Preparation method of high-bonding-force superhard nanomultilayer film, film and application thereof

Abstract

This invention relates to the field of materials science, specifically to a method for preparing a high-bonding, ultrahard nanolayered thin film, the film itself, and its applications. The film comprises a Cr / Ti metal bonding layer, a CrTiN intermediate layer, a TiNC transition layer, and an a-C:Ti nanocomposite surface layer sequentially deposited on a substrate surface. The a-C:Ti ultrahard nanolayered thin film prepared by this invention achieves multi-layer stacking at the microscale by controlling the periodic modulation structure of the bonding layer, intermediate layer, and transition layer, effectively suppressing dislocation and crack propagation. Through Ti doping modification and gradient periodic modulation structure design, the internal stress of the film is reduced, improving its bonding strength, wear resistance, and toughness, reducing the risk of coating cracking or peeling, and enhancing the film's service stability. The a-C:Ti ultrahard nanolayered thin film of this invention is particularly suitable for applications such as precision machining tool coatings, surface strengthening of aero-engine gears and bearings, and wear protection of microelectromechanical systems (MEMS).

Description

Technical Field

[0001] This invention belongs to the field of high-performance hard protective coatings and surface engineering technology, specifically relating to a method for preparing a high-adhesion ultrahard nano multilayer film, the film and its application. Background Technology

[0002] In the fields of high-performance bearings, precision molds, high-end seals and key moving parts in aerospace, the comprehensive performance requirements for surface protective coatings are extremely stringent. They not only require extremely high hardness (>50 GPa) to resist abrasive wear, but also excellent toughness to withstand impact loads, extremely low surface roughness to reduce friction and wear origins, and exceptional film-substrate adhesion to ensure long-term service reliability.

[0003] Composite thin films based on amorphous carbon and doped with titanium (Ti) show promise, but current technologies face several interconnected and fundamental bottlenecks in achieving this goal: First, there is an inherent conflict in coating performance. Pursuing ultra-high hardness often leads to the accumulation of internal stress and increased brittleness, severely weakening the adhesion; while designs aimed at improving toughness and adhesion often come at the cost of hardness. This trade-off between "hardness-toughness-adhesion" is an inherent challenge.

[0004] Second, the "initial interface quality dilemma" that determines the foundation of the coating. The long-term service life of the coating depends on a near-perfect bonding interface with the substrate. Cathodic arc technology can provide metal particles with high ionization rates, which is conducive to the formation of strong bonds. However, the "macro-particle (droplet)" contamination inherent in its process can be embedded in the initial metal bonding layer like gravel, becoming stress concentration points, wear sources, and crack initiation sites, seriously degrading the interface integrity, surface finish, and coating density.

[0005] Third, the "efficiency-quality" paradox of magnetic filtration technology. Magnetic filtration technology, introduced to solve the droplet problem, inherently contains a contradiction in its design. Traditional 90° bent-tube filtration achieves acceptable purification, but results in excessive plasma transport loss (efficiency often below 30%) and a low deposition rate, failing to meet industrial-grade production efficiency requirements. Simply increasing the bend angle to improve transport efficiency significantly weakens centrifugal filtration, leading to incomplete purification.

[0006] Fourth, the design and control precision of multilayer structures is insufficient. Simple component stacking or fuzzy gradient designs result in abrupt changes in physical (modulus, coefficient of thermal expansion) and chemical (bonding type) properties at the interfaces, which can easily become weak points for failure. Although ideal nanoscale multilayer structures can synergistically optimize performance through interface effects, existing technologies lack effective solutions for achieving precise gradual changes in composition and periodic modulation of structure at the nanoscale in complex material systems involving metals, nitrides, carbides, and amorphous carbon.

[0007] Therefore, there is an urgent need for an innovative coating technology and preparation method that can achieve breakthroughs in both the quality of the plasma source (source) and the construction of its microstructure (architecture). Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a high-bonding, ultra-hard nanolayered thin film, characterized by employing a deposition system equipped with a magnetically filtered cathode arc source, wherein the bending angle of the magnetically filtered cathode arc source is 135° and the ampere-turns of the filtering electromagnetic coil are 3600 ampere-turns; the method includes the following steps: S1. Perform plasma etching cleaning on the substrate; S2. In an inert gas atmosphere, Cr and Ti targets are alternately excited by the magnetically filtered cathode arc source to deposit a Cr / Ti nano-periodic multilayer structure as a metal bonding layer on the substrate surface. S3. In a mixed atmosphere of nitrogen and inert gas, Cr and Ti targets are excited by the magnetically filtered cathode arc source, and a CrN / TiN nano-periodic multilayer structure is deposited on the metal bonding layer as a nitride transition layer. S4. In a mixed atmosphere of nitrogen and inert gas, turn on the Ti target and the DC magnetron sputtering C target, and deposit a TiNC / CN nano-periodic multilayer structure on the nitride transition layer as a carbonitride bridging layer. S5. In a mixed atmosphere of carbon-containing reactive gas and inert gas, turn on the Ti target and C target, and deposit an aC:Ti / aC nano-periodic multilayer structure as a carbon-based functional layer on the carbonitride bridging layer.

[0009] A further technical solution is that the cathode target of the magnetically filtered cathode arc source is a cylindrical rotating cathode with a diameter of Φ100mm.

[0010] A further technical solution is that, in step S2, the alternating opening and closing period of the Cr target and the Ti target is 30-120 seconds, and the modulation period of the formed Cr / Ti nano-periodic multilayer structure is 10-50 nm.

[0011] A further technical solution is that, in step S5, the carbon-containing reactive gas is methane, and its flow rate increases stepwise from an initial value of 15-25 sccm to a final value of 50-70 sccm during the deposition process.

[0012] A high-bonding, ultra-hard nanolayered thin film, characterized in that it comprises, from the substrate outwards: a) Cr / Ti nano-periodic multilayer metal bonding layer; b) CrN / TiN nano-periodic multilayer nitride transition layer; c) TiNC / CN nano-periodic multilayer carbonitride bridging layer; d) aC:Ti / aC nano-periodic multilayer carbon-based functional layer.

[0013] A further technical solution is that the nanohardness of the film is not less than 60 GPa, and the critical load Lc2 of the scratch method is not less than 65 N.

[0014] A further technical solution is a magnetic filter bend with a bending angle of 135°, and an electromagnetic coil with an ampere-turns of 3600 for providing a magnetic field to the bend.

[0015] Application of thin films in the preparation of high-purity, high-density metal or nitride ceramic thin film layers.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. Parametric Innovation of the Magnetic Filtration System: The system uniquely employs a 135° bend angle and a matching 3600 ampere-turns high-ampere-turns filtering electromagnetic coil. This combination represents the "optimal balance point" verified through in-depth theoretical calculations and experiments. It achieves highly efficient filtration of macroscopic particles >0.3 μm (filtration efficiency >99.5%) while maintaining a high plasma transport efficiency of >50% (ensuring industrial-grade deposition rates). Furthermore, the strong magnetic field significantly enhances the ionization rate and energy of metal ions, resulting in extremely pure, highly active metal plasma suitable for depositing atomically smooth interfaces.

[0017] 2. Innovative Cathode Target Structure: A cylindrical rotating cathode with a diameter of Φ100mm is adopted. This design enables the arc spot to scan along the cylindrical surface at a uniform and stable spiral, fundamentally avoiding the violent local eruption of the arc spot in planar targets, further suppressing droplet generation at the source, and increasing the target utilization rate from less than 30% of traditional planar targets to over 70%.

[0018] 3. Innovative Coating Architecture Design: A "full-cycle nanomodulation" structure was proposed and implemented. From the innermost metal bonding layer to the outermost carbon-based functional layer, each main functional layer is composed of two sublayers with different compositions or structures, stacked alternately at nanoscale thicknesses (5-50 nm), forming a periodic internal interface. This design creates a massive number of nano-interfaces, which can both increase hardness by hindering dislocation movement and dissipate energy by inducing crack deflection, branching, and nano-bridging, thereby significantly improving toughness and effectively relaxing internal stress. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the full-cycle structure of the ultrahard nanomultilayer thin film of the present invention. From bottom to top, it shows the nano-cycle modulation structure of the substrate, Cr / Ti metal bonding layer, CrN / TiN nitride transition layer, TiNC / CN carbonitride bridging layer, and aC:Ti / aC carbon-based functional layer.

[0020] Figure 2 This is a schematic diagram of the core equipment used in the preparation method of the present invention, which focuses on showing the relative positions and connections of components such as the Φ100mm cylindrical rotating cathode, the 135° bent magnetic filter (marked as a 3600 ampere-turn coil), the vacuum chamber, the substrate holder, and the magnetron sputtering C target.

[0021] Figure 3 The image shown is a high-resolution scanning electron microscope (SEM) image of the cross-section of the thin film prepared in Example 1, which clearly shows the total thickness of each nano-periodic multilayer structure, the thickness of each sublayer, and the interface morphology, confirming the compactness and periodicity of the structure.

[0022] Figure 4 The comparison diagram shows the nanoindentation load-displacement curves of the film in Example 1 of the present invention (using conventional methods) and intuitively demonstrates that the film of the present invention has a smaller indentation depth and greater elastic recovery under the same load, indicating its higher hardness and better toughness. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example

[0024] Figure 1-4 This invention illustrates a preferred embodiment of a method for preparing a high-bonding, ultra-hard nanolayered thin film, the thin film itself, and its applications. This embodiment specifically includes: An ultrahard nano-multilayer thin film based on a 135° bent tube magnetic filtering arc and full-cycle modulation, the thin film comprising, from the substrate surface outwards: 1. High-purity nano-metal bonding layer: It is a Cr / Ti nano-periodic multilayer structure formed by alternating deposition of Cr plasma purified by magnetic filtration through the 135° bend tube and Ti plasma. Its function is to provide a clean and strong metallurgical bond with the substrate.

[0025] 2. Nanocomposite nitride transition layer: Deposited on the metal bonding layer, it is a CrN / TiN nano-periodic multilayer structure formed by the reaction deposition of purified Cr and Ti plasma in nitrogen gas, realizing a smooth transition in composition, structure and properties from metal to ceramic phase.

[0026] 3. Gradient carbonitride bridging layer: Deposited on the nitride layer, it is a TiNC / CN nano-periodic multilayer structure with a composition that gradually changes from nitrogen-rich to carbon-rich, formed by co-deposition of Ti plasma and magnetron sputtered C particles in a nitrogen atmosphere. It acts as a "chemical bonding bridge" connecting the nitride and the top carbon-based material.

[0027] 4. Nanocomposite carbon-based functional layer: Deposited on the bridging layer, it is a nano-periodic multilayer structure of alternating aC:Ti and aC layers formed by co-deposition of Ti plasma and C particles in a carbon-containing reactive gas. The aC:Ti sublayer is a nanocomposite of TiC nanocrystals embedded in an amorphous carbon matrix, providing ultra-high hardness and wear resistance; the aC sublayer provides lubrication and stress buffering.

[0028] The method for preparing the thin film employs a composite coating system consisting of a 135° bent magnetically filtered arc Cr target, a Ti target, and a DC magnetron sputtering (DC-MS) graphite target equipped with the Φ100mm cylindrical rotating cathode, characterized by the following steps: S1. Matrix pretreatment and high-energy plasma cleaning; S2. Deposition of high-purity Cr / Ti nanometal bonding layer: In an Ar atmosphere, Cr and Ti targets are alternately excited by the magnetically filtered arc source, and nano-periodic multilayers are deposited by using a program-controlled timing sequence (e.g., Cr target on for 60 seconds / off for 30 seconds, Ti target on for 60 seconds / off for 30 seconds). S3. Deposition of CrN / TiN nanocomposite nitride layer: In an Ar / N2 atmosphere, Cr and Ti targets are excited by the magnetic filter source and the N2 flow rate is simultaneously modulated (e.g., periodically switching between high and low flow rates) to deposit a nano-periodic multilayer. S4. Deposition of TiNC / CN gradient carbonitride bridging layer: In an Ar / N2 atmosphere, Ti target and C target are turned on, and a nano-periodic multilayer with gradually changing composition is deposited by periodically modulating the N2 on / off or C target current. S5. Deposition of aC:Ti / aC nanocomposite carbon-based functional layer: In an Ar / CH4 atmosphere, Ti and C targets are turned on, and CH4 flow rate is increased by gradient (e.g., 20 sccm every 15 minutes) combined with periodic modulation of Ti target current to deposit a nano-periodic multilayer with sp³ bonds on the surface.

[0029] Through the systematic innovations in hardware, process, and structure described above, this invention has achieved the following breakthrough effects:

[0030] Fabrication of ultrahard nano-multilayer thin films on the surface of cemented carbide cutting tools: Matrix: Commercial cemented carbide (WC-10%Co) turning inserts.

[0031] Equipment: as attached Figure 2 The multifunctional composite coating system shown is equipped with two independent Φ100mm cylindrical rotating cathode magnetic filter arc sources (Cr target, Ti target, filter parameters: 135° bend, 3600 ampere-turn coil).

[0032] Process steps: 1. Pretreatment (S1): The blade is ultrasonically cleaned with two ketones and ethanol for 15 minutes each, dried, and then placed in a vacuum chamber. The background vacuum is evacuated to 5.0 × 10⁻³ Pa, and 200 sccm of Ar is introduced. Ar⁺ glow discharge etching is performed at a bias voltage of -800 V for 20 minutes to thoroughly remove surface adsorbates and weak boundary layers.

[0033] 2. Deposition of the Cr / Ti bonding layer (S2): Ar working gas 100 sccm, substrate bias -75 V, temperature approximately 200°C. Program control: Start the cylindrical Cr cathode, current 120 A, deposition for 70 seconds; turn off the Cr target, start the cylindrical Ti cathode, current 160 A, deposition for 70 seconds. This constitutes one modulation cycle; repeat this cycle 20 times, for a total deposition time of approximately 46 minutes. The resulting bonding layer is approximately 0.8 μm thick, with a modulation cycle of approximately 40 nm, a smooth surface, and no droplets visible to the naked eye or microscope.

[0034] 3. Deposition of the CrN / TiN transition layer (S3): N2 was introduced at 80 sccm, while Ar was maintained at 100 sccm. Both the Cr target (160 Å) and the Ti target (160 Å) were simultaneously activated, and the bias voltage was increased to -80 V to enhance ion bombardment. The N2 flow rate was programmed to switch between "80 sccm (30 sec) / 20 sccm (30 sec)" at 1-minute intervals via a mass flow controller, thereby modulating the composition within the layer. Deposition was completed after 60 minutes, forming a dense nanocomposite layer with a thickness of approximately 1.2 μm and a modulation period of approximately 30 nm.

[0035] 4. Deposition of TiNC / CN bridging layer (S4): The Cr target is turned off. The Ti target (160 A) is kept on, and the columnar DC-MS graphite target is turned on simultaneously with a current set to 5 A. The N2 flow rate is set to 50 sccm, and the Ar flow rate to 100 sccm. The solenoid valve is controlled to switch between "N2 on (100 sccm) / N2 off (0 sccm)" every 2 minutes, while the C target current is simultaneously switched between "5 A / 8 A". Deposition is carried out for 50 minutes to form a gradient transition layer with a thickness of approximately 1.0 μm.

[0036] 5. Deposition of the aC:Ti / aC functional layer (S5): N2 is turned off. Methane (CH4) is introduced as the reactant gas, with an initial flow rate of 20 sccm and Ar at 100 sccm. The Ti target current is adjusted to 120 A, the C target current to 7 A, and the bias voltage is -70 V. A gradient process is used: the CH4 flow rate is increased by 20 sccm every 15 minutes until it reaches 60 sccm and is maintained. Simultaneously, the Ti target current is switched between 120 A and 80 A at 90-second intervals to control the thickness ratio of the aC:Ti sublayer to the aC sublayer. The total deposition time is 75 minutes, forming a nanocomposite functional layer with an outermost layer thickness of approximately 1.5 μm and a modulation period of approximately 35 nm. The total film thickness is approximately 4.5 μm.

[0037] Comparative example: Using the same equipment substrate, but replacing the magnetic filtration system with a traditional 90° bent tube filter (coil ampere-turns 2500 ampere-turns), and depositing only a simple Cr / TiN / aC:Ti three-layer structure instead of a nano-periodic modulation structure.

[0038] Performance Characterization and Comparison: 1. Surface morphology and roughness: The surface of the film in Example 1 was measured using atomic force microscopy (AFM). The arithmetic mean roughness (Ra) was 0.032 μm, and the root mean square roughness (Rq) was 0.041 μm, indicating an extremely smooth surface. The comparative film surface had a large number of submicron-sized protrusions, with Ra as high as 0.118 μm.

[0039] 2. Cross-sectional structure ( Figure 3 SEM cross-sectional images of the thin film in Example 1 show clear interfaces between layers, uniform periodicity of bright and dark stripes within the layers, and a dense structure without pores. Comparative cross-sections reveal a columnar crystalline structure and a small number of micropores.

[0040] 3. Mechanical properties ( Figure 4 Nanoindentation testing (maximum indentation depth 100 nm) showed that the nanohardness of the film in Example 1 was 64.7 GPa, the elastic modulus was 462 GPa, and the calculated H / E = 0.140 and H³ / E² = 0.63 GPa. The comparative film had a hardness of 52.3 GPa and an H³ / E² of 0.35 GPa.

[0041] 4. Bond strength: The scratch test was used. The critical load Lc2 of the film in Example 1 was 71.5 N, the acoustic emission signal was stable, and the failure manifestation was slight plastic grooving. The comparative film experienced severe brittle spalling when the load reached 48.2 N.

[0042] 5. Tribological properties: Tested on a ball-disc tribological testing machine (Si3N4 grinding balls, 5N load, dry friction). The stable coefficient of friction of the film in Example 1 was 0.18, and the calculated wear rate was 3.2 × 10⁻⁻⁻⁶. 7 mm³ / N•m. The coefficient of friction of the comparative film fluctuated significantly (0.22-0.28), and the wear rate was 8.9×10⁻ 7 mm³ / N•m.

[0043] Conclusion: This invention successfully fabricated an ultrahard nanolayered film with outstanding comprehensive performance through optimized 135° bent tube magnetic filtration technology, a Φ100mm cylindrical rotating cathode, and a full-cycle nanomodulation structure design. This film significantly surpasses traditional technologies in key indicators such as surface smoothness, film-substrate adhesion, nanohardness, toughness, and wear resistance. It is particularly suitable for surface strengthening under extreme conditions such as high-performance cutting tools, precision molding dies, and high-load bearings, and has significant industrial application value.

[0044] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A method for preparing a high-adhesion, ultrahard nanolayered thin film, characterized in that, A deposition system equipped with a magnetically filtered cathode arc source, wherein the bend angle of the magnetically filtered cathode arc source is 135° and the ampere-turns of the filtering electromagnetic coil are 3600 ampere-turns; the method includes the following steps: S1. Perform plasma etching cleaning on the substrate; S2. In an inert gas atmosphere, Cr and Ti targets are alternately excited by the magnetically filtered cathode arc source to deposit a Cr / Ti nano-periodic multilayer structure as a metal bonding layer on the substrate surface. S3. In a mixed atmosphere of nitrogen and inert gas, Cr and Ti targets are excited by the magnetically filtered cathode arc source, and a CrN / TiN nano-periodic multilayer structure is deposited on the metal bonding layer as a nitride transition layer. S4. In a mixed atmosphere of nitrogen and inert gas, turn on the Ti target and the DC magnetron sputtering C target, and deposit a TiNC / CN nano-periodic multilayer structure on the nitride transition layer as a carbonitride bridging layer. S5. In a mixed atmosphere of carbon-containing reactive gas and inert gas, turn on the Ti target and C target, and deposit an aC:Ti / aC nano-periodic multilayer structure as a carbon-based functional layer on the carbonitride bridging layer.

2. The method for preparing a high-adhesion, ultrahard nanolayered thin film according to claim 1, characterized in that, The cathode target of the magnetically filtered cathode arc source is a cylindrical rotating cathode with a diameter of Φ100mm.

3. The method for preparing a high-adhesion, ultrahard nanolayered thin film according to claim 1 or 2, characterized in that, In step S2, the alternating on / off cycle of the Cr target and Ti target is 30-120 seconds, and the modulation period of the formed Cr / Ti nano-periodic multilayer structure is 10-50 nm.

4. The method for preparing a high-adhesion, ultrahard nanolayered thin film according to claim 1, characterized in that, In step S5, the carbon-containing reactive gas is methane, and its flow rate increases stepwise from an initial value of 15-25 sccm to a final value of 50-70 sccm during the deposition process.

5. A high-bonding, ultrahard nanolayered thin film prepared by the method according to any one of claims 1 to 4, characterized in that, From the substrate outwards, the layers are sequentially: a) Cr / Ti nano-periodic multilayer metal bonding layer; b) CrN / TiN nano-periodic multilayer nitride transition layer; c) TiNC / CN nano-periodic multilayer carbonitride bridging layer; d) aC:Ti / aC nano-periodic multilayer carbon-based functional layer.

6. The thin film according to claim 5, characterized in that, The nanohardness of the film is not less than 60 GPa, and the critical load Lc2 of the scratch method is not less than 65 N.

7. The thin film according to claim 6, characterized in that, A magnetic filter bend with a bend angle of 135°, and an electromagnetic coil with an ampere-turns of 3600 for providing a magnetic field to the bend.

8. The application of the thin film according to claim 7 in the preparation of high-purity, high-density metal or nitride ceramic thin film layers.

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