A method for preparing a titanium alloy surface DLC coating

Abstract

The application belongs to the technical field of metal surface treatment, and discloses a preparation method of a DLC coating on a titanium alloy surface, which comprises the following steps: cleaning and drying a titanium alloy substrate, laser polishing treatment, laser texture treatment, deburring treatment and DLC coating deposition; the laser polishing treatment is carried out in a nitrogen atmosphere, so that the grain refinement of the titanium alloy surface and the generation of TiN crystals are realized, a transition layer with moderate hardness is provided for the DLC coating, the hardness difference between the titanium alloy and the DLC coating is moderated, the stress difference and stress concentration phenomenon caused by external force or temperature change are reduced, and the bonding force is enhanced; meanwhile, the microstructure generated by the laser texture treatment increases the contact area of the DLC coating and the titanium alloy substrate, and a mechanical interlocking structure is formed, so that the adhesion of the DLC coating is further enhanced; therefore, the bonding force between the DLC coating and the titanium alloy substrate can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of metal surface treatment technology, and more specifically, to a method for preparing a DLC coating on a titanium alloy surface. Background Technology

[0002] Titanium alloys, due to their superior properties such as high specific strength, corrosion resistance, and excellent biocompatibility, are widely used in numerous fields including aerospace, marine engineering, biomedicine, and automotive. In practical applications, the surface properties of titanium alloy components often need to be optimized before use. Among various surface treatment technologies, depositing a diamond-like carbon (DLC) coating on the surface of titanium alloys is an effective means of improving their surface properties. DLC coatings possess advantages such as high hardness, low coefficient of friction, good wear resistance, and corrosion resistance, which can significantly improve the performance of titanium alloy components during use, such as extending service life and increasing work efficiency.

[0003] However, titanium alloys themselves have relatively low hardness (generally not exceeding 350 HV), while DLC coatings have relatively high hardness, reaching over 1500 HV. This significant hardness difference results in a severe hardness mismatch at the interface between the titanium alloy surface and the DLC coating. When subjected to external impact or thermal expansion and contraction due to temperature changes, the higher hardness of the DLC layer leads to less deformation, while the lower hardness of the titanium alloy causes greater deformation. This creates a large stress difference at the interface. This stress difference leads to significant stress concentration at the interface, severely weakening the bonding force and making the DLC coating prone to peeling off from the titanium alloy surface.

[0004] Traditional coating deposition methods often simply deposit DLC coatings onto titanium alloy surfaces without adequately considering how to fundamentally enhance the adhesion between the two. Relying solely on the physical adsorption between the coating and the substrate material is far from sufficient. Under actual working conditions, this weak bonding method is unable to withstand the influence of various complex external forces, thermal stresses, and other factors.

[0005] Therefore, there is a need to find a method for preparing DLC ​​coatings on titanium alloy surfaces that can effectively improve the bonding force between the DLC coating and the titanium alloy substrate. Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing a DLC coating on a titanium alloy surface, which can effectively improve the bonding force between the DLC coating and the titanium alloy substrate.

[0007] This application provides a method for preparing a DLC coating on a titanium alloy surface, including the following steps:

[0008] A1. Clean and dry the titanium alloy substrate;

[0009] A2. The surface of the titanium alloy substrate to be processed is subjected to laser polishing in a nitrogen atmosphere to refine the grains and generate TiN crystals on the surface to be processed.

[0010] A3. Perform laser texturing treatment on the surface to be processed;

[0011] A4. Deburr the surface to be processed;

[0012] A5. Deposit a DLC coating on the surface to be processed using PVD technology.

[0013] This method employs laser polishing in a nitrogen atmosphere to refine the grains and generate TiN crystals on the titanium alloy surface. This provides a transition layer with moderate hardness for the DLC coating, mitigating the hardness difference between the titanium alloy and the DLC coating, reducing stress differences and stress concentration caused by external forces or temperature changes, and enhancing adhesion. Simultaneously, the microstructure generated by laser texturing increases the contact area between the DLC coating and the titanium alloy substrate, forming a mechanical interlocking structure, further enhancing the adhesion of the DLC coating. Therefore, it effectively improves the bonding force between the DLC coating and the titanium alloy substrate.

[0014] Preferably, step A2 includes:

[0015] A201. The surface of the titanium alloy substrate to be processed is rough polished using a continuous laser in a nitrogen atmosphere to cause grain refinement and generate TiN crystals on the surface to be processed.

[0016] A202. The surface to be processed after rough polishing is finely polished using a nanosecond pulsed laser in a nitrogen atmosphere to further reduce the roughness of the surface to be processed;

[0017] A203. Detect the mass percentage of each chemical element in the surface to be processed using EDS technology. If the mass percentage of N is not greater than the mass percentage of O, repeat step A202. If the mass percentage of N is greater than the mass percentage of O, end the laser polishing process.

[0018] By employing a step-by-step laser polishing process combined with real-time elemental detection and feedback mechanisms, the technical challenges of grain refinement and TiN crystal formation during the laser polishing of titanium alloy surfaces were effectively addressed. First, coarse polishing was performed using a continuous laser in a nitrogen atmosphere, achieving surface grain refinement and initial TiN crystal formation. Then, fine polishing was performed using a nanosecond pulsed laser to further reduce surface roughness. Finally, EDS technology was used to detect the surface elemental composition, and the decision to continue fine polishing was based on the mass percentages of N and O, ensuring the full formation of TiN crystals.

[0019] Preferably, in step A201, when using a continuous laser to perform rough polishing on the surface of the titanium alloy substrate, the laser power is set to 500W-700W, the scanning speed is set to 1000mm / s-1200mm / s, the scanning interval is set to 0.03mm-0.05mm, the defocusing amount is set to 2mm, and the spot diameter is set to 0.2mm-0.3mm.

[0020] Preferably, in step A202, when using a nanosecond pulsed laser to perform fine polishing on the surface to be processed after rough polishing, the laser power is set to 80W-100W, the pulse width is set to 15ns, the repetition frequency is set to 80KHz-120KHz, the scanning speed is set to 3000mm / s-4000mm / s, the scanning interval is set to 0.015mm-0.03mm, and the spot diameter is set to 0.1mm-0.2mm.

[0021] Preferably, step A3 includes:

[0022] The surface to be processed is laser-textured using a nanosecond pulsed laser.

[0023] The use of nanosecond pulsed lasers enables precise control and processing of titanium alloy surfaces. The nanosecond-level pulse width allows for the concentrated release of energy in an extremely short time, thereby forming specific microstructures on the titanium alloy surface without significantly affecting the overall properties of the material.

[0024] Preferably, when using a nanosecond pulsed laser to perform laser texturing on the surface to be processed, the laser power is set to 20W-60W, the pulse width is set to 150ns, the repetition frequency is set to 40KHz-70KHz, the scanning speed is set to 200mm / s-700mm / s, and the spot diameter is set to 80μm-200μm.

[0025] Preferably, when using a nanosecond pulsed laser to perform laser texturing on the surface to be processed, the area of ​​the laser texturing pattern on the surface to be processed is 5%-90%.

[0026] Preferably, step A4 includes:

[0027] The surface to be processed is finely polished using 800-1200 grit diamond sandpaper to remove burrs. During the fine polishing process, the coefficient of friction between the diamond sandpaper and the surface to be processed is monitored in real time. The deburring process is stopped when the coefficient of friction drops to a stable level.

[0028] Preferably, step A5 includes:

[0029] A501. The surface to be processed is bombarded with Ar ions in the vacuum chamber of the PVD equipment;

[0030] A502. DLC coating is deposited on the surface to be processed in the vacuum chamber of a PVD equipment.

[0031] Preferably, the titanium alloy substrate is made of TC4 titanium alloy.

[0032] Beneficial Effects: The method for preparing a DLC coating on a titanium alloy surface provided in this application includes steps such as cleaning and drying the titanium alloy substrate, laser polishing, laser texturing, deburring, and DLC coating deposition. Laser polishing in a nitrogen atmosphere refines the grains on the titanium alloy surface and generates TiN crystals, providing a transition layer with moderate hardness for the DLC coating. This mitigates the hardness difference between the titanium alloy and the DLC coating, reduces stress differences and stress concentration caused by external forces or temperature changes, and enhances adhesion. Simultaneously, the microstructure generated by laser texturing increases the contact area between the DLC coating and the titanium alloy substrate, forming a mechanical interlocking structure, further enhancing the adhesion of the DLC coating. Therefore, it effectively improves the adhesion between the DLC coating and the titanium alloy substrate. Attached Figure Description

[0033] Figure 1 A flowchart illustrating the method for preparing a DLC coating on a titanium alloy surface provided in this application embodiment. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0035] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Depositing a DLC coating on titanium alloy surfaces is an effective method to improve their surface properties. However, the significant hardness difference between the titanium alloy and the DLC coating results in weak adhesion between them. Specifically, the hardness of titanium alloys typically does not exceed 350 HV, while the hardness of DLC coatings can reach over 1500 HV. This hardness mismatch leads to severe stress concentration at the interface, making the DLC coating prone to peeling off from the titanium alloy surface. Traditional coating deposition methods often simply deposit the DLC coating onto the titanium alloy surface without adequately considering how to fundamentally enhance the adhesion between the two. Adhesion-based bonding methods are insufficient to withstand various complex external forces and thermal stresses, severely impacting the coating's durability and reliability.

[0037] To address the problem of insufficient adhesion between the DLC coating and the titanium alloy substrate, this application provides an innovative method for preparing a DLC coating on a titanium alloy surface.

[0038] Please refer to Figure 1 A method for preparing a DLC coating on a titanium alloy surface according to some embodiments of this application includes the following steps:

[0039] A1. Clean and dry the titanium alloy substrate;

[0040] A2. Laser polishing is performed on the surface of the titanium alloy substrate to be processed in a nitrogen atmosphere to refine the grains and generate TiN crystals.

[0041] A3. Perform laser texturing on the surface to be processed;

[0042] A4. Deburr the surface to be processed;

[0043] A5. Use PVD (Physical Vapor Deposition) technology to deposit a DLC coating on the surface to be processed.

[0044] This method employs laser polishing in a nitrogen atmosphere to refine the grains and generate TiN crystals on the titanium alloy surface. This provides a transition layer with moderate hardness for the DLC coating, mitigating the hardness difference between the titanium alloy and the DLC coating, reducing stress differences and stress concentration caused by external forces or temperature changes, and enhancing adhesion. Simultaneously, the microstructure generated by laser texturing increases the contact area between the DLC coating and the titanium alloy substrate, forming a mechanical interlocking structure, further enhancing the adhesion of the DLC coating. Therefore, it effectively improves the bonding force between the DLC coating and the titanium alloy substrate.

[0045] Specifically, firstly, the titanium alloy substrate is cleaned and dried to remove surface dirt and moisture, providing a clean surface for subsequent processing. Then, laser polishing is performed in a nitrogen atmosphere. The thermal effect of the laser beam causes the surface material to remelt and resolidify, resulting in grain refinement (refined grains reduce the number of grain boundaries and increase dislocation density; grain boundaries effectively hinder dislocation movement, thereby enhancing the material's resistance to deformation and increasing its hardness, thus reducing the hardness difference between the titanium alloy substrate surface and the DLC coating). Simultaneously, in the nitrogen atmosphere, titanium atoms react with nitrogen atoms to generate TiN crystals (TiN crystals have high hardness, further reducing the hardness difference between the titanium alloy substrate surface and the DLC coating). This process not only improves the surface roughness but also forms a TiN transition layer with moderate hardness. Next, laser texturing is performed, a step that uses a pulsed laser to create a microstructure on the surface. By controlling parameters such as laser power, pulse width, and repetition frequency, specific microstructures, such as micropits and microgrooves, can be formed on the surface to be processed. These microstructures increase the surface area and provide more mechanical engagement points. Subsequently, deburring is performed to remove tiny protrusions on the surface to be processed (including burrs that may be generated during laser texturing). This step further improves the surface quality of the surface to be processed, creating conditions for the uniform deposition of the DLC coating. Finally, the DLC coating is deposited using PVD technology to obtain the finished product.

[0046] The cleaning process involves removing dirt, grease, and other impurities from the surface of the titanium alloy substrate, which can be achieved through ultrasonic cleaning or chemical cleaning. The drying process involves removing moisture from the surface of the titanium alloy substrate, which can be achieved through oven drying or hot air drying.

[0047] In some possible implementations, step A1 includes:

[0048] A101. Immerse the titanium alloy substrate in an anhydrous ethanol solution for ultrasonic cleaning for 10 minutes;

[0049] A102. Immerse the titanium alloy substrate in deionized water and perform ultrasonic cleaning for 10 minutes;

[0050] A103. Dry the titanium alloy substrate.

[0051] Laser polishing refers to scanning the surface of a titanium alloy substrate with a laser beam, causing the surface material to remelt and resolidify through thermal effects. Specifically, it can be achieved using a continuous laser or a pulsed laser.

[0052] In some preferred embodiments, step A2 includes:

[0053] A201. A continuous laser is used in a nitrogen atmosphere to perform rough polishing on the surface of the titanium alloy substrate to be processed, so as to cause grain refinement and generate TiN crystals on the surface to be processed.

[0054] A202. A nanosecond pulsed laser is used in a nitrogen atmosphere to perform fine polishing on the surface to be processed after rough polishing, so as to further reduce the roughness of the surface to be processed.

[0055] A203. Detect the mass percentage of each chemical element in the surface to be processed using EDS (Energy Dispersive Spectroscopy) technology. If the mass percentage of N is not greater than the mass percentage of O, repeat step A202. If the mass percentage of N is greater than the mass percentage of O, end the laser polishing process.

[0056] By employing a step-by-step laser polishing process combined with real-time elemental detection and feedback mechanisms, the technical challenges of grain refinement and TiN crystal formation during the laser polishing of titanium alloy surfaces were effectively addressed. First, coarse polishing was performed using a continuous laser in a nitrogen atmosphere, achieving surface grain refinement and initial TiN crystal formation. Then, fine polishing was performed using a nanosecond pulsed laser to further reduce surface roughness. Finally, EDS technology was used to detect the surface elemental composition, and the decision to continue fine polishing was based on the mass percentages of N and O, ensuring the full formation of TiN crystals.

[0057] Specifically, laser polishing is performed in a nitrogen atmosphere: this provides the necessary nitrogen source for the formation of TiN crystals, while also preventing the titanium alloy surface from being oxidized.

[0058] Using a continuous laser for rough polishing: A continuous laser can provide a continuous high energy input, which is beneficial for grain refinement of titanium alloy surfaces and the formation of TiN crystals.

[0059] Fine polishing with nanosecond pulsed lasers: Nanosecond pulsed lasers can provide more precise energy control, which helps to further reduce surface roughness without damaging the formed TiN crystal.

[0060] Surface elemental composition is determined using EDS technology. This accurately assesses the formation of TiN crystals, ensuring the effectiveness of the polishing process. EDS analysis can be performed after each fine polishing step, and the analysis area can be selected from multiple representative locations on the surface to be processed.

[0061] The decision to continue fine polishing is based on the mass percentage comparison of N and O: this ensures sufficient formation of TiN crystals while avoiding the negative effects of over-polishing. When the mass percentage of N is greater than the mass percentage of O, the TiN crystals can be considered to have been sufficiently formed, and the laser polishing process can be terminated at this point.

[0062] Preferably, in step A201, when using a continuous laser to perform rough polishing on the surface of the titanium alloy substrate, the laser power is set to 500W-700W, the scanning speed is set to 1000mm / s-1200mm / s, the scanning interval is set to 0.03mm-0.05mm, the defocusing amount is set to 2mm, and the spot diameter is set to 0.2mm-0.3mm.

[0063] Specifically, the power of the continuous laser in this application is set to 500W-700W. This power range ensures sufficient energy input to promote the reorganization and grain refinement of surface materials. When the power is below 500W, it may not provide enough energy to achieve effective surface treatment; while when the power exceeds 700W, it may cause surface overheating, resulting in unnecessary material loss or surface deformation. The scanning speed is set to 1000mm / s-1200mm / s. This speed range effectively controls the laser's interaction time on the surface, balancing the treatment effect and efficiency. If the scanning speed is too slow, it may cause local overheating; if the speed is too fast, it may not achieve the expected treatment effect. The scanning interval is set to 0.03mm-0.05mm. This setting ensures that the entire surface is treated uniformly, avoiding omissions or repetitions. Too large an interval may result in some areas not being treated, while too small an interval may cause unnecessary energy waste and prolonged processing time. The defocusing amount is set to 2mm. This parameter helps to adjust the laser energy density and optimize the treatment effect. By properly defocusing, the energy distribution of the laser on the surface can be controlled, avoiding material damage caused by excessive local energy concentration. The spot diameter is set to 0.2mm-0.3mm. This range effectively controls the area processed in a single operation, affecting energy distribution and processing accuracy. A smaller spot can improve processing accuracy but may increase processing time; a larger spot can improve efficiency but may reduce accuracy.

[0064] By properly controlling parameters such as laser power, scanning speed, and scanning interval, rough polishing of titanium alloy substrate surfaces can be effectively performed in a nitrogen atmosphere. This process not only reduces surface roughness (the roughness Sa value can be reduced to below 2 μm) but also promotes grain refinement and TiN crystal formation, laying the foundation for subsequent fine polishing and DLC coating deposition. Through the above steps of rough polishing, the hardness of the processed surface can reach 900 HV-1000 HV, with a small deviation from the hardness of the DLC coating.

[0065] Preferably, in step A202, when using a nanosecond pulsed laser to perform fine polishing on the surface to be processed after rough polishing, the laser power is set to 80W-100W, the pulse width is set to 15ns, the repetition frequency is set to 80KHz-120KHz, the scanning speed is set to 3000mm / s-4000mm / s, the scanning interval is set to 0.015mm-0.03mm, and the spot diameter is set to 0.1mm-0.2mm.

[0066] Specifically, the nanosecond pulsed laser used provides extremely short pulses, which facilitates precise control of heat input and reduces the heat-affected zone. The laser power is set to 80W-100W; this appropriate power range ensures sufficient energy for surface treatment without overheating and causing surface damage. The pulse width is set to 15ns; this extremely short pulse width reduces heat accumulation effects, facilitating finer surface treatment. The repetition frequency is set to 80kHz-120kHz; a higher repetition frequency improves processing efficiency while ensuring sufficient energy density. The scanning speed is set to 3000mm / s-4000mm / s; this higher scanning speed reduces single-point heat accumulation, promoting uniform surface treatment. The scanning interval is set to 0.015mm-0.03mm; a smaller scanning interval ensures uniform surface treatment and avoids omissions. The spot diameter is set to 0.1mm-0.2mm; a smaller spot diameter increases energy density, facilitating fine processing.

[0067] By using a nanosecond pulsed laser and precisely controlling parameters such as laser power, pulse width, repetition frequency, scanning speed, scanning interval, and spot diameter, surface roughness can be further reduced on the basis of rough polishing (the roughness Sa value can be reduced to below 0.5μm), providing a better foundation for the subsequent deposition of DLC coatings.

[0068] Laser texturing refers to creating microstructures on the surface of a titanium alloy substrate using a laser beam. Specifically, a pulsed laser can be used to achieve this, and specific surface morphologies can be formed by controlling the laser parameters.

[0069] In some possible implementations, step A3 includes:

[0070] A nanosecond pulsed laser is used to perform laser texturing on the surface to be processed.

[0071] The use of nanosecond pulsed lasers enables precise control and processing of titanium alloy surfaces. The nanosecond-level pulse width allows for the concentrated release of energy in an extremely short time, thereby forming specific microstructures on the surface to be processed without significantly affecting the overall properties of the material.

[0072] Preferably, when using a nanosecond pulsed laser to perform laser texturing on the surface to be processed, the laser power is set to 20W-60W, the pulse width is set to 150ns, the repetition frequency is set to 40KHz-70KHz, the scanning speed is set to 200mm / s-700mm / s, and the spot diameter is set to 80μm-200μm.

[0073] Specifically, setting the laser power to a range of 20W-60W ensures sufficient energy for surface modification without excessively damaging the substrate. A pulse width of 150ns provides high peak power in a short time, which is beneficial for the formation of surface microstructures. Setting the repetition frequency to 40kHz-70kHz ensures sufficient pulse overlap, which is beneficial for forming a uniform surface structure. Setting the scanning speed to 200mm / s-700mm / s, matched with the repetition frequency, controls the energy input per unit area. Setting the spot diameter to 80μm-200μm determines the size range of the microstructure. This range allows the steepness of the pits or grooves textured by the laser on the titanium alloy surface to be less than 45 degrees, which is more conducive to improving the adhesion between the DLC coating and the surface to be processed. These parameters are interrelated and work together to achieve the ideal laser texturing effect. For example, the combination of power and pulse width determines the energy of a single pulse, while the combination of repetition frequency and scanning speed affects the energy distribution density on the surface. The spot diameter directly affects the size and morphology of the microstructure.

[0074] Furthermore, when using a nanosecond pulsed laser to perform laser texturing on the surface to be processed, the area of ​​the laser texturing pattern on the surface to be processed is 5%-90%.

[0075] Specifically, when the area of ​​the laser-textured pattern is no less than 5%, sufficient microstructure can be formed on the surface to be processed, effectively enhancing the adhesion of the subsequent DLC coating. This is because the textured surface forms a micro-scale uneven structure, increasing the effective contact area and thus improving the mechanical interlocking force between the DLC coating and the surface. On the other hand, when the area of ​​the laser-textured pattern does not exceed 90%, a certain proportion of the original surface can be preserved, avoiding excessive texturing that could reduce the strength of the substrate. Excessive texturing may damage the surface integrity and affect the mechanical properties of the titanium alloy substrate. By limiting the texture area, a balance can be achieved between enhancing coating adhesion and maintaining substrate strength.

[0076] The laser texture pattern can be, but is not limited to, a linear pattern, a dot pattern, a grid pattern, or an array of graphics (such as circles, triangles, rhombuses, trapezoids, etc.).

[0077] Deburring refers to removing tiny protrusions from the surface of the titanium alloy substrate, which can be achieved through mechanical polishing or chemical polishing.

[0078] In some possible implementations, step A4 includes:

[0079] Use 800-1200 grit diamond sandpaper to fine polish the surface to be processed to remove burrs. During the fine polishing process, the coefficient of friction between the diamond sandpaper and the surface to be processed is monitored in real time. The deburring process is stopped when the coefficient of friction drops to a stable level.

[0080] Diamond abrasive paper with a grit size of 800-1200 mesh effectively removes surface burrs without causing excessive damage. Lower grit abrasive paper may cause surface scratches, while excessively high grit abrasive paper may not effectively remove burrs. During the fine polishing process, the coefficient of friction between the diamond abrasive paper and the surface being processed is monitored in real time. By monitoring changes in the coefficient of friction, the effectiveness of the deburring process can be judged. As surface burrs are gradually removed, the coefficient of friction gradually decreases. Deburring is stopped once the coefficient of friction stabilizes. This criterion ensures the adequacy and effectiveness of deburring and avoids over-grinding that could damage the textured surface. A stable coefficient of friction indicates that the surface has achieved the desired deburring effect; continuing processing may result in unnecessary material loss. These technical features, working together, enable effective deburring of titanium alloy surfaces, providing favorable surface conditions for subsequent DLC coating deposition.

[0081] Among them, a friction sensor can be installed at the mechanical polishing disc used to install diamond sandpaper to realize real-time detection of the friction coefficient between diamond sandpaper and the surface to be processed during the fine polishing process.

[0082] Among them, PVD technology refers to physical vapor deposition technology, which can be achieved by methods such as magnetron sputtering, ion plating or arc ion plating to deposit DLC coatings.

[0083] In some possible implementations, step A5 includes:

[0084] A501. Ar ion bombardment of the surface to be processed is performed in the vacuum chamber of the PVD equipment;

[0085] A502. DLC coating deposition is performed on the surface to be processed in the vacuum chamber of a PVD equipment.

[0086] Ar ion bombardment can clean and activate the surface to be processed, creating favorable interface conditions for the deposition of DLC coatings. During the DLC coating deposition process, the structure and properties of the DLC coating can be controlled by adjusting parameters such as vacuum chamber temperature, gas flow rate, hot filament current, and substrate bias voltage, thereby improving the adhesion between the DLC coating and the titanium alloy substrate.

[0087] Preferably, in step A501, the surface to be processed is bombarded for 15-60 minutes under the following conditions: the temperature of the vacuum chamber is set to 180℃-300℃, and argon gas with a flow rate of 150sccm-300sccm is introduced into the vacuum chamber; the negative bias voltage of the titanium alloy substrate is set to 50V-150V, and the bias voltage duty cycle is set to 40%-60%.

[0088] During Ar ion bombardment, setting the vacuum chamber temperature to 180℃ to 300℃ ensures sufficient activity on the titanium alloy substrate surface while avoiding substrate deformation due to excessive heat. Controlling the argon flow rate to 150 sccm to 300 sccm provides an appropriate amount of Ar ions for surface bombardment, effectively cleaning the surface without causing excessive damage to the substrate. Setting the negative bias voltage of the titanium alloy substrate to 50V to 150V with a bias duty cycle of 40% to 60% allows control over the energy and bombardment frequency of the Ar ions, thereby optimizing surface cleaning and activation effects.

[0089] Preferably, in step A502, DLC coating deposition is performed on the surface to be processed for a duration of 1 hour to 4 hours under the following conditions: the temperature of the vacuum chamber is set to 180℃-300℃, and argon gas with a flow rate of 120sccm-250sccm and acetylene gas with a flow rate of 200sccm-400sccm are introduced into the vacuum chamber; the hot wire current is set to 10A-80A; the negative bias voltage of the titanium alloy substrate is set to 650V-950V; and the bias voltage duty cycle is set to 20%-80%.

[0090] During DLC ​​coating deposition, maintaining the vacuum chamber temperature between 180°C and 300°C ensures stable coating growth. Controlling the flow rates of argon and acetylene to 120 sccm to 250 sccm and 200 sccm to 400 sccm, respectively, allows for adjustment of the DLC coating's composition and structure. Setting the hot filament current to 10A to 80A affects the carbon source decomposition efficiency, thus influencing the coating's growth rate and quality. Setting the negative bias voltage of the titanium alloy substrate to 650V to 950V with a bias duty cycle of 20% to 80% controls the ion bombardment energy and frequency, thereby affecting the coating's density and internal stress. The coordinated use of these parameters enables a gradual transition between the DLC coating and the titanium alloy substrate, reducing interfacial stress and improving adhesion. For example, by adjusting the ratio of acetylene to argon, a titanium-rich carbide transition layer can be formed at the interface, further enhancing the bonding between the coating and the substrate.

[0091] Furthermore, under the above conditions, DLC coating deposition is carried out for 1 to 4 hours. The resulting DLC ​​coating surface has a micro-recessed structure corresponding to the laser textured pattern. If the titanium alloy substrate is used for oil lubrication, this micro-recessed structure provides a dynamic pressure effect for the good containment and uniform distribution of lubricating oil. In addition, the strengthening of the surface by TiN crystals makes the lubricating oil form a stable oil film, which greatly reduces the coefficient of friction.

[0092] The material of the titanium alloy substrate can be selected according to actual needs. Preferably, the titanium alloy substrate is TC4 titanium alloy. TC4 titanium alloy has high strength and low density, which provides good mechanical properties for the prepared DLC coating. Secondly, TC4 titanium alloy has excellent corrosion resistance, which complements the corrosion resistance of the DLC coating, further improving the overall corrosion resistance. In addition, TC4 titanium alloy has good biocompatibility, which makes the prepared DLC coating potentially valuable in the biomedical field. It should be noted that, according to experimental results, compared with other titanium alloys, the above method of treating TC4 titanium alloy yields the best treatment effect (the strongest adhesion between the DLC coating and the titanium alloy substrate).

[0093] In summary, the method for preparing a DLC coating on a titanium alloy surface provided in this application has at least the following advantages:

[0094] 1. Continuous laser coarse polishing generates TiN crystals to form a gradient hardness, which alleviates the hardness difference between the titanium alloy and the DLC coating, reduces the stress difference and stress concentration caused by external force or temperature changes, and enhances the bonding force; in addition, the microstructure generated by laser texture increases the contact area and forms a mechanical interlocking, which, like a "mortise and tenon structure", tightly connects the DLC coating and the titanium alloy substrate, effectively improving the coating-substrate bonding force.

[0095] 2. After treatment, the low friction coefficient of the DLC coating on the titanium alloy substrate surface, combined with the laser-textured microstructure reducing the actual contact area, and the TiN crystal and gradient hardness structure optimizing surface properties, work together to reduce the friction coefficient of the titanium alloy substrate surface. Under oil lubrication conditions, the oleophilicity of the DLC coating, combined with the micro-recessed structure, provides a hydrodynamic effect by effectively accommodating and uniformly distributing the lubricating oil. In addition, the TiN crystal strengthens the surface, resulting in the formation of a stable oil film and significantly reducing the friction coefficient.

[0096] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0097] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a DLC coating on a titanium alloy surface, characterized in that, Including the following steps: A1. Clean and dry the titanium alloy substrate; A2. The surface of the titanium alloy substrate to be processed is subjected to laser polishing in a nitrogen atmosphere to refine the grains and generate TiN crystals on the surface to be processed. Step A2 includes: A201. The surface of the titanium alloy substrate to be processed is rough polished using a continuous laser in a nitrogen atmosphere to cause grain refinement and generate TiN crystals on the surface to be processed. The laser power is set to 500W-700W, the scanning speed is set to 1000mm / s-1200mm / s, the scanning interval is set to 0.03mm-0.05mm, the defocusing amount is set to 2mm, and the spot diameter is set to 0.2mm-0.3mm; so that TiN crystals are generated on the surface to be processed and the surface hardness reaches 900HV-1000HV. A202. The surface to be processed after rough polishing is finely polished using a nanosecond pulsed laser in a nitrogen atmosphere to further reduce the roughness of the surface to be processed; The laser power is set to 80W-100W, the pulse width to 15ns, the repetition frequency to 80KHz-120KHz, the scanning speed to 3000mm / s-4000mm / s, the scanning interval to 0.015mm-0.03mm, and the spot diameter to 0.1mm-0.2mm; so that the surface roughness Sa of the surface to be processed is reduced to below 0.5μm. A203. Detect the mass percentage of each chemical element in the surface to be processed using EDS technology, and when the mass percentage of N is not greater than the mass percentage of O, execute step A202 again; when the mass percentage of N is greater than the mass percentage of O, end the laser polishing process. A3. Perform laser texturing treatment on the surface to be processed; The surface to be processed is laser-textured using a nanosecond pulsed laser; the laser power is set to 20W-60W, the pulse width to 150ns, the repetition frequency to 40KHz-70KHz, the scanning speed to 200mm / s-700mm / s, and the spot diameter to 80μm-200μm; the area of ​​the laser-textured pattern on the surface to be processed is 5%-90%, and the steepness of the micro-pits formed by the texture is less than 45°; A4. Deburr the surface to be processed; A5. Deposit a DLC coating on the surface to be processed using PVD technology.

2. The method for preparing a DLC coating on a titanium alloy surface according to claim 1, characterized in that, Step A4 includes: using 800-1200 mesh diamond sandpaper to fine polish the surface to be processed to remove burrs, and during the fine polishing process, the coefficient of friction between the diamond sandpaper and the surface to be processed is detected in real time until the coefficient of friction drops to a stable level, and then the deburring process is stopped.

3. The method for preparing a DLC coating on a titanium alloy surface according to claim 1, characterized in that, Step A5 includes: A501. The surface to be processed is bombarded with Ar ions in the vacuum chamber of the PVD equipment; A502. DLC coating is deposited on the surface to be processed in the vacuum chamber of a PVD equipment.

4. The method for preparing a DLC coating on a titanium alloy surface according to any one of claims 1-3, characterized in that, The titanium alloy substrate is made of TC4 titanium alloy.

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