A wear-resistant, friction-reducing, corrosion-resistant coating, and a method of making and using the same

Abstract

This application belongs to the field of wear-resistant and anti-corrosion coating technology, specifically relating to a wear-resistant, friction-reducing, and corrosion-resistant coating, its preparation method, and its application. The wear-resistant, friction-reducing, and corrosion-resistant coating of this application comprises a support layer with gradient porosity, a composite functional layer, a metal layer, a chromium nitride layer, and a diamond-like carbon layer, sequentially stacked. The support layer with gradient porosity is in contact with the substrate, and the porosity of the support layer gradually decreases from the contact surface between the support layer and the substrate to the contact surface between the support layer and the composite functional layer. The composite functional layer comprises Cr3C2-NiCr and NiCrSiB. The beneficial effects of this application include: the wear-resistant, friction-reducing, and corrosion-resistant coating of this application can not only prevent common abrasive wear and adhesive wear, but also prevent impact fatigue wear, three-body wear, and electrochemical corrosion, and has a self-lubricating effect that reduces the coefficient of friction, significantly improving the operating performance and service life of this structure.

Description

Technical Field

[0001] This application belongs to the field of wear-resistant and corrosion-resistant coating technology, specifically relating to a wear-resistant, friction-reducing, and corrosion-resistant coating, its preparation method, and its application. Background Technology

[0002] The disc-type powder feeding system is an important component of pulverized coal industrial boilers. A rotating perforated disc and a clamping ring form the key feeding unit of the system. During operation, the rotating perforated disc rotates horizontally within the fluidized pulverized coal, while the upper and lower clamping rings are tightly fixed to the upper and lower surfaces of the disc, providing a seal and facilitating the uniform and stable delivery of a large amount of pulverized coal to the boiler by the feed gas inside the pipe (ring). The friction pair formed by these components needs to operate continuously in the fluidized pulverized coal environment for extended periods, requiring at least 3-6 months of continuous operation during the winter heating season. Besides the traditional adhesive wear and abrasive wear inherent in friction pairs, factors affecting its service life include three other significant damage factors: impact fatigue wear, electrochemical corrosion, and three-body friction wear. In other words, the friction pair composed of the rotating perforated disc and the clamping ring is subject to the synergistic effects of these five factors: adhesive wear, abrasive wear, impact fatigue wear, three-body wear, and electrochemical corrosion.

[0003] Meanwhile, during the grinding operation of the friction pair consisting of the rotating perforated large disc and the upper and lower clamping rings of the feeding unit, the mechanical properties of both sides of the friction pair contact surface are generally uniform. Even if the mechanical properties of one or both sides of the friction pair are anisotropic, their properties along a certain direction are generally uniform. However, sometimes coal powder with a particle size of micron or adhering material between the grinding parts can become embedded in the grinding interface, changing the friction and wear state of the friction pair. This can sometimes increase the frictional resistance of the friction pair, cause significant temperature rise in local areas of the grinding parts, and, coupled with high humidity in the chamber, sometimes lead to motor speed fluctuations, thus affecting the uniformity of feeding. In severe cases, it can even cause the motor to seize up, affecting the uniformity and stability of combustion and the safety and reliability of the entire boiler system.

[0004] In coal-producing areas that partially utilize lignite and sub-bituminous coal, or coalfields located near salt beds and saline rock formations, the coal dust contains higher levels of halogens, especially chloride (Cl), which readily leach out as halogen ions upon contact with water. Halogen ions (primarily chloride ions, Cl-) - Mainly, including Br - F - I - Once introduced into an aqueous system, halogen ions significantly accelerate the electrochemical corrosion rate of metals and coatings. The mechanisms include: halide ions can penetrate or damage metals and oxide passivation films, such as FeO. xThe integrity of the film and Cr2O3 induces localized depassivation and promotes rapid dissolution of the anolyte metal. In the presence of dissimilar materials or compositional differences, such as Co and Cr, or metal / ceramic interfaces, halide ions enhance the microcouple reaction, amplifying the current density in the localized anolyte region. Under alternating contact or tribocorrosion, mechanical damage continuously exposes fresh metal, while halide ions inhibit repassivation, thus forming a vicious cycle of "mechanical-chemical coupling." This results in corrosion rates and material failure rates far exceeding the combined rates of simple mechanical wear or simple chemical corrosion. Consequently, in the humid atmosphere of a compartment containing halide ions, localized perforation, pitting, crack propagation, and spalling of the metal / coating are particularly rapid, severely shortening the service life of the friction pair. Summary of the Invention

[0005] This application provides a wear-resistant, friction-reducing, and corrosion-resistant coating that can maintain good performance and service life in environments with synergistic damage from adhesive wear, abrasive wear, impact wear, and electrochemical corrosion, as well as its preparation method and application.

[0006] The first aspect of this application provides a wear-resistant, friction-reducing, and corrosion-resistant coating, comprising a support layer with gradient porosity, a composite functional layer, a metal layer, a chromium nitride layer, and a diamond-like carbon layer arranged in sequence and overlapping each other.

[0007] The support layer with gradient porosity is in contact with the substrate, and the porosity of the support layer gradually decreases from the contact surface between the support layer and the substrate to the contact surface between the support layer and the composite functional layer. The composite functional layer includes Cr3C2-NiCr and NiCrSiB.

[0008] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the porosity of the support layer with gradient porosity is reduced from 5%-30% at the contact surface between the support layer and the substrate to 1%-5% at the contact surface between the support layer and the composite functional layer.

[0009] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the support layer includes a Cr3C2-NiCr layer.

[0010] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the mass ratio of Cr3C2-NiCr to NiCrSiB in the composite functional layer is (20-80):(80-20).

[0011] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the metal layer includes a chromium layer and / or a Ti layer.

[0012] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the number of chromium nitride layers and diamond-like carbon layers in the wear-resistant, friction-reducing, and corrosion-resistant coating is n, where n≥1, and the chromium nitride layers and diamond-like carbon layers are alternately arranged.

[0013] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the thickness of the support layer with gradient porosity is 100-300 μm.

[0014] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the thickness of the composite functional layer is 100-400 μm.

[0015] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the thickness of the metal layer is 0.3-5 μm.

[0016] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the total thickness of the chromium nitride layer is 2-15 μm. The total thickness of the chromium nitride layer is defined as the sum of the thicknesses of all alternating CrN layers. The thickness of a single chromium nitride layer is 20-400 nm.

[0017] According to some embodiments of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the total thickness of the diamond-like carbon (DLC) layer is 20 nm to 5 μm. The total thickness of the DLC layer refers to the sum of the thicknesses of all alternating DLC ​​layers. The thickness of a single DLC layer is 20-100 nm.

[0018] A second aspect of this application provides a method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating described in the first aspect of this application, comprising the following steps: (1) A support layer and a composite functional layer with gradient porosity were sequentially prepared on the substrate surface by thermal spraying. (2) A metal layer is prepared on the surface of the composite functional layer using physical vapor deposition; (3) A chromium nitride layer is prepared on the surface of the metal layer by physical vapor deposition; (4) A diamond-like layer was prepared on the surface of the chromium nitride layer by physical vapor deposition.

[0019] According to some embodiments of the method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the method for preparing the support layer with gradient porosity includes thermal spraying.

[0020] According to some embodiments of the method for preparing wear-resistant, friction-reducing, and corrosion-resistant coatings described in this application, in step (2), the composite functional layer is ground and polished before the metal layer is prepared.

[0021] According to some embodiments of the method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the composite functional layer is ground and polished until Ra is 0.02μm-0.08μm, and then the metal layer is prepared.

[0022] According to some embodiments of the method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application, the method further includes step (5) preparing a chromium nitride layer on the surface of the diamond-like layer using physical vapor deposition; then preparing a diamond-like layer on the surface of the chromium nitride layer using physical vapor deposition, and repeating step (5).

[0023] The third aspect of this application provides the application of the wear-resistant, friction-reducing, and corrosion-resistant coating described in the first aspect of this application or the wear-resistant, friction-reducing, and corrosion-resistant coating obtained by the preparation method described in the second aspect of this application in a friction pair.

[0024] According to some embodiments of the application described in this application, the friction pair comprises a friction pair consisting of a rotating perforated large disc and a clamping ring.

[0025] The beneficial effects of this application include: the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application can not only prevent common abrasive wear and adhesive wear, but also prevent impact fatigue wear, three-body wear, and electrochemical corrosion, and has a self-lubricating effect that can reduce the coefficient of friction, significantly improving the operating performance and service life of this structure. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application.

[0027] In the diagram: 1. Support layer, 2. Composite functional layer, 3. Metal layer, 4. Chromium nitride layer, 5. Diamond-like carbon layer. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0030] This application provides a wear-resistant, friction-reducing, and corrosion-resistant coating, comprising a support layer with gradient porosity, a composite functional layer, a metal layer, a chromium nitride layer, and a diamond-like carbon layer arranged in sequence and overlapping each other. The support layer with gradient porosity is in contact with the substrate, and the porosity of the support layer gradually decreases from the contact surface between the support layer and the substrate to the contact surface between the support layer and the composite functional layer. The composite functional layer includes Cr3C2-NiCr and NiCrSiB.

[0031] The wear-resistant, friction-reducing, and corrosion-resistant coating described in this application can not only prevent common abrasive wear and adhesive wear, but also prevent impact fatigue wear, three-body wear, and electrochemical corrosion. It also has a self-lubricating effect, which can reduce the coefficient of friction and significantly improve the operating performance and service life of this structure.

[0032] The wear-resistant, friction-reducing, and corrosion-resistant coating described in this application features a gradient porosity support layer structure that enables stress buffering and energy absorption under impact. The high-porosity region provides plastic deformation and microstructural energy absorption capacity, significantly reducing the peak transmission of external impact loads to the substrate, thus minimizing interfacial delamination and early fatigue failure. Furthermore, the lower high-porosity region positively impacts the release and regulation of residual stress from thermal spraying, reducing the overall cracking tendency of the coating. Simultaneously, the dense support structure formed near the low-porosity region effectively supports the localized contact stress generated by the upper dense ceramic layer CrN and DLC layer, improving the scratch resistance, impact resistance, and fatigue resistance of the entire multilayer structure. Under electrochemical corrosion conditions, this gradient structure also blocks the rapid penetration of corrosion pathways, thereby inhibiting the diffusion of water, oxygen, and halide ions into the substrate and enhancing overall corrosion resistance stability. When the support layer gradually changes from "soft to hard" (i.e., it is softer and has a lower effective modulus near the matrix, and gradually becomes denser and more rigid upwards), it is equivalent to establishing a continuous stress transmission channel between the high-modulus CrN and the matrix. The stress gradient is smoothed, the stress concentration factor is significantly reduced, thereby reducing the tensile / shear stress at crack-prone locations.

[0033] The porosity of the composite functional layer of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application is less than 1%, preferably controlled below 0.5%. The addition of the NiCrSiB self-fluxing alloy component to the coating generates good melt flow during spraying, allowing it to fill the micropores in the Cr3C2–NiCr region, thereby obtaining a more continuous and denser structure and providing a smooth and high-load-bearing interface for the subsequent PVD layer. As a composite functional layer of "load-bearing + sealing + buffering," its main functions include: providing high load-bearing capacity and a wear-resistant skeleton; the Cr3C2 hard phase ensures high hardness, resisting impact and abrasive wear, significantly improving the indentation resistance and scratch resistance of the surface layer, and maintaining structural integrity under high-speed impact / sliding wear; forming a dense barrier to inhibit electrochemical corrosion; the NiCrSiB metal matrix easily forms a dense Cr3C2–SiO2 composite passivation film in aqueous / oxygen-containing or halide-containing environments, effectively blocking the penetration of corrosive media. The NiCrSiB metallic matrix provides toughness, enabling the coating to buffer shear pulses and delay crack propagation. The synergy of hardness and toughness makes this layer the backbone of the entire multilayer structure, primarily bearing external mechanical loads. It mitigates abrupt changes in elastic modulus and differences in thermal expansion. With a higher metallic phase content than the first layer, this layer creates a smooth mechanical transition between the thermally sprayed ceramic layer and the upper PVD ceramic film CrN, reducing interfacial residual stress and improving the adhesion reliability of the Cr and CrN layers. It also enhances impact resistance: the NiCrSiB metallic phase improves toughness, allowing it to absorb some impact stress and inhibit crack initiation and propagation, thus significantly extending the service life of the multilayer coating system under impact and wear environments. Furthermore, this composite functional layer strengthens interfacial stress transfer, providing a "modulus gradient transition." Compared to the gradient porous / low-modulus structure of the support layer, this layer, due to its density and higher metallic content, has a higher effective elastic modulus, providing a support platform for a gradual transition between the upper pure Cr and CrN layers, reducing the cracking driving force of the CrN ceramic film in brittle mode. The continuous gradient from "low modulus (porosity gradient Cr3C2-NiCr) → medium modulus (Cr3C2-NiCr+NiCrSiB) → high modulus (CrN (pure Cr layer is too thin, only serving as a buffer for plastic deformation during CrN deposition)" smooths stress transmission, which is beneficial to improving the impact resistance and reliability of the entire coating system. The passivation film formed by the self-fluxing alloy of NiCrSiB enhances resistance to electrochemical corrosion. Cr and Si in NiCrSiB can rapidly form a dense Cr2O3–SiO2 composite passivation film in humid, oxygen-containing, or halide-containing environments, while the excellent wetting effect of the self-fluxing alloy on micropores completely seals off corrosion paths, inhibiting the penetration of water / oxygen / halogen ions and significantly improving overall electrochemical corrosion resistance. Compared to a simple Cr3C2–NiCr coating, the Cr3C2-NiCr+NiCrSiB composite layer has a lower average corrosion current density and a significantly reduced pitting susceptibility.

[0034] The pure chromium layer in the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application serves as a metal transition layer, effectively improving the adhesion between the composite functional layer thermal spray coating and the subsequent ceramic CrN layer. Simultaneously, the high metallic activity of Cr and the dense Cr2O3 film structure formed by its oxidation significantly enhance the coating system's resistance to electrochemical corrosion in water / oxygen and halide ion environments, thereby strengthening the overall coating's interfacial stability and environmental erosion resistance. Furthermore, high-speed, periodic impacts can be considered as short-term stress waves transmitted into the coating. Porosity / interfacial roughness causes wave scattering and internal friction, leading to a faster attenuation of the stress wave amplitude penetrating to CrN, reducing the fatigue accumulation effect. It should be noted that to achieve strong corrosion resistance and provide suitable physical support and Cr element chemical transport capabilities for the pre-plated pure Cr layer, the porosity of the surface region of this hard layer should be minimized to improve the density and isolation of the surface region.

[0035] The chromium nitride layer of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application can serve as the main functional layer for wear and corrosion prevention, providing a stable wear-resistant skeleton structure for the overall composite coating system, and playing a supporting role in bearing load and resisting scratches for the DLC layer.

[0036] The DLC layer (diamond-like carbon layer) of the wear-resistant, friction-reducing, and corrosion-resistant coating described in this application serves as the outermost layer of the coating system. The DLC layer can significantly reduce the friction coefficient of the friction pair, reduce surface adhesion and abrasive wear, and at the same time isolate the direct intrusion of external corrosive media. It plays a comprehensive role in protecting, reducing friction, and delaying wear failure of the underlying CrN and Cr transition layers, enabling the entire composite coating system to have a longer service life in the impact-wear coupled electrochemical corrosion environment.

[0037] It is particularly important to point out that the DLC layer not only serves as a friction-reducing layer but is also the core component for maintaining the long-term stable operation of the friction pair. Under harsh conditions of high-frequency impact loads, three-body friction, and electrochemical corrosion, the DLC layer plays the following key roles: ① Structural profile stability and interface sealing under extreme conditions. During the grinding process between the rotating perforated large disc and the upper and lower clamping rings, the DLC layer, with its extremely low coefficient of friction (μ<0.05) and extremely high surface chemical inertness, ensures that the friction pair can still rotate smoothly under tight pressure. This "smoothness," combined with the high density of the DLC layer itself, effectively prevents the accumulation of coal powder particles in the friction interface. By reducing the causes of three-body wear, the DLC layer maintains the geometric profile integrity of the friction pair contact surface, ensuring the sealing effect of the system under high pressure, thereby preventing coal powder leakage and the deterioration of the friction state caused by the accumulation of coal powder particles in the friction interface, which can lead to motor creep or even seizure. ② The multi-layer support system protects the DLC layer. Because DLC is a hard and brittle material, its ability to withstand high-frequency impact loads alone is limited, making it prone to cracking or spalling. This application solves this problem through the synergistic effect of a five-layer composite structure. The support layer with gradient porosity achieves stress buffering through a "soft to hard" gradual structure, while the composite functional layer provides a high-hardness skeleton to resist indentation deformation, together providing solid physical support for the DLC. The middle pure Cr transition layer, as a ductile metal layer, absorbs and disperses the residual stress transmitted from subsequent layers through micro-plastic deformation, avoiding high stress concentration at the DLC interface and achieving a stress relief and buffering effect.

[0038] In some embodiments of this application, the porosity of the support layer with gradient porosity is reduced from 5%-30% at the interface between the support layer and the substrate to 1%-5% at the interface between the support layer and the composite functional layer. The high porosity region provides a certain plastic deformation and microstructure energy absorption capacity, which can significantly reduce the peak transmission of external impact loads to the substrate and reduce interface peeling and early fatigue failure.

[0039] In some embodiments of this application, the support layer includes a Cr3C2-NiCr layer.

[0040] In some embodiments of this application, the mass ratio of Cr3C2-NiCr to NiCrSiB in the composite functional layer is (20-80):(80-20).

[0041] In some embodiments of this application, the metal layer includes a chromium layer and / or a Ti layer.

[0042] In some embodiments of this application, the number of chromium nitride layers and diamond-like carbon layers in the wear-resistant, friction-reducing, and corrosion-resistant coating is n, where n≥1, and the chromium nitride layers and diamond-like carbon layers are alternately arranged.

[0043] Furthermore, the outermost layer in the prepared state remains a complete and continuous DLC layer. The addition of DLC enables this five-layer composite system to possess extremely low friction, strong wear resistance, and long lifespan under coupled conditions such as water vapor, electrochemical corrosion, impact wear, adhesive wear, and three-body (coal powder) friction. It is the key layer for the entire coating system to achieve the triple performance of "corrosion resistance + friction reduction + impact resistance". Compared with traditional single-layer CrN or single-layer DLC, this alternating CrN / DLC multilayer structure has superior crack propagation resistance and fatigue impact resistance. Because the hard and brittle CrN and the somewhat flexible DLC are arranged alternately at the nanoscale, when external impact loads or sliding wear cause cracks to form, the cracks will be deflected, passivated, or terminated when crossing different material interfaces, thereby significantly inhibiting the tendency of cracks to penetrate the film layer and improving the impact life and fatigue crack resistance of the film layer. In addition, the multilayer structure can effectively disperse and reduce residual stress in the film, making the thicker DLC layer less prone to peeling due to high internal stress. The periodic alternation between the CrN / DLC interfaces also improves the stress transmission path, giving the entire top-layer system higher structural stability under high contact pressure. In terms of tribological properties, the outermost DLC sublayer of the multilayer structure provides an ultra-low coefficient of friction, while the inner CrN sublayer possesses high hardness and strong support capacity. Together, they achieve a lower actual contact area, less adhesive wear tendency, and superior scratch resistance. In an electrochemical corrosion environment, the dense passivation film formed by the CrN sublayer, together with the chemical inertness of the DLC, constitutes a multi-barrier system, effectively blocking the propagation paths of water, oxygen, and halide ions within the film layer, thus improving the overall corrosion resistance and long-term service life of the coating. Therefore, by designing the original fourth CrN layer and fifth DLC layer as a nanoscale periodically alternating CrN / DLC multilayer structure, the comprehensive mechanical and corrosion resistance properties of the coating under the coupled effects of impact wear, sliding friction, and electrochemical corrosion can be further enhanced, achieving higher stability and reliability than a single-layer structure.

[0044] The alternating CrN / DLC layer structure exhibits crack resistance and ensures that new CrN or DLC layers continue to appear on the surface even after wear, guaranteeing stable interfacial properties and extending the service life of the component. When CrN and DLC are periodically alternating at the nanoscale, they form a "hard / tough" interfacial blocking system and a surface state reserve system. When high-frequency impacts cause crack initiation nuclei or microcracks on the surface, the crack propagation will deflect, bifurcate, or passivate when crossing the heterogeneous interface between CrN (high modulus) and DLC (low shear nature). From an energy perspective, the alternating interface effectively absorbs impact energy and inhibits the formation of penetrating cracks, thus ensuring the integrity of the outermost DLC film under frequent impacts and preventing large-area peeling. Furthermore, it provides enhanced protection under electrochemical corrosion environments; the chemical stability of DLC shields the underlying metal from direct corrosion by halide ions (such as Cl ions). Even if micro-damage occurs in the outermost layer, the path-blocking effect of the CrN and DLC multilayer structure makes it difficult for corrosive media to form diffusion channels that penetrate into the substrate, thus maintaining the long-term mechanical reliability of the coating system. Furthermore, this alternating repeating structure provides significant coating reserve capacity; even with microscopic peeling of the surface layer over extended service life, the exposed layer is still a nanoscale CrN or DLC cyclic layer, ensuring dynamic stability of surface properties throughout the entire lifespan and extending the product's service life.

[0045] In some embodiments of this application, the thickness of the support layer with gradient porosity is 100-300 μm; for example, 100 μm, 120 μm, 150 μm, 230 μm, 260 μm, 300 μm, etc.

[0046] In some embodiments of this application, the thickness of the composite functional layer is 100-400 μm; for example, 100 μm, 150 μm, 180 μm, 230 μm, 330 μm, 400 μm, etc.

[0047] In some embodiments of this application, the thickness of the metal layer is 0.3-5 μm; for example, 0.3 μm, 0.8 μm, 1.0 μm, 1.6 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc.

[0048] In some embodiments of this application, the total thickness of the chromium nitride layer is 2-15 μm (the total thickness is defined as the sum of the thicknesses of the CrN layers in all alternating layers); for example, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc. The thickness of a single chromium nitride layer is 20-400 nm (the total thickness of the chromium nitride layer must be maintained within 2-15 μm).

[0049] In some embodiments of this application, the total thickness of the diamond-like carbon (DLC) layer is 20 nm to 5 μm (the total thickness is defined as the sum of the thicknesses of all alternating DLC ​​layers (besides traditional DLC layers such as aC:H layers, this also includes the important branch of DLC, ta-C type coatings (tetrahedral amorphous carbon layers)), which will be referred to as DLC for simplicity hereafter); for example, 20 nm, 50 nm, 80 nm, 100 nm, 160 nm, 500 nm, 0.5 μm, 1 μm, 3 μm, 5 μm, etc. The thickness of a single-layer DLC layer is 20-100 nm.

[0050] This application also provides a method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating described in the first aspect of this application, comprising the following steps: (1) A support layer and a composite functional layer with gradient porosity were sequentially prepared on the substrate surface by thermal spraying. (2) A metal layer is prepared on the surface of the composite functional layer using physical vapor deposition; (3) A chromium nitride layer is prepared on the surface of the metal layer by physical vapor deposition; (4) A diamond-like layer was prepared on the surface of the chromium nitride layer by physical vapor deposition.

[0051] In preparing the composite functional layer, Cr3C2-NiCr cermet powder and NiCrSiB self-fluxing alloy powder are mechanically mixed, and then a dense CrC and self-fluxing alloy composite functional layer is prepared using a thermal spraying system by setting parameters such as oxygen, fuel flow rate and pressure, spraying distance, powder feed rate, and spray gun movement speed. The structural characteristic of this composite functional layer is that the Cr3C2 hard phase is uniformly dispersed in the NiCr and NiCrSiB matrix, with the NiCr alloy and Cr3C2 always in contact or even embedded, while other areas are covered by NiCrSiB. Because NiCrSiB has high melt flowability during spraying, it can fill the pores and gaps within the layer in a hot state, thereby reducing the overall porosity to below 1%, preferably as low as 0.3-0.5%.

[0052] The metallic components such as Ni and Cr possess excellent metallic bond stability, which facilitates interfacial bonding and interatomic diffusion between the pure Cr layer and the substrate during deposition, thereby improving interfacial strength. Their high flatness and ordered microstructure reduce interfacial defects (such as micropores and sharp-angled pits), lowering local stress concentration during Cr layer deposition. Simultaneously, the improved surface integrity also optimizes the dynamic sealing performance and friction-reducing properties of the parts during operation. The pure Cr layer can form an extremely thin Cr2O3 film in situ during the subsequent CrN preparation process, which can prevent electrolyte ingress, reduce the corrosion current density at the interface, and resist long-term electrochemical corrosion damage through continuous oxidation repair and thickening of the Cr2O3 film from the underlying Cr. Furthermore, the potential of Cr lies between that of NiCr and CrN, reducing the occurrence of microgalvanic corrosion.

[0053] When preparing the Cr layer, a multi-arc ion plating technique is used to first perform glow discharge sputtering cleaning and etching on the part, and then the coating is prepared using a Cr target. Glow discharge cleaning and Ar ion etching are typical pretreatments for PVD. The general process involves heating the chamber to a certain temperature while simultaneously evacuating the chamber until the base vacuum reaches a certain level, followed by cleaning and etching to obtain a fresh surface. A pure Cr layer can solve the interface discontinuity problem caused by surface roughness and porosity in hard layers such as Cr3Cr2-NiCr. The surface of thermally sprayed Cr3C2-NiCr contains micro-fused Cr3C2 phase, a thin film of NiCr metal binder phase, oxides, pores, and rough peaks and valleys (Ra usually <2μm) that still exist to some extent even after grinding and polishing. These are not suitable for direct deposition of hard and brittle ceramic films such as CrN. After glow discharge cleaning and high-energy ion bombardment etching, the newly formed pure Cr layer has a continuous, clean, and activated metal interface, providing an ideal nucleation platform for subsequent CrN.

[0054] Furthermore, the Cr layer is a ductile metallic layer with a flexible structure, capable of plastic deformation. This layer can act as a toughness buffer, cushioning residual stress between subsequent layers such as CrN and the prepared layer such as Cr3C2-NiCr, reducing crack initiation in CrN under impact or cyclic loading, dispersing stress concentration, and preventing cracking or spalling. Without a Cr layer, high stress concentration may occur at the rough peaks left after polishing the sprayed coating, as well as at the hard substrate, easily leading to through-cracks under impact and wear conditions. Stress can be transferred to the underlying hard layer through appropriate micro-deformation.

[0055] In some embodiments of this application, a base layer with high plastic deformation capacity, such as a NiCr layer, is first prepared before preparing the support layer with gradient porosity. Of course, this base layer can also be omitted. If the substrate material is appropriately selected and effective pretreatment is performed before thermal spraying, the thermal spray support layer can be prepared directly. The advantage of this is that it eliminates the need for particularly precise preheating and pretreatment, allowing the part and coating to achieve excellent bonding performance. This high plastic deformation capacity base layer is optional and does not play a decisive role in the overall coating design.

[0056] In some embodiments of this application, CrN and DLC layers are prepared using AIP (Arc Ion Plating, a type of PVD), FCVA (Filtered Cathodic Vacuum Arc), UBMS (Unbalanced Magnetron Sputtering), or HiPIMS (High Power Impulse Magnetron Sputtering for Carbon) technologies. HiPIMS is preferred to make the CrN more dense, suppress the content of columnar crystals, and reduce large particles. If AIP technology must be used, the number of large particles and the uniformity of the film can be significantly reduced by adjusting deposition parameters such as arc current, pulse frequency, bias voltage, and the relative position of the arc target and the substrate. When electrochemical corrosion conditions are severe, the CrN layer, acting as an external ceramic barrier layer in a water vapor / halogen / electrochemical environment, should block corrosion paths as much as possible and possess the function of inhibiting micro-electrochemical corrosion.

[0057] The CrN layer primarily serves three key functions: wear resistance, impact resistance, and corrosion resistance. First, CrN possesses high hardness (HV≈1800-2200) and a high elastic modulus. Its dense NaCl-type crystal structure effectively resists abrasive wear and surface contact stress, helping to maintain the dimensional stability of the coating system under long-term friction conditions. Simultaneously, CrN is a typical metal nitride ceramic layer, exhibiting superior fracture toughness compared to traditional nitrides such as TiN and AlN. This allows it to inhibit accelerated crack propagation under impact loads, thereby improving the impact wear life of the coating system. Second, CrN's high chemical inertness allows it to form a stable passivation film in mixed environments such as water, air, and salt spray, effectively blocking the penetration of corrosive media and serving as the first barrier against electrochemical corrosion in the entire coating system. Furthermore, CrN has a good lattice matching relationship with the underlying pure Cr layer, resulting in a continuous and dense film that further enhances interfacial bonding strength, preventing film peeling or flaking under alternating loads. Therefore, the CrN layer not only provides a high-hardness surface, but also constitutes a key anti-electrochemical corrosion barrier in the multilayer system, providing a robust and corrosion-resistant support foundation for the outermost DLC film.

[0058] In some embodiments of this application, an appropriate negative bias is applied during deposition to increase ion energy, resulting in DLC exhibiting high sp3 bond content and low internal stress characteristics. Glow discharge cleaning should still be performed before preparation to obtain a clean and activated CrN surface (if in the same chamber, cleaning may sometimes be omitted depending on the situation), ensuring uniform nucleation of the DLC. Subsequently, carbon target deposition is performed, and the hydrogen content (e.g., aC:H or aC) is controlled to obtain the target tribological properties.

[0059] In some embodiments of this application, the method for preparing the support layer with gradient porosity includes thermal spraying.

[0060] By adjusting the thermal spraying process parameters and the spraying layer structure, the coating can form a porosity gradient structure that gradually becomes denser and harder from the inside out along the thickness direction.

[0061] In the initial stage of spraying close to the substrate, relatively low spraying energy and high powder feeding rate are used to allow the molten particles to form a certain porosity during the deposition process. At the same time, as an option, easily evaporable particles can be doped into the original powder. As the coating thickness increases, the spraying energy is gradually increased, the particle melting state is optimized, and the thermal spraying distance is reduced. This is accompanied by an optional reduction in the amount of easily evaporable particles doped into the powder, which makes the upper coating gradually denser.

[0062] In all embodiments of this application, in step (2), the composite functional layer is ground and polished before the metal layer is prepared. Various methods can be used for grinding and polishing, such as abrasive belts, grinding wheels, rubber wheels, and polishing belts, to achieve a surface roughness better than Ra 0.08 μm. The main purpose of grinding and polishing is to smooth the surface, laying the foundation for the next step of PVD processing. This provides excellent physical support and chemical compatibility for the pure Cr layer prepared by subsequent PVD.

[0063] In some embodiments of this application, the composite functional layer is ground and polished to a Ra of 0.02 μm-0.08 μm before a metal layer is prepared. For example, 0.04 μm, 0.05 μm, 0.06 μm, 0.08 μm, etc.

[0064] In some embodiments of this application, step (5) is further included: preparing a chromium nitride layer on the surface of the diamond-like carbon layer using physical vapor deposition; then preparing a diamond-like carbon layer on the surface of the chromium nitride layer using physical vapor deposition, and repeating step (5). An alternating deposition method is used to construct the CrN / DLC nanolayer structure. This multilayer structure consists of several periodically arranged CrN sublayers and DLC sublayers. The total thickness of each period is preferably 40-500 nm, where the thickness of a single CrN sublayer is 20-400 nm, and the thickness of a single DLC sublayer is 20-100 nm (in actual operation, ta-C from the DLC category is used as an example). The number of multilayer periods can be set to 10-50 periods according to requirements; and ensuring that a continuous and complete DLC layer is set on the outermost layer as the final working surface layer.

[0065] Furthermore, for friction pairs that require both high impact resistance and resistance to water / halogen-containing environments, a graded composite coating with a hard Cr3C2-NiCr base layer, a 60:40 (Cr3C2-NiCr) sub-base layer, and alternating layers of pure Cr transition and dense CrN / DLC is a good engineering compromise between hardness, impact resistance, and electrochemical corrosion resistance. If the corrosion risk is extreme, a high-metal-content self-fluxing alloy sealing layer can be locally added to the system, along with one or more layers of NiCrSiB and Cr3C2-NiCr with a higher proportion, such as 80 (Ni-alloy):20 (Cr3C2-NiCr) or 70 (Ni-alloy):30 (Cr3C2-NiCr), to further improve corrosion resistance and the gradient buffering capacity of hardness.

[0066] This application also provides an application of the wear-resistant, friction-reducing, and corrosion-resistant coating described in the first aspect of this application or the wear-resistant, friction-reducing, and corrosion-resistant coating obtained by the preparation method described in the second aspect of this application in a friction pair. The wear-resistant, friction-reducing, and corrosion-resistant coating described in this application can not only prevent common abrasive wear and adhesive wear, but also prevent impact fatigue wear, three-body wear, and electrochemical corrosion, and has a self-lubricating effect that can reduce the coefficient of friction, significantly improving the operating performance and service life of this structure.

[0067] In some embodiments of this application, the friction pair comprises a friction pair consisting of a rotating perforated large disc and a clamping ring.

[0068] The technical solution of this application will be further described below with reference to specific embodiments.

[0069] Example 1 A wear-resistant, friction-reducing, and corrosion-resistant coating is prepared on the friction surface of a key feeding unit in a pulverized coal feeding system.

[0070] Specific operating methods include: (1) A Cr3C2-NiCr support layer was prepared on the friction surface by using plasma thermal spraying technology to prepare Cr3C2-20(Ni-20Cr) powder. The powder feeding rate was controlled at 20-40 g / min, the thermal spraying distance was 110-130 mm, the powder feeding carrier gas flow rate was 200-500 L / h and the pressure was 0.3-0.35 MPa. The temperature of the thermal spraying substrate was not greater than 200℃. The coating resulted in a support layer with a porosity of approximately 200 μm, which decreased from 20% to 1% along the friction surface of the pressing ring to the surface of the support layer. (2) A 60NiCrSiB+40Cr3C2-NiCr composite functional layer with a thickness of 150μm was prepared on the surface of the support layer by using supersonic flame thermal spraying technology to prepare a mixed powder of Ni-17.5Cr-4Fe-4Si-4B-0.5C self-fluxing alloy powder and Cr3C2-20 (Ni 20Cr) cermet powder (mass ratio of the two is 6:4). The Cr3C2-20 (Ni20Cr) cermet powder used is a composite structure of Ni20Cr alloy coated with Cr3C2, that is, the Ni20Cr metal phase is continuously covered on the surface of the Cr3C2 hard particle phase through chemical coating, thereby forming a composite particle of "metal matrix-ceramic core". The reason for employing such a complex and costly method to prepare the powder is that this coating structure effectively protects the hard Cr3C2 particles, preventing localized violent reactions or insufficient interfacial wetting when the exposed Cr3C2 comes into direct contact with the B and Si-containing molten metal phases in the self-fluxing alloy powder. This prevents the formation of structural defects such as large pores, gaps, or cracks. Simultaneously, the Ni20Cr coating layer improves the thermal behavior of Cr3C2 particles during spraying, resulting in a more uniform temperature rise and more stable adhesion characteristics during the flight heating phase. Furthermore, the coated metal layer acts as an effective thermal barrier and chemical buffer, reducing the tendency of Cr3C2 to decarburize in high-temperature combustion gas environments and preventing the formation of brittle Cr7C3 or Cr... 23 C6 phase. This further improves the overall film-forming quality of the composite powder during the spraying process, resulting in a final coating with higher density and a stable hard phase structure.

[0071] (3) The composite functional layer is ground and polished to make its surface roughness better than Ra0.06μm. Then, a high-purity, high-density pure Cr layer with a thickness of 2μm is prepared on the surface of the composite functional layer using AIP technology with a pure Cr target.

[0072] (4) Using HiPIMS technology, a high-purity, high-density CrN monolayer with a thickness of approximately 150 nm is prepared on the surface of a pure Cr layer using a pure Cr target and high-purity N2 gas as the reaction source. Using HiPIMS technology, a high-density carbon ion flux is generated by high-pulse peak power under a pure Ar atmosphere using high-purity graphite as the target material. By adjusting the synchronous pulse bias voltage, a ta-C monolayer with an sp3 content (usually above 70%), high density, and low defect density is deposited on the surface of the CrN monolayer, with a thickness of approximately 50 nm. Then, a 150 nm CrN layer is prepared on the surface of the ta-C layer using HiPIMS technology, and then a 50 nm ta-C layer is prepared on the surface of the CrN layer. That is, CrN layers and ta-C layers are alternately set to form alternating layers of CrN layers and ta-C layers, and the alternation is controlled for 40 cycles until the total thickness of the alternating layers is 8 μm.

[0073] The upper and lower clamping rings prepared in Example 1 were installed into the powder feeding system, forming a feeding unit in conjunction with a rotating perforated large disc. A circulating powder feeding test was conducted. The powder feeding system was required to ensure a dense-phase coal powder supply capacity of at least 2.5 tons / hour. After one heating season of testing, the parts were removed and weighed, and it was found that the upper clamping ring had lost approximately 2.5g of weight.

[0074] Example 2 A wear-resistant, friction-reducing, and corrosion-resistant coating is prepared on the friction surface of a key feeding unit in a pulverized coal feeding system.

[0075] Specific operating methods include: (1) A Cr3C2-NiCr support layer was prepared on the friction surface of a pressing ring by supersonic flame thermal spraying technology. The powder feeding rate was controlled at 30-50 g / min, the thermal spraying distance was 120 mm, the powder feeding carrier gas flow rate was 200-500 L / h and the pressure was 0.3-0.35 MPa. The temperature of the thermal spraying substrate was not greater than 200 ℃. The coating resulted in a support layer with a porosity of 200 μm that decreased from 20% to 1% from the friction surface of the pressing ring to the surface of the support layer. (2) A 150 μm thick 60NiCrSiB+40Cr3C2-NiCr composite functional layer was prepared on the surface of a support layer using a mixture of Ni-17.5Cr-4Fe-4Si-4B-0.5C self-fluxing alloy powder and Cr3C2-20 (Ni 20Cr) cermet powder (mass ratio of 1:1). The Cr3C2-20 (Ni20Cr) powder used is a composite structure in which Cr3C2 particles are embedded in Ni20Cr alloy particles (but not necessarily all Cr3C2 is covered by Ni20Cr, "embedded"). That is, the Ni20Cr metallic phase is intermittently covered on the surface of the Cr3C2 hard particle phase through powder metallurgy and crushing. This method has significant advantages in terms of cost and efficiency.

[0076] (3) The composite functional layer is ground and polished to make its surface Ra 0.06 μm. Then, a high-purity, high-density pure Cr layer with a thickness of 2 μm is prepared on the surface of the composite functional layer using AIP technology with a pure Cr target.

[0077] (4) Using HiPIMS technology, a high-purity, high-density CrN layer with a thickness of 150 nm is prepared on the surface of a pure Cr layer using a pure Cr target and high-purity N2 gas as the reaction source; using HiPIMS technology, a high-density carbon ion flux is generated by high pulse peak power under a pure Ar atmosphere using high-purity graphite as the target material; by adjusting the synchronous pulse bias voltage, a ta-C layer with sp3 content (usually above 70%), high density and low defect density is deposited on the surface of the CrN layer, with a single layer thickness of about 50 nm. Then, a 150 nm CrN layer is prepared on the surface of the ta-C layer using HiPIMS technology, and then a 50 nm ta-C layer is prepared on the surface of the CrN layer. That is, the CrN layer and ta-C layer are alternately set to form an alternating layer, and the alternation is controlled for 20 cycles until the total thickness of the alternating layer is 4 μm.

[0078] The upper and lower clamping rings prepared in Example 2 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 2.9g of weight.

[0079] Example 3 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 3 differs from that in Example 1 only in that, during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 3, the alternating arrangement of the CrN layer and the ta-C layer results in an alternation period of 10, and the total thickness of the alternating layers is 2 μm.

[0080] The upper and lower clamping rings prepared in Example 3 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 6.8g of weight.

[0081] Example 4 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 4 differs from that in Example 1 only in that, during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 4, the alternating arrangement of the CrN layer and the ta-C layer results in an alternation period of 50, and the total thickness of the alternating layers is 10 μm.

[0082] The upper and lower clamping rings prepared in Example 4 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 6.9g of weight.

[0083] Example 5 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 5 differs from that in Example 1 only in that the thickness of the high-purity, high-density pure Cr layer prepared during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 5 is 3 μm.

[0084] The upper and lower clamping rings prepared in Example 5 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 2.5g of weight.

[0085] Example 6 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 6 differs from that in Example 1 only in that the thickness of the high-purity, high-density pure Cr layer prepared during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 6 is 5 μm.

[0086] The upper and lower clamping rings prepared in Example 6 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 10.1g of weight.

[0087] Example 7 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 7 differs from that in Example 1 only in that the thickness of the high-purity, high-density pure Cr layer prepared during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 7 is 0.1 μm.

[0088] The upper and lower clamping rings prepared in Example 7 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 15.6g of weight.

[0089] Example 8 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 8 differs from that in Example 3 only in that, during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 8, the thickness of the high-purity, high-density CrN monolayer is approximately 800 nm, and the total thickness of the alternating layers is 8.5 μm.

[0090] The upper and lower clamping rings prepared in Example 8 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 3.0g of weight.

[0091] Example 9 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 9 differs from that in Example 3 only in that, during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 9, the thickness of the high-purity, high-density CrN monolayer is approximately 1000 nm, and the total thickness of the alternating layers is 10.5 μm.

[0092] The upper and lower clamping rings prepared in Example 9 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 6.2g of weight.

[0093] Example 10 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 10 differs from that in Example 3 only in that, during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating described in Example 10, the thickness of the high-purity, high-density CrN monolayer is approximately 50 nm, and the total thickness of the alternating layers is 1 μm.

[0094] The upper and lower clamping rings prepared in Example 9 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 12.4g of weight.

[0095] Example 11 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 11 differs from that in Example 1, the thickness of the composite functional layer prepared during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 11 is 300 μm.

[0096] The upper and lower clamping rings prepared in Example 11 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 2.4g of weight.

[0097] Example 12 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 12 differs from that in Example 1 only in that the thickness of the composite functional layer prepared during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 12 is 400 μm.

[0098] The upper and lower clamping rings prepared in Example 12 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 20.8g of weight.

[0099] Example 13 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Example 13 differs from that in Example 1 only in that the thickness of the composite functional layer prepared during the preparation of the wear-resistant, friction-reducing, and corrosion-resistant coating in Example 13 is 50 μm.

[0100] The upper and lower clamping rings prepared in Example 13 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 4.5g of weight.

[0101] Comparative Example 1 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Comparative Example 1 differs from Example 1 only in that the wear-resistant, friction-reducing, and corrosion-resistant coating described in Comparative Example 1 does not contain a composite functional layer.

[0102] The upper and lower clamping rings prepared in Comparative Example 1 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 6.8g of weight.

[0103] Comparative Example 2 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Comparative Example 2 differs from Example 1 only in that the wear-resistant, friction-reducing, and corrosion-resistant coating described in Comparative Example 2 does not contain a metallic Cr layer.

[0104] The upper and lower clamping rings prepared in Comparative Example 2 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 29.9g of weight.

[0105] Comparative Example 3 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Comparative Example 3 differs from that in Example 1 only in that the wear-resistant, friction-reducing, and corrosion-resistant coating described in Comparative Example 3 does not contain a ta-C layer, and the thickness of the CrN layer is 6 μm.

[0106] The upper and lower clamping rings prepared in Comparative Example 3 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 4.6g of weight.

[0107] Comparative Example 4 The method for preparing a wear-resistant, friction-reducing, and corrosion-resistant coating on the friction surface of a key feeding unit in a pulverized coal feeding system as described in Comparative Example 4 differs from that in Example 1 only in that the wear-resistant, friction-reducing, and corrosion-resistant coating described in Comparative Example 4 does not contain a CrN layer, and the thickness of the ta-C layer is 2 μm.

[0108] The upper and lower clamping rings prepared in Comparative Example 4 were installed into the powder feeding system and used in conjunction with a rotating perforated large disc to form a feeding unit for circulating powder feeding tests (same as the test system in Example 1). After a heating season of approximately 2000 hours of testing, the upper and lower clamping rings were removed and weighed. The upper clamping ring lost approximately 22.7g of weight.

[0109] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A wear-resistant, friction-reducing, and corrosion-resistant coating, characterized in that, It includes a support layer with gradient porosity, a composite functional layer, a metal layer, a chromium nitride layer and a diamond-like carbon layer arranged in sequence and overlapping each other; The support layer with gradient porosity is in contact with the substrate, and the porosity of the support layer gradually decreases from the contact surface between the support layer and the substrate to the contact surface between the support layer and the composite functional layer. The composite functional layer includes Cr3C2-NiCr and NiCrSiB.

2. The wear-resistant, friction-reducing, and corrosion-resistant coating according to claim 1, characterized in that, The porosity of the support layer with gradient porosity decreases from 5%-30% at the interface between the support layer and the substrate to 1%-5% at the interface between the support layer and the composite functional layer; And / or, the support layer includes a Cr3C2-NiCr layer; And / or, the mass ratio of Cr3C2-NiCr to NiCrSiB in the composite functional layer is (20-80):(80-20); And / or, the metal layer includes a chromium layer and / or a Ti layer.

3. The wear-resistant, friction-reducing, and corrosion-resistant coating according to claim 1, characterized in that, The wear-resistant, friction-reducing, and corrosion-resistant coating has n layers of chromium nitride and diamond-like carbon, where n ≥ 1, and the chromium nitride and diamond-like carbon layers are alternately arranged.

4. The wear-resistant, friction-reducing, and corrosion-resistant coating according to claim 3, characterized in that, The thickness of the support layer with gradient porosity is 100-300 μm; And / or, the thickness of the composite functional layer is 100-400 μm; And / or, the thickness of the metal layer is 0.3-5 μm; And / or, the total thickness of the chromium nitride layer is 2-15 μm; preferably, the thickness of a single chromium nitride layer is 20-400 nm; And / or, the total thickness of the diamond-like carbon layer is 20 nm-5 μm; preferably, the thickness of a single diamond-like carbon layer is 20-100 nm.

5. The method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating according to any one of claims 1-4, characterized in that, Includes the following steps: (1) A support layer and a composite functional layer with gradient porosity were sequentially prepared on the substrate surface by thermal spraying. (2) A metal layer is prepared on the surface of the composite functional layer using physical vapor deposition; (3) A chromium nitride layer is prepared on the surface of the metal layer by physical vapor deposition; (4) A diamond-like layer was prepared on the surface of the chromium nitride layer by physical vapor deposition.

6. The method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating according to claim 5, characterized in that, The method for preparing the support layer with gradient porosity includes thermal spraying.

7. The method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating according to claim 5, characterized in that, In step (2), the composite functional layer is ground and polished before the metal layer is prepared; Preferably, the composite functional layer is ground and polished until Ra is 0.02μm-0.08μm before the metal layer is prepared.

8. The method for preparing the wear-resistant, friction-reducing, and corrosion-resistant coating according to claim 5, characterized in that, It also includes step (5) preparing a chromium nitride layer on the surface of the diamond-like layer using physical vapor deposition; then preparing a diamond-like layer on the surface of the chromium nitride layer using physical vapor deposition, and repeating the operation of step (5).

9. The application of the wear-resistant, friction-reducing, and corrosion-resistant coating according to any one of claims 1-4 or the wear-resistant, friction-reducing, and corrosion-resistant coating obtained by the preparation method according to any one of claims 5-8 in a friction pair.

10. The application according to claim 9, characterized in that, The friction pair comprises a rotating perforated large disc and a clamping ring.

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