Self-lubricating, anti-corrosion and wear-resistant coating and its preparation method

Abstract

The present invention relates to the technical field of surface treatment of mechanical parts, and in particular to a self-lubricating, corrosion-resistant, and wear-resistant coating and a preparation method thereof. A transition layer is provided between a coating substrate and a DLC layer, the transition layer containing a Cr-O-W-C component, and the bottom layer, the middle layer, and the surface layer are respectively a crystalline layer, a crystalline-amorphous alternating layer, and an amorphous layer. In this way, the transition layer is designed with a synergistically optimized gradient of composition, structure, and interlayer spacing, thereby gradually alleviating thermal / mechanical stress, significantly improving the spalling resistance, corrosion resistance, and service life of the coating, and further achieving synergistic improvement in the coating's corrosion-resistant, wear-resistant, and self-lubricating properties. Ultimately, a dual-gradient composite coating is constructed to alleviate the internal stress between the surface layer and the bottom layer, thereby providing long-term corrosion protection and a strong support effect for the diamond-like carbon surface layer, thereby reducing the risk of the diamond-like carbon surface layer falling off during long-term service due to galvanic corrosion, thereby improving the service life of the parts and the safety of the equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of mechanical parts, and in particular to a self-lubricating, corrosion-resistant and wear-resistant coating and a preparation method thereof. Background Art

[0002] Current marine engineering materials (such as titanium alloys, low-carbon steel, and stainless steel) cannot fully meet the high-precision, high-reliability, and long-life requirements of critical marine equipment components. Self-lubricating, corrosion-resistant, and wear-resistant coatings focus on the surface properties of materials. By redesigning and manufacturing the surface composition and structure through various surface engineering technologies, they impart special lubrication, wear resistance, and corrosion protection to the surface. This is the most effective and economical way to address friction, wear, and corrosion issues.

[0003] In recent years, hard coatings produced by thermal spraying, such as tungsten carbide-based cermets and oxide-ceramic coatings, have been considered promising coatings for wear resistance and corrosion protection in moving and transmission mechanisms due to their simple preparation process, high hardness, bonding strength, compactness, wear resistance, and corrosion resistance. Their ability to maintain their pristine surface condition after long-term service has also led to their potential as wear-resistant and corrosion-resistant coatings. However, thermally sprayed tungsten carbide and oxide-ceramic coatings offer wear resistance but lack friction reduction, often leading to increased wear and significantly reduced service life in the friction pair. Diamond-like carbon (DLC) films, a class of carbon films with diamond and graphite structures, exhibit excellent properties similar to diamond, particularly excellent tribological properties and good chemical stability. They are particularly well-suited for surface hardening of moving parts and hold broad application prospects in key components and precision molds. However, due to the significant hardness difference between the commonly used metal substrate and the coating, the films are relatively thin and suffer from defects such as high brittleness and internal stress. Directly depositing DLC films on the substrate can easily lead to film detachment or collapse under high loads. In addition, when the DLC film is applied to a high temperature, high humidity, and high salt marine environment, the corrosive medium can easily pass through the film defects to reach the substrate and cause corrosion, thereby causing the film to rupture.

[0004] In summary, it is difficult for a single hard coating or DLC film layer to independently and effectively meet the long life and high reliability requirements of moving, transmission, connection and dynamic sealing components under dynamic friction-wear-corrosion coupling damage in harsh marine environments. Summary of the Invention

[0005] The purpose of the present invention is to provide a self-lubricating, corrosion-resistant and wear-resistant coating and a preparation method thereof, so as to solve the problem that existing hard coatings cannot meet the surface protection requirements of parts in marine environments.

[0006] An embodiment of the present invention provides a self-lubricating, anti-corrosion, and wear-resistant coating, comprising:

[0007] coating substrate;

[0008] a transition layer disposed on the coating substrate, the transition layer containing a Cr-OWC component and including, from the coating substrate toward the coating substrate, a bottom layer, an intermediate layer, and a surface layer, wherein the bottom layer, the intermediate layer, and the surface layer are respectively a crystalline layer, a crystalline-amorphous alternating layer, and an amorphous layer, and the interlayer thickness of the bottom layer, the intermediate layer, and the surface layer are all 50 to 200 nm; wherein the Cr content in the transition layer gradually decreases from the bottom layer to the surface layer, and the W content in the transition layer gradually increases from the intermediate layer to the surface layer;

[0009] The DLC layer is arranged on the surface layer of the transition layer; wherein the bottom layer is a Cr2O3 layer, the middle layer is a Cr2O3-WC composite layer, and the surface layer is a WC composite layer.

[0010] Optionally, the coating substrate is a WC-Ni based cemented carbide coating.

[0011] Optionally, the thickness of the bottom layer of the transition layer is 100-170 nm, the thickness of the middle layer is 50-120 nm, and the thickness of the surface layer is 50-140 nm.

[0012] In a second aspect, the present invention further provides a method for preparing a self-lubricating, anti-corrosion, and wear-resistant coating, which is used to prepare the self-lubricating, anti-corrosion, and wear-resistant coating as described in the first aspect, comprising:

[0013] S100, after degreasing and removing oil from the substrate, the spraying position is sandblasted;

[0014] S200, preparing a coating base on the substrate surface;

[0015] S300, grinding and polishing the coating substrate;

[0016] S400, performing ion beam cleaning on the polished coating substrate;

[0017] S500, depositing a transition layer on the coating substrate;

[0018] S600: preparing a DLC layer on the transition layer.

[0019] Optionally, in S200, a coating substrate is prepared on the surface of the substrate, comprising:

[0020] The surface of the substrate that has been sandblasted and preheated is sprayed using supersonic flame spraying equipment with a carrier gas of 5-10 MPa, an oxygen flow rate of 850-1000 L / min, a kerosene flow rate of 20-30 L / h, a powder feeding rate of 50-130 g / min, a spray distance of 130-180 mm, and a spray gun moving speed of 10-30 mm / s to form a WC-Ni-based cemented carbide coating after spraying.

[0021] Optionally, in S300, the coating substrate is ground and polished, including:

[0022] Under the condition of 400-800 rpm, the sample was polished with 300, 600, 1000, 1500 and 2000 mesh diamond grinding discs in sequence until the surface roughness of the coating substrate reached Ra 0.1-0.3 μm; the thickness of the coating substrate after polishing was 50-200 μm.

[0023] Optionally, in S400, the polished coating substrate is subjected to ion beam cleaning, comprising:

[0024] The cleaning is carried out for 40 to 80 minutes using an ion beam under the conditions of a pressure of 0.2 to 0.8 Pa in a deposition furnace, an argon flow rate of 150 to 300 sccm, an ion source of 1.0 to 2.5 kW, and a negative bias voltage of 100 to 600 V.

[0025] Optionally, in S500, depositing a transition layer containing Cr-OWC components on the coating substrate includes:

[0026] S510: Pump the vacuum of the deposition furnace to 1~7×10 -3 After Pa, magnetron sputtering of Cr target was started with power of 3-8 kW, argon flow rate of 50-200 sccm, oxygen flow rate of 1-1.5 sccm, and time of 10-20 min to form Cr2O3 layer;

[0027] S520, turn off the magnetron Cr target, oxygen, and argon, and evacuate for 10–30 min;

[0028] S530, turning on the magnetron Cr target and W target, with a power of 0.5-3 kW, adjusting the relative sputtering amount of the Cr target and the W target, with an argon flow rate of 100-300 sccm and an acetylene flow rate of 1-5 sccm, and introducing a carbon source to form a Cr2O3-WC composite layer;

[0029] At step S540, the Cr target is turned off, the W target power is increased to 4-6 kW, the argon flow rate is 100-300 sccm, and the acetylene flow rate is slowly increased to 10-80 sccm to increase the carbon content and form a WC composite layer.

[0030] Optionally, in S600, preparing a DLC layer on the transition layer includes:

[0031] Turn off the W target and argon gas, increase the acetylene flow rate to 100-200 sccm, and apply a negative bias voltage of 200-900 V for 30-60 minutes to form a DLC layer with a high sp³ content.

[0032] The embodiments of the present invention have at least the following technical effects:

[0033] An embodiment of the present invention provides a self-lubricating, corrosion-resistant, and wear-resistant coating. A transition layer is set between the coating base and the DLC layer. The transition layer is designed with a synergistically optimized gradient of composition, structure, and interlayer spacing to gradually relieve thermal / mechanical stress, significantly improve the coating's anti-stripping, corrosion resistance, and service life, and further achieve synergistic improvement of the coating's corrosion resistance, wear resistance, and self-lubrication properties. Ultimately, a dual-gradient composite coating is constructed to relieve internal stress between the surface layer and the bottom layer, which is beneficial for providing long-term corrosion protection and strong support for the diamond-like surface layer, thereby reducing the risk of the diamond-like surface layer falling off during long-term service due to galvanic corrosion, thereby improving the service life of components and equipment safety.

[0034] Furthermore, using Ni-based alloys such as Ni / NiCr / NiMoCrFeCo as the bonding phase of the WC-based coating or directly using oxide ceramic-based coatings can provide long-term corrosion protection and strong support for the surface layer; the dual-gradient transition of composition and structure can achieve the relief of internal stress between the surface layer and the bottom layer, which can ensure the long-term corrosion protection, wear resistance and lubrication effect of the double-layer structure composite coating. It has been applied to water-lubricated bearing thrust plates, couplings, sleeves, spherical bearings and other components, realizing its wear-resistant, anti-corrosion and lubrication functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 A schematic diagram of the film structure of a self-lubricating, anti-corrosion, and wear-resistant coating provided in an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of an electron microscope showing a film layer of a self-lubricating, anti-corrosion and wear-resistant coating provided in an embodiment of the present invention;

[0038] Figure 3 An electron microscope schematic diagram of a transition layer of a self-lubricating, anti-corrosion, and wear-resistant coating provided in an embodiment of the present invention;

[0039] Figure 4 A flow chart of a method for preparing a self-lubricating, anti-corrosion, and wear-resistant coating provided in an embodiment of the present invention;

[0040] Figure 5 A specific flow chart of step S500 in a method for preparing a self-lubricating, anti-corrosion, and wear-resistant coating provided in an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of salt spray test image data of WC-Co-Cr, WC-Cr3C2-Ni and WC-Co as base coatings;

[0042] Figure 7 Schematic diagram of salt spray test image data of WC-Ni and WC-NiCr alloy as base coating;

[0043] Figure 8 Schematic diagram of the mechanical properties comparison between AT3 coating and AT3-DLC coating;

[0044] Figure 9 Schematic diagram comparing the tribological properties of AT3 coating and AT3-DLC coating in atmospheric environment;

[0045] Figure 10 Schematic diagram comparing the tribological properties of AT3 coating and AT3-DLC coating in seawater environment;

[0046] Figure 11 Schematic diagram comparing the corrosion resistance of AT3 coating and AT3-DLC coating;

[0047] Figure 12 Schematic diagram of the comparison of mechanical properties of WC coating and WC-DLC coating;

[0048] Figure 13 Schematic diagram of the comparison of tribological properties of WC coating and WC-DLC coating in atmospheric environment;

[0049] Figure 14 Schematic diagram comparing the tribological properties of WC coating and WC-DLC coating in seawater environment.

[0050] Icon: 100 - coating base; 200 - transition layer; 210 - base layer; 220 - middle layer; 230 - surface layer; 300 - DLC layer. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] Those skilled in the art will understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which this invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless specifically defined as such, will not be interpreted in an idealized or overly formal sense.

[0053] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a," "an," "said," and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0054] Combine Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a self-lubricating, corrosion-resistant, and wear-resistant coating, comprising: a coating base 100, a transition layer 200, and a DLC layer 300, sequentially formed on the surface of a substrate. The substrate can be considered a mechanical component. By forming a self-lubricating, corrosion-resistant, and wear-resistant coating on certain areas of the mechanical component in a specific environment, the coating can achieve corrosion and wear resistance. Optionally, the coating base 100 can be a tungsten carbide-based cermet-based coating or an oxide-based ceramic coating, with a thickness of 50 to 200 μm.

[0055] Optionally, the coating substrate 100 is a WC-Ni based cemented carbide coating or an oxide ceramic based coating. The oxide ceramic based coating may be chromium oxide, zirconium oxide, aluminum oxide, aluminum oxide-titania, or chromium oxide-titania, with the preferred oxide ceramic material being aluminum oxide-3 wt.% titanium oxide.

[0056] Specifically, the transition layer 200 is located between the coating substrate 100 and the DLC layer 300 to mitigate the difference in properties between the main component materials of the substrate and the DLC layer 300, thereby improving the protective performance of the coating. Among them, the transition layer 200 contains a Cr-OWC component, and the transition layer 200 specifically includes a bottom layer 210, an intermediate layer 220 and a surface layer 230 arranged in sequence, and the bottom layer 210 is closer to the coating substrate 100 than the intermediate layer 220 and the surface layer 230. The bottom layer 210, the intermediate layer 220 and the surface layer 230 are respectively a crystalline layer, a crystalline-amorphous alternating layer and an amorphous layer in terms of crystal. The interlayer thickness of the bottom layer 210, the intermediate layer 220 and the surface layer 230 are all 50 to 200 nm; wherein, the Cr content in the transition layer 200 gradually decreases from the bottom layer 210 to the surface layer 230, and the W content in the transition layer 200 gradually increases from the intermediate layer 220 to the surface layer 230, thereby forming a composition gradient coating, improving the interface bonding characteristics between the coating substrate 100 and the DLC layer 300, and alleviating the shedding of the coating during long-term service due to galvanic corrosion.

[0057] Furthermore, through the multi-energy field composite control process, the transition layer 200 is divided into three layers according to the structural gradient. The layers are mainly divided based on the crystal phase structure. From the bottom layer 210 to the surface layer 230 of the transition layer 200, there are a crystal layer (first layer), a crystal-amorphous alternating layer (second layer), and an amorphous layer (third layer). Figure 2 and 3 shown.

[0058] The crystal layer is a stripe-free layer. Optionally, the crystal layer is a Cr2O3 layer composed of columnar crystals. Columnar crystals refer to the structure of the crystal layer observed under a scanning electron microscope, where the crystallographic orientation is aligned in a specific direction, typically exhibiting a relatively regular columnar shape, and exhibiting certain preferred orientation growth characteristics during growth. The longitudinal grain boundaries of the columnar crystals provide a preferential path for stress release, reducing the risk of crack propagation perpendicular to the coating direction through grain boundary sliding or microcrack deflection. The thermal expansion coefficient of the columnar crystal structure is closer to that of the metal or ceramic substrate, reducing interfacial thermal mismatch stress.

[0059] The crystalline amorphous alternating layer is the second intermediate layer (coarse stripe layer). The coarse stripe-like morphology means that when the crystalline amorphous alternating layer is observed under a scanning electron microscope, a coarse line stripe-like morphology is formed due to the alternating overlap of different substances. Optionally, the crystalline amorphous alternating layer in this embodiment can be a Cr2O3-WC composite layer. The larger crystalline area and the amorphous phase interface spacing allow more plastic deformation space, and the strain energy is synergistically absorbed through the dislocation slip of the crystalline phase and the viscoelastic deformation of the amorphous phase.

[0060] The amorphous layer is the third surface layer (fine-stripe layer). A fine-stripe-like appearance refers to the fine-line, striped morphology observed under a scanning electron microscope. Fine-stripe morphology is understood as distinct from coarse-stripe morphology, with a distinct distinction between thick and thin lines, with coarse stripes being thicker than fine stripes. The uniformity of the amorphous structure and the fine stripe spacing (absence of grain boundaries or dislocations) avoid local stress concentration points, allowing residual stress to be dispersed uniformly through atomic-scale deformation. The short-range order and long-range disorder of the atomic arrangement, combined with its isotropic nature, results in highly uniform stress distribution, avoiding stress concentration at grain or phase boundaries.

[0061] Optionally, the amorphous layer is a WC composite layer, and the carbon element in the WC layer is bonded to the sp³ of the DLC film to form a strong chemical interface (because in the WC composite layer, the carbon element is combined with the tungsten element and other carbon atoms in the sp³ hybrid state. The carbon atoms in the DLC surface layer also mainly exist in the sp³ hybrid state. This same hybrid state makes the carbon element in the W-C layer and the DLC film have good matching in chemical bonding. When the W-C layer contacts the DLC film, the carbon atoms between them can be connected to each other through sp³ bonding, thereby forming a strong chemical interface), reducing the interface stress caused by bonding mismatch, the high-density interface of fine stripes and the uniformity of amorphous materials disperse the stress at the atomic scale, avoid crack initiation, and provide a seamless chemical transition for the DLC layer 300. As the outermost transition layer 200, it is necessary to take into account both uniform stress distribution and interface compatibility with the DLC layer 300 to reduce interface defects caused by sudden changes in chemical composition.

[0062] The dual-gradient design of the embodiment of the present invention alleviates thermal / mechanical stress step by step through the coordinated optimization of composition, structure and interlayer spacing, significantly improving the coating's anti-scaling, corrosion resistance and service life, and further achieving the coordinated improvement of the coating's corrosion resistance, wear resistance and self-lubrication properties. Ultimately, the construction of a dual-gradient composite coating can achieve the relief of internal stress between the surface layer and the bottom layer 210, which is beneficial to providing long-term corrosion protection and strong support for the diamond-like surface layer, thereby reducing the risk of the diamond-like surface layer falling off during long-term service due to galvanic corrosion, thereby improving the service life of components and equipment safety.

[0063] Optionally, the bottom layer of the transition layer has a thickness of 100-170 nm, the middle layer has a thickness of 50-120 nm, and the surface layer has a thickness of 50-140 nm. This thickness configuration offers the following advantages: The bottom Cr2O3 layer (100-170 nm) has different thermal expansion coefficients than the thermally sprayed oxide ceramic-based coating and the WC-based hard coating. The thicker Cr2O3 bottom layer better accommodates this difference, reducing the tensile stress generated at the interface due to the thermal expansion mismatch. Acting like a "cushion," it reduces the risk of cracking due to stress concentration and ensures that subsequent coatings do not easily fall off. The middle Cr2O3-WC layer (50-120 nm) is thinner, yet provides a certain buffering effect. Its composition gradually decreases in Cr2O3 content while increasing in W and C content. This gradual compositional transition ensures a smooth transition in the coating's physical and chemical properties, avoiding excessive internal stress caused by sudden property changes. It balances the performance differences between the bottom and surface layers, resulting in a more uniform stress distribution. Furthermore, the gradual change in composition strengthens the bond between the intermediate layer and the underlying and surface layers. The synergistic chemical bonding and physical intercalation between Cr₂O₃, W, and C prevent the loss of bonding strength caused by sudden changes in composition, enhancing the integrity and stability of the coating. The WC layer (50–140 nm) exhibits high hardness and strength, capable of withstanding high loads and friction. Its moderate thickness maintains excellent wear resistance while reducing stress concentration caused by sudden changes in hardness. As the surface layer in contact with the DLC film, it effectively distributes stress to the intermediate and underlying layers, further optimizing the stress state of the entire coating system.

[0064] Based on the same inventive concept, Figure 4 As shown, an embodiment of the present invention also provides a method for preparing a self-lubricating, anti-corrosion and wear-resistant coating, comprising:

[0065] S100, after degreasing and deoiling the substrate, the spraying position is sandblasted.

[0066] Specifically, sandblasting can remove the oxide layer on the substrate surface to increase surface activity and strengthen the bond strength between the coating and the substrate. The sand used for sandblasting can be white corundum, brown corundum, or zirconium corundum, and the grit size can be 46#, 54#, or 60#. During the sandblasting process, the blasting pressure can be controlled between 0.2 and 0.5 MPa, and the blasting distance can be controlled between 100 and 300 mm. The axial direction of the sandblasting nozzle is maintained at an angle of 70° to 90° with the sample surface. After sandblasting, the sample surface roughness is uniform and free of metallic luster. Residual sand or dust can be blown away with compressed air.

[0067] S200, preparing a coating substrate 100 on the surface of a substrate.

[0068] Optionally, the surface of the substrate that has been sandblasted and preheated is sprayed using atmospheric plasma spraying equipment, with a plasma spray gun current of 450A~650A, an argon flow rate of 30 L / min~45 L / min, a hydrogen flow rate of 4 L / min~10 L / min, a spraying distance of 100 mm~150 mm, and a powder feeding rate of 5 g / min~25 g / min, to form an oxide ceramic-based coating after spraying.

[0069] Optionally, the surface of the substrate that has been sandblasted and preheated is sprayed using supersonic flame spraying equipment, with a carrier gas pressure of 5 to 10 MPa, an oxygen flow rate of 850 to 1000 L / min, a kerosene flow rate of 20 to 30 L / h, a powder feeding rate of 50 to 130 g / min, a spray distance of 130 to 180 mm, and a spray gun movement speed of 10 to 30 mm / s to form a WC-Ni-based cemented carbide coating after spraying.

[0070] S300 , grinding and polishing the coating substrate 100 .

[0071] Specifically, under the condition of 400-800 rpm, the sample is polished with 300, 600, 1000, 1500 and 2000 mesh diamond grinding wheels in sequence until the surface roughness of the coating substrate 100 reaches Ra 0.1-0.3 μm; the thickness of the coating substrate 100 after polishing is 50-200 μm.

[0072] This embodiment achieves a balance between mechanical interlocking, chemical bonding, and stress buffering by controlling the surface roughness Ra of the coated substrate 100 within the range of 0.1 to 0.3 μm, thereby enhancing the bonding between the film layers. If the roughness is too high (Ra > 0.3 μm), sharp protrusions or deep grooves will cause localized stress concentration in the DL layer, easily leading to cracks or delamination. On the other hand, if the surface is too smooth (Ra < 0.1 μm), there will be a lack of anchor points, resulting in insufficient bonding strength. This range (0.1 to 0.3 μm) strikes a perfect balance between these two, ensuring uniform stress distribution.

[0073] S400 , performing ion beam cleaning on the polished coating substrate 100 .

[0074] Specifically, an ion beam is used for cleaning for 40 to 80 minutes under the conditions of a deposition furnace pressure of 0.2 to 0.8 Pa, an argon flow rate of 150 to 300 sccm, an ion source of 1.0 to 2.5 kW, and a negative bias voltage of 100 to 600 V.

[0075] S500 , depositing a transition layer 200 on the coating substrate 100 .

[0076] Alternatively, as Figure 5As shown, the specific process of depositing the transition layer 200 in S500 includes the following steps S510 to S540:

[0077] S510: Pump the vacuum of the deposition furnace to 1~7×10 -3 After Pa, the magnetron sputtering Cr target is turned on with a power of 3~8 kW, an argon flow rate of 50~200 sccm, and an oxygen flow rate of 1~1.5 sccm (too low an oxygen flow rate will result in metallic Cr residue, while too high an oxygen flow rate may form unstable CrO3) for 10~20 min to form a Cr2O3 layer.

[0078] The high-power magnetron sputtering used in this embodiment is beneficial to improving the sputtering rate of the Cr target and increasing the energy of the deposited particles. The migration ability of high-energy Cr atoms on the substrate surface is enhanced, and they preferentially grow along a specific crystal direction to form a columnar crystal structure, thereby improving the density of the film layer.

[0079] S520, turn off the magnetron Cr target, oxygen, and argon, and evacuate for 10 to 30 minutes.

[0080] S530, turning on the magnetron Cr target and the W target, with a power of 0.5-3 kW, and adjusting the relative sputtering amount of the Cr target and the W target, thereby forming a Cr2O3-WC composite layer.

[0081] In this example, the co-sputtering rate of Cr and W at low power (0.5-3 kW) is low, resulting in more uniform atomic mixing and forming a coarse-striped crystal structure doped with amorphous carbon. The Cr2O3 crystals are partially replaced by W and C, forming grains surrounded by an amorphous carbon network. Argon gas flows of 100-300 sccm and acetylene flows of 1-5 sccm are used to introduce a carbon source, which reacts with the sputtered W to form carbides. The incorporation of carbon disrupts the long-range order, forming an amorphous phase. Simultaneously, the metallic bonds of W and the covalent bonds of C enhance interlayer toughness, ultimately forming a Cr2O3-WC composite layer. The entire deposition time is 5-40 minutes.

[0082] At step S540, the Cr target is turned off, the W target power is increased to 4-6 kW, the argon flow rate is 100-300 sccm, and the acetylene flow rate is slowly increased to 10-80 sccm to increase the carbon content and form a WC composite layer.

[0083] In this example, the deposition process is dominated by increasing the sputtering power of the W target. High power increases the kinetic energy of W atoms, resulting in fine grains. Increasing the carbon content forms a WC composite phase, resulting in an amorphous structure. A negative bias of 50 to 150 V is used, while high-energy bombardment suppresses grain growth and promotes a fine-striped amorphous structure. The entire deposition time is 10 to 60 minutes.

[0084] As can be understood, step S510 produces a base layer 210, namely a Cr2O3 layer. This layer forms a certain chemical bond or physical bond with WC and other components, providing a stable foundation for the subsequent adhesion of the transition layer 200 and the DLC layer 300. Furthermore, Cr2O3 exhibits excellent chemical stability and oxidation resistance, preventing the oxide ceramic coating or WC-based coating on the base layer 210 from oxidizing or reacting with surrounding substances, thereby providing a protective barrier. Step S530 produces an intermediate layer 220, namely an alternating Cr2O3-WC layer. This layer gradually reduces the Cr2O3 content and increases the W content, mitigating the performance transition between Cr2O3 and W, achieving a compositional and structural transition from a predominantly Cr2O3 to a predominantly W-based layer, and enhancing the stability of the connection between the layers. The ductility of W, combined with the brittleness of Cr2O3, absorbs interfacial stress and prevents crack propagation. Carbon gradually increases from this layer, providing a pre-transition carbon-containing environment for the subsequent formation of DLC layer 300. This ensures a more balanced distribution of carbon within the coating system, contributing to the formation and stabilization of the carbon structure within DLC layer 300. Step S540 yields surface layer 230, an alternating layer of W and C. This layer, with its high W content, forms tungsten carbide with C, which bonds with the sp³ / sp² carbon bonds of DLC, reducing interfacial defects.

[0085] S600 , preparing a DLC layer 300 on the transition layer 200 .

[0086] Specifically, the W target and argon gas are turned off, the acetylene flow rate is increased to 100-200 sccm, and the negative bias voltage is 200-900 V for 30-60 minutes to form a DLC layer 300 with a high sp³ content.

[0087] In this embodiment, a high acetylene flow rate creates a carbon-rich environment. Negative bias voltage enhances ion bombardment energy, disrupting the orderly arrangement of carbon chains and forming an amorphous DLC film with a high sp³ content (diamond-like carbon). Simultaneously, high bias voltage densifies the film and reduces porosity. DLC layer 300, the final functional layer, provides surface protection for the coating system through ultra-low friction, high hardness, and chemical inertness.

[0088] In the embodiment of the present invention, the gradient transition of the composition is achieved by adjusting the power and the flow rate of the introduced gas, and the gradient of the structure is achieved by depositing different layers by fixing the sample on the turntable and rotating it to face different targets.

[0089] The embodiment of the present invention uses NiCr alloy as the bonding phase of the WC-based coating or directly uses an oxide ceramic coating, which can provide long-term corrosion protection and a strong support effect on the surface layer; the dual gradient transition of composition and structure can achieve the relief of internal stress between the surface layer and the bottom layer 210, which can ensure the long-term corrosion protection, wear resistance and lubrication effect of the double-layer structure composite coating. It has been applied to water-lubricated bearing thrust plates, couplings, sleeves, spherical bearings and other components, realizing its wear-resistant, corrosion-resistant and lubricating functions.

[0090] The present invention's embodiments studied and compared the corrosion resistance of WC-based coatings with four different binder phases: Co, NiMoCrFeCo, NiCrCoMo, and NiCrMo. The results showed that the WC-Ni-based alloy exhibited the best corrosion resistance. During preliminary exploratory research, the applicant used HVOF technology to prepare WC-based cemented carbide coatings with different binder phases, including WC-Ni, WC-Co-Cr, WC-Cr3C2-Ni, WC-NiCr alloy, and WC-Co. The corrosion resistance of the coatings was evaluated through electrochemical analysis and salt spray testing. The results further confirmed that the WC-Ni-based alloy coating possessed excellent corrosion resistance (the oxide coating itself had extremely excellent corrosion resistance and was therefore not included in the verification).

[0091] Furthermore, the applicant prepared DLC films on the surfaces of five materials: WC-Ni, WC-Co-Cr, WC-Cr3C2-Ni, WC-NiCr alloy and WC-Co. Figure 6 The salt spray test image data of WC-Co-Cr, WC-Cr3C2-Ni and WC-Co as the base coating ( Figure 6 (a) shows the image of the WC-Co-Cr base coating before the salt spray test. Figure 6 (b) shows the image of the WC-Co-Cr base coating after 1155h salt spray test. Figure 6 (c) shows the image of the WC-Cr3C2-Ni base coating before the salt spray test. Figure 6 (d) shows the image of the WC-Cr3C2-Ni base coating after 120h salt spray test. Figure 6 (e) shows the image of the WC-Co base coating before the salt spray test. Figure 6 (f) shows the image of the WC-Co base coating after 150h salt spray test). Figure 7 Salt spray test image data of WC-Ni and WC-NiCr alloy as base coating ( Figure 7 (a) shows the image of the WC-Ni alloy base coating before the salt spray test. Figure 7 (b) shows the image of the WC-Ni alloy base coating after 2470h salt spray test. Figure 7 (c) shows the image of the WC-NiCr alloy base coating before the salt spray test. Figure 7 (d) shows the image of the WC-NiCr alloy base coating after 2470h salt spray test). The salt spray results show that the coatings with WC-Co-Cr, WC-Cr3C2-Ni and WC-Co as the bottom layer 210 all have the phenomenon of DLC film peeling.

[0092] The following is a comparison of the specific performance parameters of the DLC layer 300 prepared by the applicant on the surface of the aluminum oxide-3wt.% titanium oxide ceramic coating (abbreviated as AT3 coating). Figures 8 to 11 ,in Figure 8 A comparison of the mechanical properties of an AT3 (aluminum oxide-3% wt. titanium oxide) coating and an AT3-DLC coating showed that, under the same maximum normal load, the AT3-DLC coating exhibited higher hardness and elastic modulus than the AT3 coating, with the hardness increased by 107.72%. The coating's hardness and elastic modulus contribute to improved wear resistance. The H³ / E² ratio (defined as resistance to plastic deformation) indicates that increasing this value indicates greater resistance to plastic deformation. Figure 8 (c) shows that the AT3-DLC coating significantly improves the resistance to plastic deformation.

[0093] Figure 9 Comparison of tribological properties of AT3 coating and AT3-DLC coating in atmospheric environment. Figure 10 Comparison of tribological properties of AT3 coating and AT3-DLC coating in seawater environment. Figure 9 and Figure 10 The schematic results show that the AT3-DLC coating has a lower friction coefficient and a lower wear rate than the AT3 coating in both atmospheric and seawater environments.

[0094] Figure 11 The corrosion resistance of AT3 coating and AT3-DLC coating is compared. The results show that the polarization resistance (Rp) of AT3-DLC coating reaches 4.178×10 6 Ω·cm², which is two orders of magnitude higher than that of AT3 coating. In addition, the corrosion current density of AT3-DLC coating is only 7.7441×10⁻ 9 A / cm², showing its superior corrosion resistance compared to AT3 coating.

[0095] By preparing a DLC layer 300 on the surface of the WC-NiCr alloy coating as a comparison, the specific performance parameters are compared with reference Figures 12 to 14 , Figure 12 The mechanical properties of WC coating and WC-DLC coating are compared. The results show that the hardness of WC-DLC coating is higher than that of WC coating. The hardness of coating helps to improve wear resistance. The H³ / E² value (defined as the resistance to plastic deformation) shows that as this value increases, the resistance to plastic deformation is stronger. Figure 12 (c) in Figure 3 shows that the WC-DLC coating significantly improves the resistance to plastic deformation (Note: the WC coating is WC-NiCr coating).

[0096] Figure 13 Comparison of the tribological properties of WC coating and WC-DLC coating in atmospheric environment. Figure 14 Comparison of tribological properties of WC coating and WC-DLC coating in seawater environment. Figure 13 and Figure 14 The schematic results show that the WC-DLC coating has a lower friction coefficient and a lower wear rate than the WC coating in both atmospheric and seawater environments.

[0097] comprehensive Figures 8-14 According to the comparative data, the embodiment of the present invention coats a DLC film on the surface of the thermal sprayed oxide ceramic coating and the WC-based hard coating, and designs a dual-gradient transition layer of composition and structure, which significantly improves the mechanical, tribological and corrosion resistance of the coating. Compared with the original coating, the DLC-coated composite coating not only achieves a breakthrough in a single performance, but also exhibits excellent comprehensive performance under a variety of complex working conditions and environments. This fully demonstrates that the DLC coating in the solution of the present invention can form a good composite structure with different substrate coatings, play a synergistic role, and optimize the comprehensive performance of the coating. It provides a more reliable technical solution for the application of coating materials in the fields of machinery manufacturing, marine engineering, etc., with significant innovation and practical value.

[0098] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0099] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0100] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. A person of ordinary skill in the art can understand the specific meanings of the above terms in the present invention based on the specific circumstances. In the description of this specification, specific features, structures, materials, or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-lubricating, anti-corrosion and wear-resistant coating, characterized in that: include: coating substrate; a transition layer disposed on the coating substrate, the transition layer containing a Cr-OWC component and including, from proximal to distal to the coating substrate, a bottom layer, an intermediate layer, and a surface layer, wherein the bottom layer, the intermediate layer, and the surface layer are respectively a crystalline layer composed of columnar crystals, an alternating layer of crystalline and amorphous materials having coarse stripes, and an amorphous layer having fine stripes, and the interlayer thickness of the bottom layer, the intermediate layer, and the surface layer are all 50 to 200 nm; wherein the Cr content in the transition layer gradually decreases from the bottom layer to the surface layer, and the W content in the transition layer gradually increases from the intermediate layer to the surface layer; A DLC layer, the DLC layer being disposed on a surface layer of the transition layer; The bottom layer is a Cr2O3 layer, the middle layer is a Cr2O3-WC composite layer, and the surface layer is a WC composite layer.

2. The self-lubricating, anti-corrosion and wear-resistant coating according to claim 1, characterized in that: The coating substrate is a WC-Ni based hard alloy coating or an oxide ceramic based coating.

3. The self-lubricating, anti-corrosion and wear-resistant coating according to claim 1, characterized in that: The thickness of the bottom layer of the transition layer is 100-170 nm, the thickness of the middle layer is 50-120 nm, and the thickness of the surface layer is 50-140 nm.

4. A method for preparing a self-lubricating, anti-corrosion and wear-resistant coating, for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to any one of claims 1 to 3, characterized in that: The preparation method comprises: S100, after degreasing and removing oil from the substrate, the spraying position is sandblasted; S200, preparing a coating base on the substrate surface; S300, grinding and polishing the coating substrate; S400, performing ion beam cleaning on the polished coating substrate; S500, depositing a transition layer on the coating substrate; S600: preparing a DLC layer on the transition layer.

5. The method for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to claim 4, characterized in that: In S200, a coating substrate is prepared on the surface of a substrate, including: The surface of the substrate that has been sandblasted and preheated is sprayed using atmospheric plasma spraying equipment. The plasma spray gun current is 450 A~650 A, the argon flow rate is 30 L / min~45 L / min, the hydrogen flow rate is 4L / min~10 L / min, the spraying distance is 100 mm~150 mm, and the powder feeding rate is 5 g / min~25 g / min. After spraying, an oxide ceramic-based coating is formed.

6. The method for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to claim 4, characterized in that: In S200, a coating substrate is prepared on the surface of a substrate, including: The surface of the substrate that has been sandblasted and preheated is sprayed using supersonic flame spraying equipment with a carrier gas of 5-10 MPa, an oxygen flow rate of 850-1000 L / min, a kerosene flow rate of 20-30 L / h, a powder feeding rate of 50-130 g / min, a spray distance of 130-180 mm, and a spray gun moving speed of 10-30 mm / s to form a WC-Ni-based cemented carbide coating after spraying.

7. The method for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to claim 4, characterized in that: In S300, the coating substrate is ground and polished, including: Under the condition of 400-800 rpm, the sample was polished with 300, 600, 1000, 1500 and 2000 mesh diamond grinding discs in sequence until the surface roughness of the coating substrate reached Ra 0.1-0.3 μm; the thickness of the coating substrate after polishing was 50-200 μm.

8. The method for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to claim 4, characterized in that: In S400, the polished coating substrate is subjected to ion beam cleaning, including: The cleaning is carried out for 40 to 80 minutes using an ion beam under the conditions of a pressure of 0.2 to 0.8 Pa in a deposition furnace, an argon flow rate of 150 to 300 sccm, an ion source of 1.0 to 2.5 kW, and a negative bias voltage of 100 to 600 V.

9. The method for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to claim 4, characterized in that: In S500, a transition layer containing Cr-OWC components is deposited on the coating substrate, comprising: S510: Pump the vacuum of the deposition furnace to 1~7×10 -3 After Pa, magnetron sputtering of Cr target is started with power of 3-8 kW, argon flow rate of 50-200 sccm, oxygen flow rate of 1-1.5 sccm, and time of 10-20 min to form Cr2O3 layer; S520, turn off the magnetron Cr target, oxygen, and argon, and evacuate for 10–30 min; S530, turning on the magnetron Cr target and W target, with a power of 0.5-3 kW, adjusting the relative sputtering amount of the Cr target and the W target, with an argon flow rate of 100-300 sccm and an acetylene flow rate of 1-5 sccm, and introducing a carbon source to form a Cr2O3-WC composite layer; At step S540, the Cr target is turned off, the W target power is increased to 4-6 kW, the argon flow rate is 100-300 sccm, and the acetylene flow rate is slowly increased to 10-80 sccm to increase the carbon content and form a WC composite layer.

10. The method for preparing the self-lubricating, anti-corrosion and wear-resistant coating according to claim 4, characterized in that: In S600, a DLC layer is formed on the transition layer, including: Turn off the W target and argon gas, increase the acetylene flow rate to 100-200 sccm, and negatively bias the layer at 200-900 V for 30-60 min to form a DLC layer with a high sp³ content.

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