishing is obtained. The processing method can reduce the surface roughness of the diamond / silicon carbide ceramic composite material, can avoid the influence on the mechanical properties and the heat conduction performance of the diamond / silicon carbide ceramic composite material, and can improve the processing efficiency of the diamond / silicon carbide ceramic composite material.

Description

Technical Field

[0001] This invention relates to the field of ceramic composite materials technology, and specifically to a processing method for diamond / silicon carbide ceramic composite materials. Background Technology

[0002] Diamond / silicon carbide composites, obtained by combining diamond and silicon carbide, possess ultra-high hardness and specific stiffness, while also exhibiting excellent thermal stability, wear resistance, and thermal conductivity. In the field of precision instruments, they are primarily used as materials for measuring gauges, precision bearings, and mechanical seal components. In the field of thermal management, they are mainly used as electronic packaging materials. In the field of optical components, they are primarily used as semiconductor wafer chucks and high-stability optical substrates.

[0003] However, diamond / silicon carbide composites possess high strength (three-point bending strength ≥300MPa), hardness (Vickers hardness ≥80GPa), and weak electrical conductivity (dielectric constant 40-50F / m), which significantly hinders their machinability. Particularly for diamond / silicon carbide composites with a thickness ≥20mm, traditional mechanical cutting methods are slow, and over long-term processing, the diamond grinding wheel is prone to severe wear and slippage, making grinding impossible. While femtosecond laser processing can achieve cutting, the different ablation capabilities of the laser on diamond and silicon carbide in the composite material (diamond ablation threshold is often higher than silicon carbide ablation threshold) result in greater silicon carbide ablation than diamond ablation under the same laser power. Consequently, the surface roughness is >1μm, which also affects the bending strength and thermal conductivity of the processed diamond / silicon carbide composite material, failing to meet practical engineering requirements and restricting the large-scale industrial production and application of this material. To improve processing efficiency, the most common method is to increase the power in laser processing, but this leads to an increase in silicon carbide ablation, further impacting the surface roughness, bending strength, and thermal conductivity of the processed diamond / silicon carbide composite material.

[0004] Meanwhile, during processing, due to the anisotropic characteristics of diamond and silicon carbide, there are differences in thermodynamic properties between the components. This easily leads to heat-affected zones, causing thermal damage defects such as diamond particle pull-out and delamination of the diamond / silicon carbide composite, resulting in increased surface roughness. Furthermore, component loss or compositional changes due to heat in the diamond / silicon carbide composite can also lead to a decrease in its mechanical and thermal conductivity properties.

[0005] To address the aforementioned issues, the most common approach is to alternate between traditional mechanical cutting and femtosecond laser processing. This involves first using laser processing to initially reduce the thickness, then using mechanical polishing for preliminary treatment, followed by laser processing to further reduce the thickness, and finally using mechanical polishing for final processing to reduce surface roughness. However, problems such as silicon carbide oxidation, diamond graphitization, and diamond particle pull-out still occur, leading to a decrease in the mechanical and thermal conductivity properties of the processed diamond / silicon carbide composite material. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a processing method for diamond / silicon carbide ceramic composite materials, which can reduce the surface roughness of diamond / silicon carbide ceramic composite materials, avoid affecting the mechanical and thermal conductivity properties of diamond / silicon carbide ceramic composite materials, and improve the processing efficiency of diamond / silicon carbide ceramic composite materials.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A processing method for diamond / silicon carbide ceramic composite materials comprises the following steps: a first laser processing, a first mechanical polishing, a second laser processing, a third laser processing, and a second mechanical polishing; The first laser processing involves laser processing of a diamond / silicon carbide composite material workpiece. A laser with a wavelength of 532nm is selected. After preheating the laser, it is rotated clockwise for cutting. Each processing time is 2-4 hours, cutting to a length of target length + 1mm, a width of target width + 1mm, and a height of target height + 3mm. Then, a laser with a wavelength of 1064nm is selected, and clockwise rotation is used for fine processing, keeping other parameters unchanged. Each processing time is 4-8 hours, finely processing to a length of target length, a width of target width, and a height of target height + 3mm, thus obtaining the composite material after one laser processing. In the aforementioned laser processing, the laser pulse width for cutting and fine processing is 20-50 μs, the laser output power is 2000-3500 W, the repetition frequency is 1.5-3 kHz, the working focal length is 100-180 μm, the spot radius is 50-75 μm, the laser scanning speed is 30-60 mm / min, the laser scanning interval is 10-20 μm, the defocus distance is 0.3-0.5 μm, and the number of pulses is 2-5. The first mechanical polishing involves mechanically polishing the composite material after a laser processing. During mechanical polishing, the material is cooled by spraying ceramic grinding fluid. Each polishing session lasts 10-20 hours. The material is mechanically polished until the length, width, and height are the target length + 2.5 mm, resulting in a composite material after one mechanical polishing. In the aforementioned mechanical polishing process, the grinding disc is made of stainless steel / alumina composite material with a thermal conductivity of 16 W / (m·K) and a friction coefficient of 0.5-0.9. In the aforementioned mechanical polishing process, the volume ratio of water to oxygen in the water-oxygen mixture is 5-20%. In the aforementioned mechanical polishing process, the composite material after a single laser processing is mechanically polished by grinding against a grinding disc. The grinding disc is clamped by a linear motion guide rail device with a cylinder. The workpiece sliding speed is 1500-3500 m / min, the applied pressure is 80-150 MPa, the workpiece oscillates radially, the grinding disc rotation speed is 50-160 m / min, the polishing atmosphere is a water-oxygen mixture, and the heating temperature in the polishing chamber is 200-300℃. During the first mechanical polishing process, the radial oscillation of the workpiece has a width L = 10-15 mm and a frequency of 3-8 times / min. In the aforementioned mechanical polishing process, the spraying speed of the ceramic grinding fluid is 300-500 mL / min; The method for preparing the ceramic grinding fluid comprises the following steps: preparing high-flowability diamond powder, preparing high-thermal-conductivity composite graphite powder, and mixing them; To prepare high-flowability diamond powder, diamond powder and γ-aminopropyltriethoxysilane are added to a ball mill, the ball-to-material ratio of the ball mill is controlled to 5-6:1, the rotation speed is controlled to 300-400 rpm, and the ball milling is carried out for 3-3.5 hours. L-threonine is added, and the ball milling continues for 40-50 minutes. Polyethylene glycol 4000 is added, and the ball milling continues for 40-50 minutes to obtain high-flowability diamond powder. In the preparation of high-flowability diamond powder, the mass ratio of diamond powder, γ-aminopropyltriethoxysilane, L-threonine, and polyethylene glycol 4000 is 180-190:27-30:12-13:27-30. In the preparation of high-flowability diamond powder, the particle size of the diamond powder is 20 nm; To prepare the highly thermally conductive composite graphite powder, graphite powder and sodium dodecyl sulfate are added to a ball mill. The ball-to-material ratio is controlled at 5-6:1, the rotation speed is controlled at 300-400 rpm, and the milling is carried out for 1.5-2 hours to obtain highly dispersed graphite powder. Polyvinylpyrrolidone and anhydrous ethanol are added to a reactor. The reactor temperature is controlled at 40-45℃, the rotation speed is controlled at 300-400 rpm, and the mixture is stirred for 10-15 minutes. The highly dispersed graphite powder and deionized water are then added to the reactor, and the mixture is stirred for another 3 minutes. Add tetraethyl orthosilicate for 0-40 min, continue stirring for 30-40 min, add ammonia water dropwise, continue stirring for 3-3.5 h after the addition is complete, add γ-aminopropyltriethoxysilane, continue stirring for 5-6 h, add polyethylene glycol 400, continue stirring for 50-60 min, add to a centrifuge, control the centrifuge speed to 8000-9000 rpm, centrifuge for 10-11 min, take the precipitate, wash with anhydrous ethanol and deionized water alternately 3-4 times, dry to obtain high thermal conductivity composite graphite powder; In the preparation of the high thermal conductivity composite graphite powder, the mass-to-volume ratio of graphite powder, sodium dodecyl sulfate, polyvinylpyrrolidone, anhydrous ethanol, deionized water, tetraethyl orthosilicate, ammonia, γ-aminopropyltriethoxysilane, and polyethylene glycol 400 is 200-210g:10-12g:15-18g:6000-6500mL:60-70mL:65-70mL:90-100mL:14-15mL:14-16g; In the preparation of the high thermal conductivity composite graphite powder, the particle size of the graphite powder is 100 nm; In the preparation of the high thermal conductivity composite graphite powder, the mass concentration of the ammonia water is 25%, and the dropping rate is 6-7 mL / min; The mixing process involves adding triethanolamine, dodecanoic acid, and deionized water to a reactor, controlling the reactor speed to 200-300 rpm, stirring at room temperature for 1-1.5 hours, adding lauric acid diethanolamide, polyethylene glycol 2000, and glycerol, continuing stirring for 30-40 minutes, adding high-flowability diamond powder and high thermal conductivity composite graphite powder, and continuing stirring for 1.5-2 hours to obtain a ceramic grinding fluid. In the mixture, the mass ratio of triethanolamine, dodecanoic acid, deionized water, lauric acid diethanolamide, polyethylene glycol 2000, glycerol, high-flowability diamond powder, and high thermal conductivity composite graphite powder is 15-17:7-8:120-130:11-13:10-10.5:10-12:1.9-2.1:3.4-3.6. The secondary laser processing involves laser processing the composite material after the first mechanical polishing. A laser with a wavelength of 1064nm is selected. After preheating the laser, it is rotated clockwise for fine processing. Each processing session takes 8-15 hours. The fine processing is carried out until the length is the target length, the width is the target width, and the height is the target height + 2mm, thus obtaining the composite material after secondary laser processing. In the secondary laser processing, the laser pulse width is 20-30μs, the laser output power is 3000-3500W, the repetition frequency is 2-3kHz, the working focal length is 150-180μm, the spot radius is 60-75μm, the laser scanning speed is 50-60mm / min, the laser scanning interval is 15-20μm, the defocus distance is 0.4-0.5μm, and the number of pulses is 3-5. The third laser processing involves laser processing the composite material after the second laser processing. A laser with a wavelength of 532nm is selected. After preheating the laser, it is rotated clockwise for fine processing. The laser processing conditions are set as follows: each processing time is 7-10 hours, and fine processing is carried out until the length is the target length, the width is the target width, and the height is the target height + 1mm, thus obtaining the composite material after the second laser processing. In the three laser processing steps, the laser pulse width is 20-30 μs, the laser output power is 2000-3000 W, the repetition frequency is 1.5-2 kHz, the working focal length is 100-150 μm, the spot radius is 50-60 μm, the laser scanning speed is 30-50 mm / min, the laser scanning interval is 10-15 μm, the defocus distance is 0.3-0.4 μm, and the number of pulses is 2-3. The secondary mechanical polishing involves fixing the composite material after the three laser processing steps onto a vertical machining center for mechanical polishing. During polishing, the material is cooled by spraying ceramic grinding fluid. Each polishing session lasts 5-10 hours. The mechanical polishing continues until the length, width, and height meet the target requirements, resulting in the processed diamond / silicon carbide composite material workpiece. In the secondary mechanical polishing, the material of the grinding disc and the volume ratio of water to oxygen in the water-oxygen mixture are the same as those used in the primary mechanical polishing. In the secondary mechanical polishing, the composite material after the third laser processing is mechanically polished by grinding against a grinding disc. The grinding disc is clamped by a linear motion guide device with a cylinder. The workpiece sliding speed is 1500-2000 m / min, the applied pressure is 80-100 MPa, the workpiece oscillates radially, the grinding disc rotates at a speed of 100-160 m / min, the polishing atmosphere is a water-oxygen mixture, and the heating temperature in the polishing chamber is 200-240℃. During the secondary mechanical polishing, the radial oscillation of the workpiece has a width L = 10-15 mm and a frequency of 3-8 times / min. In the secondary mechanical polishing, the spraying speed of the ceramic grinding fluid is 400-500 mL / min; In the secondary mechanical polishing, the ceramic grinding fluid is prepared using the same method as the ceramic grinding fluid used in the primary mechanical polishing.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The processing method of the diamond / silicon carbide ceramic composite material of the present invention uses 532nm and 1064nm lasers in laser processing, which are applied to the diamond / silicon carbide ceramic composite material at high power, respectively. This can graphitize the diamond part on the surface. The ablation ability of graphite and silicon carbide is similar, thus avoiding the problem of increased roughness after processing. In mechanical polishing, stainless steel / alumina composite material is used as the polishing disc, which can remove the graphite component generated in laser processing. Specifically, part of the graphite volatilizes in the form of carbon monoxide or carbon dioxide in the heated oxidation environment, and part reacts with iron to generate iron carbide (the iron ions come from the decomposition of the ferrous oxide film of the polishing disc into iron and iron oxide), thus avoiding the graphite from damaging the gold. The effects of diamond / silicon carbide composites on flexural strength and thermal conductivity; In mechanical polishing, ceramic grinding fluid was also used. The preparation of the ceramic grinding fluid involved first preparing high-flowability diamond powder, specifically by treating the diamond powder with γ-aminopropyltriethoxysilane to introduce amino groups onto the diamond powder surface, followed by the addition of L-threonine, which acts as a molecular bridging agent. L-threonine mainly binds to the amino groups on the diamond powder surface through its hydroxyl groups. Then, polyethylene glycol 4000 was added, which binds to L-threonine through its hydroxyl groups. The purpose of L-threonine is to increase the amount of polyethylene glycol 4000 bound to the diamond powder surface, further improving the hydrophilicity of the diamond powder. It can also enhance the diamond powder's properties through intermolecular forces. The fluidity of the stone powder is crucial. After applying ceramic grinding fluid, highly fluid diamond powder disperses rapidly. Some of this highly fluid diamond powder binds to and removes debris generated during grinding, while another portion adheres to the surface of the diamond / silicon carbide ceramic composite material through the high viscosity of polyethylene glycol 4000. During laser processing, the highly fluid diamond powder also plays a role in heat dissipation. Furthermore, the highly fluid nanodiamond powder acts as a stress buffer during mechanical grinding, preventing the mechanical pull-out of diamond particles from the diamond / silicon carbide ceramic composite material. Then, highly thermally conductive composite graphite powder is prepared by combining porous graphite powder with silica sol (generated by the hydrolysis of tetraethyl orthosilicate) to form… The composite of porous graphite powder and silica utilizes the graphite powder for heat conduction and dissipation, while the silica reacts with water at high temperatures, further enhancing heat dissipation. Then, γ-aminopropyltriethoxysilane is used to introduce amino groups, followed by the addition of polyethylene glycol 400. PEG 400 is bonded to the outermost layer through intermolecular forces. The combination of PEG 400 and amino groups improves dispersibility and reduces adsorption, resulting in a high thermal conductivity composite graphite powder with excellent heat dissipation and dispersibility. High-flowability diamond powder, the high thermal conductivity composite graphite powder, and other components are then mixed to obtain a ceramic grinding fluid. The heat dissipation function of the grinding fluid prevents the degradation of the material's mechanical and thermal properties due to changes in heated components during the processing of the diamond / silicon carbide ceramic composite material.In summary, by employing 532nm and 1064nm lasers, combined with mechanical polishing and ceramic grinding fluid, this invention can improve processing efficiency while reducing the surface roughness of the processed diamond / silicon carbide ceramic composite material, and also avoid affecting the bending strength and thermal conductivity of the processed diamond / silicon carbide ceramic composite material. (2) The processing method of the diamond / silicon carbide ceramic composite material of the present invention has a total processing time of 536-750h, and the surface roughness of the processed diamond / silicon carbide ceramic composite material is 0.8-1μm, the bending strength is 481-507MPa, and the thermal conductivity is 602-615W / (m·K). Detailed Implementation

[0009] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0010] In Examples 1-2 and Comparative Examples 1-3, the diamond / silicon carbide composite workpieces were all flat plates with dimensions of 400×400×23mm, which needed to be processed into flat plates with dimensions of 350×350×20mm. That is, the processed diamond / silicon carbide composite workpieces were all flat plates with dimensions of 350×350×20mm.

[0011] Example 1 A processing method for diamond / silicon carbide ceramic composite materials, specifically comprising: 1. Single-stage laser processing: The diamond / silicon carbide composite workpiece is clamped on the processing platform for laser processing. A laser with a wavelength of 532nm is selected. After preheating the laser, it is rotated clockwise for cutting. The laser processing conditions are set as follows: laser pulse width of 20μs, laser output power of 2000W, repetition frequency of 1.5kHz, working focal length of 100μm, spot radius of 50μm, laser scanning speed of 30mm / min, laser scanning spacing of 20μm, defocus distance of 0.5μm, number of pulses of 2, processing time of 2 hours per stage, 10 stages, cutting to a size of 351×351×23mm. Then, a laser with a wavelength of 1064nm is selected for fine processing. Fine processing is performed by rotating clockwise, keeping other parameters unchanged. Processing time of 8 hours per stage, 10 stages, to obtain the composite material after one laser processing, with a size of 350×350×23mm. 2. One-time mechanical polishing The composite material after one laser processing was fixed on a vertical machining center for mechanical polishing. Mechanical polishing was achieved by grinding against a grinding disc, which was clamped by a linear motion guide device with a cylinder. The mechanical polishing conditions were set as follows: workpiece sliding speed of 1500 m / min, applied pressure of 80 MPa, workpiece radial oscillation (width L=10 mm, 8 times / min), grinding disc rotation speed of 50 m / min, polishing atmosphere of water-oxygen mixture, polishing chamber heating temperature of 200℃, cooling by spraying ceramic grinding fluid during polishing, controlling the spraying speed of ceramic grinding fluid at 300 mL / min, polishing time of 10 h per polishing, and polishing 3 times to obtain a composite material with dimensions of 350×350×22.5 mm after one mechanical polishing. The grinding disc is made of stainless steel / alumina composite material with a thermal conductivity of 16 W / (m·K) and a friction coefficient of 0.5. The volume ratio of water to oxygen in the water-oxygen mixture is 5%. The method for preparing the ceramic grinding fluid is as follows: (1) Preparation of high-flow-rate diamond powder: 180g diamond powder and 27g γ-aminopropyltriethoxysilane were added to a ball mill. The ball-to-material ratio of the ball mill was controlled to 5:1 and the rotation speed was controlled to 300rpm. The ball mill was milled for 3h. 12g L-threonine was added and the ball milling was continued for 40min. 27g polyethylene glycol 4000 was added and the ball milling was continued for 40min to obtain high-flow-rate diamond powder. The diamond powder has a particle size of 20 nm; (2) Preparation of highly thermally conductive composite graphite powder: 200g of graphite powder and 10g of sodium dodecyl sulfate were added to a ball mill. The ball-to-material ratio of the ball mill was controlled to 5:1, and the rotation speed was controlled to 300 rpm. The ball milling was carried out for 1.5h to obtain highly dispersed graphite powder. 15g of polyvinylpyrrolidone and 6000mL of anhydrous ethanol were added to a reactor. The reactor temperature was controlled to 40℃, and the rotation speed was controlled to 300 rpm. The mixture was stirred for 10min. The highly dispersed graphite powder and 60mL of deionized water were added to the reactor. The mixture was stirred for another 30min. Add 65 mL of tetraethyl orthosilicate and continue stirring for 30 min. Add 90 mL of 25% ammonia water dropwise at a rate of 6 mL / min. After the addition is complete, continue stirring for 3 h. Add 14 mL of γ-aminopropyltriethoxysilane and continue stirring for 5 h. Add 14 g of polyethylene glycol 400 and continue stirring for 50 min. Add the mixture to a centrifuge and centrifuge at 8000 rpm for 10 min. Take the precipitate and wash it three times with anhydrous ethanol and deionized water. Dry the precipitate to obtain high thermal conductivity composite graphite powder. The particle size of the graphite powder is 100 nm; (3) Mixing: Triethanolamine, dodecanoic acid and deionized water are added to the reactor. The reactor speed is controlled to 200 rpm and stirred at room temperature for 1 h. Lauric acid diethanolamide, polyethylene glycol 2000 and glycerol are added and stirred for 30 min. High-flow-rate diamond powder and high thermal conductivity composite graphite powder are added and stirred for 1.5 h to obtain ceramic grinding fluid. The mass ratio of triethanolamine, dodecanoic acid, deionized water, lauric acid diethanolamide, polyethylene glycol 2000, glycerol, high-flowability diamond powder, and high thermal conductivity composite graphite powder is 15:7:120:11:10:10:1.9:3.4. 3. Secondary laser processing The composite material after one mechanical polishing was clamped on a processing platform for laser processing. A laser with a wavelength of 1064nm was selected. After preheating the laser, it was rotated clockwise for fine processing. The laser processing conditions were set as follows: laser pulse width of 20μs, laser output power of 3000W, repetition frequency of 2kHz, working focal length of 150μm, spot radius of 60μm, laser scanning speed of 50mm / min, laser scanning interval of 20μm, defocus distance of 0.5μm, number of pulses of 3, processing time of 15h per processing, and processing 10 times to obtain the composite material after two laser processing. The size is 350×350×22mm and the surface roughness is 4μm. 4. Three-stage laser processing The composite material after secondary laser processing was clamped onto a processing platform for laser processing. A laser with a wavelength of 532nm was selected. After preheating the laser, it was rotated clockwise for fine processing. The laser processing conditions were set as follows: laser pulse width of 20μs, laser output power of 3000W, repetition frequency of 1.5kHz, working focal length of 100μm, spot radius of 50μm, laser scanning speed of 30mm / min, laser scanning spacing of 15μm, defocus distance of 0.4μm, number of pulses of 2, processing time of 7h per processing, and 10 processing cycles. The composite material after three laser processing was obtained with dimensions of 350×350×21mm and a surface roughness of 3μm. 5. Secondary mechanical polishing The composite material after three laser processing was fixed on a vertical machining center for mechanical polishing. Mechanical polishing was achieved by grinding against a grinding disc, which was clamped by a linear motion guide device with a cylinder. The mechanical polishing conditions were set as follows: workpiece sliding speed of 1500 m / min, applied pressure of 80 MPa, workpiece radial oscillation (width L=10 mm, 3 times / min), grinding disc rotation speed of 100 m / min, polishing atmosphere of water-oxygen mixture, polishing chamber heating temperature of 200℃, cooling by spraying ceramic grinding fluid during polishing, controlling the spraying speed of ceramic grinding fluid at 400 mL / min, polishing time of 10 h per polishing, and polishing 40 times to obtain the processed diamond / silicon carbide composite material workpiece with dimensions of 350×350×20 mm. The grinding disc is made of stainless steel / alumina composite material with a thermal conductivity of 16 W / (m·K) and a friction coefficient of 0.5. The volume ratio of water to oxygen in the water-oxygen mixture is 5%. The preparation method of the ceramic grinding fluid is the same as that of the ceramic grinding fluid used in the first mechanical polishing step 2.

[0012] The surface roughness of the diamond / silicon carbide composite workpiece obtained in this embodiment is 0.8 μm, the bending strength is 507 MPa, and the thermal conductivity is 615 W / (m·K).

[0013] Example 2 A processing method for diamond / silicon carbide ceramic composite materials, specifically comprising: 1. Single-stage laser processing: The diamond / silicon carbide composite workpiece is clamped on the processing platform for laser processing. A laser with a wavelength of 532nm is selected. After preheating the laser, it is rotated clockwise for cutting. The laser processing conditions are set as follows: laser pulse width of 50μs, laser output power of 3500W, repetition frequency of 3kHz, working focal length of 180μm, spot radius of 75μm, laser scanning speed of 60mm / min, laser scanning spacing of 10μm, defocus distance of 0.3μm, number of pulses of 5, processing time of 4 hours per stage, 20 stages, cutting to a size of 351×351×23mm. Then, a laser with a wavelength of 1064nm is selected, and it is rotated clockwise for fine processing. Keeping other parameters unchanged, processing time of 4 hours per stage, 4 stages, to obtain the composite material after one laser processing, with a size of 350×350×23mm. 2. One-time mechanical polishing The composite material after one laser processing was fixed on a vertical machining center for mechanical polishing. Mechanical polishing was achieved by grinding against a grinding disc, which was clamped by a linear motion guide device with a cylinder. The mechanical polishing conditions were set as follows: workpiece sliding speed of 3500 m / min, applied pressure of 150 MPa, workpiece radial oscillation (width L=15 mm, 3 times / min), grinding disc rotation speed of 160 m / min, polishing atmosphere of water-oxygen mixture, polishing chamber heating temperature of 300℃, cooling by spraying ceramic grinding fluid during polishing, controlling the spraying speed of ceramic grinding fluid at 500 mL / min, polishing time of 20 h per polishing, polishing 5 times, to obtain a composite material with dimensions of 350×350×22.5 mm after one mechanical polishing. The grinding disc is made of stainless steel / alumina composite material with a thermal conductivity of 16 W / (m·K) and a friction coefficient of 0.9. The volume ratio of water to oxygen in the water-oxygen mixture is 20%. The method for preparing the ceramic grinding fluid is as follows: (1) Preparation of high-flow-rate diamond powder: 190g diamond powder and 30g γ-aminopropyltriethoxysilane were added to a ball mill. The ball-to-material ratio of the ball mill was controlled to 6:1 and the rotation speed was controlled to 400rpm. The ball mill was milled for 3.5h. 13g L-threonine was added and the ball milling was continued for 50min. 30g polyethylene glycol 4000 was added and the ball milling was continued for 50min to obtain high-flow-rate diamond powder. The diamond powder has a particle size of 20 nm; (2) Preparation of high thermal conductivity composite graphite powder: 210g of graphite powder and 12g of sodium dodecyl sulfate were added to a ball mill. The ball-to-material ratio of the ball mill was controlled to 6:1, and the rotation speed was controlled to 400 rpm. The ball milling was carried out for 2 hours to obtain highly dispersed graphite powder. 18g of polyvinylpyrrolidone and 6500mL of anhydrous ethanol were added to a reactor. The temperature of the reactor was controlled to 45℃, and the rotation speed was controlled to 400 rpm. The mixture was stirred for 15 minutes. The above highly dispersed graphite powder and 70mL of deionized water were added to the reactor. The mixture was stirred for 40 minutes. 70mL of deionized water was added to the reactor. Add 0 mL of tetraethyl orthosilicate and stir for 40 min. Add 100 mL of 25% ammonia solution at a rate of 7 mL / min. After the addition is complete, continue stirring for 3.5 h. Add 15 mL of γ-aminopropyltriethoxysilane and stir for 6 h. Add 16 g of polyethylene glycol 400 and stir for 60 min. Add the mixture to a centrifuge and centrifuge at 9000 rpm for 11 min. Take the precipitate and wash it four times with anhydrous ethanol and deionized water. Dry the precipitate to obtain high thermal conductivity composite graphite powder. The particle size of the graphite powder is 100 nm; (3) Mixing: Triethanolamine, dodecanoic acid and deionized water are added to the reactor. The reactor speed is controlled to 300 rpm and stirred at room temperature for 1.5 h. Lauric acid diethanolamide, polyethylene glycol 2000 and glycerol are added and stirred for 40 min. High-flow-rate diamond powder and high thermal conductivity composite graphite powder are added and stirred for 2 h to obtain ceramic grinding fluid. The mass ratio of triethanolamine, dodecanoic acid, deionized water, lauric acid diethanolamide, polyethylene glycol 2000, glycerol, high-flowability diamond powder, and high thermal conductivity composite graphite powder is 17:8:130:13:10.5:12:2.1:3.6. 3. Secondary laser processing The composite material after one mechanical polishing was clamped on a processing platform for laser processing. A laser with a wavelength of 1064nm was selected. After preheating the laser, it was rotated clockwise for fine processing. The laser processing conditions were set as follows: laser pulse width of 30μs, laser output power of 3500W, repetition frequency of 3kHz, working focal length of 180μm, spot radius of 75μm, laser scanning speed of 60mm / min, laser scanning spacing of 15μm, defocus distance of 0.4μm, number of pulses of 5, processing time of 8h per processing, and processing 5 times to obtain the composite material after two laser processing. The size is 350×350×22mm and the surface roughness is 5μm. 4. Three-stage laser processing The composite material after secondary laser processing was clamped on a processing platform for laser processing. A laser with a wavelength of 532nm was selected. After preheating the laser, it was rotated clockwise for fine processing. The laser processing conditions were set as follows: laser pulse width of 30μs, laser output power of 2000W, repetition frequency of 2kHz, working focal length of 150μm, spot radius of 60μm, laser scanning speed of 50mm / min, laser scanning spacing of 10μm, defocus distance of 0.3μm, number of pulses of 3, processing time of 10h per processing, and 20 processing cycles. The composite material after three laser processing was obtained with dimensions of 350×350×21mm and a surface roughness of 2μm. 5. Secondary mechanical polishing The composite material after three laser processing was fixed on a vertical machining center for mechanical polishing. Mechanical polishing was achieved by grinding against a grinding disc, which was clamped by a linear motion guide device with a cylinder. The mechanical polishing conditions were set as follows: workpiece sliding speed of 2000 m / min, applied pressure of 100 MPa, workpiece radial oscillation (width L=15 mm, 8 times / min), grinding disc rotation speed of 160 m / min, polishing atmosphere of water-oxygen mixture, polishing chamber heating temperature of 240℃, cooling by spraying ceramic grinding fluid during polishing, controlling the spraying speed of ceramic grinding fluid at 500 mL / min, polishing time of 5 h per polishing, polishing 20 times, to obtain the processed diamond / silicon carbide composite workpiece with dimensions of 350×350×20 mm. The grinding disc is made of stainless steel / alumina, with a thermal conductivity of 16 W / (m·K) and a coefficient of friction of 0.5. The volume ratio of water to oxygen in the water-oxygen mixture is 5%. The preparation method of the ceramic grinding fluid is the same as that of the ceramic grinding fluid used in the first mechanical polishing step 2.

[0014] The surface roughness of the diamond / silicon carbide composite workpiece obtained in this embodiment is 1 μm, the flexural strength is 481 MPa, and the thermal conductivity is 602 W / (m·K).

[0015] Comparative Example 1 The difference between this comparative example and Example 1 is that only a laser with a wavelength of 1064 nm is used in the fine processing; specifically: The diamond / silicon carbide composite workpiece was clamped on a processing platform for laser processing. A laser with a wavelength of 532nm was selected for cutting. After preheating the laser, it was rotated clockwise for cutting. The laser processing conditions were set as follows: laser pulse width of 20μs, laser output power of 2000W, repetition frequency of 1.5kHz, working focal length of 100μm, spot radius of 50μm, laser scanning speed of 30mm / min, laser scanning interval of 20μm, defocus distance of 0.5μm, number of pulses of 2, processing time of 2 hours per cycle, and 10 cycles were performed to cut a workpiece with dimensions of 351×351×23mm. Then, a laser with a wavelength of 1064nm was selected for fine processing. The workpiece was rotated clockwise while keeping other parameters unchanged. The processing time was 8 hours per cycle, and 40 cycles were performed to obtain a diamond / silicon carbide composite workpiece with dimensions of 350×350×20mm.

[0016] The surface roughness Ra of the processed diamond / silicon carbide composite workpiece obtained in this comparative example is 4.7 μm, the flexural strength is 334 MPa, and the thermal conductivity is 438 W / (m·K).

[0017] Comparative Example 2 The difference between this comparative example and Example 1 is that only a laser with a wavelength of 532nm is used in the fine processing; specifically: The diamond / silicon carbide composite workpiece was clamped on a processing platform for laser processing. A laser with a wavelength of 532nm was selected for cutting. After preheating the laser, it was rotated clockwise for cutting. The laser processing conditions were set as follows: laser pulse width of 20μs, laser output power of 2000W, repetition frequency of 1.5kHz, working focal length of 100μm, spot radius of 50μm, laser scanning speed of 30mm / min, laser scanning interval of 20μm, defocus distance of 0.5μm, number of pulses of 2, processing time of 2 hours per cycle, and 10 cycles. The cut was 351×351×23mm. The laser with a wavelength of 532nm was then used for fine processing, rotating clockwise while keeping other parameters unchanged. The processing time was 7 hours per cycle, and 60 cycles were performed to obtain the processed diamond / silicon carbide composite workpiece with a size of 350×350×20mm.

[0018] The surface roughness Ra of the processed diamond / silicon carbide composite workpiece obtained in this comparative example is 6.2 μm, the flexural strength is 318 MPa, and the thermal conductivity is 390 W / (m·K).

[0019] Comparative Example 3 The difference between this comparative example and Example 1 is that the use of ceramic grinding fluid is omitted in the first mechanical polishing step 2 and the second mechanical polishing step 5.

[0020] The surface roughness Ra of the processed diamond / silicon carbide composite workpiece obtained in this comparative example is 1.6 μm, the flexural strength is 352 MPa, and the thermal conductivity is 451 W / (m·K).

[0021] Comparing Example 1 with Comparative Examples 1-2, it was found that although the use of a high-power laser can shorten the processing time, it leads to increased roughness, reduced bending strength and thermal conductivity, which affects the performance of the diamond / silicon carbide composite workpiece after processing.

[0022] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0023] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A processing method for diamond / silicon carbide ceramic composite materials, characterized in that, It consists of the following steps: one laser processing, one mechanical polishing, a second laser processing, a third laser processing, and a second mechanical polishing; The first laser processing involves laser processing of a diamond / silicon carbide composite material workpiece. A laser with a wavelength of 532nm is selected. After preheating the laser, it is rotated clockwise for cutting. Each processing time is 2-4 hours, cutting to a length of target length + 1mm, a width of target width + 1mm, and a height of target height + 3mm. Then, a laser with a wavelength of 1064nm is selected, and clockwise rotation is used for fine processing, keeping other parameters unchanged. Each processing time is 4-8 hours, finely processing to a length of target length, a width of target width, and a height of target height + 3mm, thus obtaining the composite material after one laser processing. The first mechanical polishing involves mechanically polishing the composite material after a laser processing. During mechanical polishing, the material is cooled by spraying ceramic grinding fluid. Each polishing session lasts 10-20 hours. The material is mechanically polished until the length, width, and height are the target length + 2.5 mm, resulting in a composite material after one mechanical polishing. The method for preparing the ceramic grinding fluid comprises the following steps: preparing high-flowability diamond powder, preparing high-thermal-conductivity composite graphite powder, and mixing them; To prepare high-flowability diamond powder, diamond powder and γ-aminopropyltriethoxysilane are mixed and ball-milled. L-threonine is added and ball milling continues. Polyethylene glycol 4000 is added and ball milling continues to obtain high-flowability diamond powder. The preparation of high thermal conductivity composite graphite powder involves ball milling graphite powder and sodium dodecyl sulfate to obtain highly dispersed graphite powder; mixing polyvinylpyrrolidone and anhydrous ethanol, stirring at 40-45°C, adding highly dispersed graphite powder and deionized water, continuing stirring, adding tetraethyl orthosilicate, continuing stirring, adding ammonia water dropwise, continuing stirring after the dropwise addition is complete, adding γ-aminopropyltriethoxysilane, continuing stirring, adding polyethylene glycol 400, continuing stirring, adding to a centrifuge, centrifuging, collecting the precipitate, washing and drying to obtain high thermal conductivity composite graphite powder; The mixing process involves mixing triethanolamine, dodecanoic acid, and deionized water, stirring at room temperature, adding lauric acid diethanolamide, polyethylene glycol 2000, and glycerol, continuing stirring, adding high-flowability diamond powder and high-thermal-conductivity composite graphite powder, and continuing stirring to obtain a ceramic grinding fluid. The secondary laser processing involves laser processing the composite material after the first mechanical polishing. A laser with a wavelength of 1064nm is selected. After preheating the laser, it is rotated clockwise for fine processing. Each processing session takes 8-15 hours. The fine processing is carried out until the length is the target length, the width is the target width, and the height is the target height + 2mm, thus obtaining the composite material after secondary laser processing. The third laser processing involves laser processing the composite material after the second laser processing. After preheating the laser, a laser with a wavelength of 532nm is selected, and fine processing is performed by rotating clockwise. The laser processing conditions are set as follows: each processing time is 7-10 hours, and fine processing is performed until the length is the target length, the width is the target width, and the height is the target height + 1mm, thus obtaining the composite material after the second laser processing. The secondary mechanical polishing involves fixing the composite material after the three laser processing steps onto a vertical machining center for mechanical polishing. During polishing, the material is cooled by spraying ceramic grinding fluid. Each polishing session lasts 5-10 hours. The mechanical polishing continues until the length, width, and height meet the target requirements, resulting in the processed diamond / silicon carbide composite material workpiece.

2. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the aforementioned laser processing, the laser pulse width for cutting and fine processing is 20-50 μs, the laser output power is 2000-3500 W, the repetition frequency is 1.5-3 kHz, the working focal length is 100-180 μm, the spot radius is 50-75 μm, the laser scanning speed is 30-60 mm / min, the laser scanning interval is 10-20 μm, the defocus distance is 0.3-0.5 μm, and the number of pulses is 2-5.

3. The processing method for the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the aforementioned mechanical polishing process, the grinding disc is made of stainless steel / alumina composite material with a thermal conductivity of 16 W / (m·K) and a friction coefficient of 0.5-0.

9. In the aforementioned mechanical polishing process, the volume ratio of water to oxygen in the water-oxygen mixture is 5-20%. In the aforementioned mechanical polishing process, the composite material after a single laser processing is mechanically polished by grinding against a grinding disc. The grinding disc is clamped by a linear motion guide rail device with a cylinder. The workpiece sliding speed is 1500-3500 m / min, the applied pressure is 80-150 MPa, the workpiece oscillates radially, the grinding disc rotation speed is 50-160 m / min, the polishing atmosphere is a water-oxygen mixture, and the heating temperature in the polishing chamber is 200-300℃. During the first mechanical polishing process, the radial oscillation of the workpiece has a width L = 10-15 mm and a frequency of 3-8 times / min. In the aforementioned mechanical polishing process, the spraying speed of the ceramic grinding fluid is 300-500 mL / min.

4. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the preparation of high-flowability diamond powder, the mass ratio of diamond powder, γ-aminopropyltriethoxysilane, L-threonine, and polyethylene glycol 4000 is 180-190:27-30:12-13:27-30. In the preparation of high-flowability diamond powder, the particle size of the diamond powder is 20 nm.

5. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the preparation of the high thermal conductivity composite graphite powder, the mass-to-volume ratio of graphite powder, sodium dodecyl sulfate, polyvinylpyrrolidone, anhydrous ethanol, deionized water, tetraethyl orthosilicate, ammonia, γ-aminopropyltriethoxysilane, and polyethylene glycol 400 is 200-210g:10-12g:15-18g:6000-6500mL:60-70mL:65-70mL:90-100mL:14-15mL:14-16g; In the preparation of the high thermal conductivity composite graphite powder, the particle size of the graphite powder is 100 nm; In the preparation of the high thermal conductivity composite graphite powder, the mass concentration of the ammonia water is 25%, and the dropping rate is 6-7 mL / min.

6. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the mixture, the mass ratio of triethanolamine, dodecanoic acid, deionized water, lauric acid diethanolamide, polyethylene glycol 2000, glycerol, high-flowability diamond powder, and high thermal conductivity composite graphite powder is 15-17:7-8:120-130:11-13:10-10.5:10-12:1.9-2.1:3.4-3.

6.

7. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the secondary laser processing, the laser pulse width is 20-30μs, the laser output power is 3000-3500W, the repetition frequency is 2-3kHz, the working focal length is 150-180μm, the spot radius is 60-75μm, the laser scanning speed is 50-60mm / min, the laser scanning interval is 15-20μm, the defocus distance is 0.4-0.5μm, and the number of pulses is 3-5.

8. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the three laser processing steps, the laser pulse width is 20-30 μs, the laser output power is 2000-3000 W, the repetition frequency is 1.5-2 kHz, the working focal length is 100-150 μm, the spot radius is 50-60 μm, the laser scanning speed is 30-50 mm / min, the laser scanning interval is 10-15 μm, the defocus distance is 0.3-0.4 μm, and the number of pulses is 2-3.

9. The processing method of the diamond / silicon carbide ceramic composite material according to claim 1, characterized in that, In the secondary mechanical polishing, the material of the grinding disc and the volume ratio of water to oxygen in the water-oxygen mixture are the same as those used in the primary mechanical polishing. In the secondary mechanical polishing, the composite material after the third laser processing is mechanically polished by grinding against a grinding disc. The grinding disc is clamped by a linear motion guide device with a cylinder. The workpiece sliding speed is 1500-2000 m / min, the applied pressure is 80-100 MPa, the workpiece oscillates radially, the grinding disc rotates at a speed of 100-160 m / min, the polishing atmosphere is a water-oxygen mixture, and the heating temperature in the polishing chamber is 200-240℃. During the secondary mechanical polishing, the radial oscillation of the workpiece has a width L = 10-15 mm and a frequency of 3-8 times / min. In the secondary mechanical polishing, the spraying speed of the ceramic grinding fluid is 400-500 mL / min; In the secondary mechanical polishing, the ceramic grinding fluid is prepared using the same method as the ceramic grinding fluid used in the primary mechanical polishing.