A DLC diamond coating, method of making and using

Abstract

This invention discloses a DLC diamond coating, its preparation, and its application method, relating to the field of diamond-like carbon coating technology. Specifically, it includes the following steps: Step S1, substrate graded cleaning and ion etching pretreatment; Step S2, in-situ synthesis of a Ti-TiC-SiC gradient transition layer; Step S3, construction of a silicon / boron co-doped nanocomposite functional layer. This invention alleviates interfacial stress by constructing a gradient transition layer, utilizes a periodic modulation process to form a soft-hard alternating nanolayered structure, and combines a silicon-boron co-doping strategy; effectively solving the problems of high internal stress, poor adhesion, and easy high-temperature failure in coatings, achieving a balance between high hardness, high toughness, and excellent high-temperature wear resistance.

Description

Technical Field

[0001] This invention relates to the field of diamond-like carbon coating technology, specifically to a DLC diamond coating, its preparation and application method. Background Technology

[0002] With the rapid development of modern industry, the service environments of mechanical components in aerospace, automotive manufacturing, and precision machining are becoming increasingly harsh, placing higher demands on the wear resistance, friction reduction, and corrosion resistance of material surfaces. Diamond-like carbon (DLC) coatings, due to their high hardness, low coefficient of friction, and excellent chemical inertness, have become key materials for protecting core moving parts and extending their service life. However, in practical applications, mechanical components are subjected to complex conditions such as long-term high contact stress, high-speed operation, and high-temperature dry friction, which can easily lead to coating failure.

[0003] Coating failure is one of the main causes of mechanical equipment downtime and operational accidents. During the deposition process, carbon atoms mainly reach the substrate in the form of high-energy particles, easily accumulating huge internal stresses within the coating. These internal stresses often increase sharply with the increase of coating thickness. Simultaneously, the significant difference in thermal expansion coefficients and elastic moduli between the coating and the metal substrate leads to insufficient bonding strength at the interface. Under heavy loads or alternating stress, this modulus mismatch and internal stress accumulation can cause brittle fracture of the coating, and even delamination of the film-substrate interface, severely limiting its load-bearing capacity.

[0004] Furthermore, the thermal stability of existing diamond-like carbon coatings in high-temperature environments is a major bottleneck restricting their widespread application. Under the high temperatures generated by high-speed cutting or engine operation, the carbon atom structure is prone to metastable to stable state transformation, i.e., graphitization transformation, which leads to a sharp decrease in coating hardness and an abnormal increase in the coefficient of friction. Although various doping modification methods have been used to try to improve this problem, it is often difficult to balance hardness, toughness and thermal stability when dealing with complex conditions of multi-physics coupling. Single doping or structural design is difficult to suppress oxidation wear at high temperatures and cannot effectively prevent the rapid propagation of cracks inside the coating, resulting in the service life of parts under harsh conditions not meeting the expected requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a DLC diamond coating, its preparation and application method, which solves the problems existing in the background art.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a DLC diamond coating, specifically comprising the following steps:

[0007] Step S1, Substrate-level cleaning and ion etching pretreatment: The substrate to be coated is sequentially placed in acetone and anhydrous ethanol for multi-stage ultrasonic dispersion cleaning, vacuum dried, and then placed in a vacuum coating chamber; the vacuum is evacuated to a background vacuum of 3.0×10−3Pa∼8.0×10−3Pa, high-purity argon gas is introduced, the ion source is turned on, and a negative bias voltage is applied to the substrate for glow discharge cleaning; subsequently, a high-energy titanium ion beam is generated on the substrate surface using a titanium target as a cathode arc source or a magnetron sputtering source, and the substrate surface is bombarded with high-energy ions and implanted in situ to form an ion implantation hybrid layer;

[0008] Step S2, In-situ synthesis of Ti-TiC-SiC gradient transition layer: Maintain the vacuum chamber temperature at 150℃~250℃, maintain the argon flow rate, turn on the magnetron sputtering titanium target power supply and maintain the set power; During the deposition process, tetramethylsilane gas is introduced as a carbon source and silicon source through a mass flow meter; A flow gradient increasing control strategy is adopted, that is, during the deposition time, the flow rate of TMS gas is increased linearly or stepwise from 0 sccm to 30~60 sccm, so that the deposited layer smoothly transitions from pure metallic titanium phase to titanium carbide / silicon carbide ceramic phase, and an in-situ reaction generates a gradient transition layer with a thickness of 200~500nm;

[0009] Step S3: Constructing a silicon / boron co-doped nanocomposite functional layer: Turn off the titanium target, turn on the high-purity graphite target and the boron target, and maintain the TMS gas flow rate at the value at the end of step S2; drive the graphite target with a high-power pulsed magnetron sputtering power supply, and drive the boron target with a DC or pulsed power supply; implement a periodically modulated pulse bias process during deposition: set a modulation period of 10s~60s, and alternately apply a high-energy pulse bias stage and a low-energy pulse bias stage within each cycle; the high-energy pulse bias stage... Stage 1: Apply a bias voltage of -100V to -200V to induce the growth of a high sp3 content carbon framework by bombarding with high-energy carbon ions, forming a hard layer; Stage 2: Apply a bias voltage of -30V to -60V to reduce the ion bombardment energy, induce the solid solution of silicon and boron atoms in the carbon network and the precipitation of nanoclusters, forming a tough layer; Through the above alternating deposition, a soft and hard alternating nanolayer structure is grown in situ inside the coating, and the deposition continues until the total thickness reaches 1.5~4.0μm, then it is cooled and removed from the furnace.

[0010] Preferably, the multi-stage ultrasonic dispersion cleaning time in step S1 is 15-20 minutes; the specific parameters for high-energy ion bombardment and in-situ implantation are: the applied substrate bias voltage is -600V to -900V, the processing time is 5-10 minutes, so that titanium ions are implanted into the substrate at a depth of 10-30nm to form a metallurgical bonding interface.

[0011] Preferably, in the flow gradient increasing control strategy in step S2, the introduction rate of TMS gas is controlled at 2-5 sccm / min; the power density of the magnetron sputtering titanium target is 5-8 W / cm2; and the elastic modulus of the gradient transition layer gradually transitions from 180-220 GPa on the substrate side to 250-300 GPa on the functional layer side.

[0012] Preferably, the process parameters of the high-power pulsed magnetron sputtering power supply in step S3 are set as follows: peak power density of 500-800 W / cm2, pulse frequency of 200-800 Hz, pulse width of 50-200 μs, and duty cycle controlled between 2% and 10%; the power of the boron target is set to 10%-20% of the power of the graphite target.

[0013] Preferably, in the periodically modulated pulse bias process in step S3, the time proportion of the high-energy pulse bias stage is 60% to 80%, and the time proportion of the low-energy pulse bias stage is 20% to 40%; and linear voltage sliding is used when switching between the two stages, with a sliding time of 1 to 3 seconds, to prevent microcracks from being generated by abrupt interface changes.

[0014] The invention also provides a DLC diamond coating prepared by a method for preparing a DLC diamond coating, comprising, from the substrate outwards, an ion implantation mixed layer, a Ti-TiC-SiC gradient transition layer and a silicon / boron co-doped nanocomposite functional layer.

[0015] The silicon / boron co-doped nanocomposite functional layer has a composite structure in which nanocrystals are embedded in an amorphous carbon matrix, wherein the atomic percentage content of silicon is 5% to 12% and the atomic percentage content of boron is 2% to 8%.

[0016] The coating has a nanoindentation hardness of 30-40 GPa, a critical bonding force Lc2 ≥ 80 N, and internal stress controlled between 0.5-1.5 GPa.

[0017] Preferably, the coating surface roughness Ra≤0.05μm; the coefficient of friction is ≤0.1 when dry friction is performed in an atmospheric environment at 400℃, and it has the tribological properties of generating a self-lubricating transfer film containing boron oxide and graphitized carbon in situ on the friction surface.

[0018] A method for applying DLC ​​diamond coating is also provided, in which the coating is applied to the surface of cutting tools, automotive engine tappets, piston rings or bearing rolling elements to improve the wear resistance and anti-galling performance of parts under dry friction, high speed or high temperature conditions.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By constructing a transition structure with a specific gradient between the substrate and the functional layer, the problem of insufficient adhesion between the coating and the substrate due to differences in physical properties is effectively solved. By controlling the gas flow rate and power parameters during the deposition process, the transition layer achieves a smooth transition from the metallic phase to the ceramic phase. An elastic modulus buffer zone is established between the substrate and the high-hardness functional layer, which can alleviate the interfacial shear stress caused by thermal expansion mismatch and provide mechanical support when subjected to external impact. Thus, while ensuring the overall strength of the coating, it effectively prevents the coating from peeling off at the interface under high load conditions, thereby improving the film-substrate bonding strength.

[0021] By utilizing periodically varying deposition process parameters, an alternating soft and hard nanolayered structure is constructed in situ within the coating, endowing it with excellent hardness and load-bearing capacity. The low-energy deposition stage induces solid solution of doped atoms in the carbon network and precipitation of nanoclusters, forming a tough layer with stress-relieving properties. When subjected to external forces, the interlayer interface can deflect or terminate cracks, increasing the crack propagation path and energy consumption. While maintaining the coating's high wear resistance, this effectively reduces internal stress and improves fracture toughness, solving the common problem of high brittleness and easy cracking in high-hardness coatings.

[0022] By employing a specific dual-element co-doping strategy, the coating is endowed with excellent high-temperature tribological properties. The introduced non-carbon elements can suppress the graphitization transformation of carbon atoms at high temperatures, maintaining the stability of the coating structure. During high-temperature friction, the dopant elements can react with oxygen in the environment to generate an oxide transfer film with lubricating properties in situ. This film not only acts as a solid lubricant, stabilizing the coefficient of friction, but also serves as a diffusion barrier, preventing oxygen atoms from eroding into the coating. This allows the coating to maintain an extremely low wear rate even under harsh environments such as high temperature and dry friction, effectively addressing the problem of early coating failure caused by thermal effects. Detailed Implementation

[0023] Example 1

[0024] This embodiment provides a method for preparing a diamond-like carbon coating, which is applied to the surface of automotive engine tappets to solve the wear problem during lean start-up and high-speed operation. The specific process parameters are selected as follows:

[0025] In step S1, the substrate graded cleaning and ion etching pretreatment process is as follows: The engine pushrod, which is the substrate to be coated, is placed in acetone and anhydrous ethanol for multi-stage ultrasonic dispersion cleaning. The cleaning time is set to 15 minutes to thoroughly remove oil and impurities from the surface. After vacuum drying, it is placed in a vacuum coating chamber and evacuated to a base vacuum of 3.0 × 10⁻³ Pa. Then, high-purity argon gas is introduced. The ion source is turned on, and a substrate bias voltage of -600V is applied to the substrate for glow discharge cleaning. Next, a titanium target is used as the cathode arc source to bombard the substrate surface with high-energy ions and implant them in situ for 5 minutes. During this process, titanium ions are implanted to a depth of 10 nm in the substrate to form a strong ion implantation mixed layer, thereby establishing a metallurgical bonding interface between the substrate and the coating at the atomic scale, effectively preventing the coating from peeling off under high contact stress.

[0026] In step S2, the in-situ synthesis of the Ti-TiC-SiC gradient transition layer is as follows: the vacuum chamber temperature is maintained at 150°C, the argon flow rate is maintained, and the magnetron sputtering titanium target power supply is turned on, setting the power density of the magnetron sputtering titanium target to 5 W / cm²; during the deposition process, tetramethylsilane (TMS) gas is introduced through a mass flow meter, and a flow rate gradient increasing control strategy is adopted, with the TMS gas introduction rate controlled at 2 sccm / min. During the deposition time, the flow rate of the TMS gas is linearly increased from 0 sccm to 30 sccm; this operation allows the deposited layer to smoothly transition from a pure metallic titanium phase to a titanium carbide / silicon carbide ceramic phase, generating a gradient transition layer with a thickness of 200 nm in situ; the elastic modulus of this gradient transition layer gradually transitions from 180 GPa on the substrate side to 250 GPa on the functional layer side. This gradual transition of modulus can effectively alleviate the interfacial shear stress caused by the difference in thermal expansion coefficients.

[0027] In step S3, the process of constructing the silicon / boron co-doped nanocomposite functional layer is as follows: The titanium target is turned off, and the high-purity graphite target and boron target are turned on, with the TMS gas flow rate maintained at 30 sccm; a high-power pulsed magnetron sputtering HiPIMS power supply is used to drive the graphite target, with a peak power density set to 800 W / cm², a pulse frequency of 800 Hz, a pulse width of 50 μs, and a duty cycle adjusted to 2%; the power of the boron target is set to 20% of the power of the graphite target to introduce a higher boron content to improve high-temperature performance; in the periodically modulated pulse bias process, the modulation period is set to 60 s; the high-energy pulse bias stage accounts for 80% of the time, applying a bias voltage of -200 V, and the intense ion bombardment promotes the formation of a very high proportion of sp³ bonds in the coating; the low-energy pulse bias stage accounts for 20% of the time, applying a bias voltage of -60 V; the glide time during switching is 3 seconds; deposition continues until the total thickness reaches 4.0 μm;

[0028] The diamond-like carbon coating prepared in this embodiment, upon testing, showed that the atomic percentage content of silicon in the silicon / boron co-doped nanocomposite functional layer was 5%, and the atomic percentage content of boron was 2%. The coating exhibited a nanoindentation hardness of 30 GPa, a critical bonding force Lc2 of 82 N, and internal stress controlled at 0.5 GPa. The surface roughness Ra of the coating was 0.02 μm. Under dry friction in an atmospheric environment at 400℃, the coefficient of friction was 0.08, demonstrating excellent wear resistance and anti-galling performance.

[0029] Example 2

[0030] This embodiment provides a method for preparing a diamond-like carbon coating, which is applied to the surface of a cutting tool to cope with the high temperature and heat challenges generated by dry cutting; the specific process parameters are selected as follows:

[0031] In step S1, the substrate graded cleaning and ion etching pretreatment process is as follows: the cemented carbide tool, which is the substrate to be plated, is subjected to multi-stage ultrasonic dispersion cleaning for 20 minutes; vacuum is drawn to a base vacuum of 8.0 × 10⁻³ Pa; in the high-energy ion bombardment and in-situ implantation stage, the substrate bias voltage is -900V and the processing time is 10 minutes, so that titanium ions are implanted into the substrate to a depth of 30 nm; this depth of ion implantation hybrid layer can withstand the huge shear force in cutting processing;

[0032] In step S2, the in-situ synthesis of the Ti-TiC-SiC gradient transition layer is as follows: the vacuum chamber temperature is maintained at 250℃; the power density of the magnetron sputtering titanium target is set to 8W / cm²; the TMS gas introduction rate is controlled at 5sccm / min, and the TMS gas flow rate is increased stepwise from 0sccm to 60sccm; an in-situ reaction generates a gradient transition layer with a thickness of 500nm; the elastic modulus of this gradient transition layer gradually transitions from 220GPa on the substrate side to 300GPa on the functional layer side, providing a strong support platform for the subsequent high-hardness functional layer;

[0033] In step S3, the process of constructing the silicon / boron co-doped nanocomposite functional layer is as follows: A high-power pulsed magnetron sputtering HiPIMS power supply is used to drive the graphite target, with a peak power density set to 800 W / cm², a pulse frequency of 800 Hz, a pulse width of 50 μs, and a duty cycle controlled at 2%; the power of the boron target is set to 20% of the power of the graphite target to introduce a higher content of boron to improve high-temperature performance; in the periodically modulated pulse bias process, the modulation period is set to 60 s; the high-energy pulse bias stage accounts for 80% of the time, with a bias voltage of -200 V applied, and the strong ion bombardment promotes the formation of a very high proportion of sp³ bonds in the coating; the low-energy pulse bias stage accounts for 20% of the time, with a bias voltage of -60 V applied; the glide time during switching is 3 seconds; deposition continues until the total thickness reaches 4.0 μm;

[0034] The diamond-like carbon coating prepared in this embodiment has an atomic percentage content of 12% silicon and 8% boron. The coating has a nanoindentation hardness of up to 40 GPa, a critical bonding force Lc2 of 95 N, and an internal stress of 1.5 GPa. In a high-temperature friction test at 400°C, due to the in-situ formation of a self-lubricating transfer film containing boron oxide by boron, the friction coefficient is stable at 0.06, which greatly extends the tool life.

[0035] Example 3

[0036] This embodiment provides a method for preparing a diamond-like coating, which is applied to the surface of a piston ring; the process parameters are between those of Embodiment 1 and Embodiment 2, aiming to achieve a balance between hardness and toughness;

[0037] In step S1, the substrate hierarchical cleaning and ion etching pretreatment process is as follows: cleaning time 18 minutes, base vacuum degree 5.0×10⁻³Pa; high-energy ion bombardment and in-situ implantation substrate bias voltage is -750V, processing time 8 minutes, titanium ion implantation depth is about 20nm, forming a dense ion implantation hybrid layer.

[0038] In step S2, the in-situ synthesis process of the Ti-TiC-SiC gradient transition layer is as follows: chamber temperature 200℃; titanium target power density 6.5W / cm²; TMS introduction rate 3.5sccm / min, with the flow rate linearly increasing from 0sccm to 45sccm; a gradient transition layer with a thickness of 350nm is generated, and its elastic modulus achieves a smooth transition from 200GPa to 275GPa.

[0039] In step S3, the process of constructing the silicon / boron co-doped nanocomposite functional layer is as follows: the HiPIMS power supply has a peak power density of 650 W / cm², a pulse frequency of 500 Hz, a pulse width of 100 μs, and a duty cycle of 6%; the boron target power is 15% of the graphite target power; in the periodically modulated pulse bias process, the modulation period is 30 s; the high-energy pulse bias stage accounts for 70%, with a bias voltage of -150 V applied; the low-energy pulse bias stage accounts for 30%, with a bias voltage of -45 V applied; the switching slip time is 2 seconds; and the total deposition thickness is 2.8 μm.

[0040] The diamond-like carbon coating prepared in this embodiment has a silicon content of 8.5% and a boron content of 5%. The coating exhibits balanced mechanical properties, with a nanoindentation hardness of 35 GPa, a critical bonding force Lc2 of 90 N, and an internal stress of 1.0 GPa. The surface roughness Ra is 0.03 μm, and the coefficient of friction is 0.09 (at 400°C), making it very suitable for friction reduction and wear resistance of reciprocating motion parts.

[0041] Example 4

[0042] This embodiment aims to verify the effect of a combination of low-frequency HiPIMS and specific bias voltage, applicable to bearing rolling elements;

[0043] In step S1, the substrate graded cleaning and ion etching pretreatment parameters are the same as in Example 3 to ensure a good substrate condition;

[0044] In step S2, during the in-situ synthesis of the Ti-TiC-SiC gradient transition layer, the TMS flow rate was increased from 0 to 40 sccm, the introduction rate was 3 sccm / min, the titanium target power density was 6 W / cm², and a 300 nm transition layer was generated.

[0045] In step S3, the process of constructing the silicon / boron co-doped nanocomposite functional layer is as follows: HiPIMS peak power density 600 W / cm², pulse frequency 300 Hz, pulse width 150 μs, duty cycle 8%; boron target power is 12% of graphite target power; in the periodically modulated pulse bias process, the modulation period is 20 s; the high-energy pulse bias stage, i.e., the stage of applying -120V bias, accounts for 65%, and the low-energy pulse bias stage, i.e., the stage of applying -40V bias, accounts for 35%; voltage glide time is 1.5 seconds; total deposition thickness is 2.0 μm.

[0046] The diamond-like carbon coating prepared in this embodiment has a silicon content of 7% and a boron content of 3.5%. The test results show that the hardness is 32 GPa, the adhesion strength Lc2 is 88 N, and the internal stress is 0.8 GPa. The low internal stress combined with the moderate hardness makes the coating perform well in the rolling contact fatigue test, and no microcrack propagation occurs.

[0047] Example 5

[0048] This embodiment explores the combination of high TMS flow rate and rapid alternating bias voltage, which is suitable for precision mold surfaces;

[0049] In step S1, the substrate graded cleaning and ion etching pretreatment are performed according to the parameters of Example 2 to obtain the strongest interfacial bonding;

[0050] In step S2, during the in-situ synthesis of the Ti-TiC-SiC gradient transition layer, the TMS flow rate is increased from 0 to 55 sccm, the introduction rate is 4 sccm / min, and a 400 nm transition layer is generated to ensure sufficient modulus transition.

[0051] In step S3, the process of constructing the silicon / boron co-doped nanocomposite functional layer is as follows: HiPIMS peak power density 700 W / cm², pulse frequency 600 Hz, pulse width 80 μs, duty cycle 5%; boron target power is 18% of graphite target power; in the periodically modulated pulse bias process, a faster frequency switching is used and the modulation period is set to 15 s; the high-energy pulse bias stage with a -180V bias voltage accounts for 75%, and the low-energy pulse bias stage with a -50V bias voltage accounts for 25%; voltage glide time is 2.5 seconds; total deposition thickness is 3.5 μm.

[0052] The diamond-like coating prepared in this embodiment has a silicon content of 10% and a boron content of 6.5%. The coating hardness reaches 38 GPa, the adhesion force Lc2 is 92 N, and the internal stress is 1.2 GPa. This rapidly alternating growth of the nanolayer structure significantly improves the fracture toughness of the coating and exhibits excellent anti-adhesion performance during the mold demolding process.

[0053] Comparative Example 1

[0054] This comparative example illustrates the case without boron doping; compared to Example 3, the only difference is that the boron target was not turned on in step S3, and all other parameters are exactly the same; the prepared coating is a silicon-doped diamond-like carbon (Si-DLC) coating; tests show that the room temperature hardness is 28 GPa and the internal stress is 0.9 GPa; however, in the high-temperature friction test at 400℃, the coefficient of friction rapidly increased to 0.35, and the wear rate increased significantly, indicating that the lack of boron element led to intensified graphitization at high temperature and the inability to form a B2O3 self-lubricating film.

[0055] Comparative Example 2

[0056] This comparative example illustrates the case where a periodically modulated pulse bias process is not used. Compared to Example 3, the only difference is that a constant -100V bias is applied in step S3, while all other parameters are exactly the same. The prepared coating structure is relatively uniform and does not form a nanolayered structure with alternating soft and hard layers. Tests show that although the hardness reaches 33GPa, the internal stress is as high as 2.8GPa, and the critical bonding force Lc2 is only 55N. Obvious brittle spalling occurs in the scratch test, indicating that the lack of a stress release mechanism in the low-energy bias stage has a significant negative impact on the overall performance of the coating.

[0057] Comparative Example 3

[0058] This comparative example is used to illustrate the case where no gradient transition layer is used; compared with Example 3, the only difference is that TMS gas was not introduced in step S2 for gradient control, but pure titanium was directly deposited as the underlayer and then immediately step S3 was performed; the prepared coating has obvious modulus abrupt change at the interface; the test shows that although the coating body has normal hardness, the critical bonding force Lc2 is only 40N, and the coating is very easy to peel off along the interface in the thermal shock test.

[0059] To more intuitively compare the effects of each embodiment with the comparative example, the following performance comparison table is presented:

[0060] Group Nanohardness / GPa Critical bonding force Lc2 / N Internal stress / GPa Friction coefficient at 400℃ <![CDATA[Wear rate / ×10⁻¹ 6 m³ / N·m]]> Overall evaluation Example 1 30 82 0.5 0.08 3.5 Low stress, high toughness Example 2 40 95 1.5 0.06 2.1 High hardness, extremely heat resistant Example 3 35 90 1.0 0.09 2.8 Balanced performance Example 4 32 88 0.8 0.09 3.2 Good fatigue resistance Example 5 38 92 1.2 0.07 2.4 Anti-adhesion, high strength and toughness Comparative Example 1 28 85 0.9 0.35 18.5 High temperature failure Comparative Example 2 33 55 2.8 0.12 6.8 High stress, prone to peeling Comparative Example 3 34 40 1.1 0.10 7.2 Poor bonding strength

[0061] As can be seen from the table above and the analysis of the above embodiments, the present invention, through the organic combination of substrate graded cleaning and ion etching pretreatment, in-situ synthesis of Ti-TiC-SiC gradient transition layer, and construction of silicon / boron co-doped nanocomposite functional layer, especially by utilizing periodically modulated pulse bias voltage process, successfully solves the contradiction between high hardness and high internal stress in traditional diamond-like coatings. Examples 1-5 all exhibit excellent comprehensive mechanical properties and high-temperature tribological properties, while the comparative examples have obvious defects in high-temperature wear resistance, adhesion, or internal stress control, respectively. This fully demonstrates the inventiveness and practicality of the technical solution of the present invention.

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a DLC diamond coating, characterized in that, include: Step S1, Substrate-level cleaning and ion etching pretreatment: The substrate to be coated is sequentially placed in acetone and anhydrous ethanol for multi-stage ultrasonic dispersion cleaning, vacuum dried, and then placed in a vacuum coating chamber; the vacuum is evacuated to a background vacuum of 3.0×10−3Pa∼8.0×10−3Pa, high-purity argon gas is introduced, the ion source is turned on, and a negative bias voltage is applied to the substrate for glow discharge cleaning; using a titanium target as a cathode arc source or magnetron sputtering source, a high-energy titanium ion beam is generated on the substrate surface to bombard the substrate surface with high-energy ions and implant them in situ, forming an ion implantation hybrid layer; Step S2, In-situ synthesis of Ti-TiC-SiC gradient transition layer: Maintain the vacuum chamber temperature at 150℃~250℃, maintain the argon flow rate, turn on the magnetron sputtering titanium target power supply and maintain the set power; introduce tetramethylsilane gas through a mass flow meter during the deposition process; increase the TMS gas flow rate linearly or stepwise from 0 sccm to 30~60 sccm, and generate a gradient transition layer with a thickness of 200~500 nm in situ. Step S3: Constructing a silicon / boron co-doped nanocomposite functional layer: Turn off the titanium target, turn on the high-purity graphite target and the boron target, and maintain the flow rate of TMS gas at the value at the end of step S2; drive the graphite target with a high-power pulsed magnetron sputtering power supply, and drive the boron target with a DC or pulsed power supply. The modulation period is set to 10s to 60s. In each period, a high-energy pulse bias stage and a low-energy pulse bias stage are applied alternately. During the high-energy pulse bias stage, a bias voltage of -100V to -200V is applied. During the low-energy pulse bias stage, a bias voltage of -30V to -60V is applied. The material is deposited alternately until the total thickness reaches 1.5 to 4.0μm, and then cooled and removed from the furnace.

2. The method for preparing a DLC diamond coating according to claim 1, characterized in that, The multi-stage ultrasonic dispersion cleaning time in step S1 is 15-20 minutes; the specific parameters for high-energy ion bombardment and in-situ implantation are: the applied substrate bias voltage is -600V to -900V, the processing time is 5-10 minutes, so that titanium ions are implanted into the substrate at a depth of 10-30nm to form a metallurgical bonding interface.

3. The method for preparing a DLC diamond coating according to claim 1, characterized in that, In the flow gradient increasing control strategy in step S2, the introduction rate of TMS gas is controlled at 2-5 sccm / min; the power density of the magnetron sputtering titanium target is 5-8 W / cm2; and the elastic modulus of the gradient transition layer gradually transitions from 180-220 GPa on the substrate side to 250-300 GPa on the functional layer side.

4. The method for preparing a DLC diamond coating according to claim 1, characterized in that, The process parameters of the high-power pulsed magnetron sputtering power supply in step S3 are set as follows: peak power density of 500-800 W / cm2, pulse frequency of 200-800 Hz, pulse width of 50-200 μs, and duty cycle of 2%-10%; the power of the boron target is set to 10%-20% of the power of the graphite target.

5. The method for preparing a DLC diamond coating according to claim 1, characterized in that, In the periodically modulated pulse bias process in step S3, the time proportion of the high-energy pulse bias stage is 60% to 80%, and the time proportion of the low-energy pulse bias stage is 20% to 40%. Furthermore, linear voltage sliding is used when switching between the two stages, with a sliding time of 1 to 3 seconds, to prevent microcracks from being generated by abrupt interface changes.

6. A DLC diamond coating prepared by the method for preparing a DLC diamond coating according to any one of claims 1-5, characterized in that, From the substrate outwards, it includes an ion implantation hybrid layer, a Ti-TiC-SiC gradient transition layer, and a silicon / boron co-doped nanocomposite functional layer. The silicon / boron co-doped nanocomposite functional layer has a composite structure in which nanocrystals are embedded in an amorphous carbon matrix, wherein the atomic percentage content of silicon is 5% to 12% and the atomic percentage content of boron is 2% to 8%. The coating has a nanoindentation hardness of 30-40 GPa, a critical bonding force Lc2 ≥ 80 N, and internal stress controlled between 0.5-1.5 GPa.

7. The DLC diamond coating according to claim 6, characterized in that, The coating surface roughness Ra≤0.05μm; the coefficient of friction is ≤0.1 when dry friction is performed in an atmospheric environment at 400℃, and it has the tribological properties of generating a self-lubricating transfer film containing boron oxide and graphitized carbon in situ on the friction surface.

8. A method of using the DLC diamond coating as described in claim 6 or 7, characterized in that, The coating is applied to the surface of cutting tools, automotive engine tappets, piston rings, or bearing rolling elements to improve the wear resistance and anti-galling properties of components under dry friction, high-speed, or high-temperature conditions.