Method for preparing lubricating protective coating on surface of silicon carbide substrate

Abstract

The invention discloses a method for preparing a lubricating protective coating on the surface of a silicon carbide substrate, and belongs to the technical field of composite coating preparation, and the method comprises the following steps: (1) carrying out cleaning and drying pretreatment on the silicon carbide substrate, or sequentially carrying out cleaning and drying pretreatment and surface texturing treatment on the silicon carbide substrate; (2) carrying out surface roughening treatment on the silicon carbide substrate treated in the step (1), then putting the silicon carbide substrate into suspension containing nano-diamond, carrying out ultrasonic oscillation and crystal planting, taking out the silicon carbide substrate, drying the silicon carbide substrate, and preparing a diamond coating by utilizing hot filament chemical vapor deposition; and (3) taking boron nitride as a raw material, and compounding the boron nitride and the diamond coating on the silicon carbide substrate treated in the step (2) by utilizing a spin-coating method or a magnetron sputtering method to obtain the lubricating protective coating. According to the method, the diamond / boron nitride composite coating is used for achieving surface lubricating protection of the silicon carbide substrate, implementation is easy, and the lubricating effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of composite coating preparation, and in particular to a method for preparing a lubricating protective coating on the surface of a silicon carbide substrate. Background Art

[0002] In demanding industrial scenarios such as petrochemicals and precision manufacturing, mechanical sealing systems are often required to operate under high-pressure conditions for long periods of time. This high-pressure environment significantly increases the load on the sealing surface, placing stringent demands on the mechanical properties of the sealing material. The sealing material must possess sufficiently high strength and rigidity. If this condition is not met, the sealing surface can easily deform due to pressure, causing leakage or accelerated wear, ultimately leading to mechanical seal failure. Silicon carbide is a material with high strength, high rigidity, and high elastic modulus. It has high compressive strength and can stably withstand complex stress loads under harsh conditions such as high pressure and strong impact, meeting the requirements of use. However, silicon carbide has significant shortcomings in its tribological properties under dry friction conditions. It does not have the function of self-lubrication. When silicon carbide material contacts and moves relative to another type of hard, non-self-lubricating material, if there is no lubricating liquid medium, the friction coefficient between the interfaces will increase sharply due to the inherent high hardness and low surface energy characteristics of the material, leading to systemic safety accidents. Therefore, it is necessary to provide a lubricating coating on the surface of the silicon carbide material to reduce its dry friction coefficient.

[0003] Diamond coating is a high-performance functional thin film material with the advantages of low friction and wear resistance, high thermal conductivity and corrosion resistance. It is widely used in precision manufacturing, aerospace, semiconductor and other fields. It is an advanced lubricating and protective material with great potential. Boron nitride is an advanced ceramic material with a graphite-like layered structure. Its types include hexagonal boron nitride and cubic boron nitride. In hexagonal boron nitride, nitrogen atoms and boron atoms are arranged in sp 2 Hybridization forms a hexagonal lattice. In cubic boron nitride, nitrogen atoms and boron atoms are sp 3 Hybridization forms a cubic lattice, which also has broad application prospects in the field of surface protection.

[0004] Chinese patent publication CN102586762A discloses a method for preparing diamond films by multi-element doped hot-filament chemical vapor deposition. Using silicon, silicon carbide, or silicon nitride ceramics, cemented carbide, or refractory metals as substrates, the invention employs CVD as the deposition method. Organic compounds containing Si, Si and N, Si and B, or Si, N, and B are simultaneously added to a reaction gas mixture of hydrogen and acetone (or acetone and methanol) vapor to form a multi-element doping system. The resulting coatings are submicron or nanometer-scale diamond films with adjustable thicknesses between 10 and 50 μm. These films exhibit wear and corrosion resistance, low friction coefficient, and ease of grinding and polishing.

[0005] Chinese patent publication CN108950537A discloses a self-lubricating cubic boron nitride (CBN) coated cutting tool and its preparation method. The cutting tool substrate is coated with a CBN coating containing CsF, Mo, and ZrO2. The coating is produced by electron beam cladding of a CBN powder mixture composed of 55-65% CBN, 15-20% Ni, 5-8% CsF, 5-8% Mo, and 5-10% ZrO2 by weight. During the cutting process, the CsF, Mo, and ZrO2 react in situ at high temperatures to form Cs2MoO4, providing lubrication at relatively high cutting temperatures.

[0006] Although the above inventions are all related to the preparation of lubricating coatings, they do not involve the technical content of collaboratively constructing a lubricating coating by a composite process of a diamond coating and a boron nitride coating. Summary of the Invention

[0007] In order to address the deficiencies in the above-mentioned prior art, the present invention provides a method for preparing a lubricating protective coating on the surface of a silicon carbide substrate. The method utilizes a diamond / boron nitride composite coating to achieve surface lubrication protection of the silicon carbide substrate. The method has simple steps, is easy to implement, and has good lubrication effect.

[0008] The specific technical solutions adopted are as follows: A method for preparing a lubricating protective coating on a surface of a silicon carbide substrate comprises the following steps: (1) performing a cleaning and drying pretreatment on the silicon carbide substrate, or performing a cleaning and drying pretreatment and a surface texturing treatment on the silicon carbide substrate in sequence; (2) roughening the surface of the silicon carbide substrate treated in step (1), placing it in a suspension containing nanodiamonds and ultrasonically vibrating the substrate to plant the nanodiamonds, taking it out and drying it, and then preparing a diamond coating by hot wire chemical vapor deposition, wherein the diamond coating is a micron-crystalline diamond coating, a nanocrystalline diamond coating or an ultra-nanocrystalline diamond coating; (3) Boron nitride is used as a raw material, and the boron nitride and diamond coating are compounded on the silicon carbide substrate treated in step (2) by spin coating or magnetron sputtering to obtain a lubricating protective coating.

[0009] The diamond coating has a strong bonding force with the silicon carbide substrate, which serves as a supporting layer. Boron nitride serves as a surface lubricating layer with excellent lubrication properties. After boron nitride is compounded with the diamond coating, diamond and boron nitride play a synergistic role in reducing friction.

[0010] Specifically, the pretreatment method includes: ultrasonically cleaning the silicon carbide substrate using acetone, ethanol and deionized water in sequence, and then drying it with nitrogen gas after cleaning.

[0011] Specifically, laser texturing is used for surface texturing treatment, with a square or circular texture shape, a side length of the square being 0.1 to 1 mm, a spacing of 50 to 1000 μm, and a diameter of the circle being 50 to 600 μm, and a spacing of 50 to 100 μm.

[0012] Preferably, during the surface texturing treatment, the laser wavelength is 1.064 μm, the spot diameter is 30-60 μm, the laser pulse power is 6-12 W, the pulse width is 4-25 μs, the scanning speed is 4-6 mm / s, the spot overlap rate is ≥90%, the processing rate is 800-1500 mm / s, and the processing frequency is 60-100 KHz.

[0013] Preferably, in step (2), the silicon carbide substrate treated in step (1) is ground using a 5-30 wt% diamond micron powder aqueous solution to improve its surface roughness, and the grinding time is 10-60 min.

[0014] Preferably, in step (2), the size of the nanodiamonds in the suspension containing nanodiamonds is 30 to 1000 nm, the concentration of the suspension containing nanodiamonds is 0.1 to 8 wt%, and the ultrasonic oscillation time is 0.1 to 1.5 h.

[0015] Tantalum wire is used to prepare diamond coating by hot wire chemical vapor deposition. The process parameters are: methane flow rate of 4-12 sccm, hydrogen flow rate of 200-400 sccm, nitrogen flow rate of 0-20 sccm, deposition pressure of 1.8-2.5 KPa, deposition temperature of 1000-1200 °C, wire pitch of 6-10 mm, and deposition time of 3-10 h.

[0016] Preferably, the diamond coating is a micron-crystalline diamond coating, and the boron nitride raw material used is hexagonal boron nitride. The micron-crystalline diamond coating and hexagonal boron nitride can achieve a better synergistic wear reduction effect.

[0017] Preferably, in step (3), boron nitride powder with a particle size of 0.1 to 5 μm is used, and an ethanol solvent is used to prepare a spin coating solution with a concentration of 20 to 50 g / L. The spin coating is performed at a spin coating speed of 10 to 25 r / min for 20 seconds to 10 minutes to composite the boron nitride with the diamond coating.

[0018] Preferably, the magnetron sputtering method uses boron nitride as the target material and RF power supply, and the specific deposition parameters include: RF power of 150-250 W, argon 35-50 sccm, nitrogen 10-20 sccm, sputtering pressure 0.6-1.2 Pa, deposition temperature: 450-650°C, and sputtering time of 4-8 h.

[0019] Magnetron sputtering is more effective than spin coating, with stronger bonding force and better uniformity. Spin coating is suitable for silicon carbide substrates with surface texturing.

[0020] The present invention also provides a silicon carbide-based material with a lubricating protective coating, which is prepared by the method of preparing a lubricating protective coating on the surface of a silicon carbide substrate, wherein diamond is used as a supporting layer and surface boron nitride is used as a lubricating layer.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts hot wire chemical vapor deposition, simple spin coating or magnetron sputtering deposition to realize the preparation of diamond / boron nitride composite coating on the surface of silicon carbide substrate. The operation is simple and the repeatability is good. Diamond serves as the supporting layer and the surface boron nitride serves as the lubricating layer.

[0022] (2) After boron nitride is composited with diamond coating by spin coating or magnetron sputtering, the friction coefficient of the composite coating is significantly reduced.

[0023] (3) The bonding force between the diamond coating prepared by hot wire chemical vapor deposition and the silicon carbide substrate is high, and the bonding force between the boron nitride prepared by magnetron sputtering and the diamond coating is even stronger. When the boron nitride and diamond coating are composited by spin coating, it is more suitable for the silicon carbide substrate that has been subjected to surface texturing treatment. The surface texturing treatment can play the role of storing wear debris. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a comparison chart of the friction coefficients of the micron-crystalline diamond (MCD) coating and the MCD / BN composite coating in Example 1.

[0025] Figure 2 This is a comparison chart of the wear rates of the micron-crystalline diamond (MCD) coating and the MCD / BN composite coating in Example 1.

[0026] Figure 3 This is a comparison chart of the friction coefficients of the ultrafine nanodiamond (UNCD) coating and the UNCD / BN composite coating in Example 3.

[0027] Figure 4 This is a comparison chart of the wear rates of the ultrafine nanodiamond (UNCD) coating and the UNCD / BN composite coating in Example 3.

[0028] Figure 5 This is the SEM image of the MCD coating in Example 1.

[0029] Figure 6 This is the SEM image of the MCD / BN composite coating in Example 1.

[0030] Figure 7This is the SEM image of the MCD / BN composite coating in Example 4.

[0031] Figure 8 This is the SEM image of the MCD / BN composite coating in Example 5. DETAILED DESCRIPTION

[0032] In order to make the objects, features and advantages of the present invention more clearly understood, a detailed description is given below using specific embodiments. In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in the various embodiments of the present invention can be combined accordingly without conflicting with each other.

[0033] Example 1 (1) Take a silicon carbide substrate and ultrasonically clean it with acetone, ethanol and deionized water in sequence, and then blow dry it with nitrogen; (2) Place the silicon carbide substrate treated in step (1) on the polishing disk of the polishing machine and grind the silicon carbide substrate with a 5wt% aqueous solution of diamond micron powder (brand W40) to enhance the surface roughness of the substrate. The grinding time is 10 min. After grinding, the silicon carbide substrate is ultrasonically cleaned in an alcohol solution for 20 min, and then transferred to a 5wt% alcohol solution containing nanodiamonds (brand W0.01). Ultrasonic treatment is performed for 20 min to perform substrate crystallization treatment, and then the substrate surface is blown dry with compressed nitrogen. The silicon carbide substrate carrying diamond seeds prepared by the above process was placed in a hot wire chemical vapor deposition equipment to deposit and prepare a micron-crystalline diamond coating. Tantalum wire was used for hot wire chemical vapor deposition. The process parameters were: methane flow rate of 12 sccm, hydrogen flow rate of 400 sccm, nitrogen flow rate of 0 sccm, deposition pressure of 2.3 KPa, deposition temperature of 1200 ℃, wire pitch of 8 mm, and deposition time of 7 h. Micron-crystalline diamond coating (MCD coating) was prepared.

[0034] (3) Boron nitride powder with a particle size of 1 μm was used to prepare a spin coating solution with a concentration of 25 g / L using ethanol solvent. The spin coating was performed at a speed of 15 r / min for 2 min to composite the boron nitride with the micron-crystalline diamond coating to prepare an MCD / BN composite coating.

[0035] Example 2 (1) Take a silicon carbide substrate and ultrasonically clean it with acetone, ethanol and deionized water in sequence, and then blow dry it with nitrogen; (2) Place the silicon carbide substrate treated in step (1) on the polishing disk of the polishing machine and grind the silicon carbide substrate with a 5wt% aqueous solution of diamond micron powder (brand W40) to enhance the surface roughness of the substrate. The grinding time is 10 min. After grinding, the silicon carbide substrate is ultrasonically cleaned in an alcohol solution for 20 min, and then transferred to a 5wt% alcohol solution containing nanodiamonds (brand W0.01). Ultrasonic treatment is performed for 20 min to perform substrate crystallization treatment, and then the substrate surface is blown dry with compressed nitrogen. The silicon carbide substrate carrying diamond seeds prepared by the above process was placed in a hot wire chemical vapor deposition equipment to deposit and prepare a nanocrystalline diamond coating. Tantalum wire was used for hot wire chemical vapor deposition. The process parameters were: methane flow rate of 4 sccm, hydrogen flow rate of 400 sccm, nitrogen flow rate of 15 sccm, deposition pressure of 1.8 KPa, deposition temperature of 1050 ℃, wire pitch of 8 mm, and deposition time of 6 h. Nanocrystalline diamond coating (NCD coating) was prepared.

[0036] (3) Boron nitride powder with a particle size of 1 μm was used to prepare a spin coating solution with a concentration of 25 g / L using ethanol solvent. The spin coating was performed at a speed of 15 r / min for 2 min to composite the boron nitride with the nanocrystalline diamond coating to obtain an NCD / BN composite coating.

[0037] Example 3 (1) Take a silicon carbide substrate and ultrasonically clean it with acetone, ethanol and deionized water in sequence, and then blow dry it with nitrogen; (2) Place the silicon carbide substrate treated in step (1) on the polishing disk of the polishing machine and grind the silicon carbide substrate with a 5wt% aqueous solution of diamond micron powder (brand W40) to enhance the surface roughness of the substrate. The grinding time is 10 min. After grinding, the silicon carbide substrate is ultrasonically cleaned in an alcohol solution for 20 min, and then transferred to a 5wt% alcohol solution containing nanodiamonds (brand W0.01). Ultrasonic treatment is performed for 20 min to perform substrate crystallization treatment, and then the substrate surface is blown dry with compressed nitrogen. The silicon carbide substrate carrying diamond seeds prepared by the above process was placed in a hot wire chemical vapor deposition equipment to deposit and prepare an ultrananocrystalline diamond coating. Tantalum wire was used for hot wire chemical vapor deposition. The process parameters were: methane flow rate of 12 sccm, hydrogen flow rate of 400 sccm, nitrogen flow rate of 20 sccm, deposition pressure of 2.0 KPa, deposition temperature of 1000 ℃, wire pitch of 10 mm, and deposition time of 7 h. Ultrananocrystalline diamond coating (UNCD coating) was prepared.

[0038] (3) Boron nitride powder with a particle size of 1 μm was used to prepare a spin coating solution with a concentration of 25 g / L using ethanol solvent. The spin coating was performed at a speed of 15 r / min for 2 min to composite the boron nitride with the ultra-nanocrystalline diamond coating to obtain a UNCD / BN composite coating.

[0039] Example 4 The only difference between this embodiment and Example 1 is that after the silicon carbide substrate is cleaned and dried for pretreatment, a surface texturing treatment is also performed. Laser texturing is used for the surface texturing treatment, with a square as the texture shape and a square size of 1×1 mm. During the surface texturing treatment, the laser wavelength is 1.064 μm, the spot diameter is 50 μm, the laser pulse power is 8 W, the pulse width is 10 μs, the scanning speed is 5 mm / s, the spot overlap rate is ≥90%, the processing rate is 900 mm / s, and the processing frequency is 70 kHz. The other process conditions are the same as those in Example 1, and an MCD / BN composite coating is prepared.

[0040] Example 5 The only difference between this embodiment and embodiment 1 is that, in step (3), the boron nitride and diamond coating are composited on the silicon carbide substrate treated in step (2) by spin coating or magnetron sputtering. The magnetron sputtering method uses boron nitride as a target material and a radio frequency power supply. The specific deposition parameters include: radio frequency power of 150 W, argon 35 sccm, nitrogen 10 sccm, sputtering pressure 0.8 Pa, deposition temperature: 500 ° C, and sputtering time of 6 h, to prepare an MCD / BN composite coating.

[0041] Sample analysis like Figure 1 and Figure 2 As shown in the figure, the friction coefficient of the MCD coating in Example 1 is 0.12, and the wear rate is 1.321×10 -6 mm³ / (N·m), the friction coefficient of the MCD / BN composite coating in Example 1 is 0.08, and the wear rate is 1.496×10 -6 mm³ / (N·m), the friction coefficient decreased by 33.3%, and the wear rate increased slightly by 13.2%.

[0042] like Figure 3 and Figure 4 As shown in Figure 3, the friction coefficient of the UNCD coating in Example 3 is 0.07, and the wear rate is 2.585×10 -6 mm³ / (N·m), the friction coefficient of the UNCD-BN composite coating in Example 3 is 0.05, and the wear rate is 1.385×10 -6 mm³ / (N·m), the friction coefficient decreased by 28.5%, and the wear rate decreased by 46.4%.

[0043] Figure 5 and Figure 6 They are SEM morphology images of the MCD coating and the MCD / BN composite coating in Example 1, respectively, indicating that the boron nitride and micron-crystalline diamond coating are successfully composited.

[0044] Figure 7 This is a SEM image of the MCD / BN composite coating in Example 4. The MCD / BN composite coating was successfully prepared on a silicon carbide substrate that had undergone surface texturing treatment.

[0045] Figure 8 This is the SEM image of the MCD / BN composite coating in Example 5. It can be seen that the magnetron sputtering method has stronger bonding force and better uniformity than the spin coating method.

[0046] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a lubricating protective coating on a silicon carbide substrate, characterized in that: The following steps are involved: (1) performing a cleaning and drying pretreatment on the silicon carbide substrate, or performing a cleaning and drying pretreatment and a surface texturing treatment on the silicon carbide substrate in sequence; (2) roughening the surface of the silicon carbide substrate treated in step (1), placing it in a suspension containing nanodiamonds and ultrasonically vibrating the substrate to plant the nanodiamonds, taking it out and drying it, and then preparing a diamond coating by hot wire chemical vapor deposition, wherein the diamond coating is a micron-crystalline diamond coating, a nanocrystalline diamond coating or an ultra-nanocrystalline diamond coating; (3) Boron nitride is used as a raw material, and the boron nitride and diamond coating are compounded on the silicon carbide substrate treated in step (2) by spin coating or magnetron sputtering to obtain a lubricating protective coating.

2. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: Laser texturing is used for surface texturing treatment, with a square or circle as the texture shape, the side length of the square being 0.1 to 1 mm, and the diameter of the circle being 50 μm to 600 μm.

3. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 2, wherein: During surface texturing treatment, the laser wavelength is 1.064 μm, the spot diameter is 30-60 μm, the laser pulse power is 6-12 W, the pulse width is 4-25 μs, the scanning speed is 4-6 mm / s, the spot overlap rate is ≥90%, the processing rate is 800-1500 mm / s, and the processing frequency is 60-100 kHz.

4. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: In step (2), the silicon carbide substrate treated in step (1) is ground using a 5 to 30 wt% diamond micron powder aqueous solution to improve its surface roughness, and the grinding time is 10 to 60 minutes.

5. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: In step (2), the concentration of the suspension containing nanodiamonds is 0.1 to 8 wt%, and the ultrasonic oscillation time is 0.1 to 1.5 h.

6. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: Tantalum wire is used to prepare diamond coating by hot wire chemical vapor deposition. The process parameters are: methane flow rate of 4-12 sccm, hydrogen flow rate of 200-400 sccm, nitrogen flow rate of 0-20 sccm, deposition pressure of 1.8-2.5 KPa, deposition temperature of 1000-1200 °C, wire pitch of 6-10 mm, and deposition time of 3-10 h.

7. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: The diamond coating is a micron-crystalline diamond coating, and the boron nitride raw material used is hexagonal boron nitride.

8. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: In step (3), boron nitride powder with a particle size of 0.1 to 5 μm is used and an ethanol solvent is used to prepare a spin coating solution with a concentration of 20 to 50 g / L. The spin coating is performed at a spin coating speed of 10 to 25 r / min for 20 seconds to 10 minutes to composite the boron nitride with the diamond coating.

9. The method for preparing a lubricating protective coating on a silicon carbide substrate according to claim 1, wherein: The magnetron sputtering method uses boron nitride as the target material and RF power supply. The specific deposition parameters include: RF power of 150-250 W, argon 35-50 sccm, nitrogen 10-20 sccm, sputtering pressure 0.6-1.2 Pa, deposition temperature: 450-650°C, and sputtering time of 4-8 h.

10. A silicon carbide-based material with a lubricating protective coating, characterized in that: The lubricating protective coating is prepared by the method for preparing a lubricating protective coating on the surface of a silicon carbide substrate according to any one of claims 1 to 9.

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