A preparation process of high-hardness wear-resistant and corrosion-resistant AlCrN / AlCrBN multi-layer composite coating

Abstract

The application discloses a preparation process of a high-hardness wear-resistant and corrosion-resistant AlCrN / AlCrBN multilayer composite coating and relates to the technical field of protective coatings. The AlCrN / AlCrBN multilayer composite coating has gradient stress regulation and strengthening and toughening synergy, and a gradient structure design of a Cr transition layer / CrN buffer layer / AlCrN-AlCrBN nanometer multilayer modulation coating / AlCrBN functional layer is adopted. The Cr transition layer has good plasticity and metal wetting, forms a strong metal bond with a substrate, and buffers a lattice mismatch. The CrN buffer layer has moderate hardness and a thermal expansion coefficient between the substrate and the superhard layer, and layer-by-layer digestion of thermal stress is achieved. The heterogeneous interface of the nanometer multilayer modulation coating is a "fracture hindering wall", forces cracks to turn and branch, and significantly improves the comprehensive toughness of the coating, so that the problem of large internal stress and easy cracking of a traditional AlCrBN coating is solved.

Description

Technical Field

[0001] This invention relates to the field of protective coating technology, specifically to a preparation process for a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating. Background Technology

[0002] Modern manufacturing is transforming from "traditional manufacturing" to "extreme manufacturing." High-speed cutting, dry machining, and the aerospace and automotive industries are placing increasingly stringent performance requirements on precision components. Workpieces often face the combined effects of high temperature, high pressure, variable loads, and highly corrosive media. Coating technology, as a core means of improving the surface resistance of materials, has become a crucial link in the industrial chain.

[0003] While traditional CrN or TiN coatings can extend workpiece life to some extent, they suffer from insufficient hardness and poor overall performance in ultra-high hardness material processing scenarios. The emergence of aluminum-containing coatings (such as AlCrN) has significantly improved the coating's oxidation resistance. The dense Al2O3 protective film formed by Al at high temperatures significantly enhances the coating's serviceability in environments above 900°C. However, in pursuit of higher processing precision, AlCrBN nanocomposite coatings, formed by introducing boron (B), have significantly improved hardness due to the special structure of amorphous phase encapsulating nanocrystals. However, they suffer from extremely high internal stress and a large difference in thermal expansion coefficient with the substrate. Direct deposition of these coatings can easily lead to film cracking or adhesion failure, limiting their large-scale application in high-performance precision parts.

[0004] Therefore, developing a coating preparation technology that can both leverage the superhard properties of element B and ensure film quality and substrate bonding strength has become a key issue that urgently needs to be addressed in the field of surface engineering. Summary of the Invention

[0005] The purpose of this invention is to provide a preparation process for a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a preparation process for a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating, wherein a multilayer composite coating is sequentially deposited on a substrate using multi-arc ion plating technology. The multilayer composite coating, from the substrate outwards, sequentially includes a Cr transition layer, a CrN buffer layer, an AlCrN / AlCrBN nano-multilayer modulated coating, and an AlCrBN functional layer. The atomic percentages of the chemical composition of the prepared composite coating are: N 45.0~50.0 at.%, Al 27.5~29.6 at.%, Cr 18.2~23.5 at.%, B 2.0~3.5 at.%, hardness ≥30 GPa, bonding strength 60~70 N, elastic modulus 350~450 GPa, and wear rate ≤10⁻. 7mm³ / (N·m), corrosion current density ≤1×10⁻ 8 A / cm²; including at least the following steps:

[0007] S1: Target and substrate preparation, selecting alloy targets containing Al and Cr elements, alloy targets containing Al, Cr and B elements, and Cr metal targets; selecting substrate materials and performing surface treatment and cleaning;

[0008] S2: Sputtering equipment debugging: Fix the substrate on the coating chamber rotating frame, evacuate to the preset vacuum level, and set the sputtering distance between the target and the substrate and the substrate frame rotation speed;

[0009] S3: Thin film growth. After plasma bombardment etching of the substrate, a Cr transition layer, a CrN buffer layer, an AlCrN / AlCrBN nano-multilayer modulation coating and an AlCrBN functional layer are deposited sequentially. Nitrogen gas is introduced as a reaction gas during the deposition process to control the deposition pressure, substrate bias and arc source current.

[0010] S4: Post-treatment, which involves annealing the deposited coating.

[0011] Furthermore, in the alloy target containing Al and Cr elements, the mass fraction of Al is 65%–75% and the mass fraction of Cr is 25%–35%;

[0012] The alloy target containing Al, Cr, and B elements has an Al mass fraction of 60%–66%, a Cr mass fraction of 24%–30%, and a B mass fraction of 8%–12%.

[0013] The purity of the target materials is no less than 99.5%.

[0014] Furthermore, the substrate material includes at least silicon wafers, stainless steel, and hard alloys;

[0015] The surface treatment is a cross-grinding and polishing method;

[0016] The cleaning process involves sequentially ultrasonically cleaning in acetone, alcohol, and deionized water for 25–35 minutes each, followed by drying with nitrogen gas.

[0017] Furthermore, the sputtering distance is 15–20 cm, the substrate holder rotation speed is 1–2 r / min, and the vacuum level is not higher than 3.0 × 10⁻⁶. -3 Pa.

[0018] Furthermore, the conditions for plasma bombardment etching are as follows: 120~180 sccm of high-purity argon gas is introduced, the substrate bias voltage is -180~-220V, the etching current is 100~120A, the voltage is 40~45V, and the etching time is 25~35min.

[0019] Furthermore, the conditions for depositing the Cr transition layer are as follows:

[0020] High-purity argon gas of 100~150 sccm is introduced, the deposition pressure is 0.4~0.6 Pa, the substrate bias voltage is -80~-120 V, the arc source current is 100~120 A, and the Cr transition layer thickness is 0.1~0.2 μm.

[0021] Furthermore, the conditions for depositing the CrN buffer layer are as follows:

[0022] Nitrogen gas at 1000~1200 sccm was introduced, the deposition pressure was 0.6~1.0 Pa, the substrate bias voltage was -100~-150 V, the arc source current was 100~120 A, and the CrN buffer layer thickness was 0.25~0.4 μm.

[0023] Furthermore, the AlCrN / AlCrBN nano-multilayer modulated coating is formed by alternating deposition of alloy targets containing Al and Cr elements and alloy targets containing Al, Cr, and B elements.

[0024] The modulation period of the AlCrN / AlCrBN nanolayered modulation coating is 5~50nm, the modulation ratio of the AlCrN layer to the AlCrBN layer is 1:1.2~3, and the deposition conditions are as follows:

[0025] Nitrogen gas at 1000~1200 sccm is introduced, the deposition pressure is 2.0~2.3 Pa, the substrate bias voltage is -100~-150 V, the arc source current of the alloy target containing Al and Cr is 80~120 A, the arc source current of the alloy target containing Al, Cr and B is 100~140 A, and the coating thickness is 0.3~0.6 μm.

[0026] Furthermore, the conditions for depositing the AlCrBN functional layer are as follows: nitrogen gas is introduced at 1000~1200 sccm, the deposition pressure is 2.0~2.3 Pa, the substrate bias voltage is -100~-150 V, the arc source current is 100~140 A, and the AlCrBN functional layer thickness is 0.4~1.0 μm.

[0027] Furthermore, the annealing conditions are as follows:

[0028] Hold at 400-550℃ for 0-60 minutes in a nitrogen atmosphere of 50-100 sccm, then cool to room temperature in an inert gas atmosphere.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. This invention features gradient stress regulation and synergistic toughening. Through the gradient structure design of Cr transition layer / CrN buffer layer / AlCrN-AlCrBN nano-multilayer modulated coating / AlCrBN functional layer, the Cr transition layer, with its good plasticity and metal wettability, forms a strong metallic bond with the matrix, buffering lattice mismatch; the CrN buffer layer has moderate hardness and a thermal expansion coefficient between the matrix and the superhard layer, absorbing thermal stress layer by layer; the heterogeneous interface of the nano-multilayer modulated coating acts as a "fracture barrier wall", forcing cracks to turn and branch, significantly improving the overall toughness of the coating, and solving the problem of high internal stress and easy cracking of traditional AlCrBN coatings.

[0031] 2. The present invention combines high hardness and extreme stability. The coating forms a "nanocrystalline-amorphous" composite structure (nc-(Al,Cr)N / a-BN) at the microscopic level. The B element inhibits the coarsening of AlCrN grains and significantly improves hardness through the Hall-Petch effect. At high temperature, the Al element forms a dense Al2O3 passivation film, and the B element forms a self-healing oxide. The dual protection mechanism improves the oxidation resistance temperature. The nano-multilayer structure hinders corrosion channels, enhances chemical inertness and corrosion resistance, and ensures the stability of the coating in high-temperature and corrosive environments.

[0032] 3. The present invention has excellent wear-corrosion coupling protection performance. The extremely high chemical inertness of the coating maintains micro-density within the wear trajectory, inhibiting the synergistic destructive effect of friction and corrosion. At the micro-cracks generated by wear, Al and B elements react rapidly with the environment to form a self-healing nano-oxide film, which has both solid lubrication and electrochemical barrier functions. The gradient multilayer structure changes the diffusion path of the corrosive medium and prolongs its penetration time to the substrate. Even if the surface layer is locally damaged, the underlying coating can still provide continuous protection, which greatly improves the coating's long-term service capability and dimensional accuracy retention under wear-corrosion coupling conditions.

[0033] 4. The process of this invention is stable and controllable, and has high industrial application value. By optimizing the multi-arc ion plating parameters, the problems of "target poisoning" and "molten droplet splashing" in the nitriding process of aluminum chromium boron alloy targets are solved. The process has a high degree of standardization and strong repeatability. The prepared coating can be widely used in key components in aerospace, automobile manufacturing, precision molds and other fields, which can significantly extend the service life, reduce the frequency of production changeover and production costs, and provide theoretical support and practical basis for surface protection technology in extreme environments. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the target arrangement in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the multilayer composite coating structure prepared according to the present invention;

[0037] Figure 3 The XRD diffraction pattern of the coating of this invention;

[0038] Figure 4 This is a wear morphology diagram of the coating of the present invention;

[0039] Figure 5 This is a diagram showing the electrochemical results of the coating after friction in this invention. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0041] Example 1:

[0042] Please see Figures 1-5 A process for preparing a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating is disclosed. The process employs multi-arc ion plating technology to sequentially deposit a multilayer composite coating on a substrate. The multilayer composite coating, from the substrate outwards, comprises a Cr transition layer, a CrN buffer layer, an AlCrN / AlCrBN nano-multilayer modulated coating, and an AlCrBN functional layer. The atomic percentages of the prepared composite coating are: N 45.0~50.0 at.%, Al 27.5~29.6 at.%, Cr 18.2~23.5 at.%, B 2.0~3.5 at.%, with a hardness ≥30 GPa, adhesion strength 60~70 N, elastic modulus 350~450 GPa, and wear rate ≤10⁻. 7 mm³ / (N·m), corrosion current density ≤1×10⁻ 8 A / cm²; including at least the following steps:

[0043] S1: Target and substrate preparation, selecting alloy targets containing Al and Cr elements, alloy targets containing Al, Cr and B elements, and Cr metal targets; selecting substrate materials and performing surface treatment and cleaning;

[0044] S2: Sputtering equipment debugging: Fix the substrate on the coating chamber rotating frame, evacuate to the preset vacuum level, and set the sputtering distance between the target and the substrate and the substrate frame rotation speed;

[0045] S3: Thin film growth. After plasma bombardment etching of the substrate, a Cr transition layer, a CrN buffer layer, an AlCrN / AlCrBN nano-multilayer modulation coating and an AlCrBN functional layer are deposited sequentially. Nitrogen gas is introduced as a reaction gas during the deposition process to control the deposition pressure, substrate bias and arc source current.

[0046] S4: Post-treatment, which involves annealing the deposited coating.

[0047] I. Target and Substrate Preparation

[0048] 1. Target selection: Aluminum-chromium-boron alloy, aluminum-chromium alloy, and chromium metal targets with a purity of 99.5% or higher are selected. The alloy composition of the AlCrB target is (wt.%) 63% aluminum, 27% chromium, and 10% boron, and the alloy composition of the AlCr target is (wt.%) 70% aluminum and 30% chromium.

[0049] 2. Substrate Selection: Substrate materials include silicon wafers, 316 stainless steel, and cemented carbide blocks. Before coating, the sample surface needs to be ground and polished. All processes employ a cross-cutting method to avoid directional scratches, laying a solid foundation for subsequent high-quality thin film growth.

[0050] 3. Substrate Cleaning: The substrate was ultrasonically cleaned sequentially in acetone, alcohol, and deionized water for 30 minutes each time. Afterward, the substrate was dried with nitrogen and placed back into the cavity. These cleaning steps effectively removed impurities and contaminants from the substrate surface, ensuring a clean substrate surface and providing excellent conditions for subsequent film growth.

[0051] II. Sputtering Equipment Commissioning

[0052] 1. Parameter settings: Select a multi-arc ion plating equipment, and set the sputtering distance between the target and the substrate to 15-20 cm.

[0053] 2. Vacuum treatment and substrate rotation: The cleaned substrate is placed into the vacuum chamber of the equipment, and the chamber is evacuated to a vacuum level of 3×10⁻⁶. -3 Below Pa. This high vacuum environment significantly reduces the adverse effects of external impurities on thin film growth. Simultaneously, to ensure coating uniformity, the substrate holder rotates at a constant speed of 2 r / min, allowing the thin film to uniformly receive sputtered material during growth, thereby improving the film's quality and performance.

[0054] III. Thin Film Growth Stage

[0055] 1. The substrate is heated to 300-400℃ in a vacuum environment and held for 1-2 hours to more effectively remove adsorbates and moisture from the substrate surface, while creating suitable temperature conditions for subsequent thin film growth.

[0056] 2. The sample holder rotation speed is set to 1-2 r / min to ensure uniform Ar ion bombardment of the substrate surface. 150 sccm of high-purity argon gas is introduced into the vacuum chamber, and IET cleaning is performed for 30 minutes under a substrate bias of -200V to remove surface impurities. The etching current is 100-120A, the voltage is 40-45V, and the etching time is 25-35 min.

[0057] 3. A Cr metal transition layer was prepared using a Cr target. High-purity argon gas (100-150 sccm) was introduced, and the rotation speed of the rotating platform was adjusted to 1-2 r / min to ensure uniform deposition. During the deposition of the Cr transition layer, the arc source current was set to 100-120 A, the deposition pressure to 0.4-0.6 Pa, the bias voltage to -100 V, and the deposition thickness to 150-200 nm.

[0058] 4. Prepare a CrN intermediate layer using a metal Cr target, introduce 1000-1200 sccm of nitrogen gas, adjust the rotation speed of the rotating frame to 1 r / min-2 r / min to ensure the uniformity of the coating, set the deposition pressure to 0.6-1.0 Pa, set the substrate bias voltage to -100V~-150V, turn on the Cr target, and set the arc source current to 100A-120A.

[0059] 5. Prepare AlCrN / AlCrBN nanolayer structures using AlCrB and AlCr targets. Purge with 1000-1200 sccm of nitrogen gas and adjust the rotation speed of the rotating frame to 1 r / min-2 r / min to ensure coating uniformity. Set the deposition pressure to 2.0-2.3 Pa and the substrate bias voltage to -100V to -150V. Use AlCrB and AlCr targets for alternating deposition, with the arc source current of the AlCrB target being 100A-140A and the arc source current of the AlCr target being 80A-120A.

[0060] 6. Prepare AlCrBN functional layers using an AlCrB target. Purge with 1000-1200 sccm of nitrogen gas, adjust the rotation speed of the rotating frame to 1 r / min-2 r / min to ensure uniform coating, set the deposition pressure to 2.0-2.3 Pa, set the substrate bias voltage to -100V to -150V, and set the AlCrB target arc source current to 100A-140A.

[0061] 7. A high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating was prepared, wherein the thickness of the Cr metal transition layer was 0.1-0.2 μm, the thickness of the CrN intermediate layer was 0.25-0.4 μm, the thickness of the AlCrN / AlCrBN nano-multilayer modulation coating was 0.3-0.6 μm, the modulation period of the AlCrN / AlCrBN nano-multilayer was 5-50 nm, the modulation ratio of the AlCrN layer to the AlCrBN layer was 1:1.2~3, and the thickness of the AlCrBN functional layer was 0.4-1.0 μm.

[0062] 8. The chemical composition of the composite coating surface is nitrogen, aluminum, chromium, and boron, specifically in atomic percentage: N 45.0-50.0 at.%, Al 27.5-29.6 at.%, Cr 18.2-23.5 at.%, B 2.0-3.5 at.%. The composite coating has a hardness of over 30 GPa, an adhesion strength of 60-70 N, an elastic modulus of 350-450 GPa, and a wear rate and corrosion current density reaching 10. -7 mm 3 / (Nm) and 1×10 -8 A / cm 2 It has advantages such as high hardness, high toughness, low coefficient of friction, good wear resistance, and corrosion resistance.

[0063] IV. Post-processing stage

[0064] 1. Annealing Treatment: After film growth and doping are completed, the film undergoes in-situ annealing. Under nitrogen atmosphere at 50-100 sccm, the film is held at 400-550℃ for 0-60 minutes to prevent thermal stress caused by sudden cooling. Heating is then turned off, and the film is cooled to room temperature under an inert gas atmosphere. Annealing treatment can further improve the crystallinity of the film, eliminate internal stress, and promote diffusion and uniform distribution between layers, thereby improving the film's performance and stability.

[0065] 2. Performance testing and optimization: The prepared AlCrBN multilayer films were subjected to relevant performance tests and structural characterization.

[0066] The optimized preparation method described above allows for more precise control of the growth of AlCrBN multilayer films, improving film quality and performance, and providing strong support for the development of the protective coating field.

[0067] Example 2:

[0068] This embodiment proposes the following specific operations based on the above embodiment one:

[0069] This embodiment employs an arc ion plating system to prepare a high-hardness, high-wear-resistant, and corrosion-resistant AlCrN / AlCrBN nano-multilayer composite coating. The substrate materials used include cemented carbide blocks, 316L stainless steel sheets, and silicon wafers. All substrate materials underwent rigorous pretreatment processes, including ultrasonic cleaning (30 minutes each with acetone, alcohol, and deionized water sequentially) and vacuum chamber plasma glow discharge cleaning (Ar ion bombardment, -200V bias, for 30 minutes) to remove surface impurities. The equipment is equipped with six independently controlled target sources: two AlCr targets, two Cr targets, and two AlCrB targets. The deposition rate was calibrated before the formal experiment to provide a stable and reliable process foundation for subsequent coating deposition. The target arrangement is as follows... Figure 1 As shown.

[0070] The equipment was heated to 350°C, and all subsequent experimental procedures were conducted at this deposition temperature.

[0071] First, plasma bombardment etching was performed using a titanium target at a current of 100 A, a voltage of 42 V, and an etching time of 30 min. Then, a Cr metal transition layer was prepared using a Cr target, with 100 sccm of high-purity argon gas introduced and the rotation speed of the rotating frame adjusted to 2 r / min to ensure uniformity of particle bombardment on the substrate surface.

[0072] During the deposition of the Cr transition layer, the arc source current was set to 100 A, the deposition pressure to 0.58 Pa, the bias voltage to -100 V, the deposition time to 14 min, and the deposition thickness to 0.2 μm. A CrN intermediate layer was then prepared using a metallic Cr target. Nitrogen gas was introduced at 1000 sccm, and the rotor speed was adjusted to 2 r / min to ensure coating uniformity. The deposition pressure was 2.3 Pa, the substrate bias voltage to -150 V, the arc source current to 100 A, the deposition time to 18 min, and the deposition thickness to 300 nm. The Cr transition layer exhibits good plasticity and excellent metal wettability, enabling it to form strong metallic bonds with steel or hard alloy substrates. This layer effectively buffers the lattice mismatch between the subsequent ceramic layer and the metal substrate. The subsequently introduced CrN buffer layer, with moderate hardness and a thermal expansion coefficient between that of the substrate and the ultra-hard layer, can progressively absorb the thermal stress accumulated during coating growth.

[0073] Based on the first two layers, an AlCrN / AlCrBN nanolayer structure was prepared using AlCrB and AlCr targets. AlCrB and AlCr targets were deposited alternately, with a modulation period of 30 nm (10 nm for the AlCrN layer and 20 nm for the AlCrBN layer), and a modulation ratio of 1:2. The specific deposition process parameters were as follows: 1000 sccm of nitrogen gas was introduced, the rotary table speed was adjusted to 2 r / min, the AlCrBN layer used an AlCrB target, the deposition pressure was 2.3 Pa, the substrate bias was set to -150 V, and the AlCrB target arc source current was 100 A; the AlCrN layer used an AlCr target, the deposition pressure was 2.3 Pa, the substrate bias was set to -120 V, and the AlCr target arc source current was 80 A. A total of 20 deposition cycles were performed, resulting in a total modulation coating thickness of 0.6 μm.

[0074] Finally, the AlCrBN functional layer was prepared. During the preparation process, the uniform distribution of the coating was ensured by maintaining the rotating frame speed at 2 r / min. At the same time, 1000 sccm of nitrogen gas was introduced as the reaction gas and the vacuum pressure of 2.3 Pa was maintained at the film gauge to allow the AlCrB target material to be deposited. The arc source current was set to 100 A, the bias voltage to -150 V, the deposition time to 55 min, and the deposition thickness to be 1 μm.

[0075] Figure 2 The diagram shows the structure of the prepared nano-multilayer composite coating, in which a Cr metal transition layer, a CrN intermediate layer, an AlCrN / AlCrBN nanocomposite multilayer, and an AlCrBN functional layer are sequentially deposited on the substrate.

[0076] Chemical composition analysis was performed on the surface of the prepared nano-multilayer composite coating. The coating is composed of five elements: N, Al, Cr, and B. The specific composition is shown in Table 1, which was analyzed by EDS combined with XPS.

[0077] Table 1. Elemental content of high-hardness, high-wear-resistant and corrosion-resistant AlCrN / AlCrBN nano-multilayer materials

[0078]

[0079] Figure 3 The XRD diffraction pattern of the prepared nano-multilayer composite coating shows that the AlCrBN coating is composed of a single-phase NaCl-type AlCrBN solid solution. The diffraction peak of the fcc-AlCrBN phase is located between FCC-AlN and FCC-CrN, which reflects that Cr in the CrN lattice is replaced by Al to form a solid solution.

[0080] Table 2 shows the hardness and elastic modulus of the prepared nano-multilayer composite coating, indicating that the coating has good mechanical properties.

[0081] Table 2 Hardness and Elastic Modulus

[0082]

[0083] Figure 4 The wear morphology of the prepared nano-multilayer composite coating is shown, and the test results show that the wear rate of the coating is 6.23 × 10⁻⁶. -7 mm 3 The wear rate of / Nm is higher than that of AlCrBN coatings in existing literature, indicating that the multilayer structure in this invention effectively improves the wear resistance of the coating.

[0084] Figure 5 The image shows the electrochemical results of the prepared nano-multilayer composite coating after friction. The test results also show that the multilayer structure in this invention effectively blocks Cl. -1 The ion corrosion channels significantly improve the corrosion resistance of the coating under wear conditions.

[0085] The advantages of the above embodiments are as follows:

[0086] 1. Synergistic mechanism of gradient stress regulation and toughening

[0087] This invention achieves a scientific distribution and dynamic balance of internal stress and a multi-layered interface blocking effect through a precisely designed Cr transition layer / CrN buffer layer / AlCrN-AlCrBN intermediate layer / AlCrBN layer gradient multi-layer structure. The coating forms nanoscale multi-layer interfaces by alternating deposition of AlCrN and AlCrBN. These interfaces, acting as natural barriers to dislocation movement, effectively absorb energy generated by external loads. Unlike the abrupt interface jumps in traditional coatings, this invention utilizes the buffering effect of Cr / CrN to reduce the shear stress between the coating and the substrate, resulting in a qualitative leap in the overall toughness of the coating.

[0088] 2. High hardness and extreme stability brought about by nanocomposite structures

[0089] The AlCrBN nanolayered coating prepared by this invention exhibits a typical "nanocrystalline-amorphous" composite structure (nc-(Al,Cr)N / a-BN) at the microscopic level, demonstrating excellent mechanical resistance. Grain refinement and strengthening: The introduction of boron (B) effectively suppresses AlCrN grain coarsening, significantly improving the coating hardness through the Hall-Petch effect. This high hardness remains stable even under high-temperature friction conditions.

[0090] Exceptional high-temperature oxidation resistance: During high-temperature processing, Al atoms on the coating surface preferentially undergo selective oxidation, forming a dense Al₂O₃ passivation film. Simultaneously, Bo (B) atoms may form self-healing oxides. This dual protection mechanism effectively prevents the diffusion of oxygen atoms into the coating interior. The coating's oxidation resistance temperature is significantly improved.

[0091] Chemical inertness and corrosion resistance: The nano-multilayer structure effectively blocks corrosion channels caused by micropore defects common in multi-arc ion plating processes. This gives the coating extremely strong resistance to penetration when facing corrosive media such as acids, alkalis, and salt spray.

[0092] 3. In-depth exploration of the coupling mechanism between wear and corrosion and its beneficial effects

[0093] In actual service environments, workpieces are often not simply subjected to mechanical wear, but rather to a "wear-corrosion coupling" condition involving friction and corrosion. This invention, through in-depth corrosion studies of AlCrN / AlCrBN samples after friction, reveals the excellent chemical and mechanical stability of this coating under extreme conditions.

[0094] a. Effective suppression of synergistic destructive effects

[0095] Traditional single-layer coatings are prone to mechanical stripping of the passivation film during friction, exposing the fresh metal substrate. In corrosive media (such as seawater, cutting fluid, or acidic atmospheres), this can induce severe electrochemical corrosion, further exacerbating mechanical wear and creating a destructive effect where "1+1>2". This invention utilizes the extremely high chemical inertness of the AlCrBN nanocomposite structure, maintaining microscopic density within the wear scar. Studies show that even after subjected to severe friction, the corrosion current density in the wear region remains at an extremely low level. This effectively inhibits the penetration of corrosive media into the substrate through wear cracks.

[0096] b. Electrochemical passivation repair within the wear track

[0097] A key highlight of this invention is that the coating possesses a certain degree of "interfacial passivation repair" capability after friction occurs. When the AlCrN / AlCrBN multilayer structure is subjected to cutting stress and microcracks are generated, the exposed Al and B elements rapidly react with oxygen or electrolytes in the environment. They form a continuous, self-healing nano-oxide film (such as an Al2O3-borate composite) inside the wear pit. This film not only acts as a solid lubricant but also functions as an electrochemical barrier. It significantly improves the polarization resistance after wear. The wear resistance and corrosion resistance of the coating are simultaneously extended.

[0098] c. A gradient barrier to block "penetrating corrosion"

[0099] Observation of the corrosion morphology of the cross-section after friction revealed that the gradient multilayer design of this invention successfully alters the diffusion path of the corrosive medium. In ordinary coatings, corrosion often penetrates directly along columnar grain boundaries perpendicular to the surface. However, in the multilayer system of this invention, the nano-interfaces between layers act as a "labyrinthine" barrier layer. The corrosive medium is forced to diffuse laterally along the interlayer boundaries. This change in path significantly prolongs the time it takes for the medium to reach the Cr transition layer and the substrate. Even if the surface AlCrBN layer experiences localized loss, the underlying AlCrN / AlCrBN nanolayers and CrN buffer layer still provide continuous electrochemical protection. This greatly improves the coating's resistance to spalling under complex alternating loads.

[0100] d. Improve long-term service accuracy under heavy load environments

[0101] The results of the study on the coupling of friction and corrosion show that, after long-term abrasion cycles, the coating of this invention exhibits significantly lower pit depth and corrosion product accumulation compared to the control sample. This means that the workpiece not only does not break under harsh operating conditions but also maintains its dimensional accuracy over a long period. This is of crucial significance for precision molds and aerospace seals. It not only reduces fit failures caused by material loss but also avoids stress concentration induced by corrosion pits, thereby reducing the risk of fatigue fracture in components. The multilayer composite process of this invention, through scientific intervention in the abrasion coupling process, lays a solid materials science foundation for achieving long-life and highly reliable service of equipment.

[0102] In summary:

[0103] The multilayer composite system proposed in this invention, consisting of a Cr transition layer, a CrN buffer layer, an AlCrN-AlCrBN alternating deposition intermediate layer, and an AlCrBN functional layer, is not a simple additive process but a precise design based on interfacial mechanics and stress gradient theory. First, Cr acts as a "vanguard," addressing the fundamental issue. The pure Cr layer possesses excellent plasticity and superior metal wettability, enabling it to form strong metallic bonds with steel or hard alloy substrates. This layer effectively buffers the lattice mismatch between the subsequent ceramic layer and the metal substrate. The subsequently introduced CrN buffer layer acts as a "shock absorber." Its moderate hardness and coefficient of thermal expansion, falling between that of the substrate and the ultra-hard layer, allow it to progressively absorb the thermal stress accumulated during coating growth. Second, the synergy between the intermediate and functional layers aims to find a perfect balance between hardness and toughness. In this invention, by precisely controlling the alternating deposition of AlCrN / AlCrBN, a large number of heterogeneous interfaces are artificially created. These interfaces act as microscopic "fracture barriers." When a crack initiates inside the coating and attempts to propagate longitudinally, a sudden change in modulus at the interface forces the crack to change direction, branch, or dissipate energy at the interface. This design cleverly avoids the microstructural loosening problem that may occur under high-pressure preparation.

[0104] In summary, the gradient multilayer coating system constructed in this invention not only provides a standardized technical route for preparing high-performance multi-element composite coatings, but also has significant industrial application value. By optimizing the multi-arc ion plating parameters, the problems of "target poisoning" and "molten droplet splashing" in the nitriding process of aluminum-chromium-boron alloy targets are solved, enabling the prepared coating to possess high hardness, excellent friction-reducing and self-lubricating properties, and outstanding chemical stability. This can not only significantly extend the service life of key components in aerospace, automotive manufacturing, and other fields, and reduce production changeover frequency and costs, but also provide important theoretical support and practical basis for developing next-generation surface protection technologies for extreme environments.

[0105] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A preparation process for a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating, characterized in that: A multi-layer composite coating is sequentially deposited on a substrate using multi-arc ion plating technology. The multi-layer composite coating, from the substrate outwards, comprises a Cr transition layer, a CrN buffer layer, an AlCrN / AlCrBN nano-multilayer modulated coating, and an AlCrBN functional layer. The process includes at least the following steps: S1: Target and substrate preparation, selecting alloy targets containing Al and Cr elements, alloy targets containing Al, Cr and B elements, and Cr metal targets; selecting substrate materials and performing surface treatment and cleaning; S2: Sputtering equipment debugging: Fix the substrate on the coating chamber rotating frame, evacuate to the preset vacuum level, and set the sputtering distance between the target and the substrate and the substrate frame rotation speed; S3: Thin film growth. After plasma bombardment etching of the substrate, a Cr transition layer, a CrN buffer layer, an AlCrN / AlCrBN nano-multilayer modulation coating and an AlCrBN functional layer are deposited sequentially. Nitrogen gas is introduced as a reaction gas during the deposition process to control the deposition pressure, substrate bias and arc source current. S4: Post-treatment, which involves annealing the deposited coating.

2. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The alloy target containing Al and Cr has an Al mass fraction of 65%–75% and a Cr mass fraction of 25%–35%. The alloy target containing Al, Cr, and B elements has an Al mass fraction of 60%–66%, a Cr mass fraction of 24%–30%, and a B mass fraction of 8%–12%. The purity of the target materials is no less than 99.5%.

3. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The substrate material includes at least silicon wafers, stainless steel, and hard alloys; The surface treatment is a cross-grinding and polishing method; The cleaning process involves sequentially ultrasonically cleaning in acetone, alcohol, and deionized water for 25–35 minutes each, followed by drying with nitrogen gas.

4. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The sputtering distance is 15–20 cm, the substrate holder rotation speed is 1–2 r / min, and the vacuum level is not higher than 3.0 × 10⁻⁶. - 3 Pa.

5. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The conditions for plasma bombardment etching are as follows: 120~180 sccm of high-purity argon gas is introduced, the substrate bias voltage is -180~-220V, the etching current is 100~120A, the voltage is 40~45V, and the etching time is 25~35min.

6. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The conditions for depositing the Cr transition layer are: High-purity argon gas of 100~150 sccm is introduced, the deposition pressure is 0.4~0.6 Pa, the substrate bias voltage is -80~-120 V, the arc source current is 100~120 A, and the Cr transition layer thickness is 0.1~0.2 μm.

7. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The conditions for depositing the CrN buffer layer are as follows: Nitrogen gas at 1000~1200 sccm was introduced, the deposition pressure was 0.6~1.0 Pa, the substrate bias voltage was -100~-150 V, the arc source current was 100~120 A, and the CrN buffer layer thickness was 0.25~0.4 μm.

8. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The AlCrN / AlCrBN nano-multilayer modulated coating is formed by alternating deposition of alloy targets containing Al and Cr elements and alloy targets containing Al, Cr and B elements. The modulation period of the AlCrN / AlCrBN nanolayered modulation coating is 5~50nm, the modulation ratio of the AlCrN layer to the AlCrBN layer is 1:1.2~3, and the deposition conditions are as follows: Nitrogen gas at 1000~1200 sccm is introduced, the deposition pressure is 2.0~2.3 Pa, the substrate bias voltage is -100~-150 V, the arc source current of the alloy target containing Al and Cr is 80~120 A, the arc source current of the alloy target containing Al, Cr and B is 100~140 A, and the coating thickness is 0.3~0.6 μm.

9. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: The conditions for depositing the AlCrBN functional layer are as follows: nitrogen gas is introduced at 1000~1200 sccm, the deposition pressure is 2.0~2.3 Pa, the substrate bias voltage is -100~-150 V, the arc source current is 100~140 A, and the AlCrBN functional layer thickness is 0.4~1.0 μm.

10. The preparation process of a high-hardness, wear-resistant, and corrosion-resistant AlCrN / AlCrBN multilayer composite coating according to claim 1, characterized in that: Annealing conditions are as follows: Hold at 400-550℃ for 0-60 minutes in a nitrogen atmosphere of 50-100 sccm, then cool to room temperature in an inert gas atmosphere.

Images