Graphene-diamond composite coating, and preparation method and application thereof

Abstract

The application discloses a graphene-diamond composite coating and a preparation method and application thereof, and belongs to the technical field of materials. The graphene-diamond composite coating comprises a diamond coating and a graphene coating; graphene sp2 bond structure is covalently combined with diamond sp3 bond structure; and the graphene coating has a graphene structure with non-parallel growth mainly in a vertical direction. The graphene-diamond composite coating has small lattice mismatch between the diamond and the graphene, avoids volume expansion caused in a friction heat process, and has the advantages that the diamond coating can provide a support layer for the graphene, forms super-strong C-C covalent bonds at an interface, and significantly improves the adhesion strength of the graphene; the graphene can avoid brittle fracture of the diamond, and significantly improves the lubricating performance of the surface of the diamond coating. The composite coating has better wear resistance, a low friction coefficient and excellent oxidation resistance, and can remain stable under high-temperature and high-load working conditions, so that the service life and processing efficiency of wear-resistant parts are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a graphene-diamond composite coating and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of mechanical and energy fields, higher requirements are put forward for the durability, energy loss and lubrication performance of key power components in extreme environments such as high temperature and high pressure. Graphene has become a hot spot in the research of material science due to its excellent lubrication performance. However, the low bending stiffness of graphene leads to the easy occurrence of wrinkling phenomenon when bearing load, thereby producing additional energy dissipation in the sliding friction process, which is not conducive to maintaining its ideal layered structure, and accordingly affects its wear resistance.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The present application aims to provide a graphene-diamond composite coating and a preparation method and application thereof, so as to solve or improve the above technical problems.

[0005] The present application can be realized as follows:

[0006] In a first aspect, the present application provides a graphene-diamond composite coating, which comprises a diamond coating and a graphene coating.

[0007] The diamond coating is arranged on the surface of a hard alloy substrate, and the graphene sp2 bond structure in the graphene coating is covalently combined with the diamond sp3 bond structure in the diamond coating. The graphene coating has a graphene structure that is mainly vertically and non-parallelly grown in the direction away from the diamond coating.

[0008] In optional embodiments, the graphene-diamond composite coating has at least one of the following characteristics:

[0009] Characteristic 1: the thickness of the diamond coating is 1 μm to 15 μm;

[0010] Characteristic 2: the diamond in the diamond coating is ultra-nanocrystalline diamond, nanocrystalline diamond or microcrystalline diamond;

[0011] Characteristic 3: the thickness of the graphene coating is 1 μm to 5 μm.

[0012] In optional embodiments, the average grain size of the ultra-nanocrystalline diamond is 5 nm to 30 nm; or, the average grain size of the nanocrystalline diamond is 40 nm to 100 nm; or, the average grain size of the microcrystalline diamond is 1000 nm to 3000 nm.

[0013] In optional embodiments, the graphene-diamond composite coating further has at least one of the following characteristics:

[0014] Characteristic 4: the graphene-diamond composite coating has a friction coefficient of no more than 0.1;

[0015] Characteristic 5: the graphene-diamond composite coating has a wear rate of no more than 1x10 -6 mm 3 / Nm.

[0016] In a second aspect, the present application provides a method for preparing a graphene-diamond composite coating as defined in any one of the preceding embodiments, comprising the following steps: preparing a diamond coating on a surface of a cemented carbide substrate, preparing a liquid catalyst layer on a surface of the diamond coating, preparing a graphene coating on a surface of the liquid catalyst layer; and etching the residual liquid catalyst layer.

[0017] In optional embodiments, the cemented carbide substrate is etched and cleaned before the diamond coating is prepared.

[0018] In optional embodiments, the diamond coating is prepared by hot filament chemical vapor deposition, and the preparation conditions of the diamond coating include: a deposition power of 1500W-2500W, a deposition pressure of 1mbar-10mbar, a hydrogen flow rate of 9000sccm-18000sccm, a methane flow rate of 100sccm-500sccm, a deposition temperature of 800°C-1000°C, and a deposition time of 6h-30h.

[0019] In optional embodiments, the liquid catalyst layer is prepared by coating a liquid metal on the surface of the diamond coating using a drop casting method.

[0020] In optional embodiments, the liquid metal is coated in an amount of 0.5g / cm 2 -5g / cm 2 .

[0021] In optional embodiments, the liquid metal includes at least one of liquid gallium, liquid copper, and liquid nickel.

[0022] In optional embodiments, the liquid metal includes liquid gallium.

[0023] In optional embodiments, the graphene coating is prepared by a tube furnace high-temperature treatment technique, and the preparation conditions of the graphene coating include: the quartz tube is evacuated to a degree of 10mtorr-30mtorr, the hydrogen flow rate is 100sccm-1000sccm, the growth temperature is 700°C-1200°C, and the growth time is 10min-40min.

[0024] In a third aspect, the present application provides a graphene-diamond composite coating material, comprising a substrate and a graphene-diamond composite coating as any of the preceding embodiments disposed on the surface of the substrate.

[0025] In a fourth aspect, the present application provides a wear-resistant part having the graphene-diamond composite coating material as any of the preceding embodiments.

[0026] The present application has the following advantages:

[0027] The graphene-diamond composite coating provided by the present application comprises a diamond coating and a graphene coating. The diamond coating can act as a support phase and a solid carbon source for the graphene coating. The diamond has high mechanical properties, which can provide strong support, reduce the wrinkling and edge wrapping of the graphene, thereby maintaining a more orderly sliding interface and potentially improving the wear resistance of the graphene.

[0028] In the present application, the graphene structure of the graphene coating is mainly vertically non-parallel growth away from the diamond coating in combination with the interface of the diamond coating. Compared with the graphene grown in parallel form, the graphene structure grown in the mainly vertically non-parallel orientation provided by the present application can endow the coating with excellent wear resistance, low friction coefficient and excellent oxidation resistance, and can also remain stable under high temperature and high load working conditions, thereby significantly improving the service life and processing efficiency of the wear-resistant part.

[0029] In addition, in the present application, the diamond coating provides a solid carbon source for the growth of the graphene coating, without the need for external introduction of carbon precursors, thereby simplifying the preparation process. From the perspective of microstructure, the diamond and graphene have small lattice mismatch, which avoids the volume expansion caused by friction heat. Moreover, both diamond and graphene are allotropes of carbon, the high hardness of the diamond coating can provide a support layer for the graphene, and form a super-strong C-C covalent bond at the interface, thereby significantly improving the adhesion strength of the graphene; the flexibility of the graphene can avoid brittle fracture of the diamond, and significantly improve the lubrication performance of the surface of the diamond coating, and the two complement each other.

[0030] It should be further emphasized that, according to the current prior art, the general graphene growth is layer growth, not more than 10 layers, and the thickness is about 1-4 nm; the present application first proposes the idea of mainly vertically non-parallel growth of graphene (i.e. vertical growth), and successfully provides a specific scheme for realizing this idea, including the preparation method and the preparation conditions, thereby effectively providing a graphene material with better wear resistance and sliding resistance. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0032] Figure 1 The structure morphology diagram of the graphene-diamond composite coating prepared for the present application embodiment 1;

[0033] Figure 2 The Raman spectrum diagram of the diamond coating in the present application embodiment 1;

[0034] Figure 3 The Raman spectrum diagram of the graphene-diamond composite coating prepared in the present application embodiment 1. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0036] The graphene-diamond composite coating and the preparation method and application thereof provided by the present application will be specifically described below.

[0037] The present application provides a graphene-diamond composite coating, which comprises a diamond coating and a graphene coating. The diamond coating is arranged on the surface of a hard alloy substrate, and the graphene sp2 bond structure in the graphene coating is covalently combined with the diamond sp3 bond structure in the diamond coating. The graphene coating has a graphene structure that is mainly vertically and non-parallelly grown in the direction away from the diamond coating from the interface combined with the diamond coating.

[0038] The above diamond coating can be used as a bearing phase and a solid carbon source of the graphene coating. The diamond has high mechanical properties, can provide strong support, reduce the wrinkling and edge wrapping of the graphene, thereby maintaining a more orderly sliding interface and potentially improving the wear resistance of the graphene. However, in the prior art, the combination of the graphene coating and the diamond coating mainly relies on weak van der Waals force, and such a binding force is usually insufficient to withstand a high-load friction environment, and therefore it is difficult to be applied on a workpiece with a complex shape or irregular shape.

[0039] Based on this, in the preparation process, a liquid catalyst layer is introduced between the graphene coating and the diamond coating, which is used to induce the in-situ growth of the graphene coating on the diamond coating under high temperature conditions to form the graphene-diamond composite coating. By introducing the catalyst layer, the self-limiting kinetics characteristics thereof can be utilized to promote the seamless growth of the graphene sp2 bond structure on the diamond sp3 bond structure, so that the graphene coating and the diamond coating have excellent bonding strength, and the application of the composite coating on a complex-shaped or irregular workpiece is realized. Moreover, in the preparation process, the residual liquid catalyst layer is etched, so that most of the catalyst layer can be removed.

[0040] In the present application, the graphene structure of the graphene coating is mainly vertically non-parallel growth in the direction away from the diamond coating from the interface combined with the diamond coating. The non-parallel growth form includes growth in the direction perpendicular to the combination interface, growth in the direction vertical to the combination interface, and growth in the direction at a certain angle (such as 5°, 10°, 20°, 30°, 40°, 50°, 60°, 70° or 80°, etc.) to the combination interface. Compared with the graphene grown in parallel form, the graphene grown in the direction guided by the catalyst crystal face in the present application can produce larger graphene crystals and accumulate into irregular structures. The above structure can endow the coating with excellent wear resistance, low friction coefficient and excellent oxidation resistance, and can also remain stable under high temperature and high load working conditions, thereby significantly improving the service life and processing efficiency of the wear-resistant part.

[0041] In addition, in the present application, the diamond coating can also provide a solid carbon source for the growth of the graphene coating, without the need to introduce a carbon precursor from the outside, thereby simplifying the preparation process. From the perspective of microstructure, the lattice mismatch between diamond and graphene is small, which avoids the volume expansion caused by friction heat. Moreover, diamond and graphene are both allotropes of carbon, the high hardness of the diamond coating can provide a support layer for graphene and form a super-strong C-C covalent bond at the interface, thereby significantly improving the adhesion strength of graphene; the flexible property of graphene can avoid brittle fracture of diamond and significantly improve the lubrication performance of the diamond coating surface, and the two form a complementary advantage.

[0042] In some optional embodiments, the thickness of the diamond coating can be 1 μm to 15 μm, such as 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm or 15 μm, etc., and can also be other values within the range of 1 μm to 15 μm.

[0043] If the thickness of the diamond coating is less than 1 μm, the solid carbon source supply is prone to be insufficient, which is not conducive to the growth of the vertical graphene; if the thickness of the diamond coating is greater than 15 μm, the number of graphene layers and the thickness are prone to be increased, and even parallel graphite state is formed.

[0044] The diamond in the diamond coating can be ultra-nanocrystalline diamond, nanocrystalline diamond or microcrystalline diamond. The average grain size of the ultra-nanocrystalline diamond can be 5-30 nm, such as 5 nm, 10 nm, 15 nm, 20 nm, 25 nm or 30 nm, or other values within the range of 5-30 nm. The average grain size of the nanocrystalline diamond can be 40-100 nm, such as 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, or other values within the range of 40-100 nm. The average grain size of the microcrystalline diamond can be 1000-3000 nm, such as 1000 nm, 1500 nm, 2000 nm, 2500 nm or 3000 nm, or other values within the range of 1000-3000 nm.

[0045] If the average grain size of the diamond in the diamond coating is too large, it is easy to cause large grain boundaries in the coating, and these grain boundaries are potential stress concentration points, thereby increasing the possibility of micro-cracks in the coating when stressed, and reducing the overall fracture toughness of the coating.

[0046] In some optional embodiments, the thickness of the graphene coating can be 1-5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, or other values within the range of 1-5 μm.

[0047] If the thickness of the graphene coating is too thin, it cannot form a continuous and uniform protective barrier, and is not sufficient to absorb and disperse the force applied to the surface, thereby causing the coating to be prone to cracking or peeling when subjected to mechanical impact or pressure; if the thickness of the graphene coating is too thick, it will affect the overall flexibility of the coating, reducing its applicability in applications that require bending or stretching. Furthermore, the increased layer thickness can cause uneven stress between the interfaces, causing the coating to separate or fall off as a whole.

[0048] In some embodiments, the friction coefficient of the graphene-diamond composite coating described above is not more than 0.1, for example, it can be 0.081-0.099, such as 0.081, 0.082, 0.088, 0.091, 0.095 or 0.099, or other values within the range of 0.081-0.099. In some more typical embodiments, the friction coefficient of the graphene-diamond composite coating is 0.081-0.082.

[0049] In some embodiments, the wear rate of the graphene-diamond composite coating described above is not more than 1 x 10 -6 mm 3 / Nm, for example, it can be 1 x 10 -7mm 3 / Nm~1 -6 mm 3 / Nm, such as 1 -7 mm 3 / Nm, 2.1 -7 mm 3 / Nm, 2.2 - 7 mm 3 / Nm, 2.5 -7 mm 3 / Nm, 3.6 -7 mm 3 / Nm or 1 -6 mm 3 / Nm, etc., can also be 1 -7 mm 3 / Nm~1 -6 mm 3 / Nm. In some typical embodiments, the wear rate of the graphene-diamond composite coating is 1 -6 mm 3 / Nm~1.0 -7 mm 3 / Nm.

[0050] Correspondingly, the application further provides a preparation method of the graphene-diamond composite coating, which can include the following steps: preparing a diamond coating on the surface of the cemented carbide substrate, preparing a liquid catalyst layer on the surface of the diamond coating, preparing a graphene coating on the surface of the liquid catalyst layer, and etching the residual liquid catalyst layer.

[0051] In some embodiments, the cemented carbide substrate is etched and cleaned before the diamond coating is prepared.

[0052] The specific material, shape and size of the cemented carbide substrate are not limited, and the corresponding substrate can be selected according to the application scene of the required part, such as a cemented carbide flat sample, a cemented carbide milling cutter and a workpiece substrate of a cemented carbide milling cutter.

[0053] The time of ultrasonic etching can be 1 min~6 min, such as 1 min, 2 min, 3 min, 4 min, 5 min or 6 min, etc. The time of cleaning can be 10 min~20 min, such as 10 min, 15 min or 20 min, etc.

[0054] In some embodiments, the diamond coating can be prepared by using a hot-wire chemical vapor deposition technology. By using the hot-wire chemical vapor deposition technology, it is beneficial to deposit the diamond coating on the surface of an irregular workpiece substrate and uniformly.

[0055] The preparation conditions of the diamond coating can include: a deposition power of 1500 W to 2500 W, a deposition gas pressure of 1 mbar to 10 mbar, a hydrogen flow rate of 9000 sccm to 18000 sccm, a methane flow rate of 100 sccm to 500 sccm, a deposition temperature of 800℃ to 1000℃, and a deposition time of 6h to 30h.

[0056] The deposition power can be 1500 W, 1600 W, 1700 W, 1800 W, 1900 W, 2000 W, 2100 W, 2200 W, 2300 W, 2400 W, or 2500 W, or other values within the range of 1500 W to 2500 W.

[0057] The deposition gas pressure can be 1 mbar, 2 mbar, 3 mbar, 4 mbar, 5 mbar, 6 mbar, 7 mbar, 8 mbar, 9 mbar, or 10 mbar, or other values within the range of 1 mbar to 10 mbar.

[0058] The hydrogen flow rate can be 9000 sccm, 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm, 14000 sccm, 15000 sccm, 16000 sccm, 17000 sccm, or 18000 sccm, or other values within the range of 9000 sccm to 18000 sccm.

[0059] The methane flow rate can be 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, or 500 sccm, or other values within the range of 100 sccm to 500 sccm.

[0060] The deposition temperature can be 800℃, 850℃, 900℃, 950℃, or 1000℃, or other values within the range of 800℃ to 1000℃.

[0061] The deposition time can be 6h, 12h, 18h, 24h, or 30h, or other values within the range of 6h to 30h.

[0062] Under the above hot-wire chemical vapor deposition conditions, a large-area and highly uniform diamond layer can be covered on the surface of a complex workpiece substrate, unaffected by the irregular structure of the substrate, ensuring high bearing and excellent adhesion of graphene.

[0063] In some embodiments, a drop casting method can be used to coat a liquid metal on the surface of the diamond coating to form a liquid catalyst layer. The metal catalyst layer can effectively increase the growth rate of graphene, reduce the temperature and pressure conditions for graphene growth, and significantly reduce the production cost of the composite coating, which is conducive to the large-scale application of the technology.

[0064] The coating amount of the liquid metal can be 0.5 g / cm 2 ~ 5 g / cm 2 , such as 0.5 g / cm 2 , 1 g / cm 2 , 2 g / cm 2 , 3 g / cm 2 , 4 g / cm 2 , or 5 g / cm 2 , and other values within the range of 0.5 g / cm 2 ~ 5 g / cm 2 . Accordingly, the thickness of the liquid metal catalyst layer can be 10 nm ~ 300 nm, such as 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, or 300 nm, etc.

[0065] If the amount of liquid metal is too small, it can hinder its catalytic effect in graphene growth; if the amount of liquid metal is too large, it can lead to the formation of parallel graphene layers with weak van der Waals forces, inhibiting the growth of non-parallel graphene structures.

[0066] As an example, the liquid metal can include at least one of liquid gallium, liquid copper, and liquid nickel, but is not limited thereto. In some preferred embodiments, the liquid metal includes liquid gallium.

[0067] In some embodiments, a tube furnace high temperature treatment technology can be used to prepare the graphene coating. By placing the substrate with a diamond coating and a liquid metal catalyst layer in a high temperature environment, carbon atoms in the diamond coating can be promoted to diffuse onto the liquid metal catalyst layer; under the action of the liquid metal catalyst layer, these carbon atoms are rearranged and form a non-parallel graphene coating in a non-parallel orientation.

[0068] The preparation conditions of the graphene coating can include: the vacuum degree of the quartz tube is 10mtorr ~ 30mtorr, the hydrogen flow rate is 100sccm ~ 1000sccm, the growth temperature is 700℃ ~ 1200℃, and the growth time is 10min ~ 40min.

[0069] The vacuum degree of the quartz tube can be 10mtorr, 15mtorr, 20mtorr, 25mtorr, or 30mtorr, and other values within the range of 10mtorr ~ 30mtorr.

[0070] The hydrogen flow rate can be 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm or 1000 sccm, etc., or other values within the range of 100 sccm to 1000 sccm.

[0071] If the hydrogen flow rate is too low, there will not be enough hydrogen to etch the defect edges, increasing the edge structural defects of the diamond and graphene coating, and reducing the adhesion of the diamond coating and the graphene coating.

[0072] The growth temperature can be 700℃, 800℃, 900℃, 1000℃, 1100℃ or 1200℃, etc., or other values within the range of 700℃ to 1200℃.

[0073] Under the above high-temperature preparation conditions, the carbon atoms in the diamond layer can effectively migrate to the liquid metal catalyst layer, and it is also conducive to the stable growth of graphene in a non-parallel form. If the growth temperature is lower than 700℃, the graphene growth will be slow; if the growth temperature is higher than 1200℃, the coating and the substrate structure will be damaged, and the bonding strength of the coating interface will be reduced.

[0074] The growth time can be 10 min, 15 min, 20 min, 25 min, 30 min, 35 min or 40 min, etc., or other values within the range of 10 min to 40 min.

[0075] In some embodiments, etching the residual liquid catalyst layer can be performed by using concentrated hydrochloric acid, and the etching time can be, for example, 1 min.

[0076] As described above, the existing preparation technology relies on weak van der Waals forces to achieve the combination of the graphene coating and the diamond coating, but in a high-temperature friction environment, the insufficient bonding force caused by weak interaction will accelerate the decay due to thermodynamic instability, limiting its service life and performance in the field of friction. The present application uses hot wire chemical vapor deposition technology to deposit a diamond coating on the surface of a complex workpiece substrate, and uses a liquid metal catalyst layer and high-temperature technology to achieve in-situ growth and stable adhesion of a vertically dominant non-parallel graphene coating on the diamond coating, thereby improving the durability of the graphene-diamond composite coating in a friction environment. In addition, this technology is simple, efficient and highly adaptable, solving the problems of high equipment cost, low production efficiency and complex process control in conventional methods, and can cover a variety of complex-shaped and sized workpiece substrates, greatly expanding its application potential in the industrial field.

[0077] Further, the present application also provides a graphene-diamond composite coating material, which comprises a substrate and the graphene-diamond composite coating on the surface of the substrate.

[0078] Further, the present application also provides a wear-resistant part having the graphene-diamond composite coating material, and other structures can be provided on the basis of the need.

[0079] The features and performances of the present application are further described in detail below in combination with embodiments.

[0080] Embodiment 1

[0081] The present embodiment provides a graphene-diamond composite coating material, which is prepared by the following method:

[0082] Step (1): etching and cleaning.

[0083] The YG6 cemented carbide flat sample is sequentially immersed in a mixed strong acid solution containing HCl and HNO3, a Murakami strong alkali solution and a mixed strong acid solution containing HCl and HNO3, and is subjected to ultrasonic etching for 1 min, 3 min and 2 min, respectively, and then is sequentially placed in isopropanol and deionized water and is subjected to ultrasonic cleaning for 10 min, respectively, and then is dried by nitrogen blowing.

[0084] Step (2): depositing a nanocrystalline diamond coating by using hot filament chemical vapor deposition technology.

[0085] The thickness of the diamond coating is 2 μm, and the average grain size is 40 nm. The main process parameters of the hot filament chemical vapor deposition are as follows: the deposition power is 2000 W, the deposition pressure is 5 mbar, the hydrogen flow rate is 10000 sccm, the methane flow rate is 200 sccm, the deposition temperature is 800 ℃, and the deposition time is 8 h.

[0086] Step (3): coating a liquid gallium metal catalytic layer by using a dripping method.

[0087] The coating thickness is 30 nm, the mass of the liquid gallium metal used is 1 g, and the coating area is 2 cm 2 .

[0088] Step (4): inducing the growth of a graphene coating in a non-parallel form by using a tube furnace high-temperature technology.

[0089] Specifically, the substrate having the deposited nanodiamond coating and the liquid gallium metal catalytic layer is placed in a tube furnace, the vacuum degree is extracted to 10 mtorr, the hydrogen flow rate is set to 200 sccm, the growth temperature is 800 ℃, and the growth time is 10 min, so as to obtain a graphene coating with a thickness of 2 μm.

[0090] Step (5): etching the residual liquid gallium metal catalytic layer. Specifically, concentrated hydrochloric acid is used for etching for 1 min.

[0091] After the above-prepared nanodiamond coating is annealed in a tube furnace at high temperature, carbon atoms in the diamond diffuse to the liquid gallium metal catalytic layer, promoting the rearrangement of carbon atoms and the seamless growth of graphene sp2 bond structure in a perpendicular main non-parallel orientation on the diamond sp3 bond structure, forming a graphene-diamond composite coating, as shown in Figure 1 The experiment shows that the above-prepared graphene-diamond composite coating is converted from a diamond sp3 characteristic Raman peak to an sp2 characteristic Raman peak, and the Raman spectrum curve is as shown in Figure 2 and 3 After 1800s of long-time friction, the graphene-diamond composite coating still has good wear resistance.

[0092] Example 2

[0093] This example provides a graphene-diamond composite coating material, which is prepared by the following method:

[0094] Step (1): etching and cleaning.

[0095] The milling cutter is sequentially immersed in a mixed strong acid solution containing HCl and HNO3, a Murakami strong alkali solution, and a mixed strong acid containing HCl and HNO3, and is subjected to ultrasonic etching for 1 min, 3 min, and 2 min, respectively, and then is sequentially placed in isopropyl alcohol and deionized water and is subjected to ultrasonic cleaning for 10 min, respectively, and then is dried with nitrogen.

[0096] Step (2): depositing a microcrystalline diamond coating by using hot wire chemical vapor deposition technology.

[0097] The thickness of the diamond coating is 4 μm, and the average grain size is 2000 nm. The main process parameters of the hot wire chemical vapor deposition are as follows: the deposition power is 2300 W, the deposition pressure is 1 mbar, the hydrogen flow rate is 18000 sccm, the methane flow rate is 300 sccm, the deposition temperature is 900°C, and the deposition time is 12 h.

[0098] Step (3): coating a liquid gallium metal catalytic layer by using a dripping method.

[0099] The coating thickness is 100 nm, the mass of the liquid gallium metal used is 3 g, and the coating area is 6 cm 2 .

[0100] Step (4): inducing the growth of a graphene coating in a non-parallel form by using tube furnace high-temperature technology.

[0101] Specifically, the substrate with the deposited micron-crystalline diamond coating and the liquid gallium metal catalytic layer is placed in a tube furnace, vacuum is extracted to 20 mtorr, hydrogen flow is set to 500 sccm, growth temperature is set to 900 °C, and growth time is set to 20 min, to obtain a graphene coating with a thickness of 3 μm.

[0102] Step (5): same as Example 1.

[0103] After the micron-crystalline diamond coating prepared above is annealed at high temperature in the tube furnace, carbon atoms in the diamond diffuse to the liquid gallium metal catalytic layer, promoting rearrangement of the carbon atoms and seamless growth of the graphene sp2 bond structure in a non-parallel orientation on the diamond sp3 bond structure, to form a graphene-diamond composite coating. Experiments show that the graphene-diamond composite coating prepared above is converted from a diamond sp3 characteristic Raman peak to a sp2 characteristic Raman peak, the interface is stable, and the graphene-diamond composite coating has good bonding strength. In the friction process, the graphene-diamond composite coating has good wear resistance and service life.

[0104] Example 3

[0105] The present embodiment provides a graphene-diamond composite coating material prepared by the following method:

[0106] Step (1): etching and cleaning.

[0107] The micro drill is sequentially immersed in a mixed strong acid solution containing HCl and HNO3, a Murakami strong alkali solution, and a mixed strong acid containing HCl and HNO3, and is subjected to ultrasonic etching for 1 min, 3 min, and 2 min, respectively. Subsequently, the micro drill is sequentially placed in isopropyl alcohol and deionized water, and is subjected to ultrasonic cleaning for 10 min, respectively. Subsequently, the micro drill is dried with nitrogen.

[0108] Step (2): depositing an ultra-nanocrystalline diamond coating by using hot filament chemical vapor deposition technology.

[0109] The thickness of the diamond coating is 5 μm, and the average grain size is 20 nm. The main process parameters of the hot filament chemical vapor deposition are as follows: deposition power is 1500 W, deposition pressure is 8 mbar, hydrogen flow is 9000 sccm, methane flow is 100 sccm, deposition temperature is 1000 °C, and deposition time is 14 h.

[0110] Step (3): coating a liquid gallium metal catalytic layer by using a drop coating method.

[0111] The coating thickness is 200 nm, the mass of the liquid gallium metal used is 4 g, and the coating area is 8 cm 2 .

[0112] Step (4): inducing growth of a graphene coating in a non-parallel form by using a tube furnace high-temperature technology.

[0113] Specifically, the substrate on which the deposited ultrananocrystalline diamond coating and the liquid gallium metal catalytic layer are placed in a tube furnace, the vacuum degree is extracted to 30mtorr, the hydrogen flow is set to 100sccm, the growth temperature is 1000℃, and the growth time is 30min, to obtain a graphene coating with a thickness of 4μm.

[0114] Step (5): same as Example 1.

[0115] After the above prepared ultrananocrystalline diamond coating is annealed at high temperature in a tube furnace, the carbon atoms in the diamond diffuse to the liquid gallium metal catalytic layer, promoting the rearrangement of the carbon atoms and the seamless growth of the graphene sp2 bond structure in a non-parallel orientation on the diamond sp3 bond structure, forming a graphene-diamond composite coating. Experiments show that the graphene-diamond composite coating prepared above converts from diamond sp3 characteristic Raman peaks to sp2 characteristic Raman peaks, has a stable interface and good bonding strength. In the friction process, it has good wear resistance and service life.

[0116] Example 4

[0117] This embodiment provides a graphene-diamond composite coating material, which is prepared by the following method:

[0118] Step (1): etching and cleaning: same as Example 2.

[0119] Step (2): depositing a nanocrystalline diamond coating using hot wire chemical vapor deposition technology.

[0120] The thickness of the diamond coating is 8μm, and the average grain size is 70nm. The main process parameters of the hot wire chemical vapor deposition are as follows: deposition power is 2100W, deposition pressure is 2mbar, hydrogen flow is 12000sccm, methane flow is 300sccm, deposition temperature is 1000℃, and deposition time is 20h.

[0121] Step (3): coating a liquid gallium metal catalytic layer using a drop coating method.

[0122] The coating thickness is 300nm, the mass of the liquid gallium metal used is 5g, and the coating area is 10cm 2 .

[0123] Step (4): inducing the growth of a graphene coating in a non-parallel form using a tube furnace high-temperature technology.

[0124] Specifically, the substrate with the deposited nanocrystalline diamond coating and the liquid gallium metal catalytic layer is placed in a tube furnace, vacuum is extracted to 15 mtorr, hydrogen flow is set to 400 seem, growth temperature is set to 1100 °C, and growth time is set to 40 min, to obtain a graphene coating with a thickness of 5 μm.

[0125] Step (5): same as Example 1.

[0126] After the above-prepared nanocrystalline diamond coating is annealed at high temperature in a tube furnace, carbon atoms in the diamond diffuse to the liquid gallium metal catalytic layer, promoting rearrangement of the carbon atoms and seamless growth of the graphene sp2 bond structure in a non-parallel orientation on the diamond sp3 bond structure, to form a graphene-diamond composite coating. Experiments show that the graphene-diamond composite coating prepared above has a conversion from a diamond sp3 characteristic Raman peak to a sp2 characteristic Raman peak, a stable interface, and good bonding strength. In a cutting working condition, the graphene-diamond composite coating has good wear resistance and service life.

[0127] Example 5

[0128] This example provides a graphene-diamond composite coating material prepared by the following method:

[0129] Step (1): same as Example 1.

[0130] Step (2): depositing an ultrananocrystalline diamond coating by using hot wire chemical vapor deposition technology.

[0131] The diamond coating has a thickness of 1 μm and an average grain size of 5 nm. The main process parameters of the hot wire chemical vapor deposition are as follows: deposition power is 1500 W, deposition pressure is 1 mbar, hydrogen flow is 9000 seem, methane flow is 100 seem, deposition temperature is 900 °C, and deposition time is 30 h.

[0132] Step (3): coating a liquid copper metal catalytic layer by using a dripping method.

[0133] The liquid copper metal used has a mass of 0.5 g, and the coated area is the same as that in Example 1.

[0134] Step (4): inducing growth of a graphene coating in a non-parallel form by using tube furnace high-temperature technology.

[0135] Specifically, the substrate with the deposited nanocrystalline diamond coating and the liquid copper metal catalytic layer is placed in a tube furnace, vacuum is extracted to 15 mtorr, hydrogen flow is set to 400 seem, growth temperature is set to 1100 °C, and growth time is set to 40 min, to obtain a graphene coating with a thickness of 5 μm.

[0136] Step (5): same as Example 1.

[0137] The prepared ultra-nanocrystalline diamond coating is subjected to high-temperature annealing in a tube furnace, carbon atoms in the diamond diffuse to the liquid copper metal catalytic layer, promoting the rearrangement of carbon atoms and the seamless growth of graphene sp2 bond structure on the diamond sp3 bond structure in a non-parallel orientation, forming a graphene-diamond composite coating.

[0138] Example 6

[0139] This example provides a graphene-diamond composite coating material, which is prepared by the following method:

[0140] Step (1): same as Example 1.

[0141] Step (2): depositing a micron-sized diamond coating using hot filament chemical vapor deposition technology.

[0142] The thickness of the diamond coating is 15 μm, and the average grain size is 3000 nm. The main process parameters of hot filament chemical vapor deposition are as follows: deposition power is 2500 W, deposition pressure is 10 mbar, hydrogen flow rate is 18000 sccm, methane flow rate is 500 sccm, deposition temperature is 1000 °C, and deposition time is 6 h.

[0143] Step (3): coating a liquid nickel metal catalytic layer using the drop method.

[0144] The mass of the liquid nickel metal used is 5 g, and the coated area is the same as in Example 1.

[0145] Step (4): using tube furnace high-temperature technology to induce the growth of graphene coating in a non-parallel form.

[0146] Specifically, the substrate with deposited nanodiamond coating and liquid nickel metal catalytic layer is placed in a tube furnace, vacuumed to 30 mtorr, set to a hydrogen flow rate of 1000 sccm, a growth temperature of 1200 °C, and a growth time of 20 min, to obtain a graphene coating with a thickness of 5 μm.

[0147] Step (5): same as Example 1.

[0148] The prepared micron-sized diamond coating is subjected to high-temperature annealing in a tube furnace, carbon atoms in the diamond diffuse to the liquid nickel metal catalytic layer, promoting the rearrangement of carbon atoms and the seamless growth of graphene sp2 bond structure on the diamond sp3 bond structure in a non-parallel orientation, forming a graphene-diamond composite coating.

[0149] Comparative Example 1

[0150] The preparation method provided by the present comparative example is basically the same as that of example 1, except that the liquid metal catalytic layer in steps (3) and (5) is replaced by a non-liquid metal catalytic layer.

[0151] The experimental results show that the graphene coating obtained in the present comparative example is parallelly oriented. Using the same friction and wear test parameters, it is found that after a long time of friction, the friction curve shows severe jitter, and the wear resistance is poor.

[0152] Comparative Example 2

[0153] The preparation method provided by the present comparative example is basically the same as that of example 1, except that step (3) is not performed.

[0154] The experimental results show that the liquid gallium metal catalytic layer is not deposited on the surface of the diamond coating, which leads to the failure to catalyze the growth of vertical graphene. In addition, the diamond surface loses the lubrication and friction reduction effect of graphene, and a large number of wear particles appear in the friction interface, leading to the occurrence of abrasive wear, and the lubrication performance is poor.

[0155] Comparative Example 3

[0156] The preparation method provided by the present comparative example is basically the same as that of example 1, except that the deposition time in step (2) is replaced by 5h.

[0157] The experimental results show that the diamond coating obtained in the present comparative example has a thickness of only 500nm, and does not completely cover the surface of the complex workpiece substrate, which cannot effectively catalyze the growth of graphene by the catalytic layer, and the lubrication and wear resistance are poor.

[0158] Comparative Example 4

[0159] The preparation method provided by the present comparative example is basically the same as that of example 1, except that the growth temperature in step (4) is set to 600℃.

[0160] The experimental results show that at a lower annealing temperature, the carbon atoms in the diamond layer cannot effectively migrate to the catalytic layer, leading to slow growth and uneven coverage of the non-parallelly oriented graphene, and the adhesion between the diamond and the graphene is poor, and the wear resistance is poor.

[0161] Comparative Example 5

[0162] The preparation method provided by the present comparative example is basically the same as that of example 1, except that the hydrogen flow rate in step (4) is set to 50sccm.

[0163] The experimental results show that, under the condition of less hydrogen flow, there is not enough hydrogen to etch the edge of the defect, which increases the edge structural defect of the diamond and graphene coating, and reduces the adhesion of the diamond coating and the graphene coating.

[0164] Comparative Example 6

[0165] The preparation method provided by the present comparative example is basically the same as that of Example 1, except that in step (2), the thickness of the diamond coating is 20 μm.

[0166] Comparative Example 7

[0167] The preparation method provided by the present comparative example is basically the same as that of Example 2, except that in step (2), the average grain size of the microcrystalline diamond is 5000 nm.

[0168] Comparative Example 8

[0169] The preparation method provided by the present comparative example is basically the same as that of Example 1, except that in step (4), the thickness of the graphene coating is 0.6 nm.

[0170] Comparative Example 9

[0171] The preparation method provided by the present comparative example is basically the same as that of Example 1, except that in step (4), the thickness of the graphene coating is 6 μm.

[0172] Comparative Example 10

[0173] The preparation method provided by the present comparative example is basically the same as that of Example 1, except that in step (3), the coating amount of liquid metal gallium is 0.1 g, and the coating area remains unchanged.

[0174] Comparative Example 11

[0175] The preparation method provided by the present comparative example is basically the same as that of Example 1, except that in step (3), the coating amount of liquid metal gallium is 8 g, and the coating area remains unchanged.

[0176] Test Example

[0177] The performance of the composite coatings obtained in Examples 1-6 and Comparative Examples 1-11 above is compared, and the results are shown in Table 1.

[0178] The test conditions for the friction coefficient of the diamond coating and the graphene coating are ball-on-disc friction, a rotation speed of 0.2 m / s, a load of 5 N, and a rotation radius of 5 mm; the formula for calculating the wear rate is W = V / (F x S); wherein V is the wear amount, in mm 3 ; F is the sliding distance, in m; and S is the load, in N.

[0179] Table 1 performance comparison results table

[0180]

[0181]

[0182] As can be seen from Table 1, the graphene-diamond composite coating provided by the application has better wear resistance and low friction coefficient, which is beneficial to improve the service life of the corresponding wear-resistant parts.

[0183] In summary, the scheme provided by the application has at least the following advantages:

[0184] The graphene-diamond composite coating provided by the application can provide strong support due to the high mechanical properties of diamond, reduce the wrinkling and edge wrapping of graphene, thereby maintaining an ordered sliding interface and potentially improving the wear resistance of graphene. By introducing a liquid metal catalyst layer, the self-limiting dynamics characteristics thereof can be utilized to promote the seamless growth of the sp2 bond structure of graphene on the sp3 bond structure of diamond, providing the possibility for direct synthesis of graphene and combination with diamond, helping to form more covalent bond connections with graphene, enhancing the bonding strength of the graphene-diamond composite coating interface, and improving its stability under friction conditions. In addition, the above-mentioned graphene-diamond composite coating preparation method is simple and efficient, and can be deposited on workpiece substrates of complex shape and size in a large area, and applied on wear-resistant devices.

[0185] In a more preferred embodiment of the application, by controlling the thickness and grain of diamond in hot wire chemical vapor deposition within a suitable range, uniform coverage of the diamond coating on the surface of an irregular workpiece substrate can be ensured, and sufficient carbon source and bearing capacity can be provided for the growth of the graphene coating.

[0186] In a more preferred embodiment of the application, by controlling the amount of liquid metal in the liquid metal catalyst layer within a suitable range, the migration of carbon atoms in the diamond coating to the surface of the liquid metal catalyst layer can be activated, and the carbon atoms can be rearranged into a graphene coating to grow in a direction of vertical main non-parallel orientation.

[0187] In a more preferred embodiment of the application, by controlling the growth temperature and time of graphene within a suitable range, the graphene-diamond composite coating prepared can have better wear resistance.

[0188] The above is only a preferred embodiment of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A graphene-diamond composite coating, characterized in that, Including diamond coating and graphene coating; The diamond coating is applied to the surface of a cemented carbide substrate. The graphene sp2 bonds in the graphene coating are covalently bonded to the diamond sp3 bonds in the diamond coating. The graphene coating has a non-parallel graphene structure with predominantly perpendicular growth from the interface bonded to the diamond coating away from it. The thickness of the diamond coating is 1 μm to 15 μm. The diamond in the diamond coating is ultra-nanocrystalline diamond, nanocrystalline diamond, or microcrystalline diamond. The average grain size of the ultra-nanocrystalline diamond is 5 nm to 30 nm; the average grain size of the nanocrystalline diamond is 40 nm to 100 nm; the average grain size of the microcrystalline diamond is 1000 nm to 3000 nm; and the thickness of the graphene coating is 1 μm to 5 μm. The preparation of the graphene-diamond composite coating includes the following steps: preparing a diamond coating on the surface of a cemented carbide substrate, preparing a liquid catalyst layer on the surface of the diamond coating, preparing a graphene coating on the surface of the liquid catalyst layer, and etching the remaining liquid catalyst layer; Diamond coatings were prepared using hot-wire chemical vapor deposition (HFCVD). The preparation conditions for the diamond coatings included: deposition power of 1500W~2500W, deposition gas pressure of 1mbar~10mbar, hydrogen flow rate of 9000sccm~18000sccm, methane flow rate of 100sccm~500sccm, deposition temperature of 800℃~1000℃, and deposition time of 6h~30h. Liquid metal was applied to the surface of the diamond coating using a drop-casting method to form the liquid catalyst layer; the coating amount of the liquid metal was 0.5 g / cm³. 2 ~5g / cm 2 ; The graphene coating was prepared using a tube furnace high-temperature treatment technology. The preparation conditions of the graphene coating included: vacuum degree of quartz tube to 10 mtorr~30 mtorr, hydrogen flow rate of 100 sccm~1000 sccm, growth temperature of 700℃~1200℃, and growth time of 10 min~40 min.

2. The graphene-diamond composite coating according to claim 1, characterized in that, The graphene-diamond composite coating also has at least one of the following characteristics: Feature 1: The coefficient of friction of the graphene-diamond composite coating does not exceed 0.1; Feature 2: The wear rate of the graphene-diamond composite coating does not exceed 1×10⁻⁶. -6 mm 3 / Nm.

3. A method for preparing a graphene-diamond composite coating as described in claim 1 or 2, characterized in that, Includes the following steps: A diamond coating is prepared on the surface of a cemented carbide substrate, a liquid catalyst layer is prepared on the surface of the diamond coating, and a graphene coating is prepared on the surface of the liquid catalyst layer. The remaining liquid catalyst layer is etched; Diamond coatings were prepared using hot-wire chemical vapor deposition (HFCVD). The preparation conditions for the diamond coatings included: deposition power of 1500W~2500W, deposition gas pressure of 1mbar~10mbar, hydrogen flow rate of 9000sccm~18000sccm, methane flow rate of 100sccm~500sccm, deposition temperature of 800℃~1000℃, and deposition time of 6h~30h. Liquid metal was applied to the surface of the diamond coating using a drop-casting method to form the liquid catalyst layer; the coating amount of the liquid metal was 0.5 g / cm³. 2 ~5g / cm 2 ; The graphene coating was prepared using a tube furnace high-temperature treatment technology. The preparation conditions of the graphene coating included: vacuum degree of quartz tube to 10 mtorr~30 mtorr, hydrogen flow rate of 100 sccm~1000 sccm, growth temperature of 700℃~1200℃, and growth time of 10 min~40 min.

4. The preparation method according to claim 3, characterized in that, The cemented carbide substrate is first etched and cleaned, and then the diamond coating is prepared.

5. The preparation method according to claim 3, characterized in that, The liquid metal includes at least one of liquid gallium, liquid copper, and liquid nickel.

6. The preparation method according to claim 5, characterized in that, The liquid metal includes liquid gallium.

7. A graphene-diamond composite coating material, characterized in that, It includes a substrate and a graphene-diamond composite coating as described in claim 1 or 2 disposed on the surface of the substrate.

8. A wear-resistant part, characterized in that, The wear-resistant part has the graphene-diamond composite coating material as described in claim 7.

Images