A method for producing a carbon-based composite coating

Abstract

A preparation method of a carbon-based composite coating, comprising the following steps: step S10, sequentially forming a diamond coating and a catalytic layer on the surface of a workpiece substrate; step S11, forming a graphene coating on the surface of the catalytic layer; and step S12, removing the residual catalytic layer to form a carbon-based composite coating containing the diamond coating and the graphene coating on the surface of the workpiece substrate. In the present application, the catalytic layer is uniformly deposited on the surface of the diamond coating by using the magnetron sputtering technology, which provides an ideal interface for growing a more uniform and complete graphene coating; and the mixed acid solution can selectively etch the catalytic layer without damaging the diamond and graphene coatings by changing the proportion of each component and finely adjusting the corrosion degree and speed of the mixed acid solution, thereby further ensuring the direct contact between the diamond coating and the graphene coating, increasing the active sites on the diamond surface, helping to form more covalent bond connections with the graphene, and thus enhancing the bonding strength of the carbon-based composite coating interface and improving its stability under high-temperature friction conditions.

Description

Technical Field

[0001] This invention relates to the field of material surface treatment technology, and in particular to a method for preparing a carbon-based composite coating. Background Technology

[0002] With the rapid development of the aerospace and automotive industries, higher demands are being placed on the performance of critical moving components under high-temperature conditions. Although traditional materials such as metal alloys and ceramics have good wear resistance at room temperature, they often fail due to oxidation or reduced hardness in high-temperature environments. Carbon-based materials, especially diamond and graphene, have shown great potential in the field of high-temperature wear resistance due to their superior hardness, wear resistance, and oxidation resistance.

[0003] Currently, existing technologies rely on weak van der Waals forces to bond graphene and diamond coatings. While this method allows the two materials to be combined, the weak interactions leading to insufficient bonding strength under high-temperature friction environments cause accelerated degradation due to thermodynamic instability, limiting its lifespan and performance in friction applications. Furthermore, one of the key steps in graphene growth is the precise etching of the catalyst layer on the diamond surface, a step requiring extremely high precision and control. If the etching process of the catalyst layer cannot be precisely controlled, it will lead to uneven graphene growth and interfacial bonding strength, thus affecting its final quality and performance. While conventional methods such as chemical vapor deposition (CVD) can grow graphene on diamond surfaces, the etching process of the catalyst layer is difficult to control, and when dealing with large-area or complex-shaped substrates, the uniformity between the graphene and diamond coatings is poor, resulting in insufficient adhesion between them. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a method for preparing a carbon-based composite coating, which can precisely control the etching process of the catalytic layer, thereby improving the uniformity between the graphene coating and the diamond coating and enhancing the adhesion between the two.

[0005] A method for preparing a carbon-based composite coating includes the following steps:

[0006] Step S10: A diamond coating is formed on the surface of the workpiece substrate using a deposition method, and a catalytic layer is formed on the surface of the diamond coating using magnetron sputtering technology.

[0007] Step S11: The workpiece substrate containing the catalyst layer is subjected to high-temperature annealing to induce carbon atoms to grow in situ on the surface of the catalyst layer, and the in situ grown carbon atoms are uniformly arranged to form a graphene coating.

[0008] Step S12: Immerse the workpiece substrate containing the graphene coating in a mixed acidic solution and perform ultrasonic etching while controlling the corrosion intensity and speed to remove the residual catalyst layer, that is, form a carbon-based composite coating containing a combination of diamond coating and graphene coating on the surface of the workpiece substrate.

[0009] Compared to existing technologies, this invention utilizes magnetron sputtering technology, which facilitates the uniform deposition of a catalytic layer on the surface of the diamond coating. This catalytic layer provides an ideal interface for the growth of a more uniform and complete graphene coating. Furthermore, by altering the proportions of the components and finely adjusting the etching intensity and rate of the mixed acidic solution, selective etching of the catalytic layer can be performed without damaging the diamond and graphene coatings. This further ensures direct contact between the diamond and graphene coatings, increases the number of active sites on the diamond surface, and helps to form more covalent bonds with graphene. Consequently, it enhances the bonding strength of the carbon-based composite coating interface and improves its stability under high-temperature friction conditions.

[0010] Further, in step S12, the mixed acidic solution includes water, concentrated hydrochloric acid and nitric acid, wherein the volume percentage of water is 65% to 70%, the volume percentage of hydrochloric acid is 5% to 7%, and the volume percentage of nitric acid is 23% to 27%.

[0011] The etching time is 30–180 s, and the etching temperature is 25–35 ℃.

[0012] Furthermore, in step S11, the heating rate of the high-temperature annealing is 6-30℃ / min, the annealing temperature is 800-1100℃, and the holding time is 5-20min.

[0013] Furthermore, in step S10, the parameters of the magnetron sputtering technology are: argon flow rate of 25-50 sccm, substrate bias of -70-30V, deposition power of 100-1000W, deposition pressure of 0.2-0.5Pa, and deposition time of 3-15min.

[0014] Furthermore, the catalyst layer is a nickel catalyst layer or a copper catalyst layer, and its thickness is 50–200 nm.

[0015] Furthermore, in step S10, the thickness of the diamond coating is 1 to 10 μm.

[0016] Furthermore, the diamond particles in the diamond coating are nano-sized or micro-sized, wherein the average grain size of the nano-sized particles is 50-100 nm, and the average grain size of the micro-sized particles is 1000-2000 nm. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the deposition of the carbon-based composite coating in this invention;

[0018] Figure 2 This is a structural morphology diagram of the carbon-based composite coating in this invention;

[0019] Figure 3 This is the Raman spectrum of the nanodiamond coating in this invention;

[0020] Figure 4 This is the Raman spectrum of the graphene coating in this invention;

[0021] Figure 5 This is a graph showing the friction coefficient of the carbon-based composite coating at a friction temperature of 400℃ in this invention.

[0022] Figure 6 This is a curve showing the coefficient of friction of the diamond coating at a friction temperature of 400℃ in this invention.

[0023] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0025] Please see Figure 1 and Figure 2 An embodiment of the present invention provides a method for preparing a carbon-based composite coating, comprising the following steps:

[0026] Step S10: A diamond coating is formed on the surface of the workpiece substrate using a deposition method, and a catalytic layer is formed on the surface of the diamond coating using magnetron sputtering technology.

[0027] It should be noted that in this step, the specific material, shape and size of the workpiece substrate are not limited. The corresponding substrate can be selected according to the application scenario of the required part, such as cemented carbide flat sample and cemented carbide milling cutter.

[0028] Preferably, the diamond coating can be prepared by hot-wire chemical vapor deposition, plasma vapor deposition or low-pressure chemical vapor deposition, and the thickness of the diamond coating is 1 to 10 μm.

[0029] Specifically, the thickness of the diamond coating can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm, or any other value in the range of 1 to 10μm.

[0030] Preferably, the diamond particles in the diamond coating are nano-sized or micro-sized, serving as a solid carbon source for catalyzing the growth of graphene. The average grain size of the nano-sized particles is 50–100 nm, and the average grain size of the micro-sized particles is 1000–2000 nm.

[0031] Specifically, the average grain size of the nanocrystalline diamond coating can be 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, or any other value in the range of 50 to 100nm.

[0032] Specifically, the average grain size of the micron-sized diamond coating can be 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm or 2000nm, or any other value in the range of 1000 to 2000nm.

[0033] It should be noted that if the thickness of the diamond coating is less than 1 μm, there is a risk of insufficient supply of solid carbon source, which is not conducive to the growth of graphene. If the thickness of the diamond coating is greater than 10 μm, it is easy to increase the number and thickness of graphene layers, and even form graphite.

[0034] Preferably, in step S10, the parameters of the magnetron sputtering technology are: argon flow rate of 25-50 sccm, substrate bias of -70-30V, deposition power of 100-1000W, deposition pressure of 0.2-0.5Pa, and deposition time of 3-15min.

[0035] Specifically, the argon flow rate can be 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm or 50 sccm, or any other value within the range of 25 to 50 sccm.

[0036] Specifically, the substrate bias voltage can be -70V, -60V, -50V, -40V or -30V, or any other value in the range of -70V to -30V.

[0037] Specifically, the deposition power can be 100W, 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W or 1000W, or any other value in the range of 100 to 1000W.

[0038] Specifically, the deposition pressure can be 0.2 Pa, 0.25 Pa, 0.3 Pa, 0.35 Pa, 0.4 Pa, 0.44 Pa, or 0.5 Pa, or any other value in the range of 0.2 to 0.5 Pa.

[0039] Specifically, the deposition time can be 3 min, 5 min, 7 min, 10 min, 12 min or 15 min, or any other value within the range of 3 to 15 min.

[0040] It should be noted that under the above magnetron sputtering deposition conditions, a large-area and highly uniform catalytic layer can be guaranteed to be covered on the diamond coating surface, unaffected by the irregular structure of the substrate, thus ensuring uniform growth and excellent adhesion of graphene.

[0041] Preferably, the catalyst layer is a nickel catalyst layer or a copper catalyst layer, and the thickness is 50-200 nm.

[0042] Specifically, the thickness of the catalyst layer can be 50nm, 70nm, 90nm, 110nm, 130nm, 150nm, 170nm, 190nm or 200nm, or any other value in the range of 50 to 200nm.

[0043] It should be noted that if the thickness of the catalyst layer is less than 50 nm, it will easily hinder its catalytic effect in graphene growth. If it is greater than 200 nm, it will be difficult to completely remove the residual catalyst layer, which will increase the risk of abrasive wear.

[0044] Step S11: The workpiece substrate containing the catalyst layer is subjected to high-temperature annealing to induce carbon atoms to grow in situ on the surface of the catalyst layer, and the in situ grown carbon atoms are uniformly arranged to form a graphene coating.

[0045] Furthermore, in step S11, the heating rate of the high-temperature annealing is 6-30℃ / min, the annealing temperature is 800-1100℃, and the holding time is 5-20min.

[0046] Specifically, the heating rate can be 6℃ / min, 10℃ / min, 14℃ / min, 18℃ / min, 22℃ / min, 26℃ / min or 30℃ / min, or any other value in the range of 6 to 30℃ / min.

[0047] Specifically, the annealing temperature can be 800℃, 900℃, 1000℃ or 1100℃, or any other value within the range of 800 to 1100℃.

[0048] Specifically, the heat preservation time can be 5 min, 10 min, 15 min or 20 min, or any other value within the range of 5 to 20 min.

[0049] It should be noted that under the above annealing conditions, carbon atoms in the diamond layer can effectively diffuse and migrate to the catalyst layer. Under the action of the catalyst layer, these carbon atoms rearrange uniformly to form a graphene coating. If the heating temperature is below 800℃, the graphene growth will be uneven and slow; if the heating temperature is above 1100℃, the coating structure will be damaged and the surface quality of the coating will be reduced.

[0050] Step S12: Immerse the workpiece substrate containing the graphene coating in a mixed acidic solution and perform ultrasonic etching while controlling the corrosion intensity and speed to remove the residual catalyst layer, that is, form a carbon-based composite coating containing a combination of diamond coating and graphene coating on the surface of the workpiece substrate.

[0051] It should be noted that this step involves ultrasonic etching in an ultrasonic machine. After etching, deionized water is used for rinsing to promote stable contact between the diamond coating and the graphene coating.

[0052] Preferably, in this step, to ensure that the mixed acidic solution can accurately dissolve the catalyst layer without damaging the diamond coating and the graphene coating, the mixed acidic solution includes water, concentrated hydrochloric acid and nitric acid, wherein the volume percentage of water is 65% to 70%, the volume percentage of hydrochloric acid is 5% to 7%, and the volume percentage of nitric acid is 23% to 27%.

[0053] The etching time is 30–180 s, and the etching temperature is 25–35 ℃.

[0054] Specifically, the percentage of water in the total volume of the solution can be 65%, 66%, 67%, 68%, 69%, or 70%, or any other value within the range of 65% to 70%.

[0055] Specifically, the percentage of hydrochloric acid in the total volume of the solution can be 5%, 6%, or 7%, or any other value within the range of 5% to 7%.

[0056] Specifically, the percentage of nitric acid in the total volume of the solution can be 23%, 24%, 25%, 26%, or 27%, or any other value within the range of 23% to 27%.

[0057] Specifically, the etching time can be 30s, 60s, 90s, 120s, 150s or 180s, or any other value within the range of 30 to 180s.

[0058] Specifically, the etching temperature can be 25℃, 27℃, 29℃, 31℃, 33℃ or 35℃, or any other value within the range of 25 to 35℃.

[0059] It should be clarified that within the above-mentioned etching time limit, if the volume ratio of hydrochloric acid and nitric acid is too small, the catalyst layer cannot be effectively and accurately etched, reducing the etching efficiency; if the volume ratio of hydrochloric acid and nitric acid is too large, it is easy to damage the diamond and graphene coatings, or even damage the substrate material, making it difficult to control the etching depth and shape, increasing surface roughness, and affecting high-temperature friction performance.

[0060] If the etching time is less than 30 seconds, the catalyst layer will not be completely removed, affecting the direct contact between diamond and graphene, and may even easily cause abrasive wear and oxidative wear during subsequent high-temperature friction. If the etching time is more than 180 seconds, it may easily damage the edge structure of the diamond and graphene coatings and reduce their structural quality.

[0061] If the etching temperature is below 25℃, the etching residue is difficult to remove completely, and may even affect the curing and stabilization process of the upper and lower coating interfaces. If the etching temperature is above 35℃, it is difficult to control the etching depth, and may even promote side reactions such as substrate degradation and corrosion in non-target areas.

[0062] The carbon-based composite coating provided in this application is obtained by preparing a high-temperature lubricating carbon-based composite coating on the surface of a workpiece substrate using the method provided in this application.

[0063] The wear-resistant part provided in this application embodiment is prepared by using the coating provided in this application embodiment, or by preparing a high-temperature lubricating carbon-based composite coating on the surface of a workpiece substrate using the coating preparation method provided in this application.

[0064] In summary, this invention utilizes magnetron sputtering technology to uniformly deposit a catalytic layer on the surface of the diamond coating. This catalytic layer provides an ideal interface for the growth of a more uniform and complete graphene coating. Furthermore, the mixed acidic solution, by altering the proportions of its components and finely adjusting its etching intensity and rate, can selectively etch the catalytic layer without damaging the diamond and graphene coatings. This further ensures direct contact between the diamond and graphene coatings, increases the number of active sites on the diamond surface, and facilitates the formation of more covalent bonds with graphene, thereby enhancing the bonding strength of the carbon-based composite coating interface and improving its stability under high-temperature friction conditions. Moreover, the preparation method of this application is simple and efficient, and can be uniformly deposited on workpiece substrates with complex shapes and sizes, enabling its application in high-temperature wear-resistant devices.

[0065] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0066] Example 1

[0067] This embodiment provides a method for preparing a carbon-based composite coating, including the following steps:

[0068] (1) Cleaning: The cemented carbide flat sample was immersed in anhydrous ethanol and deionized water in sequence for 10 minutes of ultrasonic cleaning, and then dried with nitrogen.

[0069] (2) A nanocrystalline diamond coating was deposited using hot filament chemical vapor deposition technology, with a thickness of 1 μm and an average grain size of 50 nm.

[0070] (3) A nickel catalyst layer with a thickness of 70 nm was deposited using magnetron sputtering technology. The main process parameters of magnetron sputtering are as follows: deposition power of 100 W, deposition gas pressure of 0.5 Pa, argon flow rate of 50 sccm, substrate bias of -50 V, and deposition time of 5 min.

[0071] (4) High-temperature annealing is used to catalyze the growth of graphene coating. Specifically, the substrate with deposited diamond coating and nickel catalyst layer is placed in a tube furnace, and in a vacuum environment, the heating temperature is set to 800℃, the heating rate is 6℃ / min, and the holding time is 5min.

[0072] (5) Prepare a mixed acidic solution of water, concentrated hydrochloric acid, and nitric acid to etch the residual nickel catalyst layer. Water accounts for 68.85% of the total volume of the solution, hydrochloric acid accounts for 6.15% of the total volume, and nitric acid accounts for 25% of the total volume. The etching time is 60s and the etching temperature is 25℃.

[0073] After high-temperature annealing, carbon atoms in the diamond diffuse into the nickel catalyst layer, promoting carbon atom rearrangement and forming a graphene coating. Precise etching with a mixed acidic solution effectively removes the residual catalyst layer, ensuring the quality of both the diamond and graphene coatings and promoting stable contact between them, forming a carbon-based composite coating, such as... Figure 2 As shown in the figure. Experiments show that the carbon-based composite coating prepared above exhibits a transformation of diamond characteristic peaks into D, G, and 2D peaks, as indicated by the Raman spectral curves. Figure 3 and 4 As shown. High-temperature friction and wear results show an average friction coefficient of 0.5571 (e.g., Figure 5 As shown in the figure, it has good high-temperature wear resistance.

[0074] Example 2

[0075] This embodiment provides a method for preparing a carbon-based composite coating, including the following steps:

[0076] (1) Cleaning: The carbide end mill was immersed in anhydrous ethanol and deionized water in sequence for 10 minutes of ultrasonic cleaning, and then dried with nitrogen.

[0077] (2) A micron-sized diamond coating was deposited using plasma chemical vapor deposition technology, with a thickness of 4 μm and an average grain size of 1000 nm.

[0078] (3) A nickel catalyst layer with a thickness of 140 nm was deposited using magnetron sputtering technology. The main process parameters of magnetron sputtering are as follows: deposition power of 200 W, deposition gas pressure of 0.4 Pa, argon flow rate of 40 sccm, substrate bias of -40 V, and deposition time of 10 min.

[0079] (4) High-temperature annealing is used to catalyze the growth of graphene coating. Specifically, the substrate with deposited diamond coating and nickel catalyst layer is placed in a tube furnace, and in a vacuum environment, the heating temperature is set to 900℃, the heating rate is 10℃ / min, and the holding time is 10min.

[0080] (5) Prepare a mixed acidic solution of water, concentrated hydrochloric acid, and nitric acid to etch the residual nickel catalyst layer. Water accounts for 67% of the total volume of the solution, hydrochloric acid accounts for 6% of the total volume, and nitric acid accounts for 27% of the total volume. The etching time is 100s and the etching temperature is 27℃.

[0081] After high-temperature annealing, carbon atoms in the diamond diffuse into the nickel catalyst layer, promoting carbon atom rearrangement and forming a graphene coating. Precise etching with a mixed acidic solution effectively removes the residual catalyst layer, ensuring the quality of both the diamond and graphene coatings and promoting stable contact between them, forming a carbon-based composite coating. Experiments show that the prepared carbon-based composite coating exhibits diamond characteristic peaks transformed into D, G, and 2D peaks, with a stable interface and good bonding strength. Under high-temperature cutting conditions, it demonstrates excellent high-temperature wear resistance and lifespan.

[0082] Example 3

[0083] This embodiment provides a method for preparing a carbon-based composite coating, including the following steps:

[0084] (1) Cleaning: The carbide end mill was immersed in anhydrous ethanol and deionized water in sequence for 10 minutes of ultrasonic cleaning, and then dried with nitrogen.

[0085] (2) A micron-sized diamond coating was deposited using plasma chemical vapor deposition technology, with a thickness of 6 μm and an average grain size of 1500 nm.

[0086] (3) A nickel catalyst layer with a thickness of 170 nm was deposited using magnetron sputtering technology. The main process parameters of magnetron sputtering are as follows: deposition power of 500 W, deposition gas pressure of 0.3 Pa, argon flow rate of 30 sccm, substrate bias of -60 V, and deposition time of 13 min.

[0087] (4) High-temperature annealing is used to catalyze the growth of graphene coating. Specifically, the substrate with deposited diamond coating and nickel catalyst layer is placed in a tube furnace, and in a vacuum environment, the heating temperature is set to 1000℃, the heating rate is 20℃ / min, and the holding time is 12min.

[0088] (5) Prepare a mixed acidic solution of water, concentrated hydrochloric acid, and nitric acid to etch the residual nickel catalyst layer. Water accounts for 70% of the total volume of the solution, hydrochloric acid accounts for 5% of the total volume, and nitric acid accounts for 25% of the total volume. The etching time is 120 s and the etching temperature is 29 °C.

[0089] After high-temperature annealing, carbon atoms in the diamond diffuse into the nickel catalyst layer, promoting carbon atom rearrangement and forming a graphene coating. Precise etching with a mixed acidic solution effectively removes the residual catalyst layer, ensuring the quality of both the diamond and graphene coatings and promoting stable contact between them, forming a carbon-based composite coating. Experiments show that the prepared carbon-based composite coating exhibits diamond characteristic peaks transformed into D, G, and 2D peaks, with a stable interface and good bonding strength. Under high-temperature cutting conditions, it demonstrates excellent high-temperature wear resistance and lifespan.

[0090] Example 4

[0091] This embodiment provides a method for preparing a carbon-based composite coating, including the following steps:

[0092] (1) Cleaning: The carbide end mill was immersed in anhydrous ethanol and deionized water in sequence for 10 minutes of ultrasonic cleaning, and then dried with nitrogen.

[0093] (2) A micron-sized diamond coating with a thickness of 10 μm and an average grain size of 2000 nm was deposited using plasma chemical vapor deposition technology.

[0094] (3) A nickel catalyst layer with a thickness of 200 nm was deposited using magnetron sputtering technology. The main process parameters of magnetron sputtering are as follows: deposition power of 1000 W, deposition gas pressure of 0.2 Pa, argon flow rate of 25 sccm, substrate bias of -70 V, and deposition time of 15 min.

[0095] (4) High-temperature annealing is used to catalyze the growth of graphene coating. Specifically, the substrate with deposited diamond coating and nickel catalyst layer is placed in a tube furnace, and in a vacuum environment, the heating temperature is set to 1100℃, the heating rate is 30℃ / min, and the holding time is 15min.

[0096] (5) Prepare a mixed acidic solution of water, concentrated hydrochloric acid, and nitric acid to etch the residual nickel catalyst layer. Water accounts for 69% of the total volume of the solution, hydrochloric acid accounts for 6% of the total volume, and nitric acid accounts for 25% of the total volume. The etching time is 180 s and the etching temperature is 35 °C.

[0097] After high-temperature annealing, carbon atoms in the diamond diffuse into the nickel catalyst layer, promoting carbon atom rearrangement and forming a graphene coating. Etching with an acidic solution further promotes stable contact between the diamond and graphene coatings, forming a carbon-based composite coating. Experiments show that the prepared carbon-based composite coating exhibits diamond characteristic peaks transforming into D, G, and 2D peaks, with a stable interface and good bonding strength. Under high-temperature cutting conditions, it demonstrates excellent high-temperature wear resistance and lifespan.

[0098] Comparative Example 1

[0099] The preparation method provided in this comparative example is basically the same as that in Example 1, except that steps (2), (3) and (4) are not performed.

[0100] Experimental results show that no characteristic peaks of graphene appeared on the surface of the diamond coating obtained in this comparative example. Using the same tribological parameters, the high-temperature tribological results show an average friction coefficient of 0.6327 (e.g., ...). Figure 6 As shown in the figure, it has poor high-temperature wear resistance.

[0101] Comparative Example 2

[0102] The preparation method provided in this comparative example is basically the same as that in Example 1, except that step (4) is not performed.

[0103] Experimental results show that the lack of etching with an acidic solution to remove residual nickel catalyst leads to reduced adhesion between the diamond and graphene interfaces. Furthermore, a large number of wear particles appear at the friction interface, resulting in abrasive wear and poor high-temperature wear resistance.

[0104] Comparative Example 3

[0105] The preparation method provided in this comparative example is basically the same as that in Example 1, except that the deposition time in step (3) is replaced with 2 min.

[0106] Experimental results show that the nickel catalyst layer is only 20 nm thick and does not completely cover the diamond coating surface, thus failing to effectively catalyze the growth of graphene and exhibiting poor high-temperature wear resistance.

[0107] Comparative Example 4

[0108] The preparation method provided in this comparative example is basically the same as that in Example 1, except that the heating temperature in step (4) is replaced with 700°C.

[0109] Experimental results show that at lower annealing temperatures, carbon atoms in the diamond layer cannot effectively migrate to the catalyst layer, resulting in slow graphene growth and uneven coverage, leading to poor high-temperature wear resistance.

[0110] Comparative Example 5

[0111] The preparation method provided in this comparative example is basically the same as that in Example 1, except that the etching time in step (5) is replaced with 200s.

[0112] Experimental results show that over a longer etching time, the edge structure of the diamond and graphene coatings is damaged, increasing structural defects and reducing the adhesion of the diamond and graphene coatings.

[0113] Comparative Example 6

[0114] The preparation method provided in this comparative example is basically the same as that in Example 1, except that the percentage of nitric acid in the total volume in step (5) is changed to 30%.

[0115] Experimental results show that under a high nitric acid content, the diamond coating, graphene coating, and substrate all suffered varying degrees of damage. Irregular etching depths and shapes appeared at the etching interface, which greatly increased the surface roughness, caused severe fluctuations in the friction curve, and reduced high-temperature friction performance.

[0116] The data results of the above embodiments and comparative examples are summarized in Table 1.

[0117] Table 1 Results of high-temperature friction coefficient and wear rate

[0118] High temperature friction coefficient High temperature wear rate Example 1 0.5571 <![CDATA[1.08×10 -6 mm 3 (N·m) -1 ]]> Example 2 0.5627 <![CDATA[2.21×10 -6 mm 3 (N·m) -1 ]]> Example 3 0.5688 <![CDATA[2.64×10 -6 mm 3 (N·m) -1 ]]> Example 4 0.5709 <![CDATA[5.35×10 -6 mm 3 (N·m) -1 ]]> Comparative Example 1 0.6327 <![CDATA[8.01×10 -6 mm 3 (N·m) -1 ]]> Comparative Example 2 0.7211 <![CDATA[8.75×10 -6 mm 3 (N·m) -1 ]]> Comparative Example 3 0.7891 <![CDATA[1.65×10 -5 mm 3 (N·m) -1 ]]> Comparative Example 4 0.8003 <![CDATA[2.68×10 -5 mm 3 (N·m) -1 ]]> Comparative Example 5 0.8921 <![CDATA[4.68×10 -5 mm 3 (N·m) -1 ]]> Comparative Example 6 0.7845 <![CDATA[1.25×10 -5 mm 3 (N·m) -1 ]]>

[0119] Comparing Examples 1 and 2-4 in Table 1, it can be concluded that when the thickness of the diamond coating, the average grain size, the thickness of the nickel catalyst layer, the high-temperature annealing temperature, and the etching time of the mixed acid solution vary within specific ranges—namely, the diamond coating thickness is in the range of 1–10 μm, the average grain size is in the range of 50–2000 nm, the nickel catalyst layer thickness is in the range of 70–200 nm, the high-temperature annealing temperature is in the range of 800–1100 °C, and the mixed acid solution etching time is in the range of 60–180 s—the carbon-based composite coating can maintain a stable interface and good high-temperature wear resistance. This indicates that within the optimized range of these parameters, the high-temperature friction performance of the carbon-based composite coating is reliably guaranteed. Further comparison of Example 1 and Comparative Examples 1-6 reveals that when the diamond coating is not composited with the graphene structure, residual nickel catalyst is not removed by etching with an acidic solution, the nickel catalyst layer thickness is as low as 20 nm, the high-temperature annealing temperature is as low as 700 °C, the etching time of the mixed acidic solution is increased to 200 s, or the proportion of nitric acid in the mixed acidic solution exceeds 30%, the diamond and graphene carbon-based composite coating cannot form a stable interface during friction, resulting in decreased interfacial adhesion and poor surface uniformity, thus exhibiting a high coefficient of friction and wear rate. These findings highlight the importance of optimizing and controlling these key parameters when preparing high-performance carbon-based composite coatings.

[0120] In a preferred embodiment of this application, by controlling the thickness of the nickel catalyst layer in magnetron sputtering within a suitable range, a more uniform catalyst layer can be obtained on the surface of an irregular workpiece substrate containing a diamond coating, thus ensuring the uniform deposition of the graphene coating.

[0121] In a preferred embodiment of this application, by controlling the annealing temperature within a suitable range, carbon atoms in the diamond coating are activated to migrate to the surface of the catalyst layer, promoting the rearrangement of carbon atoms into a graphene coating, thus ensuring that a carbon-based composite coating is obtained.

[0122] In a preferred embodiment of this application, by controlling the etching time within a suitable range, the carbon-based composite coating can be guaranteed to have better high-temperature wear resistance.

[0123] In this specification, the various embodiments are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Furthermore, the above-described embodiments merely illustrate several implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing a carbon-based composite coating, characterized in that, Includes the following steps: Step S10: A diamond coating is formed on the surface of the workpiece substrate using a deposition method, and a catalyst layer is formed on the surface of the diamond coating using magnetron sputtering technology. The catalyst layer is a nickel catalyst layer or a copper catalyst layer with a thickness of 50~200 nm. The parameters of the magnetron sputtering technology are: argon flow rate of 25~50 sccm, substrate bias voltage of -70~-30 V, deposition power of 100~1000 W, deposition pressure of 0.2~0.5 Pa, and deposition time of 3~15 min. Step S11: The workpiece substrate containing the catalyst layer is subjected to high-temperature annealing to induce carbon atoms to grow in situ on the surface of the catalyst layer, and the in situ grown carbon atoms are uniformly arranged to form a graphene coating. The heating rate of the high-temperature annealing is 6~30℃ / min, the annealing temperature is 800~1100℃, and the holding time is 5~20 min. Step S12: Immerse the workpiece substrate containing the graphene coating in a mixed acidic solution, and perform ultrasonic etching while controlling the etching intensity and speed to remove the residual catalyst layer. That is, form a carbon-based composite coating containing a combination of diamond coating and graphene coating on the surface of the workpiece substrate. The mixed acidic solution includes water, concentrated hydrochloric acid and nitric acid, wherein the volume percentage of water is 65%~70%, the volume percentage of hydrochloric acid is 5%~7%, the volume percentage of nitric acid is 23%~27%, the etching time is 30~180s, and the etching temperature is 25~35℃.

2. The method for preparing the carbon-based composite coating according to claim 1, characterized in that, In step S10, the thickness of the diamond coating is 1~10μm.

3. The method for preparing the carbon-based composite coating according to claim 2, characterized in that, The diamond particles in the diamond coating are nano-sized or micro-sized, wherein the average grain size of the nano-sized particles is 50~100 nm, and the average grain size of the micro-sized particles is 1000~2000 nm.

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