Composite coating with corrosion resistance and self-lubricating performance, preparation method and mechanical part

Abstract

The invention belongs to the technical field of composite coatings, and particularly provides a composite coating with corrosion resistance and self-lubricating performance, a preparation method and a mechanical part. A periodic nano laminated structure composed of a metal bonding layer, an alloy toughening layer and a metal compound strengthening layer is used as an intermediate support body to be combined with surface DLC, so that the problem of early failure caused by poor toughness, weak interface bonding and insufficient corrosion protection of a traditional DLC coating under harsh working conditions of corrosion, impact and wear coupling is effectively solved; the excellent surface performance of DLC can be kept, and meanwhile the binding force, toughness and corrosion resistance of a coating are improved.

Description

Technical Field

[0001] This invention belongs to the field of composite coating technology, and specifically provides a composite coating with both corrosion resistance and self-lubricating properties, as well as its preparation method and mechanical components. Background Technology

[0002] DLC (Diamond-Like Carbon) coatings, due to their high hardness, low coefficient of friction, and excellent chemical inertness, have shown great application potential in high-end machinery, precision molds, and medical devices. However, under complex environments involving corrosion, impact, and wear, these coatings are prone to premature failure, leading to loss of coating function or secondary damage, thereby reducing the service life of components.

[0003] Currently, DLC coatings mostly employ a three-layer structure: a metal base layer, a metal carbide transition layer, and a DLC surface lubricating layer. Commonly used base metals include Cr and Ti, and metal compounds such as chromium carbide and tungsten carbide. This coating structure is simple and easy to prepare, but it has certain disadvantages when the coating is exposed to corrosive media, subjected to strong impacts, or subjected to severe wear. 1. Monolayer metals or metal carbides, when of a certain thickness, are prone to columnar crystal growth. The defect and impurity densities at the grain boundaries of columnar crystals are high, which easily leads to corrosion.

[0004] 2. Elemental chromium (Cr) has high hardness and a certain degree of brittleness. Its carbides, CrCx, are even more brittle. On softer substrates such as aluminum alloys, when the coating surface is subjected to high external loads, the eggshell effect is significant, and the coating is prone to brittle cracking or peeling. The coating design has limited ability to mitigate external impacts.

[0005] 3. High-stress, highly brittle metal carbides are prone to developing microcracks on their surface when the coating grows to a certain thickness. This can be considered a design flaw in corrosive application environments, as corrosive media can penetrate deep into the substrate through the cracks and induce corrosion.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] One objective of this invention is to solve the problem that traditional DLC coatings (metal / carbide / DLC three-layer structure) are prone to failure under harsh conditions of corrosion, wear, and impact coupling.

[0008] To achieve the above objectives, the present invention provides a composite coating that combines corrosion resistance and self-lubrication properties, wherein the composite coating comprises, from the inside out, a periodic nanolayer and a surface DLC layer. The periodic nanolayer is composed of n sequentially stacked composite stack units, where n is an integer greater than 1. Each composite stack unit includes, from the inside out, a metal bonding layer, an alloy toughening layer, and a metal compound reinforcement layer stacked sequentially.

[0009] Further, the material of the metal bonding layer is set to chromium, titanium, zirconium, molybdenum, or tungsten; when the material of the metal bonding layer is chromium, the material of the alloy toughening layer is a nickel-chromium alloy; when the material of the metal bonding layer is titanium, the material of the alloy toughening layer is a titanium-aluminum alloy, a titanium-aluminum-vanadium alloy, or a titanium-zirconium alloy; when the material of the metal bonding layer is molybdenum, the material of the alloy toughening layer is a molybdenum-titanium alloy or a molybdenum-based alloy with tungsten, rhenium, tantalum, zirconium, or hafnium as alloying elements; when the material of the metal bonding layer is tungsten, the material of the alloy toughening layer is a tungsten-molybdenum alloy or a tungsten-based alloy with rhenium, tantalum, or niobium as alloying elements; when the material of the metal bonding layer is zirconium, the material of the alloy toughening layer is a zirconium-niobium alloy; the material of the metal compound reinforcement layer is a carbide, nitride, or carbonitride corresponding to the metal element in the metal bonding layer or the alloy toughening layer; and / or, the composite coating is applied to a steel substrate, a lightweight alloy substrate, and a hard alloy substrate.

[0010] Further, the thickness of the first metal bonding layer in contact with the substrate is 0.2~0.5 μm; the total thickness of each composite stack unit is 0.05~0.3 μm; the thickness of the last metal compound reinforcement layer in contact with the surface DLC layer is 0.1~1.0 μm; the thickness of the surface DLC layer is 0.5~5 μm; the value of n ranges from 4 to 20; and / or, when applied to a lightweight alloy substrate, the material of the metal bonding layer is Ti, the material of the alloy toughening layer is TiAlV alloy, wherein the mass percentage of Al is 3%~7% and the mass percentage of V is 2%~6%; the material of the metal compound reinforcement layer is titanium carbonitride; and the surface DLC layer is a Ti-doped DLC layer.

[0011] In other embodiments, a mechanical component is provided, wherein the working surface of the component is provided with the composite coating as described above.

[0012] In other embodiments, a method for preparing a composite coating is provided, which can be used to prepare the composite coating with both corrosion resistance and self-lubricating properties as described above; the method includes: pretreating the substrate, including cleaning, vacuum heating and plasma etching; depositing the periodic nanolayers on the substrate using an alternating cycle process of magnetron sputtering and reactive magnetron sputtering, wherein each cycle includes: sequentially depositing a metal bonding layer and an alloy toughening layer using magnetron sputtering; depositing a metal compound reinforcement layer on the alloy toughening layer using reactive magnetron sputtering in a reactive gas atmosphere; repeating the above deposition process n times; and depositing a surface DLC layer on the periodic nanolayers using a plasma-assisted chemical vapor deposition process.

[0013] Furthermore, the step of pretreating the substrate includes: cleaning the steel substrate or lightweight alloy substrate, placing it in a vacuum chamber, and evacuating the vacuum level to no higher than 5 × 10⁻⁶. -5 The temperature was increased to 150°C and held for 40 minutes, followed by plasma etching with argon gas. The vacuum level during etching was 8 × 10⁻⁶ mbar. -5 mbar.

[0014] Furthermore, in the step of depositing the periodic nanolayers on the substrate using an alternating cyclic process of magnetron sputtering and reactive magnetron sputtering, when preparing a coating for a steel substrate, the metal bonding layer is a Cr layer, deposited by sputtering with a pure Cr target; the alloy toughening layer is a NiCr alloy layer, deposited by sputtering with a NiCr alloy target; and the metal compound strengthening layer is a chromium carbide layer, obtained by reactive sputtering by turning on the pure Cr target and introducing acetylene. When preparing a coating for a lightweight alloy substrate, the metal bonding layer is a Ti layer, the alloy toughening layer is a TiAlV alloy layer, deposited by sputtering with a pure Ti target and a TiAlV alloy target, respectively; and the metal compound strengthening layer is a TiCN layer, obtained by reactive sputtering by keeping the pure Ti target on while simultaneously introducing acetylene and nitrogen.

[0015] Further, the steps for preparing periodic nanolayers applied to a steel substrate include: depositing a (Cr / NiCr / CrCx)n layer on the steel substrate using an alternating cyclic process of magnetron sputtering and reactive sputtering. Each cycle includes: turning on a pure Cr target and depositing a Cr layer on the steel substrate by magnetron sputtering under an argon atmosphere, applying a DC bias of -50 to -150 V during the deposition process, with the power of the pure Cr target being 5 to 20 kW and the argon flow rate being 100 to 300 sccm; turning off the pure Cr target and turning on a NiCr alloy target, wherein the atomic ratio of Cr to Ni in the NiCr alloy target is 80:20, and depositing a NiCr layer by magnetron sputtering under an argon atmosphere, applying a DC bias of -50 to -150 V during the deposition process, with the power of the NiCr alloy target being 5 to 20 kW and the argon flow rate being 100 to 300 sccm. sccm; turn off the NiCr alloy target, turn on the pure Cr target again, and simultaneously introduce acetylene gas at a flow rate of 20~150 sccm into the vacuum chamber. Deposit a CrCx layer on the NiCr layer using reactive magnetron sputtering. Apply a DC bias voltage of -50 ~ -150 V during the deposition process. The power of the pure Cr target is 5~20 kW. Repeat the above three-step deposition process n times to form a periodic nanolayer consisting of n Cr / NiCr / CrCx units. The thickness of the first Cr layer in contact with the steel substrate is 0.2~0.5 μm, the thickness of the last CrCx layer in contact with the subsequent DLC layer is 0.1~0.3 μm, and the thickness of each single layer in each of the remaining cycle units is 0.05~0.2 μm. The number of cycles n is 5~20.

[0016] Further, the step of preparing the periodic nanolayers applied to a lightweight alloy substrate includes: depositing the (Ti / TiAlV / TiCN)n layer on the lightweight alloy substrate using an alternating cyclic process of magnetron sputtering and reactive sputtering. Each cycle includes: turning on the pure Ti target and depositing a Ti layer on the lightweight alloy substrate by magnetron sputtering under an argon atmosphere, applying a DC bias of -50 to -150 V during the deposition process, wherein the power of the pure Ti target is 5 to 20 kW and the argon flow rate is 150 to 300 sccm; turning off the pure Ti target and turning on the TiAlV alloy target, wherein the mass percentage of Al in the TiAlV alloy target is 3% to 7% and the mass percentage of V is 2% to 6%, depositing a TiAlV layer by magnetron sputtering under an argon atmosphere, applying a DC bias of -50 to -150 V during the deposition process, wherein the power of the TiAlV alloy target is 5 to 20 kW and the argon flow rate is 150 to 300 sccm. sccm; turn off the TiAlV alloy target, turn on the pure Ti target again, and simultaneously introduce acetylene gas and nitrogen gas into the vacuum chamber. The acetylene gas flow rate is 20~150 sccm, and the nitrogen gas flow rate is 50~200 sccm. Deposit a TiCN layer on the TiAlV layer by reactive magnetron sputtering. During the deposition process, apply a pulsed DC bias voltage of -50~-120 V. The power of the pure Ti target is 5~20 kW. Repeat the above three-step deposition process n times to form a periodic nanolayer consisting of n Ti / TiAlV / TiCN units. The thickness of the first Ti layer in contact with the substrate is 0.2~0.5 μm, the thickness of the last TiCN layer in contact with the subsequent DLC layer is 0.2~1.0 μm, and the total thickness of each cycle unit is 0.1~0.3 μm. The number of cycles n is 6.

[0017] Further, the step of depositing the surface DLC layer on the periodic nanostack using plasma-assisted chemical vapor deposition (PCVD) includes: for a steel substrate, the surface DLC deposition step is as follows: all metal targets are turned off, and only acetylene gas with a flow rate of 20-150 sccm is introduced into the vacuum chamber. The DLC layer is deposited on the periodic nanostack using PCVD. During the deposition process, a pulsed bias voltage is applied, the frequency of which is 40 kHz and the duty cycle is 80%. The deposition process is controlled by adjusting the bias current within the range of 2-5 A. The final thickness of the DLC layer is 0.5-5 μm. For a lightweight alloy substrate, the surface Ti-DLC deposition step is as follows: the TiAlV alloy target is turned off, the pure Ti target is kept on, its power is reduced to 1-5 kW, and acetylene gas with a flow rate of 100-300 sccm is introduced into the vacuum chamber. Acetylene gas in sccm is used to co-deposit Ti-doped DLC layers on the periodic nanolayers using a combination of plasma-assisted chemical vapor deposition and magnetron sputtering. During the deposition process, a pulsed bias voltage is applied, and the deposition process is controlled by adjusting the bias current within the range of 2 to 5 A.

[0018] Based on the foregoing description, those skilled in the art will understand that in the aforementioned technical solution of this invention, a periodic nanolayered structure composed of a metal bonding layer, an alloy toughening layer, and a metal compound reinforcing layer is used as an intermediate support to bond with the surface DLC layer. This effectively solves the problem of early failure of traditional DLC coatings under harsh conditions of coupled corrosion, impact, and wear due to poor toughness, weak interfacial bonding, and insufficient corrosion protection. It can improve the coating's adhesion, toughness, and corrosion resistance while maintaining the excellent surface properties of DLC. Attached Figure Description

[0019] To more clearly illustrate the technical solution of the present invention, some embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that the same reference numerals may indicate the same or similar parts or components in different drawings; the drawings of the present invention are not necessarily drawn to scale. In the drawings: Figure 1 This is a flowchart of a method for preparing a composite coating in some embodiments of the present invention. Detailed Implementation

[0020] Those skilled in the art should understand that the embodiments described below are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. These partial embodiments are intended to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those skilled in the art without creative effort should still fall within the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can also refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] The following reference Figure 1 This will be used to describe in detail the methods for preparing composite coatings in some embodiments of the present invention. Figure 1 This is a flowchart of a method for preparing a composite coating in some embodiments of the present invention.

[0024] It should be noted beforehand that, for ease of description and to enable those skilled in the art to quickly understand the technical solution of this invention, the following description only focuses on technical features that are strongly related (directly or indirectly related) to the technical problem and / or concept to be solved by this invention. Technical features that are less related to the technical problem and / or concept to be solved by this invention will not be described in detail. Since such less related technical features are common knowledge in the field, the omission of such less related features will not result in insufficient disclosure of this invention.

[0025] In some embodiments of the present invention, a composite coating with both corrosion resistance and self-lubricating properties is provided. The composite coating comprises, from the inside out, a periodic nanolayer and a surface DLC layer. The periodic nanolayer consists of n sequentially stacked composite stack units, where n is an integer greater than 1. Each periodic nanolayer composite stack unit comprises, from the inside out, a sequentially stacked metal bonding layer, an alloy toughening layer, and a metal compound reinforcing layer, to form a coating structure of (metal / metal alloy / metal compound)n / DLC on the substrate surface. This solves the problem of easy failure of traditional DLC coatings (metal / carbide / DLC three-layer structure) under harsh conditions of corrosion, wear, and impact coupling by stacking n composite stack units (i.e., (metal / metal alloy / metal compound)) under the surface DLC layer. n This allows stress to be transferred downwards through the layers when subjected to external load impacts or friction on the DLC surface. The underlying nano-interfaces disperse and dissipate the concentrated destructive energy, preventing through-cracks and overall coating peeling. Simultaneously, the chemical stability of each layer in the periodic stack (e.g., CrCx, TiCN, DLC) provides a chemical barrier, effectively reducing the corrosive effects of corrosive media (e.g., Cl). - The corrosion of the substrate by H2O is mitigated. In addition, the mutual solubility of elements between layers or the formation of chemical bonds (such as C / N in Ti and TiCN) ensure strong interfacial bonding. Under the stable support of the periodic nanolayers, the DLC surface layer can fully utilize its low coefficient of friction, high wear resistance and chemical inertness to improve the corrosion resistance and self-lubricating properties of the composite coating.

[0026] Optionally, the number of iterations n can range from 4 to 20.

[0027] The thickness of the first metal bonding layer in contact with the substrate can be set to 0.2~0.5 μm, the total thickness of each composite stack unit can be set to 0.05~0.3 μm, the thickness of the last metal compound reinforcement layer in contact with the surface DLC layer can be set to 0.1~1.0 μm, and the thickness of the surface DLC layer can be set to 0.5~5 μm.

[0028] The metal bonding layer is made of chromium, titanium, zirconium, molybdenum or tungsten.

[0029] Specifically, when the metal bonding layer is made of chromium, the alloy toughening layer is made of nickel-chromium alloy, suitable for steel substrates. When the metal bonding layer is made of titanium, the alloy toughening layer is made of titanium-aluminum alloy, titanium-aluminum-vanadium alloy, or titanium-zirconium alloy, suitable for lightweight alloy substrates, such as aluminum or titanium alloy substrates. When the metal bonding layer is made of molybdenum, the alloy toughening layer is made of molybdenum-titanium alloy or a molybdenum-based alloy with tungsten, rhenium, tantalum, zirconium, or hafnium as alloying elements, suitable for cemented carbide substrates. When the metal bonding layer is made of tungsten, the alloy toughening layer is made of tungsten-molybdenum alloy or a tungsten-based alloy with rhenium, tantalum, or niobium as alloying elements, suitable for cemented carbide substrates. When the metal bonding layer is made of zirconium, the alloy toughening layer is made of zirconium-niobium alloy, suitable for various substrates, such as steel substrates, lightweight alloy substrates, and cemented carbide substrates.

[0030] The metal compound reinforcement layer is made of carbides, nitrides, or carbonitrides of the metal elements in the corresponding metal bonding layer or alloy toughening layer.

[0031] The composite coating of this invention can be applied to various substrates, including steel substrates, lightweight alloy substrates, and hard alloy substrates.

[0032] Preferably, the present invention takes the application of composite coating to a steel substrate or a lightweight alloy substrate as an example for specific illustration.

[0033] When applied to a steel substrate, the metal bonding layer is made of Cr, the alloy toughening layer is made of NiCr alloy, and the metal compound strengthening layer is made of chromium carbide, nitride, or carbonitride. Because Cr matches the crystal lattice of the steel substrate, it easily forms a strong bond. NiCr alloy is a solid solution strengthening system; the addition of Ni greatly improves the toughness and corrosion resistance of Cr. CrCx provides high hardness support and has good chemical affinity with C in DLC.

[0034] When applied to lightweight alloy matrices, the metal bonding layer is made of Ti, the alloy toughening layer is made of TiAlV alloy, and the metal compound reinforcement layer is made of titanium carbonitride. Ti has excellent compatibility with Al and Ti alloy matrices. TiAlV alloy (similar to Ti-6Al-4V) exhibits excellent specific strength, toughness, and biocompatibility. TiCN combines high hardness, wear resistance, and good chemical stability. Meanwhile, the alloy toughening layer, TiAlV alloy, has an Al mass percentage of 3%–7% and a V mass percentage of 2%–6%. The surface DLC layer is a Ti-doped DLC layer; the doped Ti atoms form compositional continuity with the underlying TiCN layer, significantly improving the interfacial bonding between the DLC and the hard support layer and reducing internal stress.

[0035] In other embodiments of the present invention, a mechanical component is provided, wherein the working surface of the mechanical component is provided with the composite coating as described above.

[0036] Optionally, the mechanical component can be an engine piston ring, a fuel injection system component, a precision mold, or a medical device, with a base material of steel; or, the mechanical component can be an automobile engine piston, an aircraft engine component, or a human orthopedic implant, with a base material of aluminum alloy or titanium alloy.

[0037] like Figure 1 As shown, in some embodiments of the present invention, a method for preparing a composite coating is provided, which can be used to prepare the composite coating described above that combines corrosion resistance and self-lubricating properties. The method includes: Step S110 involves pre-treating the substrate, including cleaning, vacuum heating, and plasma etching. The substrate includes steel, lightweight alloy, and hard alloy substrates, with the lightweight alloy substrate including, but not limited to, aluminum alloy or titanium alloy substrates.

[0038] Clean the steel or lightweight alloy substrate, place it in a vacuum chamber, and evacuate the vacuum level to no higher than 5 × 10⁻⁶. -5 The temperature was increased to 150°C and held for 40 minutes, followed by plasma etching with argon gas. The vacuum level during etching was 8 × 10⁻⁶ mbar. -5 mbar.

[0039] Specifically, the steel or lightweight alloy substrate is ultrasonically cleaned using organic solvents (such as acetone or ethanol) to remove macroscopic contaminants such as oil, fingerprints, and dust, and then dried with high-purity nitrogen or dry air. Next, the steel or lightweight alloy substrate is loaded into a vacuum chamber, and the vacuum pump is started to reduce the pressure inside the chamber from atmospheric pressure (approximately 1000 mbar) to 5 × 10⁻⁶ mbar. -5 The steel or lightweight alloy substrate and chamber walls are uniformly heated to 150°C using a heater and maintained at this temperature for 40 minutes. Finally, high-purity argon gas is introduced into the chamber, which has been evacuated to a high vacuum. By adjusting the opening of the inlet and outlet valves, the gas pressure inside the chamber is dynamically balanced at 8 × 10⁻⁶ mbar. -5 mbar is used to apply a high voltage (typically hundreds to thousands of volts of negative bias) to the chamber, ionizing the argon gas inside and forming a "plasma" composed of argon ions, electrons, and excited-state argon atoms. This completely eliminates macroscopic contaminants, adsorbed gases, and natural oxide films, thereby improving the adhesion of subsequent coatings and greatly reducing the occurrence of coating blistering or easy peeling.

[0040] Step S120: A periodic nanolayer is deposited on the substrate using an alternating cycle of magnetron sputtering and reactive magnetron sputtering. Each cycle includes: sequentially depositing a metal bonding layer and an alloy toughening layer using magnetron sputtering; depositing a metal compound reinforcement layer on the alloy toughening layer using reactive magnetron sputtering in a reactive gas atmosphere; and repeating the above deposition process n times.

[0041] The metal bonding layer is made of chromium, titanium, zirconium, molybdenum or tungsten.

[0042] Specifically, when the metal bonding layer is made of chromium, the alloy toughening layer is made of nickel-chromium alloy, suitable for steel substrates. When the metal bonding layer is made of titanium, the alloy toughening layer is made of titanium-aluminum alloy, titanium-aluminum-vanadium alloy, or titanium-zirconium alloy, suitable for lightweight alloy substrates, such as aluminum or titanium alloy substrates. When the metal bonding layer is made of molybdenum, the alloy toughening layer is made of molybdenum-titanium alloy or a molybdenum-based alloy with tungsten, rhenium, tantalum, zirconium, or hafnium as alloying elements, suitable for cemented carbide substrates. When the metal bonding layer is made of tungsten, the alloy toughening layer is made of tungsten-molybdenum alloy or a tungsten-based alloy with rhenium, tantalum, or niobium as alloying elements, suitable for cemented carbide substrates. When the metal bonding layer is made of zirconium, the alloy toughening layer is made of zirconium-niobium alloy, suitable for various substrates, such as steel substrates, lightweight alloy substrates, and cemented carbide substrates.

[0043] The metal compound reinforcement layer is made of carbides, nitrides, or carbonitrides of the metal elements in the corresponding metal bonding layer or alloy toughening layer.

[0044] The thickness of the first metal bonding layer in contact with the substrate can be set to 0.2~0.5 μm, the total thickness of each composite stack unit can be set to 0.05~0.3 μm, the thickness of the last metal compound reinforcement layer in contact with the surface DLC layer can be set to 0.1~1.0 μm, and the thickness of the surface DLC layer can be set to 0.5~5 μm.

[0045] In some specific embodiments, when preparing a coating for a steel substrate, the metal bonding layer is set as a Cr layer, deposited by sputtering with a pure Cr target. Because the first layer of Cr has good lattice matching and mutual solubility with Fe (the main element in steel), high-energy Cr atoms / ions bombard the substrate surface under negative bias, achieving shallow implantation and interdiffusion. This forms a strong solid solution or metallic bond with the iron atoms in the substrate, ensuring the overall coating adheres firmly to the substrate surface. Simultaneously, in subsequent cycles, the pure Cr layer can form a continuous compositional transition with the Cr element in the underlying CrCx layer, alleviating interfacial stress. The alloy toughening layer is a NiCr alloy layer, deposited by sputtering with a NiCr alloy target. The hardness and modulus of the NiCr layer are between those of the underlying pure Cr and the upper CrCx, providing a gradient transition in mechanical properties and reducing interfacial stress caused by abrupt property changes. Furthermore, the Cr element in the NiCr target ensures good chemical compatibility with the upper and lower Cr layers, facilitating strong interfacial bonding. When microcracks form in the upper hard and brittle layer (CrCx), the crack tip extends to the relatively "soft" NiCr layer. The NiCr layer undergoes plastic deformation, absorbing the energy of the crack propagation and blunting or deflecting the crack tip, preventing it from penetrating vertically downwards and effectively improving the coating's impact resistance. The metal compound reinforcement layer is a chromium carbide layer. It is obtained by reactive sputtering with a pure Cr target and acetylene. Cr atoms / ions sputtered from the pure Cr target react chemically with ionized acetylene gas (providing carbon active particles) in the plasma on the substrate surface or during flight, generating chromium carbide (CrCx). Because CrCx has very high hardness (far higher than Cr and NiCr), it provides support for the top layer of DLC, preventing the DLC from plastically collapsing under load. At the same time, CrCx is chemically stable and can form a corrosion barrier at the interface, effectively blocking water, oxygen, chloride ions and other substances from penetrating downwards. Furthermore, the Cr in CrCx has an affinity for the underlying NiCr, and the carbon on its surface can form strong CC or C-Me bonds with the DLC to be deposited, further achieving strong interfacial bonding.

[0046] Because the three-layer structure has limited function in a single cycle, after n repetitions, dozens or even hundreds of nanoscale interfaces are formed. This forces any corrosive medium to penetrate these n CrCx barrier layers and diffuse laterally at each interface, resulting in an exponentially extended diffusion path. A crack needs to penetrate n alternating "hard (CrCx)-soft (NiCr)" interlayers sequentially, with energy being consumed layer by layer. Furthermore, by adapting the thickness of the chromium layer, the overall performance of the composite coating is improved. Specifically, thickening the first layer ensures the formation of a more complete and robust metallurgical bonding zone; thickening the last layer provides a more solid substrate and ensures that the surface has sufficient hardness and chemical inertness to perfectly support and bond the DLC layer; the intermediate layer is nanoscaled, and the nanoscale layer thickness can maximize the interface effect, suppress columnar crystal growth, and obtain the best stress state and comprehensive performance.

[0047] Specifically, a cyclic process alternating between magnetron sputtering and reactive sputtering is used to deposit (Cr / NiCr / CrCx)n layers on a steel substrate, with each cycle including: Turn on the pure Cr target and deposit a Cr layer on the steel substrate by magnetron sputtering in an argon atmosphere. Apply a DC bias of -50 ~ -150 V during the deposition process. The power of the pure Cr target is 5 ~ 20 kW and the argon flow rate is 100 ~ 300 sccm. The pure Cr target is turned off, and the NiCr alloy target is turned on. The atomic ratio of Cr to Ni in the NiCr alloy target is 80:20. The NiCr layer is deposited by magnetron sputtering under an argon atmosphere. A DC bias voltage of -50 ~ -150 V is applied during the deposition process. The power of the NiCr alloy target is 5 ~ 20 kW, and the argon flow rate is 100 ~ 300 sccm. The NiCr alloy target was turned off, and the pure Cr target was turned on again. At the same time, acetylene gas with a flow rate of 20~150 sccm was introduced into the vacuum chamber. A CrCx layer was deposited on the NiCr layer by reactive magnetron sputtering. A DC bias voltage of -50 ~ -150 V was applied during the deposition process. The power of the pure Cr target was 5~20 kW. The above three-step deposition process is repeated n times to form a periodic nanolayer composed of n Cr / NiCr / CrCx units.

[0048] The thickness of the first Cr layer in contact with the steel substrate is 0.2~0.5 μm, the thickness of the last CrCx layer in contact with the subsequent DLC layer is 0.1~0.3 μm, and the thickness of each single layer in the remaining cycle units is 0.05~0.2 μm; the number of cycles n is set to 5~20 times.

[0049] In other specific embodiments, when preparing coatings for use on lightweight alloy substrates, the metal bonding layer is a Ti layer, and the alloy toughening layer is a TiAlV alloy layer, deposited by sputtering using pure Ti targets and TiAlV alloy targets, respectively. Ti has a good affinity with Al and can form various intermetallic compounds (such as TiAl3). The deposited Ti atoms react and interdiffuse with the Al substrate surface, forming a strongly chemically bonded transition layer. Simultaneously, the Ti atoms deposited on the Ti alloy substrate have a near-perfect lattice match, forming an atomically dense metallurgical bond with the strongest adhesion, greatly improving interfacial adhesion. The alloy toughening layer uses a TiAlV alloy layer. Since pure Ti has good toughness but generally low strength, the addition of Al and V to form a TiAlV solid solution can improve strength and hardness, while also possessing good plastic deformation capacity. Its mechanical properties (hardness, modulus) are between those of soft substrate / pure Ti and hard TiCN, enabling gradient transition and absorbing impact energy. At the same time, TiAlV is Ti-based, ensuring perfect chemical compatibility with the upper and lower Ti layers. The metal compound reinforcement layer is a TiCN layer, obtained through reactive sputtering by keeping a pure Ti target open while simultaneously introducing acetylene and nitrogen gas. Specifically, Ti particles sputtered from the Ti target react with C and N reactive particles in the plasma to generate titanium carbonitride. TiCN has extremely high hardness, providing stable support for the top-layer DLC; TiCN is chemically extremely stable, corrosion-resistant, and oxidation-resistant, serving as a top-level barrier against corrosive media (body fluids, salt spray); the Ti in TiCN is compatible with the underlying TiAlV layer, and the C and N atoms on its surface have good chemical affinity with the DLC (mainly carbon) to be deposited, facilitating the formation of strong C-C or CN bonds and easily forming strong interfacial bonds. Compared to TiC and TiN, TiCN combines the high hardness of TiC and the toughness and lower coefficient of friction of TiN, resulting in superior overall mechanical properties and lower residual stress.

[0050] By controlling the thickness of each layer to ensure it operates at the nanoscale, columnar crystal growth is suppressed to the greatest extent (improving corrosion resistance), inducing an ultra-hard effect, and forcing cracks to propagate into the next tough layer (TiAlV) before they can fully extend within the thin hard layer (TiCN), thus maximizing energy dissipation efficiency. The final TiCN layer is thickened to form a direct contact interface with the DLC, providing a smoother and more robust final surface, which is beneficial for the growth of high-quality DLC. Simultaneously, it increases the final corrosion and wear margin; even if the DLC experiences localized wear, the thicker TiCN layer can still provide long-term protection.

[0051] Specifically, a cyclic process alternating between magnetron sputtering and reactive sputtering is used to deposit (Ti / TiAlV / TiCN)n layers on a lightweight alloy substrate. Each cycle includes: Turn on the pure Ti target and deposit a Ti layer on the lightweight alloy substrate by magnetron sputtering in an argon atmosphere. Apply a DC bias of -50 ~ -150 V during the deposition process. The power of the pure Ti target is 5 ~ 20 kW and the argon flow rate is 150 ~ 300 sccm. The pure Ti target was turned off, and the TiAlV alloy target was turned on. The mass percentage of Al in the TiAlV alloy target was 3%~7%, and the mass percentage of V was 2%~6%. The TiAlV layer was deposited by magnetron sputtering under an argon atmosphere. A DC bias voltage of -50 ~ -150 V was applied during the deposition process. The power of the TiAlV alloy target was 5~20 kW, and the argon flow rate was 150~300 sccm. The TiAlV alloy target was turned off, and the pure Ti target was turned on again. At the same time, acetylene gas and nitrogen gas were introduced into the vacuum chamber. The flow rate of acetylene gas was 20~150 sccm, and the flow rate of nitrogen gas was 50~200 sccm. A TiCN layer was deposited on the TiAlV layer by reactive magnetron sputtering. During the deposition process, a pulsed DC bias voltage of -50 ~ -120 V was applied, and the power of the pure Ti target was 5~20 kW. Repeat the above three-step deposition process n times to form a periodic nanolayer composed of n Ti / TiAlV / TiCN units.

[0052] The thickness of the first Ti layer in contact with the substrate is 0.2~0.5 μm, preferably 0.3 μm. The thickness of the last TiCN layer in contact with the subsequent DLC layer is 0.2~1.0 μm, and the total thickness of each cycle unit is 0.1~0.3 μm.

[0053] Preferably, the number of cycles n is 6. Compared to 5-20 cycles for steel-based systems, this is because, considering the characteristics of the lightweight alloy matrix (softer and more easily deformable) and Ti-based material systems, 6 cycles are sufficient to construct an effective multi-interface barrier and energy dissipation structure, while avoiding the introduction of excessive macroscopic stress on the soft substrate due to excessive total thickness of the laminate, thus achieving the best balance between performance and reliability.

[0054] Step S130: A surface DLC layer is deposited on the periodic nanolayer using plasma-assisted chemical vapor deposition (PCVD) technology.

[0055] It should be noted that the term "surface DLC" in this invention is a general term. The surface DLC can be DLC containing H, TAC without hydrogen, or a lubricating film formed on the substrate surface by doped M-DLC, such as Ti-DLC, Cr-DLC, W-DLC, Si-DLC, and N-DLC, etc., without specific limitations here.

[0056] For steel substrates, the surface DLC deposition steps are as follows: all metal targets are turned off, and only acetylene gas with a flow rate of 20~150 sccm is introduced into the vacuum chamber. A plasma-assisted chemical vapor deposition process is used to deposit a DLC layer on a periodic nanolayer stack. During the deposition process, a pulsed bias voltage with a frequency of 40 kHz and a duty cycle of 80% is applied. The deposition process is controlled by adjusting the bias current within the range of 2~5 A. The final thickness of the DLC layer is 0.5~5 μm.

[0057] During the deposition of DLC on a steel substrate, it is crucial to completely eliminate the source of metal particles to ensure the purity of the DLC layer. If the metal target remains on, sputtered metal atoms (such as Cr) will mix into the growing DLC ​​film, forming metal-doped DLC (such as Cr-DLC). For steel substrates, the goal is to obtain an intrinsic (or near-intrinsic) diamond-like carbon film with the highest hardness and lowest coefficient of friction on the outermost layer. Metal doping typically reduces the hardness of the DLC and may alter its tribological properties.

[0058] For lightweight alloy substrates, the surface Ti-DLC deposition process is as follows: The TiAlV alloy target is turned off, while the pure Ti target remains on, with its power reduced to 1–5 kW. Acetylene gas at a flow rate of 100–300 sccm is introduced into the vacuum chamber. A combined plasma-assisted chemical vapor deposition (PACVD) and magnetron sputtering process is used to co-deposit a Ti-doped DLC layer on the periodic nanolayer stack. A pulsed bias voltage is applied during deposition, and the deposition process is controlled by adjusting the bias current within the range of 2–5 A. By doping the surface DLC layer with Ti, the doped Ti atoms achieve compositional continuity with the underlying TiCN layer, significantly improving the interfacial bonding between the DLC and the hard support layer and reducing internal stress.

[0059] After completing the (Ti / TiAlV / TiCN)n stack deposition, the TiAlV alloy target needs to be shut down, while the pure Ti target remains in low-power operation. This is because pure DLC (especially high-sp) 3 The ta-C content exhibits extremely high modulus (~500 GPa) and large compressive stress, which still differs from TiCN (modulus ~400 GPa). Adding an appropriate amount of Ti can effectively reduce the elastic modulus and internal stress of DLC, making it more compatible with the mechanical properties of the TiCN support layer, thereby reducing stress concentration at the interface. Shutting off the TiAlV alloy to stop the supply of Al and V elements and prevent these elements from being incorporated into the final functional layer ensures the purity of the surface composition (mainly C and Ti).

[0060] Example 1: Preparation of (Cr / NiCr / CrCx)8DLC coating on steel substrate

[0061] After cleaning and removing surface stains, the coated products are placed in a vacuum furnace and evacuated to a vacuum level of 5×10. -5 Heat to 150°C (mbar) and hold for 40 minutes. When the vacuum reaches 8 × 10⁻⁶ mbar... -5 After mbar, plasma etching is initiated to further remove oxides from the substrate surface through argon ion bombardment. Following these steps, the magnetron sputtering deposition process is then started.

[0062] A pure Cr target was turned on, and a Cr layer was deposited on a steel substrate by magnetron sputtering in an argon atmosphere. A DC bias of -100V was applied during the deposition process. The power of the pure Cr target was 10 kW and the argon flow rate was 300 sccm. The pure Cr target was turned off, and the NiCr alloy target was turned on. The atomic ratio of Cr to Ni in the NiCr alloy target was 80:20. The NiCr layer was deposited by magnetron sputtering under an argon atmosphere. A DC bias of -100V was applied during the deposition process. The power of the NiCr alloy target was 10kW and the argon flow rate was 300 sccm. The NiCr alloy target was turned off, the pure Cr target was turned on again, and acetylene gas with a flow rate of 40 sccm was introduced into the vacuum chamber. A CrCx layer was deposited on the NiCr layer by reactive magnetron sputtering. A DC bias of -100V was applied during the deposition process, and the power of the pure Cr target was 10kW. The above three-step deposition process is repeated 8 times to form a periodic nanolayer consisting of 8 Cr / NiCr / CrCx units.

[0063] The thickness of the first Cr layer in contact with the steel substrate is 0.3 μm, the thickness of the last CrCx layer in contact with the subsequent DLC layer is 0.3 μm, and the thickness of each single layer in the remaining cycle units is 0.1 μm.

[0064] All metal targets were shut off, and only acetylene gas at a flow rate of 40 sccm was introduced into the vacuum chamber. A plasma-assisted chemical vapor deposition process was used to deposit a DLC layer on the periodic nanolayer stack. During the deposition process, a pulsed bias voltage with a frequency of 40 kHz and a duty cycle of 80% was applied, and the deposition process was controlled by adjusting the bias current within the range of 3A. The final thickness of the DLC layer was 2 μm.

[0065] Example 2: Preparation of (Ti / TiAlV / TiCN)6 (Ti-DLC) coating on aluminum alloy substrate.

[0066] After cleaning and removing surface stains, the coated products are placed in a vacuum furnace and evacuated to a vacuum level of 5×10. -5 Heat to 150°C (mbar) and hold for 40 minutes. When the vacuum reaches 8 × 10⁻⁶ mbar... -5After mbar, plasma etching is initiated to further remove oxides from the substrate surface through argon ion bombardment. Following these steps, the magnetron sputtering deposition process is then started.

[0067] A pure Ti target was turned on, and a Ti layer was deposited on a lightweight alloy substrate by magnetron sputtering in an argon atmosphere. A DC bias of -100V was applied during the deposition process. The power of the pure Ti target was 10kW and the argon flow rate was 300 sccm. The pure Ti target was turned off, and the TiAlV alloy target was turned on. The TiAlV alloy target has an Al mass percentage of 6% and a V mass percentage of 4%. The TiAlV layer was deposited by magnetron sputtering in an argon atmosphere. A DC bias of -100V was applied during the deposition process. The power of the TiAlV alloy target was 10 kW and the argon flow rate was 300 sccm. The TiAlV alloy target was turned off, and the pure Ti target was turned on again. At the same time, acetylene gas and nitrogen gas were introduced into the vacuum chamber. The flow rate of acetylene gas was 40 sccm and the flow rate of nitrogen gas was 70 sccm. The TiCN layer was deposited on the TiAlV layer by reactive magnetron sputtering. A pulsed DC bias of -100V was applied during the deposition process. The power of the pure Ti target was 10kW. The above three-step deposition process is repeated 6 times to form a periodic nanolayer consisting of 6 Ti / TiAlV / TiCN units.

[0068] The thickness of the first Ti layer in contact with the substrate is 0.3 μm, the thickness of the last TiCN layer in contact with the subsequent DLC layer is 0.2 μm, and the total thickness of each cycle unit is 0.3 μm.

[0069] The TiAlV alloy target was turned off, while the pure Ti target was kept on and its power was reduced to 3kW. Acetylene gas with a flow rate of 200ccm was introduced into the vacuum chamber. A Ti-doped DLC layer was co-deposited on the periodic nanolayer using a combination of plasma-assisted chemical vapor deposition and magnetron sputtering. A pulsed bias voltage was applied during the deposition process, and the deposition process was controlled by adjusting the bias current within the range of 3A.

[0070] To systematically verify the performance advantages of the periodic nanolayered composite coating described in this invention compared to traditional DLC coatings, researchers designed and conducted comparative experiments including scratch adhesion tests, neutral salt spray corrosion tests, and impact wear fatigue tests. The experiments selected a traditional DLC coating (Cr / CrWC / WC / DLC structure) as the control group, and two preferred structures prepared according to the above steps of this invention—the (Cr / NiCr / CrC(N))x / DLC structure for steel substrates and the (Ti / TiAlV / TiC(N))x / DLC structure for lightweight alloy substrates—as the experimental groups. The aim was to quantitatively evaluate the performance improvements in three key dimensions: adhesion, corrosion resistance, and resistance to dynamic loads.

[0071] Scratch adhesion test: Test 1

[0072] The samples used 45# steel substrates. Two steel substrates of the same size were selected and precision polished. A traditional DLC coating (Cr / CrWC / WC / DLC structure) and a (Cr / NiCr / CrC(N))x / DLC structure coating were then prepared on the steel substrates, ensuring that the DLC layer thickness of both structures was maintained at 1–5 μm, the total thickness of the (Cr / NiCr / CrC(N))x composite layer of this invention was ≤5 μm, and the total thickness of the Cr / CrWC / WC layer in the traditional DLC coating was ≤5 μm. A scratch tester equipped with a diamond conical indenter (120° apex angle, 10 μm tip radius) was used to apply loads to the surfaces of both coatings under linear loading (0–100 N, loading rate 10 N / min) and constant speed scratching (5 mm / min). The critical load for the first cracking or peeling of the coating was monitored using an optical microscope and an acoustic emission sensor. Each sample was tested three times at three locations: center, upper left, and lower right, and the average value was taken as the adhesion value. The results showed that the adhesion of the traditional DLC coating was 30 N, while the (Cr / NiCr / CrC(N))x / DLC structure coating of the present invention reached 35 N.

[0073] Test 2

[0074] The samples used aluminum alloy or titanium alloy substrates. Two substrates of the same size and material were selected and precision polished to prepare a traditional DLC coating (Cr / CrWC / WC / DLC structure) and the (Ti / TiAlV / TiC(N))x / DLC structure coating of the present invention. The DLC layer thickness of both coatings was 1~5 μm, the total thickness of the (Ti / TiAlV / TiC(N))x composite layer of the present invention was ≤5 μm, and the total thickness of the Cr / CrWC / WC layer in the traditional DLC coating was ≤5 μm. A scratch tester equipped with a diamond conical indenter (120° apex angle, 10 μm tip radius) was used to apply loads to the surfaces of the two coatings under linear loading (0-100 N, loading rate 10 N / min) and constant speed scratch (5 mm / min). The critical load for the first cracking or peeling of the coating was monitored by optical microscopy and acoustic emission sensor. Each sample was tested three times at three locations: center, upper left, and lower right, and the average value was taken as the adhesion value. The results showed that the adhesion of the traditional DLC coating (structure Cr / CrWC / WC / DLC) was 30 N, while the adhesion of the (Ti / TiAlV / TiC(N))x / DLC structure coating of the present invention reached 38 N.

[0075] Therefore, it can be seen that the two coatings obtained by the method of the present invention have a 16.7%-26.7% improvement in scratch adhesion test compared with the traditional Cr / CrWC / WC / DLC, which shows that the nano-layer structure significantly enhances the bonding strength between the coating and the substrate through stress buffering of the alloy toughening layer and gradient support of the metal compound layer.

[0076] Salt spray corrosion test: Test 3

[0077] Based on Test 1, two coatings were obtained: a traditional DLC coating (Cr / CrWC / WC / DLC structure) with the same dimensions and thickness, using steel plates as the substrate, and the (Cr / NiCr / CrC(N))x / DLC structure coating of this invention. Both coatings were ultrasonically cleaned with anhydrous ethanol and dried, then suspended in a salt spray chamber with the coating surface facing the salt spray inlet for testing. The test conditions were: 5% NaCl solution (pH 6.5-7.2), temperature 35±1°C, and continuous spraying. Observations were made every 4 hours, and the time when the first corrosion pit with an area ≥0.01 mm² appeared on the coating surface was recorded. The traditional DLC coating showed corrosion pits after 28 hours, while the Cr-based composite coating of this invention did not show corrosion pits within a test period exceeding 48 hours.

[0078] Test 4

[0079] Based on Test 2, two coatings were obtained: a traditional DLC coating (Cr / CrWC / WC / DLC) with the same dimensions and thickness, using aluminum alloy or titanium alloy substrates, and the (Ti / TiAlV / TiC(N))x / DLC structure coating of this invention. Both coatings were ultrasonically cleaned with anhydrous ethanol and dried, then suspended in a salt spray chamber with the coating surface facing the salt spray inlet for testing. The test conditions were: 5% NaCl solution (pH 6.5-7.2), temperature 35±1°C, and continuous spraying. Observations were made every 4 hours, and the time when the first corrosion pit with an area ≥0.01 mm² appeared on the coating surface was recorded. The traditional DLC coating showed corrosion pits after 28 hours, while the Ti-based composite coating of this invention showed an extended first corrosion time of 40 hours.

[0080] Therefore, it can be seen that the two coatings obtained by the method of the present invention have improved corrosion resistance by 71.4% and 42.9% respectively compared with the traditional Cr / CrWC / WC / DLC in salt spray corrosion test. This shows that the "maze-like" barrier constructed by the periodic nanolayer effectively extends the diffusion path of the corrosive medium and blocks the rapid penetration channels along defects such as columnar crystals.

[0081] Impact wear fatigue test: Test 5

[0082] Two steel cylinders with a sample size of φ10 mm × 20 mm were selected as substrates. A conventional DLC coating (structure Cr / CrWC / WC / DLC) and the (Cr / NiCr / CrC(N))x / DLC structure coating of the present invention were prepared on the surfaces of the two substrates, respectively. The thickness of the DLC layer in both structures was kept at 1~5 μm, the total thickness of the (Cr / NiCr / CrC(N))x composite layer of the present invention was ≤5 μm, and the total thickness of the Cr / CrWC / WC layer in the conventional DLC coating was ≤5 μm.

[0083] Referring to patent CN114235616B, a testing machine capable of simultaneously applying vertical impact force and parallel friction force was used. Two coating surfaces were tested separately under the following conditions: normal impact force 20N, tangential friction force 10N, impact frequency 166Hz, and the impact point located in a 2 mm diameter area at the center of the sample. After every 10,000 impacts, the impact point was observed using a 50x optical microscope to check for cracks ≥0.1 mm in length, peeling ≥0.01 mm² in area, or coating wear-through. Traditional DLC coatings showed fatigue cracks after 180,000 impacts, while the Cr-based coating of this invention could withstand 250,000 impacts without significant failure.

[0084] Test 6

[0085] Two aluminum or titanium alloy cylinders with a sample size of φ10 mm × 20 mm were selected as substrates. A conventional DLC coating (structure Cr / CrWC / WC / DLC) and the (Ti / TiAlV / TiC(N))x / DLC structure coating of the present invention were prepared on the surfaces of the two substrates, respectively. The DLC layer thickness of both structures was kept at 1~5 μm, the total thickness of the (Cr / NiCr / CrC(N))x composite layer of the present invention was ≤5 μm, and the total thickness of the Cr / CrWC / WC layer in the conventional DLC coating was ≤5 μm.

[0086] Referring to patent CN114235616B, a testing machine capable of simultaneously applying vertical impact force and parallel friction force was used. Two coating surfaces were tested separately under the following conditions: normal impact force 20 N, tangential friction force 10 N, impact frequency 166 Hz, and the impact point located in a 2 mm diameter area at the center of the sample. After every 10,000 impacts, the impact point was observed using a 50x optical microscope to check for cracks ≥0.1 mm in length, peeling ≥0.01 mm² in area, or coating wear-through. Traditional DLC coatings exhibit fatigue cracks after 180,000 impacts, while the Ti-based composite coating of this invention can withstand 220,000 impacts without significant failure.

[0087] Therefore, it can be seen that the two coatings obtained by the method of the present invention have improved the fatigue resistance of the traditional Cr / CrWC / WC / DLC coating by 38.9% and 22.2% respectively in the impact wear fatigue test. This shows that the nano-periodic unit of "metal bonding layer-alloy toughening layer-metal compound reinforcement layer" can effectively passivate and deflect microcracks under cyclic loading, and avoid catastrophic peeling of the coating through a multi-level energy dissipation mechanism.

[0088] Therefore, the two composite coatings of this invention are significantly superior to traditional DLC coatings in terms of adhesion, corrosion resistance and impact fatigue resistance. This verifies that the periodic nanolayer structure systematically improves the reliability and service life of the coating in harsh environments through synergistic mechanisms such as mechanical gradient transition, multi-interface stress dispersion and long-range barrier of corrosive media.

[0089] Those skilled in the art will understand that, based on the foregoing description, the present invention effectively solves the problem of early failure of traditional DLC coatings under harsh conditions of corrosion, impact, and wear coupling due to poor toughness, weak interfacial bonding, and insufficient corrosion protection. This is achieved by using a periodic nanolayered structure composed of a metal bonding layer, an alloy toughening layer, and a metal compound reinforcing layer as an intermediate support bonded to the surface DLC. It maintains the excellent surface properties of DLC while improving the coating's adhesion, toughness, and corrosion resistance.

[0090] The technical solutions of the present invention have been described in conjunction with several embodiments above. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Without departing from the technical principles of the present invention, those skilled in the art can disassemble and combine the technical solutions in the above embodiments, and can also make equivalent changes or substitutions to related technical features. Any changes, equivalent substitutions, improvements, etc., made within the technical concept and / or technical principles of the present invention will fall within the scope of protection of the present invention.

Claims

1. A composite coating that combines corrosion resistance and self-lubricating properties, characterized in that, The composite coating comprises, from the inside out, a periodic nanolayer and a surface DLC layer. The periodic nanolayer is composed of n sequentially stacked composite stack units, where n is an integer greater than 1. Each composite stack unit includes, from the inside out, a metal bonding layer, an alloy toughening layer, and a metal compound reinforcement layer stacked sequentially.

2. The composite coating according to claim 1, characterized in that, The metal bonding layer is made of chromium, titanium, zirconium, molybdenum or tungsten; When the metal bonding layer is made of chromium, the alloy toughening layer is made of nickel-chromium alloy; when the metal bonding layer is made of titanium, the alloy toughening layer is made of titanium-aluminum alloy, titanium-aluminum-vanadium alloy, or titanium-zirconium alloy; when the metal bonding layer is made of molybdenum, the alloy toughening layer is made of molybdenum-titanium alloy or a molybdenum-based alloy with tungsten, rhenium, tantalum, zirconium, or hafnium as alloying elements; when the metal bonding layer is made of tungsten, the alloy toughening layer is made of tungsten-molybdenum alloy or a tungsten-based alloy with rhenium, tantalum, or niobium as alloying elements; when the metal bonding layer is made of zirconium, the alloy toughening layer is made of zirconium-niobium alloy. The metal compound reinforcement layer is made of a carbide, nitride, or carbonitride corresponding to the metal element in the metal bonding layer or the alloy toughening layer; and / or, The composite coating is applied to steel substrates, lightweight alloy substrates, and hard alloy substrates.

3. The composite coating according to claim 2, characterized in that, The thickness of the first metal bonding layer in contact with the substrate is 0.2~0.5 μm; the total thickness of each composite stack unit is 0.05~0.3 μm; the thickness of the last metal compound reinforcement layer in contact with the surface DLC layer is 0.1~1.0 μm; the thickness of the surface DLC layer is 0.5~5 μm; the value of n ranges from 4 to 20; and / or, When applied to the lightweight alloy matrix, the metal bonding layer is made of Ti, the alloy toughening layer is made of TiAlV alloy, wherein the mass percentage of Al is 3%~7% and the mass percentage of V is 2%~6%; the metal compound strengthening layer is made of titanium carbonitride; and the surface DLC layer is a Ti-doped DLC layer.

4. A mechanical component, characterized in that, The working surface of the component is provided with a composite coating that combines corrosion resistance and self-lubrication properties as described in any one of claims 1 to 3.

5. A method for preparing a composite coating, characterized in that, The method is capable of preparing a composite coating with both corrosion resistance and self-lubricating properties as described in any one of claims 1 to 3; the method comprises: The substrate is pretreated, including cleaning, vacuum heating and plasma etching; The periodic nanolayers are deposited on the substrate using an alternating cycle process of magnetron sputtering and reactive magnetron sputtering, wherein each cycle includes: sequentially depositing a metal bonding layer and an alloy toughening layer using magnetron sputtering; depositing a metal compound reinforcement layer on the alloy toughening layer using reactive magnetron sputtering in a reactive gas atmosphere; and repeating the above deposition process n times. A surface DLC layer is deposited on the periodic nanolayer using a plasma-assisted chemical vapor deposition process.

6. The method according to claim 5, characterized in that, The step of pretreating the matrix includes: Clean the steel or lightweight alloy substrate, place it in a vacuum chamber, and evacuate the vacuum level to no higher than 5 × 10⁻⁶. - 5 The temperature was increased to 150°C and held for 40 minutes; then argon gas was introduced for plasma etching, with a vacuum level of 8 × 10⁻⁶ during etching. -5 mbar.

7. The method according to claim 6, characterized in that, In the step of depositing the periodic nanolayers on the substrate using an alternating cyclic process of magnetron sputtering and reactive magnetron sputtering, When preparing a coating for use on the steel substrate, the metal bonding layer is a Cr layer, which is deposited by pure Cr target sputtering. The alloy toughening layer is a NiCr alloy layer, which is deposited by sputtering using a NiCr alloy target; the metal compound strengthening layer is a chromium carbide layer, which is obtained by reactive sputtering by turning on the pure Cr target and introducing acetylene. When preparing a coating applied to the lightweight alloy substrate, the metal bonding layer is a Ti layer, the alloy toughening layer is a TiAlV alloy layer, which are deposited by sputtering using a pure Ti target and a TiAlV alloy target, respectively; the metal compound strengthening layer is a TiCN layer, which is obtained by reactive sputtering by keeping the pure Ti target on while simultaneously introducing acetylene and nitrogen gas.

8. The method according to claim 7, characterized in that, The step of preparing the periodic nanolayers applied to the steel substrate includes: A (Cr / NiCr / CrCx)n stack is deposited on the steel substrate using a cyclic process alternating between magnetron sputtering and reactive sputtering, each cycle comprising: Turn on the pure Cr target and deposit a Cr layer on the steel substrate by magnetron sputtering under an argon atmosphere. During the deposition process, apply a DC bias voltage of -50 ~ -150 V. The power of the pure Cr target is 5 ~ 20 kW and the argon flow rate is 100 ~ 300 sccm. The pure Cr target is turned off, and the NiCr alloy target is turned on. The atomic ratio of Cr to Ni in the NiCr alloy target is 80:

20. The NiCr layer is deposited by magnetron sputtering under an argon atmosphere. A DC bias voltage of -50 ~ -150 V is applied during the deposition process. The power of the NiCr alloy target is 5 ~ 20 kW, and the argon flow rate is 100 ~ 300 sccm. The NiCr alloy target is turned off, the pure Cr target is turned on again, and acetylene gas with a flow rate of 20~150 sccm is introduced into the vacuum chamber. The CrCx layer is deposited on the NiCr layer by reactive magnetron sputtering. During the deposition process, a DC bias voltage of -50~-150 V is applied, and the power of the pure Cr target is 5~20 kW. The above three-step deposition process is repeated n times to form a periodic nanolayer consisting of n Cr / NiCr / CrCx units; wherein the thickness of the first Cr layer in contact with the steel substrate is 0.2~0.5 μm, the thickness of the last CrCx layer in contact with the subsequent DLC layer is 0.1~0.3 μm, and the thickness of each single layer in each of the remaining cycle units is 0.05~0.2 μm; the number of cycles n is 5~20.

9. The method according to claim 7, characterized in that, The step of preparing the periodic nanolayers applied to the lightweight alloy matrix includes: A (Ti / TiAlV / TiCN)n stack is deposited on the lightweight alloy substrate using a cyclic process alternating between magnetron sputtering and reactive sputtering, wherein each cycle includes: Turn on the pure Ti target and deposit a Ti layer on the lightweight alloy substrate by magnetron sputtering in an argon atmosphere. During the deposition process, apply a DC bias voltage of -50 ~ -150 V. The power of the pure Ti target is 5 ~ 20 kW and the argon flow rate is 150 ~ 300 sccm. The pure Ti target is turned off, and the TiAlV alloy target is turned on. The TiAlV alloy target has an Al mass percentage of 3%~7% and a V mass percentage of 2%~6%. The TiAlV layer is deposited by magnetron sputtering under the argon atmosphere. A DC bias voltage of -50~-150 V is applied during the deposition process. The power of the TiAlV alloy target is 5~20 kW, and the argon flow rate is 150~300 sccm. The TiAlV alloy target is turned off, and the pure Ti target is turned on again. At the same time, acetylene gas and nitrogen gas are introduced into the vacuum chamber. The flow rate of the acetylene gas is 20~150 sccm, and the flow rate of the nitrogen gas is 50~200 sccm. The TiCN layer is deposited on the TiAlV layer by reactive magnetron sputtering. During the deposition process, a pulsed DC bias voltage of -50~-120 V is applied. The power of the pure Ti target is 5~20 kW. The above three-step deposition process is repeated n times to form a periodic nanolayer consisting of n Ti / TiAlV / TiCN units; wherein the thickness of the first Ti layer in contact with the substrate is 0.2~0.5 μm, the thickness of the last TiCN layer in contact with the subsequent DLC layer is 0.2~1.0 μm, and the total thickness of each cycle unit is 0.1~0.3 μm; the number of cycles n is 6.

10. The method according to claim 8 or 9, characterized in that, The step of depositing the surface DLC layer on the periodic nanolayer using plasma-assisted chemical vapor deposition includes: For the steel substrate, the surface DLC deposition step is as follows: all metal targets are turned off, and only acetylene gas with a flow rate of 20~150 sccm is introduced into the vacuum chamber. A plasma-assisted chemical vapor deposition process is used to deposit a DLC layer on the periodic nanostack. During the deposition process, a pulsed bias voltage is applied. The frequency of the pulsed bias voltage is 40 kHz and the duty cycle is 80%. The deposition process is controlled by adjusting the bias current in the range of 2~5 A. The final thickness of the DLC layer is 0.5~5 μm. For the lightweight alloy substrate, the surface DLC layer is a Ti-doped DLC layer; the surface Ti-DLC deposition steps are as follows: turn off the TiAlV alloy target, keep the pure Ti target on, reduce its power to 1~5 kW, introduce acetylene gas with a flow rate of 100~300 sccm into the vacuum chamber, and use a combination of plasma-assisted chemical vapor deposition and magnetron sputtering to co-deposit a Ti-doped DLC layer on the periodic nanolayer stack. During the deposition process, a pulsed bias voltage is applied, and the deposition process is controlled by adjusting the bias current within the range of 2~5 A.

Images