A method for improving the friction and wear resistance of diamond coatings and articles

Abstract

The application provides a method and a part for improving the friction-reducing and wear-resisting performance of a diamond coating, and belongs to the technical field of surface engineering. The diamond coating part is placed on an inclined motion platform, the inclined motion platform is made to move regularly and stop at equal intervals in one direction, the laser is made to move repeatedly, the laser focus is ensured to be located on the surface of the initial diamond coating at all times, the surface of the initial diamond coating is simultaneously graphitized and flattened, a flattened graphite layer is formed, the thickness of the flattened graphite layer is greater than the height difference between the highest point and the lowest point of the topographic profile of the surface of the initial diamond coating, and finally the flattened graphite layer is mechanically cleaved to form carbon nanosheets. The method provided by the application can generate carbon nanosheets with high bonding strength with the diamond coating on the basis of realizing the controllable flattening of the surface of the diamond coating, and can effectively improve the friction-reducing and wear-resisting effect of the diamond coating.

Description

Technical Field

[0001] This invention relates to the field of surface engineering technology, and in particular to a method and component for improving the friction-reducing and wear-resistant properties of diamond coatings. Background Technology

[0002] Conventional diamond coatings possess many excellent properties that approach or even surpass those of natural diamonds, such as extremely high hardness and thermal conductivity, high wear resistance, and good chemical stability. Furthermore, the preparation of diamond coatings is not limited by the shape of the substrate and can be directly deposited on substrates with complex shapes. These superior properties make them ideal high-performance coating materials, and they have been widely used on the surfaces of sliding friction pairs requiring lubrication and wear resistance, such as cutting tools, mechanical seals, wire drawing dies, and bearings.

[0003] However, untreated conventional diamond coatings have uneven thickness and high surface roughness, resulting in poor interfacial friction conditions that cannot meet the requirements of high-performance engineering surfaces, severely restricting the further widespread application of diamond coatings. Currently, a large amount of research is dedicated to solving the problems faced by the further widespread application of conventional diamond coatings. Based on whether the grain size of the diamond coating changes, there are two main strategies: one is to change the grain size of the diamond coating, and the other is to use diamond coating surface smoothing technology.

[0004] Changing the grain size of the diamond coating involves controlling process parameters to reduce the grain size of the deposited diamond coating. The surface roughness of the diamond coating decreases with decreasing grain size, and the corresponding interfacial friction state is improved. However, reducing the grain size leads to an increase in grain boundary area. Since grain boundaries are mainly composed of amorphous carbon phases, this significantly reduces the adhesion of the diamond coating to the substrate and the hardness of the diamond coating. Although multilayer composite diamond coatings exhibit good impact resistance, substrate adhesion, and interfacial friction state, the coating thickness and the complexity of the deposition process are major obstacles to their widespread engineering application.

[0005] Diamond coating surface smoothing technology essentially involves the large-area removal of the protruding edges and corners of diamond coatings. Existing diamond coating smoothing technologies mainly include mechanical polishing, thermochemical polishing, chemical-assisted mechanical polishing, ion beam polishing, and laser polishing. While these technologies can achieve good polishing results to a certain extent, they all have limitations in their development and wider engineering applications. These limitations include complex operation, high cost, long processing time, inability to be used on complex shapes and large-area surfaces, and potential damage to the coating or limited improvement in coating performance. For example, mechanical polishing, thermochemical polishing, and chemical-assisted mechanical polishing are contact polishing methods. Although they can significantly reduce the surface roughness of diamond coatings and improve their performance to some extent, they are limited to planar and spherical surfaces, and their polishing efficiency is limited. Furthermore, due to the thinness of the diamond coating, the inherent long-term impact and vibration during contact polishing inevitably lead to damage to the diamond coating. Ion beam polishing and laser polishing are non-contact polishing methods that can polish irregular samples. However, ion beam polishing is limited by the size of the reaction chamber, making it unsuitable for polishing large-area diamond coatings. It is also relatively complex and costly. Laser polishing is currently the fastest method for polishing diamond coatings. From the perspective of the interaction between laser and diamond, it can be divided into thermal laser polishing and cold laser polishing. Thermal laser polishing is based on thermal diffusion, using a laser pulse with a relatively long duration to rapidly raise the temperature at the incident point on the diamond surface, causing graphitization phase transition and sublimation removal. Although thermal laser polishing is low-cost, due to localized thermal effects, a graphitized phase transition layer often remains on the polished surface, requiring additional annealing or acid pickling for removal. Furthermore, localized instantaneous thermal effects can cause the diamond coating to burn through or peel off. Cold laser polishing uses a laser pulse duration shorter than the thermal diffusion time, enabling one-step polishing without surface graphitization. However, the high equipment cost limits the development of this technology to some extent. Furthermore, although existing diamond coating planarization techniques can reduce the roughness of diamond coatings to some extent, they have limited effect on improving the friction performance of diamond coating surfaces. For example, under dry friction conditions, it is difficult to maintain a stable coefficient of friction below 0.1 when facing friction pairs such as steel, titanium alloys, and alumina. Summary of the Invention

[0006] The purpose of this invention is to provide a method and a component for improving the friction-reducing and wear-resistant properties of diamond coatings. The method provided by this invention can generate carbon nanosheets with high bonding strength to the diamond coating while achieving controllable smoothing of the diamond coating surface, which can effectively improve the friction-reducing and wear-resistant effects of the diamond coating.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for improving the friction-reducing and wear-resistant properties of diamond coatings, comprising the following steps:

[0009] A diamond-coated part is provided, the diamond-coated part comprising a substrate and an initial diamond coating attached to the surface of the substrate, wherein the height difference between the highest and lowest points of the topographic profile of the surface of the initial diamond coating is denoted as the minimum uniform ablation thickness.

[0010] The diamond-coated part is placed on an inclined motion platform, which then performs regular, unidirectional, and equally spaced pauses. Simultaneously, a laser performs a repetitive scribing motion, with the direction of the laser's repetitive scribing motion perpendicular to the direction of movement of the diamond-coated part. This achieves simultaneous graphitization and planarization of the initial diamond coating surface, resulting in a precursor device. The precursor device includes a substrate, an ungraphitized diamond coating attached to the substrate surface, and a planarized graphite layer attached to the surface of the ungraphitized diamond coating. The thickness of the planarized graphite layer is greater than the minimum uniform ablation thickness, and during the simultaneous graphitization and planarization process, the laser focus remains on the surface of the initial diamond coating.

[0011] The smoothed graphite layer is mechanically cleaved to form a carbon nanosheet layer composed of carbon nanosheets.

[0012] Preferably, the initial diamond coating thickness in the diamond-coated part is 2–10 μm, and the surface roughness is 0.4–1 μm.

[0013] Preferably, the angle between the tilting motion platform and the horizontal plane is 5° to 89°.

[0014] Preferably, the process of simultaneous graphitization and planarization further includes: heat dissipation treatment of the substrate of the diamond-coated part.

[0015] Preferably, during the synchronous graphitization and planarization process, the motion relationship between the tilting motion platform on which the diamond-coated part is placed and the laser satisfies the following: the laser's single scribing time is equal to the pause time between two adjacent movements of the tilting motion platform, and the pause time between two adjacent laser scribings is equal to the time of a single movement of the tilting motion platform; wherein, both the tilting motion platform and the laser move at a constant speed during the motion.

[0016] Preferably, the tilting motion platform on which the diamond-coated part is placed includes, before its first movement, performing a pre-scribing scan with the laser to form graphite lines.

[0017] Preferably, the average power of the laser during the pre-scribing scan is 0.1 to 2 W higher than the average power of the laser during the repetitive scribing motion.

[0018] Preferably, the laser pulse width during the pre-scribing scan is independent of the laser pulse width during the repetitive scribing motion, and is greater than 1 ps.

[0019] Preferably, the difference between the thickness of the smoothed graphite layer and the minimum uniform ablation thickness is 0.1 to 1 μm.

[0020] The present invention provides a component prepared by the method described in the above technical solution, comprising a substrate, a non-graphitized diamond coating attached to the surface of the substrate, and a carbon nanosheet layer attached to the surface of the non-graphitized diamond coating, wherein the carbon nanosheet layer is composed of carbon nanosheets.

[0021] Beneficial Effects: This invention uses an initial diamond coating as raw material. First, a laser is used to induce graphitization on the surface of the initial diamond coating while simultaneously controlling the surface smoothing to form a smoothed graphite layer. Then, the smoothed graphite layer is mechanically cleaved into carbon nanosheets, thereby generating carbon nanosheets with high bonding strength to the diamond coating while achieving controllable surface smoothing. Results from the embodiments show that the diamond coating surface treated by the method of this invention exhibits better friction reduction and wear resistance under dry friction and heavy load conditions, while effectively suppressing adhesive wear of friction pairs. Furthermore, the method provided by this invention is simple to operate, highly efficient, and low-cost, which is conducive to its widespread application.

[0022] Furthermore, compared to other methods for preparing carbon nanosheets on the surface of diamond coatings (such as chemical vapor deposition, which cannot control the thickness and surface roughness of the diamond coating and is complex and time-consuming), the method of the present invention can precisely control the thickness and surface roughness of the diamond coating while generating carbon nanosheets with high bonding strength with the diamond coating, thus meeting the application requirements of various scenarios. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating simultaneous graphitization and planarization in an embodiment of the present invention;

[0024] Figure 2 The image shows a scanning electron microscope (SEM) image of the surface of the diamond-coated carbon nanosheet fabrication prepared in Example 1.

[0025] Figure 3 The surface Raman spectrum of the diamond-coated carbon nanosheet fabrication prepared in Example 1;

[0026] Figure 4Transmission electron microscope (TEM) image of a cross-section of the diamond-coated carbon nanosheet fabrication prepared in Example 1;

[0027] Figure 5 The friction coefficient curves of the diamond-coated carbon nanosheet part prepared in Example 1 and the original diamond-coated part are compared.

[0028] Figure 6 Comparison of the wear surfaces of the diamond-coated carbon nanosheet part prepared in Example 1 and the original diamond-coated part;

[0029] Figure 7 The image shows a comparison of the wear surfaces of the friction pair corresponding to the diamond-coated carbon nanosheet part prepared in Example 1 and the original diamond-coated part.

[0030] Figure 8 The image shows a scanning electron microscope (SEM) image of the surface after laser irradiation treatment in Comparative Example 1. Detailed Implementation

[0031] This invention provides a method for improving the friction-reducing and wear-resistant properties of diamond coatings, comprising the following steps:

[0032] A diamond-coated part is provided, the diamond-coated part comprising a substrate and an initial diamond coating attached to the surface of the substrate, wherein the height difference between the highest and lowest points of the topographic profile of the surface of the initial diamond coating is denoted as the minimum uniform ablation thickness.

[0033] The diamond-coated part is placed on an inclined motion platform, which then performs regular, unidirectional, and equally spaced pauses. Simultaneously, a laser performs a repetitive scribing motion, with the direction of the laser's repetitive scribing motion perpendicular to the direction of movement of the diamond-coated part. This achieves simultaneous graphitization and planarization of the initial diamond coating surface, resulting in a precursor device. The precursor device includes a substrate, an ungraphitized diamond coating attached to the substrate surface, and a planarized graphite layer attached to the surface of the ungraphitized diamond coating. The thickness of the planarized graphite layer is greater than the minimum uniform ablation thickness, and during the simultaneous graphitization and planarization process, the laser focus remains on the surface of the initial diamond coating.

[0034] The smoothed graphite layer is mechanically cleaved to form a carbon nanosheet layer composed of carbon nanosheets.

[0035] This invention provides a diamond-coated part, comprising a substrate and an initial diamond coating adhered to the surface of the substrate. This invention does not specifically limit the material and size of the substrate; any substrate with materials and dimensions known to those skilled in the art can be used. Specifically, the substrate material can be steel, titanium alloy, or cemented carbide; the cemented carbide is preferably YG6 cemented carbide; the preferred dimensions of the substrate are: width × length × thickness of (2–16) mm × (2–16) mm × (2–4) mm, specifically 8 mm × 8 mm × 2 mm, 10 mm × 10 mm × 4 mm, 12 mm × 12 mm × 4 mm, or 16 mm × 16 mm × 4 mm. This invention does not impose any particular limitations on the thickness and surface roughness of the initial diamond coating; the selection can be made according to the actual application scenario. In this invention, the thickness of the initial diamond coating is preferably 2–10 μm, specifically 8 μm, 9 μm, or 10 μm. The thickness of the initial diamond coating is specifically the distance from the median line of the morphological profile to the interface with the substrate. The surface roughness is preferably 0.4–1 μm, specifically 0.6 μm, 0.7 μm, or 0.8 μm. This invention does not impose any particular limitations on the preparation method of the initial diamond coating; it can be prepared using a hot-wire chemical vapor deposition method.

[0036] This invention defines the height difference between the highest and lowest points of the initial diamond coating surface morphology as the minimum uniform ablation thickness. Preferably, this invention utilizes a profilometer to measure the morphology of the initial diamond coating surface, extracts the height difference between the highest and lowest points of the morphology, and defines this height difference as the minimum uniform ablation thickness. This invention does not specifically limit the type of profilometer used; either a contact profilometer or an optical profilometer is acceptable, preferably an optical profilometer, and more preferably a three-dimensional confocal optical profilometer.

[0037] In this invention, the diamond-coated part is preferably subjected to ultrasonic cleaning to remove surface oil stains and impurities, which helps to ensure the subsequent controllable and simultaneous graphitization and planarization of the initial diamond coating surface. In this invention, the cleaning agent used for ultrasonic cleaning is preferably anhydrous ethanol, and the ultrasonic cleaning time is preferably 3-6 minutes; this invention does not have a special limitation on the power of ultrasonic cleaning, and any power known to those skilled in the art can be used.

[0038] After ultrasonic cleaning of the diamond-coated part, the present invention places the ultrasonically cleaned diamond-coated part on an inclined motion platform, causing the inclined motion platform on which the diamond-coated part is placed to perform regular unidirectional, equally spaced pauses, while a laser performs repetitive scribing motion, with the direction of the laser's repetitive scribing motion perpendicular to the direction of movement of the diamond-coated part. This achieves simultaneous graphitization and planarization of the initial diamond coating surface, resulting in a precursor device. The precursor device includes a substrate, an ungraphitized diamond coating attached to the surface of the substrate, and a planarized graphite layer attached to the surface of the ungraphitized diamond coating. The thickness of the planarized graphite layer is greater than the minimum uniform ablation thickness. In the present invention, the angle between the inclined motion platform and the horizontal plane is preferably 5° to 89°, more preferably 60° to 89°, and even more preferably 75° to 80°.

[0039] In this invention, during the simultaneous graphitization and planarization process, the laser focus is preferably always located on the surface of the initial diamond coating. This invention preferably achieves simultaneous graphitization and planarization of the diamond coating surface by controlling the motion relationship between the diamond-coated workpiece and the laser scribing, ensuring the laser focus remains on the initial diamond coating surface. In this invention, during the simultaneous graphitization and planarization process, the motion relationship between the tilting motion platform holding the diamond-coated workpiece and the laser preferably satisfies the following: the laser scribing time for a single stroke is equal to the pause time between two adjacent strokes of the tilting motion platform, and the pause time between two adjacent laser scribing strokes is equal to the time of a single stroke of the tilting motion platform; wherein, both the tilting motion platform and the laser preferably move at a constant speed during the motion.

[0040] In this invention, the laser pulse width is preferably greater than 1 ps during the repetitive scribing motion, more preferably 1–1000 ns, and even more preferably 10–100 ns. In this invention, the thickness of the planarized graphite layer formed by laser irradiation is significantly affected by the laser pulse width, exhibiting an exponential relationship; the larger the laser pulse width, the greater the thickness of the planarized graphite layer and the greater the heat-affected depth. The initial diamond coating is relatively thin, and the thermodynamic properties between the initial diamond coating and the substrate differ significantly, which can easily lead to coating burn-through, coating detachment, and inaccurate control of the planarization graphitization process during laser irradiation. This invention preferably controls the laser pulse width within the aforementioned range, which helps to avoid the above problems.

[0041] In this invention, the average power of the laser during the repetitive line-drawing motion is preferably 3-20W, more preferably 10-16W, and even more preferably 13-14W. Other parameters of the laser during the repetitive line-drawing motion can be selected according to actual conditions. In embodiments of this invention, the laser wavelength is preferably 1064nm, 532nm, or 355nm; the pulse frequency is preferably 10-200kHz, more preferably 20-50kHz; and the beam waist spot diameter is preferably 10-80μm, specifically 10μm, 20μm, 50μm, 60μm, or 80μm.

[0042] In this invention, the laser single-stroke scribing speed can be selected according to actual conditions; in the embodiments of this invention, the laser single-stroke scribing speed is preferably 20-80 mm / s, more preferably 30-40 mm / s. In this invention, the movement speed of the tilting motion platform is preferably 1-5 mm / s, more preferably 4-5 mm / s; the movement spacing of the tilting motion platform (i.e., the displacement of the tilting motion platform moving at equal intervals) can be selected according to actual conditions; in the embodiments of this invention, the movement spacing of the tilting motion platform is preferably 1-4 μm, more preferably 1-2 μm.

[0043] This invention uses laser irradiation to graphitize diamond. The laser's focal plane is typically horizontal. If the workpiece is tilted, it will not coincide with the horizontal plane, creating an angle. In this case, during laser filling scans, many areas of the workpiece will not be at the focal point, leading to uneven ablation (i.e., graphitization) of the workpiece surface. For example, the workpiece surface near the focal point may be ablated, while areas significantly deviated from the focal point may not be ablated. This invention achieves full filling scans of the entire initial diamond coating surface by controlling the movement of the diamond-coated workpiece. Specifically, the laser scans one row of the workpiece at the focal point, then the workpiece moves to expose an adjacent new row to the laser focal point, and the laser scans again, repeating this cycle until the entire initial diamond coating surface is filled.

[0044] In this invention, the simultaneous graphitization and planarization process preferably further includes: heat dissipation treatment of the substrate of the diamond-coated part. In this invention, the heat dissipation treatment preferably includes air cooling or water cooling; this invention preferably uses heat dissipation treatment to reduce the temperature at the initial diamond coating and substrate interface, thereby reducing interfacial thermal stress.

[0045] In the process of simultaneous graphitization and planarization described in this invention, the surface of the initial diamond layer is irradiated by a high-energy laser beam, causing the temperature at the incident point to rise rapidly. When the temperature exceeds the diamond graphitization temperature (700°C), the diamond surface will graphitize. This invention, through simultaneous graphitization and planarization, causes the diamond on the surface of the initial diamond layer to graphitize (the portion of diamond in contact with the substrate surface does not graphitize) and simultaneously and controllably planarizes the coating surface, obtaining the precursor device. The precursor device includes a substrate, an ungraphitized diamond coating attached to the substrate surface, and a planarized graphite layer attached to the surface of the ungraphitized diamond coating. In this invention, the difference between the thickness of the planarized graphite layer (denoted as the ultimate ablation thickness) and the minimum uniform ablation thickness is preferably 0.1–1 μm, more preferably 0.1–0.5 μm, specifically 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, or 0.5 μm. In this invention, the surface roughness of the ungraphitized diamond coating is preferably 0.30 to 0.38 μm, more preferably 0.30 to 0.34 μm.

[0046] Unlike other diamond materials, diamond coatings are very thin. Conventional laser irradiation methods involve vertical laser irradiation, where the laser beam is perpendicular to the workpiece surface. During vertical laser irradiation, the diamond coating is easily burned through. This invention employs a tilted laser scanning method, where the laser beam is not perpendicular to the workpiece surface (in specific embodiments of this invention, the laser beam is perpendicular to the horizontal plane, and the diamond-coated workpiece is placed on a tilted motion platform, thus tilting the workpiece to form an angle with the horizontal plane, ensuring that the laser beam is not perpendicular to the surface of the diamond-coated workpiece). This reduces the depth of the effect of laser irradiation overheating, achieving controllable flat graphitization of the diamond coating surface. It also reduces the sudden peeling of the coating caused by high instantaneous thermal stress at the interface between the diamond coating and the substrate.

[0047] In this invention, the tilting motion platform on which the diamond-coated part is placed preferably includes, before its first movement, performing a pre-scribing scan with the laser to form a graphite line. In this invention, the number of pre-scribing scans is preferably greater than one, more preferably five. This invention preferably forms a graphite line through multiple pre-scribing scans, which facilitates the subsequent simultaneous graphitization and planarization of the initial diamond coating surface to obtain a smooth graphite layer. In this invention, the average power of the laser during the pre-scribing scan is preferably 0.1–2 W higher than the average power of the laser during the repeated scribing motion, more preferably 0.1–0.5 W higher, and even more preferably 0.2–0.3 W higher. Other parameters of the laser during the pre-scribing scan are preferably the same as those during the repeated scribing motion, and will not be repeated here.

[0048] In this invention, compared to graphite, diamond has very weak light absorption. Furthermore, because the initial diamond coating is thin, it is easily burned through. This invention uses pre-scribed scanning to lower the initial graphitization threshold, ensuring that subsequent initial graphitization of the diamond coating surface is performed while simultaneously achieving a controllable smooth coating surface. Specifically, diamond has good light transmittance and weak laser absorption. During laser irradiation, diamond defects absorb more energy, leading to initial graphitization and diffusion. Since diamond defects are random, the graphite generated at these defects is also random. This invention, through pre-scribed scanning, first forms a uniform graphite line at the starting point of scanning the entire initial diamond coating surface. Graphite's weak light transmittance and easy light absorption allow the initial graphite line to uniformly absorb laser energy and diffuse towards the subsequent filling direction, forming uniform graphite. Subsequent laser energy is absorbed by the graphite and continues to diffuse, ultimately resulting in a smooth graphitized surface across the entire initial diamond coating.

[0049] After obtaining graphite lines through pre-scribing scanning, the present invention causes an inclined motion platform on which the diamond-coated part is placed to perform regular unidirectional, equally spaced pauses, while simultaneously causing a laser to perform repeated scribing motions. The direction of the laser's repeated scribing motions is perpendicular to the direction of movement of the diamond-coated part, thereby achieving synchronous graphitization and planarization of the initial diamond coating surface to obtain a precursor device. Figure 1 This is a schematic diagram of simultaneous graphitization and planarization in an embodiment of the present invention. The left side is a processing schematic diagram, and the right side is a schematic diagram of the relationship between the diamond-coated part and the laser movement. First, the laser performs a pre-scribing scan at the starting point of the initial diamond coating surface to form a graphite line. Then, the inclined motion platform on which the diamond-coated part is placed performs a regular unidirectional, equally spaced stop motion, while the laser performs a repetitive scribing motion. The direction of the laser's repetitive scribing motion is perpendicular to the direction of movement of the diamond-coated part. That is, after each equally spaced movement of the diamond-coated part stops, the laser scans. After each laser scan stops, the diamond-coated part performs equally spaced movement, and this cycle continues until the entire initial diamond coating surface is filled and scanned to obtain the precursor device.

[0050] After obtaining the precursor device, the present invention mechanically cleaves the planarized graphite layer in the precursor device to form a carbon nanosheet layer composed of carbon nanosheets. In this invention, the mechanical cleaving preferably includes scratch mechanical cleaving or tape cleaving, more preferably scratch mechanical cleaving. In this invention, the scratching speed of the scratch mechanical cleaving is preferably 2–4 m / s, more preferably 3–4 m / s; the pressure is preferably 2–4 N, more preferably 2–3 N.

[0051] This invention provides a component prepared using the method described above, comprising a substrate, a non-graphitized diamond coating adhered to the surface of the substrate, and a carbon nanosheet layer adhered to the surface of the non-graphitized diamond coating, wherein the carbon nanosheet layer is composed of carbon nanosheets. In this invention, the lateral dimensions of the carbon nanosheets are preferably in the submicron range, more preferably 0.1–0.6 μm; the carbon nanosheets have a multilayer structure, preferably less than 20 layers. The component provided by this invention prepares carbon nanosheets based on rapid surface planarization of the diamond coating, precisely controlling the thickness and surface roughness of the diamond coating while generating carbon nanosheets with high bonding strength to the diamond coating. This meets the application requirements of various scenarios, such as diamond-coated cutting tools, diamond-coated mechanical seals, or diamond-coated wire drawing dies. Diamond-coated cutting tools require a certain thickness of the diamond coating, typically 3–4 μm, while diamond-coated mechanical seals and diamond-coated wire drawing dies require a high degree of flatness in the diamond coating.

[0052] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] Example 1

[0054] (1) Provide a diamond-coated part, the diamond-coated part comprising a substrate and an initial diamond coating attached to the surface of the substrate, the substrate being YG6 cemented carbide, the width × length × thickness of the substrate being 10mm × 10mm × 4mm, the thickness of the initial diamond coating being 9μm and the surface roughness being 0.7μm; the morphological profile of the surface of the initial diamond coating is measured using a three-dimensional confocal optical profilometer, and the height difference (i.e., the minimum uniform ablation thickness) between the lowest and highest points of the morphological profile is extracted to be 2μm; the diamond-coated part is ultrasonically cleaned in anhydrous ethanol for 3 minutes to remove surface oil stains and impurities;

[0055] (2) Place the cleaned diamond-coated part from step (1) on an inclined motion platform with an angle of 80° to the horizontal plane. Use a laser to perform five pre-scribing scans on the initial diamond coating surface to form a graphite line at the starting point. Then, make the inclined motion platform on which the diamond-coated part is placed perform regular unidirectional, equally spaced pauses, while the laser performs repeated scribing motions. The direction of the laser's repeated scribing motions is perpendicular to the direction of movement of the diamond-coated part, thereby achieving simultaneous graphitization and smoothing of the initial diamond coating surface. A precursor device is obtained, comprising a substrate, an ungraphitized diamond coating attached to the surface of the substrate, and a planarized graphite layer attached to the surface of the ungraphitized diamond coating. During the simultaneous graphitization and planarization process, the substrate of the diamond-coated component is subjected to air cooling heat dissipation treatment, and the motion relationship between the tilting motion platform on which the diamond-coated component is placed and the laser satisfies the following: the laser's single scribing time is equal to the pause time between two adjacent movements of the tilting motion platform, and the pause time between two adjacent laser scribings is equal to the time of a single movement of the tilting motion platform.

[0056] The inclined motion platform and the laser move at a constant speed during the motion. The speed of the inclined motion platform is 5 mm / s, and the movement interval is 2 μm. The average power of the laser during the pre-scribing scan is 16.5 W, and the average power of the laser during the repeated scribing motion is 16 W. Other parameters of the laser during the pre-scribing scan and the repeated scribing motion include: scribing speed (i.e., scanning speed) of 40 mm / s, pulse width of 100 ns, laser wavelength of 1064 nm, pulse frequency of 20 kHz, and beam waist spot diameter of 60 μm.

[0057] The thickness (i.e., the ultimate ablation thickness) of the planarized graphite layer in the precursor device is 2.3 μm, and the surface roughness of the ungraphitized diamond coating is 0.34 μm.

[0058] (3) The precursor device in step (2) is mechanically cleaved by a reciprocating rubbing device to form a carbon nanosheet layer composed of carbon nanosheets on the smoothed graphite layer, that is, the carbon nanosheet layer is formed on the surface of the ungraphitized diamond coating to obtain a diamond coating-carbon nanosheet layer part; the rubbing speed of the mechanical cleaving is 2m / s and the pressure is 2N.

[0059] Example 2

[0060] The method described in Example 1 is followed, with the following differences:

[0061] (1) The minimum uniform ablation thickness is 2.2 μm; the initial diamond coating thickness is 10 μm, the surface roughness is 0.8 μm, and the width × length × thickness of the substrate is 16 mm × 16 mm × 4 mm;

[0062] (2) The angle between the tilting motion platform and the horizontal plane is 75°; the average power of the laser during pre-scribing scanning is 14.3W, and the average power of the laser during repeated scribing motion is 14W; the thickness of the planarized graphite layer in the precursor device is 2.6μm, and the surface roughness of the ungraphitized diamond coating is 0.38μm.

[0063] (3) The scratching speed of the mechanical cleavage is 3m / s and the pressure is 4N.

[0064] Example 3

[0065] The method described in Example 1 is followed, with the following differences:

[0066] (1) The minimum uniform ablation thickness is 1.8 μm; the surface roughness of the initial diamond coating is 0.8 μm; and the width × length × thickness of the substrate is 12 mm × 12 mm × 4 mm.

[0067] (2) The movement spacing of the tilting motion platform is 1 μm; the average power of the laser during the pre-scribing scan is 10.2 W, and the average power of the laser during the repeated scribing motion is 10 W. Other parameters of the laser during the pre-scribing scan and the repeated scribing motion include: scanning speed of 20 mm / s, pulse width of 10 ns, laser wavelength of 355 nm, pulse frequency of 50 kHz, and beam waist spot diameter of 50 μm; the thickness of the planarized graphite layer in the precursor device is 2 μm, and the surface roughness of the ungraphitized diamond coating is 0.30 μm.

[0068] (3) The scratching speed of the mechanical cleavage is 3 m / s.

[0069] Example 4

[0070] The method described in Example 1 is followed, with the following differences:

[0071] (1) The minimum uniform ablation thickness is 1.5 μm; the initial diamond coating thickness is 8 μm, the surface roughness is 0.6 μm, and the width × length × thickness of the substrate is 8 mm × 8 mm × 2 mm.

[0072] (2) The movement spacing of the tilting motion platform is 1 μm; the average power of the laser during the pre-scribing scan is 13.3 W, and the average power of the laser during the repeated scribing motion is 13 W. Other parameters of the laser during the pre-scribing scan and the repeated scribing motion include: scanning speed of 20 mm / s, pulse frequency of 20 kHz, and beam waist spot diameter of 20 μm; the thickness of the planarized graphite layer in the precursor device is 1.6 μm, and the surface roughness of the ungraphitized diamond coating is 0.30 μm.

[0073] (3) The scratching speed of the mechanical cleavage is 4 m / s and the pressure is 3 N.

[0074] Characterization and performance testing

[0075] Figure 2 The image shows a scanning electron microscope (SEM) image of the surface of the diamond-coated carbon nanosheet fabrication prepared in Example 1. The results show that the surface of the diamond-coated carbon nanosheet fabrication prepared in Example 1 has a large number of densely arranged carbon nanosheet structures, and the lateral size of the carbon nanosheets is in the submicron range (0.1-0.6 μm).

[0076] Figure 3 The surface Raman spectrum of the diamond-coated carbon nanosheet fabrication prepared in Example 1 is shown. The results indicate that the surface of the diamond-coated carbon nanosheet fabrication prepared in Example 1 has four characteristic peaks: D peak (1352 cm⁻¹). -1 ), G peak (1582cm) -1 ), 2D peak (2714cm) -1 ) and D+D' peak (2945cm) -1 ), where I 2D / I G The high ratio of 0.42 indicates that the densely arranged sheet-like structure is a multilayer (less than 20 layers) carbon nanosheet structure.

[0077] Figure 4 The image shows a cross-sectional transmission electron microscope (TEM) image of the diamond-coated carbon nanosheet component prepared in Example 1 (the Pt protective layer in the image is a protective layer set during sample preparation to protect the integrity of the surface structure of the component when taking TEM images). The results show that the diamond coating and the cemented carbide substrate maintain a good interfacial contact in the diamond-coated carbon nanosheet component prepared in Example 1, and the diamond coating structure is intact without obvious cracking. The thickness is 6.7 μm, indicating that the instantaneous high temperature generated during laser scanning is well confined in the depth direction.

[0078] The diamond-coated carbon nanosheets prepared in Example 1 were compared with the original diamond-coated part through a tribological wear test. Specifically, a tribological wear tester was used to evaluate the improvement of the tribological properties of the diamond-coated part by the method provided in this invention. The test parameters were as follows: load 100 N; reciprocating sliding length 2 mm; number of cycles 240,000; reciprocating frequency 6 Hz; friction pair was SUS304 friction pin.

[0079] Figure 5 The graph shows a comparison of the friction coefficient curves of the diamond-coated carbon nanosheet part prepared in Example 1 and the original diamond-coated part. The results show that, compared with the original diamond-coated part, the friction coefficient of the diamond-coated carbon nanosheet part prepared in Example 1 is reduced by 67%, and the friction coefficient is less than 0.1 with less fluctuation, indicating an excellent friction reduction effect.

[0080] Figure 6 The image shows a comparison of the worn surfaces of the diamond-coated carbon nanosheet part prepared in Example 1 and the original diamond-coated part. The results show that after 24,000 cycles of reciprocating sliding under heavy load and dry friction conditions, the grains on the surface of the original diamond-coated part were worn flat, accompanied by a large amount of adhering material; while no obvious adhering material was found on the surface of the diamond-coated carbon nanosheet part prepared in Example 1, and many sheet-like structures were still retained on the surface, indicating an excellent wear reduction effect.

[0081] Figure 7 The images show a comparison of the wear surfaces of the friction pair corresponding to the diamond-coated carbon nanosheet component prepared in Example 1 and the original diamond-coated component. The results show that the wear surface of the original diamond-coated component exhibits numerous pores, corresponding to adhesions on the diamond coating surface, indicating significant adhesive wear. However, no large pores were found on the wear surface of the friction pair corresponding to the diamond-coated carbon nanosheet component prepared in Example 1, indicating that adhesive wear was significantly suppressed.

[0082] Comparative Example 1

[0083] The initial diamond coating of the diamond-coated part in Example 1 was treated using the laser irradiation treatment method described in CN 112479203 A (A method and part for in-situ generation of anti-friction graphene film on diamond surface). Specifically, laser irradiation treatment was performed using a vertical irradiation method. The specific operating parameters included: laser wavelength of 1064nm, pulse frequency of 20kHz, spot diameter of 20μm, average laser power of 5W, scanning speed of 15mm / s, and scanning spacing of 1μm.

[0084] Figure 8The image shown is a scanning electron microscope image of the surface after laser irradiation in Comparative Example 1. The results show that the diamond coating was directly burned through and detached, exposing the cemented carbide substrate.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the friction-reducing and wear-resistant properties of diamond coatings, comprising the following steps: A diamond-coated part is provided, the diamond-coated part comprising a substrate and an initial diamond coating attached to the surface of the substrate, wherein the height difference between the highest and lowest points of the topographic profile of the surface of the initial diamond coating is denoted as the minimum uniform ablation thickness. The diamond-coated part is placed on an inclined motion platform, which then performs regular, unidirectional, and equally spaced pauses. Simultaneously, a laser performs a repetitive scribing motion, with the direction of the laser's repetitive scribing motion perpendicular to the direction of movement of the diamond-coated part. This achieves simultaneous graphitization and planarization of the initial diamond coating surface, resulting in a precursor device. The precursor device includes a substrate, an ungraphitized diamond coating attached to the substrate surface, and a planarized graphite layer attached to the surface of the ungraphitized diamond coating. The thickness of the planarized graphite layer is greater than the minimum uniform ablation thickness, and during the simultaneous graphitization and planarization process, the laser focus remains on the surface of the initial diamond coating. The smoothed graphite layer is mechanically cleaved to form a carbon nanosheet layer composed of carbon nanosheets.

2. The method according to claim 1, characterized in that, The initial diamond coating thickness in the diamond-coated part is 2–10 μm, and the surface roughness is 0.4–1 μm.

3. The method according to claim 1, characterized in that, The angle between the tilting motion platform and the horizontal plane is 5° to 89°.

4. The method according to claim 1, characterized in that, The process of simultaneous graphitization and planarization also includes: heat dissipation treatment of the substrate of the diamond-coated part.

5. The method according to any one of claims 1 to 4, characterized in that, During the synchronous graphitization and planarization process, the motion relationship between the tilting motion platform on which the diamond-coated part is placed and the laser satisfies the following: the laser's single scribing time is equal to the pause time between two adjacent movements of the tilting motion platform, and the pause time between two adjacent laser scribings is equal to the time of a single movement of the tilting motion platform; wherein, both the tilting motion platform and the laser move at a constant speed during the motion.

6. The method according to claim 5, characterized in that, Before its first movement, the tilting motion platform on which the diamond-coated part is placed includes: performing a pre-scribing scan with the laser to form graphite lines.

7. The method according to claim 6, characterized in that, The average power of the laser during the pre-scribing scan is 0.1 to 2 W higher than the average power of the laser during the repetitive scribing motion.

8. The method according to claim 6 or 7, characterized in that, The laser pulse width during the pre-scribing scan is independent of the laser pulse width during the repeated scribing motion and is greater than 1 ps.

9. The method according to claim 1, characterized in that, The difference between the thickness of the smoothed graphite layer and the minimum uniform ablation thickness is 0.1 to 1 μm.

10. An article, prepared by the method according to any one of claims 1 to 9, comprising a substrate, a non-graphitized diamond coating attached to the surface of the substrate, and a carbon nanosheet layer attached to the surface of the non-graphitized diamond coating, wherein the carbon nanosheet layer is composed of carbon nanosheets.

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