Ceramic-based self-lubricating composite coating modified by paO / dDSA anti-rust oil immersion and preparation method thereof

Abstract

The application provides a PAO / DDSA rust-proof oil immersion modified ceramic-based self-lubricating composite coating and a preparation method, and relates to the technical field of composite coating preparation and surface modification. The preparation method comprises the following steps: S1, a ceramic coating is sprayed on a metal base material by using a thermal spraying process; S2, liquid composite rust-proof oil containing synthetic base oil and corrosion inhibitor is heated to a preset temperature; S3, vacuum immersion treatment is performed on the ceramic coating; and S4, cooling to room temperature to obtain the ceramic-based self-lubricating composite coating. The method is simple and efficient in the preparation process, and the coating is endowed with excellent self-adaptive lubricating capacity and active long-acting corrosion resistance without affecting the mechanical properties of the ceramic coating. The test results show that the friction coefficient of the composite coating is reduced to below 0.1, and the composite coating can pass the 3000h neutral salt spray test.

Description

Technical Field

[0001] This invention relates to the field of composite coating preparation and surface modification technology, specifically to a ceramic-based self-lubricating composite coating modified by PAO / DDSA rust-preventive oil impregnation and its preparation method. Background Technology

[0002] In various marine engineering equipment and high-end mechanical systems, such as ship power components, seawater pumps and valves, and transmission mechanisms of offshore drilling platforms, key moving friction components are subjected to extreme and harsh conditions for extended periods, including high humidity, high salt spray, seawater erosion, and alternating heavy-load wet and dry conditions. The coupled effect of friction, wear, and seawater corrosion is a major contributing factor to decreased energy efficiency, reduced reliability, and even premature failure in such equipment. Statistics show that mechanical failures caused by friction, wear, and lubrication failure account for as much as 60%, and in the marine environment, the introduction of corrosive media further exacerbates wear, creating a vicious cycle of abrasion. Therefore, developing high-performance surface protective coatings that integrate low friction, high wear resistance, and strong corrosion resistance is of crucial engineering significance for ensuring the long-term and reliable service of marine equipment. Thermal spraying technology, especially atmospheric plasma spraying, is a commonly used process for preparing hard ceramic coatings on metal substrates. These coatings are widely used in the aforementioned fields due to their high hardness, good wear resistance, and corrosion resistance. However, the inherent rapid melting-solidification characteristics of atmospheric plasma spraying inevitably lead to intrinsic microscopic defects such as pores, microcracks, and lack of interlayer bonding within the coating. These defects create three major technical bottlenecks in marine environments: First, these interconnected microscopic defects form rapid channels for corrosive media in the seawater environment (such as moisture, salt spray, and chloride ions in seawater) to penetrate into the coating and the metal substrate, greatly accelerating the electrochemical corrosion of the base metal and causing the coating to peel off from the inside. Second, ceramic materials have inherently poor lubricity. Under conditions of insufficient seawater lubrication or boundary lubrication, the coefficient of friction between the coating and the mating parts of the friction pair is high (usually >0.5), leading to severe abrasive wear. Third, under alternating wet and dry or alternating load conditions, stress concentration easily occurs at the pores and crack tips, which can easily induce crack propagation and peeling of the coating under mechanical loads, affecting its load-bearing stability and wear resistance life.

[0003] To address the aforementioned problems, existing technologies primarily focus on two directions for improvement, but neither can perfectly meet the stringent requirements of the marine environment. The first approach involves introducing solid lubricants to reduce friction. For example, this can be achieved by compounding the powder coating or introducing graphite, molybdenum disulfide, etc., into the coating powder or through subsequent processes. Patent CN106086766A discloses a method for in-situ synthesis of solid lubricants within coating defects. While this method achieves a lower coefficient of friction, it has significant limitations: First, laser texturing only treats the surface layer of the coating and cannot seal the penetrating pores within the coating. Seawater can still penetrate along unsealed deep defects, leading to insufficient corrosion resistance. Second, PTFE is a solid lubricant; once the surface layer is worn away, the inner layer cannot replenish it, resulting in a limited lubrication life and making it unsuitable for marine equipment with long service cycles. The second approach involves using sealing agents to physically seal coating defects. Traditional brushing processes using resins, paraffin, etc., have poor penetration depth and density. The invention patent with publication number CN118685728B proposes to fill the pores of the coating by vacuum impregnation with palm wax, stearic acid, etc. Although this method can achieve better physical sealing and a certain lubrication and friction reduction effect, it still has key drawbacks: First, these waxy or organic acid materials only play a passive physical isolation role and lack active chemical corrosion protection capabilities, and cannot inhibit the trace corrosive media that have penetrated to the coating-substrate interface; second, under the action of seawater scouring or frictional heat, the waxy materials are easy to soften and run off, resulting in rapid failure of the lubrication and sealing functions, poor long-term effectiveness, and inability to achieve active protection of the metal substrate.

[0004] Current technologies generally lack a simple method to simultaneously, deeply, and effectively address the coupled lubrication-wear-corrosion failure problem of plasma-sprayed ceramic coatings in marine / seawater environments. Therefore, it is necessary to research a composite coating suitable for marine environments, possessing deep penetration, adaptive dynamic lubrication capabilities, and active chemical corrosion inhibition and rust prevention functions. This coating should achieve the formation of a self-replenishing lubricating film at the friction interface while simultaneously imparting long-lasting and active resistance to seawater corrosion, thus solving the aforementioned technical problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a ceramic-based self-lubricating composite coating modified by PAO / DDSA rust-preventive oil impregnation and its preparation method. The aim is to provide a novel ceramic-based self-lubricating composite coating for moving friction components in harsh marine environments, integrating low friction, high wear resistance, and active long-term corrosion protection. Using a thermally sprayed ceramic coating as a template, a functional rust-preventive oil composed of synthetic oil polyalphaolefin (PAO) and the highly efficient corrosion inhibitor dodecenyl succinic anhydride (DDSA) is introduced. Through an optimized vacuum impregnation process, the rust-preventive oil penetrates into the intrinsic defect structures such as interconnected pores and microcracks within the coating. During friction, the rust-preventive oil stored in the intrinsic defect structures is triggered by frictional stress to overflow, providing fluid lubrication on one hand, and in the other hand, DDSA molecules undergo in-situ tribochemical reactions with the metal on the friction pair surface, generating a dense bidirectional metal-carboxylate boundary lubrication film, achieving dynamic adaptive friction reduction and wear resistance. Simultaneously, DDSA molecules can actively passivate the exposed metal substrate at coating defects through chemical adsorption, providing active chemical corrosion protection. This preparation method is simple and efficient, and without affecting the mechanical properties of the ceramic coating, it endows the coating with excellent adaptive lubrication ability and active long-term anti-corrosion performance.

[0006] In a first aspect, embodiments of the present invention provide a PAO / DDSA rust-preventive oil impregnation-modified ceramic-based self-lubricating composite coating, comprising: The thermally sprayed ceramic coating substrate has an intrinsic defect structure at the micro / nano scale; Liquid composite rust-preventive oil filling the intrinsic defect structure of the thermally sprayed ceramic coating substrate; The liquid composite rust inhibitor remains liquid at room temperature and contains synthetic base oil and corrosion inhibitors that can chemically adsorb and / or undergo in-situ tribochemical reactions with metal surfaces. When subjected to frictional loads, the liquid composite rust-preventive oil can be continuously released from the intrinsic defect structure to the friction interface, forming a two-way boundary lubrication film, while providing active chemical corrosion protection to the thermally sprayed ceramic coating substrate.

[0007] As a further improvement of the present invention, the synthetic base oil is a polyalphaolefin, and the corrosion inhibitor is dodecenyl succinic anhydride; the mass fraction of the corrosion inhibitor in the liquid composite rust-preventive oil is 0.5% to 5.0%.

[0008] As a further improvement of the present invention, the intrinsic defect structure includes pores, microcracks, and unbonded interlayer regions; the liquid composite rust-preventive oil penetrates through a vacuum impregnation process and is stably retained in the intrinsic defect structure based on the capillary action at the micro / nano scale, forming a micro oil reservoir, and dynamically replenishes the bidirectional boundary lubricating film by triggering exudation through frictional stress; the kinematic viscosity of the liquid composite rust-preventive oil at 40°C is 350~450 mmHg.2 / s.

[0009] As a further improvement of the present invention, the bidirectional boundary lubrication film is a bidirectional metal-carboxylate boundary lubrication film, which is formed by in-situ tribochemical reactions between the corrosion inhibitor and the coating surface and the friction pair surface. This is mainly because the anhydride groups of DDSA undergo a ring-opening reaction under friction, forming metal-carboxylate boundary lubrication films with the surfaces of the friction components (e.g., zirconium ions in the ZrO2 grinding ball) and the coating surface (e.g., Al2O3), respectively. Bidirectional means that metal-carboxylate reaction films are formed on both the ZrO2 grinding ball and the coating (Al2O3) surfaces.

[0010] As a further improvement of the present invention, the ceramic coating substrate of the thermal spraying is any one of oxide ceramic coating, carbide ceramic coating, and nitride ceramic coating, and the thickness is 100~300μm.

[0011] Secondly, embodiments of the present invention provide a method for preparing a PAO / DDSA rust-preventive oil impregnation-modified ceramic-based self-lubricating composite coating, comprising the following steps: S1, using a thermal spraying process, a ceramic coating is sprayed onto a metal substrate to obtain a thermally sprayed ceramic coating substrate with micro / nano-scale intrinsic defect structures; S2, heating the liquid composite rust-preventive oil containing synthetic base oil and corrosion inhibitor to a preset temperature to reduce viscosity and improve fluidity; S3, the thermally sprayed ceramic coating substrate is completely immersed in the liquid composite rust-preventive oil heated in step S2, and vacuum impregnation is performed to allow the rust-preventive oil to penetrate into the intrinsic defect structure of the thermally sprayed ceramic coating substrate. S4. Cool to room temperature to restore the liquid composite rust-preventive oil to a stable liquid state and remove excess rust-preventive oil from the surface of the thermally sprayed ceramic coating substrate to obtain a PAO / DDSA rust-preventive oil impregnated and modified ceramic-based self-lubricating composite coating.

[0012] As a further improvement of the present invention, in step S1, the thermal spraying process adopts atmospheric plasma spraying, and the process parameters include: plasma spray gun current of 450~650A, argon flow rate of 30~45L / min, hydrogen flow rate of 4~12L / min, spray distance of 90~140mm, and powder feeding rate of 20~60g / min.

[0013] As a further improvement of the present invention, in step S2, the heating temperature is 50~70°C.

[0014] As a further improvement of the present invention, in step S3, the conditions for vacuum impregnation are: pressure of -0.040 to -0.085 MPa and impregnation time of 40 to 60 min.

[0015] Thirdly, the embodiments of the present invention provide the application of the PAO / DDSA rust-preventive oil impregnation modified ceramic-based self-lubricating composite coating, which is used in friction components for friction reduction, wear resistance, and corrosion resistance.

[0016] Beneficial effects: 1. The preparation method provided by this invention uses a thermally sprayed ceramic coating as a template, introduces a liquid composite rust-preventive oil, and after heating to reduce its viscosity, it is then penetrated into the inherent pores and intrinsic defect structures such as micro / nano cracks inside the ceramic coating through a vacuum impregnation process. After cooling, it is stably retained in the intrinsic defect structure by capillary action, and finally obtains a ceramic-based self-lubricating strong anti-corrosion composite coating. The preparation method is simple, fast, and efficient, and achieves excellent self-adaptive lubrication ability without affecting the comprehensive mechanical properties of the ceramic coating. Moreover, by actively sealing the defect structure of the traditional thermally sprayed ceramic coating through the rust-preventive oil, the corrosion resistance of the coating is significantly improved, thereby achieving a perfect unity of the structure, tribological properties, and corrosion resistance of the thermally sprayed ceramic coating.

[0017] 2. The preparation method provided by the present invention can effectively control the microstructure, mechanical properties, tribological properties and corrosion resistance of the composite coating by adjusting the thermal spraying parameters, including voltage, current, spray distance, etc., as well as the heating temperature, time and vacuum degree during vacuum impregnation of rust-preventive oil.

[0018] 3. When the composite coating prepared in this invention is applied to friction conditions, an in-situ tribochemical reaction can occur on the friction surface, forming a bidirectional metal-carboxylate boundary lubricating film. This chemical friction film not only has low friction characteristics but also actively passivates the metal surface and blocks the erosion of corrosive ions, effectively preventing direct contact between the micro-roughness peaks of the contact surface, thereby achieving the purpose of reducing the friction coefficient and significantly reducing wear. The polar functional groups of DDSA facilitate chemisorption, forming a dense molecular layer on the pore walls and substrate. The chemisorbed molecules trigger an in-situ tribochemical reaction at the sliding interface, which is confirmed by FTIR analysis of the coating and XPS analysis of the grinding ball. This bidirectional boundary film connects to the coating and the surface of the friction components due to its high nanoscale adhesion, thus forming bidirectional lubrication. During the friction process, the combined effects of high temperature in the micro-region, high contact stress, and trace amounts of moisture in the environment cause the succinic anhydride ring in the DDSA molecule to undergo in-situ ring-opening and hydrolysis reactions, thereby producing intermediate products containing dicarboxyl groups. After the ring-opening reaction, the generated active carboxyl groups react with metal cations (such as Al) from the coating and friction pair at the friction interface. 3+ Ti 4+ or transferred Zr 4+ The reaction forms a metal-carboxylate composite friction film that is attached to the coating and the surface of the friction pair, respectively.

[0019] 4. In the composite coating provided by this invention, the liquid composite rust-preventive oil penetrates into the intrinsic microscopic defect structure of the composite coating through vacuum impregnation, forming a micro-oil reservoir. During friction, the liquid composite rust-preventive oil continuously overflows to dynamically replenish the lubricating film, ensuring not only long-term effective lubrication of the coating, but also providing excellent corrosion inhibition and sealing effects through DDSA active molecules, significantly improving the corrosion resistance of the composite coating. This successfully achieves a synergistic effect of active lubrication, dynamic self-replenishment, and active chemical corrosion protection.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0022] Figure 1 This is a flowchart illustrating the preparation process of the rust-preventive oil / alumina-titanium oxide composite coating in Example 1 of the present invention.

[0023] Figure 2 The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the surface of the rust-preventive oil / alumina-titanium oxide composite coating of Example 1 of the present invention.

[0024] Figure 3 This is a scanning electron microscope image and elemental distribution diagram of the alumina-titanium oxide coating surface of Comparative Example 1 of the present invention.

[0025] Figure 4 The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the surface of the PAO oil / alumina-titanium oxide composite coating of Comparative Example 2 of this invention.

[0026] Figure 5 The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the cross-section of the rust-preventive oil / alumina-titanium oxide composite coating of Example 1 of the present invention.

[0027] Figure 6 The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the cross-section of the alumina-titanium oxide coating of Comparative Example 1 of this invention.

[0028] Figure 7 The image shows a scanning electron microscope (SEM) image and elemental distribution diagram of the cross-section of the PAO oil / alumina-titanium oxide composite coating of Comparative Example 2 of this invention.

[0029] Figure 8 The coefficient of friction of the coatings prepared in Example 1 and Comparative Examples 1-2 of this invention is ( ) Figure 8 As shown in Figure a), wear rate ( Figure 8 (as shown in b) and 3D wear morphology ( Figure 8 As shown in C, D, and E), the test was conducted according to ASTM G133-22 standard, with a sliding speed of 9 cm / s and a load of 9 N.

[0030] Figure 9 The images shown are SEM images of the coatings prepared in Example 1 and Comparative Examples 1-2 after friction experiments (wherein, Figure 9 In Figure a, the SEM image of the AT3 coating prepared in Comparative Example 1 after a friction experiment is shown. Figure 9 b is a SEM image of the AT3-PAO coating prepared in Comparative Example 2 after a friction experiment; Figure 9 (c is a SEM image of the AT3-ARO coating prepared in Example 1 after a friction experiment).

[0031] Figure 10 These are FTIR images of the coatings prepared in Example 1 and Comparative Example 2 of the present invention before and after a friction experiment.

[0032] Figure 11 XPS images of ZrO2 paired spheres after friction experiments of the coatings prepared in Example 1 and Comparative Example 2 of this invention (wherein, Figure 11 In the diagram, a represents the C 1s spectrum; Figure 11 b represents the O 1s spectrum; Figure 11 In the middle, c represents the Al 2p spectrum; Figure 11 (d represents the Zr 3d spectrum).

[0033] Figure 12 The polarization curves are for the coatings prepared in Examples 1-3 and Comparative Examples 1-2 of this invention.

[0034] Figure 13 The coefficient of friction of the coatings in Examples 1-3 and Comparative Example 2 of this invention was tested according to ASTM G133-22 standard, with a sliding speed of 9 cm / s and a load of 9 N.

[0035] Figure 14 The polarization curves are for the coatings prepared in Examples 1, 3 and Comparative Examples 1 to 4 of the present invention.

[0036] Figure 15 The results of the salt spray test on the anti-rust oil / alumina-titanium oxide composite coating of Example 1 of the present invention are shown. Detailed Implementation

[0037] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0039] In the description of the embodiments of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "multiple" means two or more, unless otherwise explicitly defined.

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0041] In the description of the embodiments of this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0042] In the description of the embodiments of the present invention, the term "multiple" refers to two or more (including two), similarly, "multiple groups" refers to two or more (including two groups), and "multiple pieces" refers to two or more (including two pieces).

[0043] To address the technical problems of existing lubricating materials, such as easy softening and loss under continuous high-temperature friction, only providing passive physical isolation to the metal substrate, lacking active chemical corrosion protection, uneven distribution of the lubricating phase in the pores, and weak self-repairing ability due to the depletion of solid lubricant during continuous friction, this invention provides a PAO / DDSA rust-inhibiting oil-modified ceramic-based self-lubricating composite coating and its preparation method. By compounding PAO base oil with DDSA corrosion inhibitor to form a liquid composite rust-inhibiting oil, and then using a vacuum impregnation process to completely fill the three-dimensional interconnected pore network of the thermally sprayed ceramic coating, a synergistic protection system integrating lubrication, corrosion prevention, and self-repair is formed. In the high humidity, high salt spray, and seawater conditions of the ocean, frictional heat, shear force, and capillary action trigger the real-time flow of the rust-preventive oil. PAO provides low-shear fluid lubrication to reduce the coefficient of friction, while the polar anhydride groups of DDSA undergo in-situ tribochemical reactions with the metal surface to generate a bidirectional metal-carboxylate boundary lubricating film, achieving low friction and wear resistance. Simultaneously, DDSA actively passivates the exposed metal substrate through chemical adsorption, rapidly forming a protective layer to inhibit electrochemical corrosion when local wear or microcracks appear. Furthermore, the liquid composite rust-preventive oil forms a physical barrier by densely filling the micro-nano pore defect structure, extending the corrosion path, while the subsurface oil automatically overflows during wear and achieves dynamic self-repair through capillary pressure difference and mechanical extrusion frictional stress. This overcomes the defect of traditional solid lubricants that fail once the surface layer is depleted, thus effectively solving the technical problem of corrosion and wear failure of ceramic coatings in marine environments.

[0044] In this embodiment of the invention, the tribological properties of the prepared coating were characterized using a Retchet multi-functional friction and wear testing machine in accordance with the ASTM G133-22 standard. The characterization conditions were as follows: mode: ball-and-disc type, with a 5 mm diameter zirconia ball as the paired ball, and a sliding speed of 9 cm / s, an amplitude of 2.5 mm, and 16,200 cycles. The tribological properties were studied, and all tests were conducted at room temperature of 25 ± 2 °C and relative humidity of 40 ± 5%.

[0045] In the examples, salt spray tests were conducted in a neutral salt spray atmosphere according to the GB / T 10125-2021 standard.

[0046] Example 1 Please see Figure 1 As shown, this invention provides a method for preparing a ceramic-based self-lubricating composite coating modified by PAO / DDSA rust-preventive oil impregnation, comprising the following steps: S1. An alumina-3wt.% titanium oxide coating (commercially available Al2O3-3wt.% TiO2 powder, particle size 22-45μm) with a thickness of 300μm was prepared on the surface of an aluminum alloy substrate using atmospheric plasma spraying. The sprayed alumina-titanium oxide coating was carefully polished to a roughness of 0.2μm and then ultrasonically cleaned to remove contaminants and abrasive debris generated during the polishing process. The optimized plasma spraying parameters were set as follows: arc current of 500 A, voltage of 67 V, main gas (argon) flow rate of 35 L / min, secondary gas (hydrogen) flow rate of 6 L / min, powder supply rate of 30 g / min, and spray gun movement speed of 0.8 m / s. The spraying distance was maintained at 120 mm.

[0047] S2, the rust-preventive oil consists of PAO oil (primarily acting as a carrier, diluent, and film-forming agent) and 5% by mass of DDSA (C 16 H 26 The liquid composite rust-preventive oil is prepared by heating to 60°C in a vacuum drying oven using O3. The kinematic viscosity (40°C) of the oil is 390.21 mm. 2 / s.

[0048] S3. The polished alumina-titanium oxide coating is immersed in rust-preventive oil and held under pressure of -0.08MPa for 40 minutes to allow the rust-preventive oil to penetrate into the intrinsic defect structure of the thermally sprayed ceramic coating substrate.

[0049] S4. Remove the prepared composite coating and cool it to room temperature. Then remove excess rust-preventive oil from the surface of the alumina-titanium oxide coating. The resulting rust-preventive oil / alumina-titanium oxide ceramic-based composite coating is denoted as AT3-ARO coating.

[0050] The AT3-ARO coating prepared in Example 1 mainly comprises: The thermally sprayed ceramic coating substrate has an intrinsic defect structure at the micro / nano scale; Liquid composite rust-preventive oil filling the intrinsic defect structure of the thermally sprayed ceramic coating substrate; The liquid composite rust inhibitor remains liquid at room temperature and contains synthetic base oil and corrosion inhibitors that can chemically adsorb and / or undergo in-situ tribochemical reactions with metal surfaces. Under frictional loads, especially in marine friction conditions, the liquid composite rust inhibitor can be continuously released from the intrinsic defect structure to the friction interface, forming a two-way boundary lubrication film, while providing active chemical corrosion protection to the thermally sprayed ceramic coating substrate.

[0051] In the AT3-ARO coating prepared in Example 1 of this invention, the PAO / DDSA liquid composite rust inhibitor utilizes the intrinsic defect structure of the three-dimensional micro / nanopore network inherent in the thermally sprayed ceramic coating as a micro reservoir, significantly different from traditional physical impregnation methods. Under marine friction conditions, the PAO / DDSA liquid composite rust inhibitor dynamically overflows to the friction interface of the coating surface through capillary action and mechanical extrusion friction stress. PAO provides fluid lubrication, while DDSA, due to its chemical reactivity, forms a bidirectional metal-carboxylate chemical protective boundary lubricating film in situ with the exposed metal surface (including the coating metal phase and the friction pair components) under friction, resulting in a bonding strength far exceeding that of a physical lubricating film. This PAO / DDSA binary composite system's physical-chemical dual-effect synergistic mechanism, through the real-time self-supply and dynamic replenishment of the bidirectional lubricating film during friction, achieves a synergistic effect of low friction, wear resistance, and active seawater corrosion resistance. This is key to maintaining an ultra-long lifespan and low wear rate even after 3000 hours of salt spray testing.

[0052] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that only step S1 is performed to obtain an aluminum oxide-3wt.% titanium oxide coating, denoted as AT3 coating.

[0053] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that after obtaining the alumina-3wt.% titanium oxide coating in step S1, the rust-preventive oil was replaced with pure PAO oil during the vacuum impregnation process in step S3. The heating temperature and vacuum pressure conditions were the same, resulting in a PAO oil / alumina-titanium oxide ceramic matrix composite coating, denoted as AT3-PAO coating.

[0054] Example 2 The difference from Example 1 is that the mass fraction of DDSA in the liquid composite rust inhibitor is different, taking 0.5%, and is recorded as AT3-PAO-0.5wt.%DDSA coating.

[0055] Example 3 The difference from Example 1 is that the mass fraction of DDSA in the liquid composite rust inhibitor is different, taking 1%, and recorded as AT3-PAO-1wt.%DDSA coating.

[0056] Comparative Examples 3-4 The difference from Example 1 is that the corrosion inhibitor in the liquid composite rust inhibitor is sodium petroleum sulfonate SPS (mass fractions of 1% and 5%, respectively), which are denoted as AT3-PAO-1wt.%SPS coating and AT3-PAO-5wt.%SPS coating, respectively.

[0057] Performance verification was performed on the examples and comparative examples, and the results are as follows: Figures 2 to 15 As shown.

[0058] After friction testing, a well-covered lubricating film (bidirectional metal-carboxylate boundary lubricating film) was formed on the wear marks of the rust-preventive oil / alumina-titanium oxide ceramic-based composite coating (AT3-ARO coating) prepared in Example 1 of this invention. This film provides excellent lubrication performance and load-bearing capacity for the coating. The liquid composite rust-preventive oil can penetrate into the microscopic defect structure of the coating through vacuum impregnation, continuously overflowing during friction to replenish the lubricating film and ensuring long-term effective lubrication. Furthermore, the neutral salt spray test results of this composite coating show that it exhibits excellent corrosion resistance.

[0059] Scanning electron microscope (SEM) images and elemental distribution diagrams of the surface and cross-section of the rust-preventive oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 are shown below. Figure 2 and Figure 5 As shown. From Figure 2 and Figure 5 It can be seen that, through the vacuum impregnation process, liquid composite rust-preventive oil can completely penetrate into the inherent defect structure of the pores and microcracks inside the ceramic coating.

[0060] The rust-preventive oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 was tested according to ASTM G133-22 standard. At a sliding speed of 9 cm / s and a load of 9 N, the coefficient of friction, wear rate, and 3D wear morphology are as follows: Figure 8 As shown. From Figure 8 As can be seen from Figure a, compared to the AT3 coating of Comparative Example 1, the AT3-ARO coating of Example 1 has a friction coefficient reduced by 85%, dropping below 0.1. From... Figure 8 As can be seen from Figure b, the wear resistance of the AT3-ARO coating in Example 1 is significantly improved. After 16,200 cycles, the wear rate decreased from 47.98 × 10⁻⁶. -7 mm 3 / N·m decreased to 5.76×10 -7 mm 3 / N·m and below. From Figure 8 As can be seen from the image, the depth of the wear track is only 1.6 μm, the bottom of the wear track is flat, and the roughness Ra is only 174 nm.

[0061] SEM images of the rust-preventive oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 after friction testing are shown below. Figure 9 As shown in c. As a surfactant, the presence of DDSA helps to form a chemisorbed boundary lubrication film. Figure 9The elemental distribution map shown provides evidence of the formation of a protective friction film. The strong and more uniform signals of characteristic elements such as carbon and oxygen in the AT3-ARO wear traces confirm that the DDSA-modified composite oil actively diffuses and adheres to the sliding friction interface, forming a carbon-rich boundary lubrication film. This maintains the integrity of the film and prevents direct contact between the ceramic and ceramic micro-protrusions.

[0062] The FTIR of the anti-rust oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 after friction test is as follows: Figure 10 As shown, the spectrum of the worn AT3-ARO coating reveals the characteristics of tribochemical reactions. During the friction process, the combined effects of high temperature in the micro-region, high contact stress, and trace amounts of moisture in the environment lead to in-situ ring-opening and hydrolysis of the succinic anhydride ring in the DDSA molecule, producing intermediate products containing dicarboxyl groups. The asymmetric and symmetric stretching vibration peaks of the carboxylate ion appear between 1550 and 1600 cm⁻¹. -1 and 1400 to 1450 cm -1 The characteristic absorption of the C–O bond appears in the range of 1100 to 1200 cm⁻¹. -1 Within the range. The emergence of the above-mentioned new peaks provides chemical evidence for tribochemical coordination reactions. After the ring-opening reaction, the generated active carboxyl groups react with metal cations (such as Al) from the coating and friction pair surfaces at the tribochemical interface. 3+ Ti 4+ or transferred Zr 4+ The reaction forms a metal-carboxylate composite friction film adhering to the ceramic surface. Changes in the infrared spectrum reveal the principle behind the low wear of the AT3-ARO coating: the polar DDSA additive undergoes chemisorption at the friction interface and is activated by frictional energy, using a ring-cracking and coordination mechanochemical pathway to fix the metal-carboxylate boundary protective film together via chemical bonds.

[0063] XPS values ​​of the ZrO2 paired spheres (friction pair) after friction testing of the rust-preventive oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 are as follows: Figure 11 As shown. Figure 11 The C 1s and ? shown in a Figure 11Figure b shows the O 1s spectrum, revealing the lubricant transferred and attached to the paired spheres. The 284.8 eV main peak in the C 1s spectrum is attributed to the C–C and C–H hydrocarbon chains of the base oil. The AT3-ARO coating exhibits a high C=O atomic percentage of 3.28%. This confirms that under frictional stress, polar DDSA molecules in the ARO migrate from the pores of the coating and attach to the ZrO2 paired spheres via chemisorption. The O 1s spectrum also confirms this phenomenon, showing the separation peaks of organic bonds such as C=O and C–O, and inorganic oxides such as ZrO2 and Al2O3. Meanwhile, figures c and d in Figure 11 further confirm the presence of transferred Al elements (in the form of Al2O3) on the surface of the paired spheres and the chemical state of Zr elements within the paired spheres themselves. The higher concentration of polar groups on the surface of the ARO-lubricated paired spheres indicates the formation of a chemisorbed organic transfer film. In the bidirectional boundary lubrication mechanism, both the coating and the surface of the mating ball are shielded by anchored polar molecules, thereby reducing direct micro-surface contact between the ceramic and the mating part, thus achieving the low coefficient of friction and wear rate observed in the AT3-ARO system.

[0064] The polarization curve of the rust-preventive oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 is as follows: Figure 12 As shown, the AT3-ARO coating exhibits a high corrosion potential and a low corrosion current. This active protection mechanism is attributed to the chemisorption of DDSA molecules, where charged carboxyl groups adhere to the pore walls and the exposed substrate, while the uncharged 12-carbon chain tails extend outwards, thereby forming a dense, self-assembled boundary film capable of repelling water and chloride ions.

[0065] The salt spray test results of the rust-preventive oil / alumina-titanium oxide ceramic matrix composite coating (AT3-ARO coating) prepared in Example 1 are as follows: Figure 15 As shown. From Figure 15 As can be seen, the corrosion resistance is significantly improved. After 3000 hours of neutral salt spray test, there are no obvious corrosion marks on the sample surface.

[0066] Scanning electron microscope (SEM) images and elemental distribution diagrams of the surface and cross-section of the alumina-titanium oxide composite coating (AT3 coating) in Comparative Example 1 are shown below. Figure 3 and Figure 6 As shown. From Figure 3 and Figure 6 It can be seen that unmelted or partially melted particles, microcracks, and irregularly shaped micropores (intrinsic defect structures) are distributed throughout the surface and cross-section of the coating. These inherent multi-scale internal defects intertwine to form a complex 3D capillary network, which typically acts as capillary permeation channels for corrosive media.

[0067] The alumina-titanium oxide composite coating (AT3 coating) prepared in Comparative Example 1 was tested according to ASTM G133-22 standard. At a sliding speed of 9 cm / s and a load of 9 N, the coefficient of friction, wear rate, and 3D wear morphology are as follows: Figure 8 As shown. From Figure 8 As can be seen, the coating has a high coefficient of friction of 0.658 and a high wear rate of 47.98 × 10⁻⁶. -7 mm 3 The wear depth of over 80 μm and the high surface roughness Ra confirm that the coating has suffered severe wear damage.

[0068] SEM images of the alumina-titanium oxide composite coating (AT3 coating) after friction experiments in Comparative Example 1 are shown below. Figure 9 As shown in a, the worn surface of the AT3 coating exhibits wide and deep furrows, plastic deformation, and large-scale delamination. Due to the lack of lubrication, a high-stress contact forms between the ceramic skeleton and the zirconia substrate, leading to wear and adhesive wear. Figure 8 The high coefficient of friction and wear depth shown in Figures a, b, and c are consistent. The potentiodynamic polarization curve of the alumina-titanium oxide composite coating (AT3 coating) in Comparative Example 1 is shown below. Figure 12 As shown, the sprayed AT3 coating exhibited the most negative corrosion potential (-0.78 V) and the highest corrosion current (1.2 × 10⁻⁶ V). -5 A / cm 2 This high corrosion sensitivity stems from the multidimensional defects inherent in the APS process (porosity, microcracks, and sputtering boundaries), which act as capillary channels for rapid electrolyte penetration.

[0069] Scanning electron microscope (SEM) images and elemental distribution diagrams of the surface and cross-section of the PAO oil / alumina-titanium oxide composite coating (AT3-PAO coating) in Comparative Example 2 are shown below. Figure 4 and Figure 7 As shown. From Figure 4 and Figure 7 It can be seen that, through the vacuum impregnation process, PAO oil can penetrate into the inherent pores and microcracks inside the ceramic coating.

[0070] The PAO oil / alumina-titanium oxide composite coating (AT3-PAO coating) prepared in Comparative Example 2 was tested according to ASTM G133-22 standard. At a sliding speed of 9 cm / s and a load of 9 N, the coefficient of friction was as follows: Figure 8 As shown in Figure a, from Figure 8 As can be seen from Figure a, compared to the AT3 coating in Comparative Example 1, the friction coefficient of the AT3-PAO coating in Comparative Example 2 is reduced by approximately 80%, decreasing to around 0.13. From... Figure 8As can be seen from Figure b, the wear resistance of the AT3-PAO coating is improved; after 16,200 cycles, the wear rate decreased from 47.98 × 10⁻⁶. -7 mm 3 / N·m decreased to 7.78×10 -7 mm 3 / N·m or less. As can be seen from d in Figure 8, the wear track depth (approximately 0.8 μm) and surface roughness R of the AT3-PAO coating are... a (212nm) are all greater than those of Example 1 shown in Figure 8e. This indicates that although pure PAO oil has a physical friction-reducing effect, it cannot form a highly adhesive chemical protective boundary film in the absence of chemically inhibiting active molecules (DDSA), and therefore its long-term wear resistance is not as good as that of Example 1.

[0071] SEM images of the PAO oil / alumina-titanium oxide ceramic matrix composite coating (AT3-PAO coating) prepared in Comparative Example 2 after friction experiments are shown below. Figure 9 As shown in b, it can be seen that PAO stored in the micropores is transferred to the surface to provide basic lubrication under local high-pressure sliding conditions, but a lubricating film formed by PAO oil only exists in a small portion of the wear track. Therefore, purely physical adsorption of PAO is insufficient to maintain a stable and continuous lubricating film under local high-pressure sliding conditions.

[0072] The FTIR of the PAO oil / alumina-titanium oxide ceramic matrix composite coating (AT3-PAO coating) prepared in Comparative Example 2 after friction test is as follows: Figure 10 As shown. The spectral curve of the worn AT3-PAO surface retains the characteristic absorption peaks of the original PAO oil, including those located between 2800 and 3000 cm⁻¹. -1 and 1300 to 1500 cm -1 The -CH2 and -CH3 vibration peaks in the region did not show any new functional group peaks. This indicates that the nonpolar PAO remains stable during friction, provides physical-fluid lubrication at the contact interface, and does not chemically react with the ceramic surface. This explains why it is easily extruded under continuous high-pressure shear, resulting in limited wear resistance.

[0073] XPS values ​​of the ZrO2 paired spheres after friction testing of the PAO oil / alumina-titanium oxide ceramic matrix composite coating (AT3-PAO coating) prepared in Comparative Example 2 are as follows: Figure 11 As shown. Figure 11 The 284.8 eV main peak in the C 1s spectrum shown in a is attributed to the C–C and C–H hydrocarbon chains of the base oil. Figure 11The C=O and C–O organic bonds shown in b, as well as the inorganic oxide peaks of ZrO2 and Al2O3, combined with the chemical states of Al and Zr elements confirmed by c and d in Figure 11, prove that only slight oxidation of PAO and physical adsorption on the paired spheres exist during the friction process.

[0074] The potentiodynamic polarization curves of the PAO oil / alumina-titanium oxide ceramic matrix composite coating (AT3-PAO coating) prepared in Comparative Example 2 are shown below. Figure 12 As shown, after vacuum impregnation with base oil PAO, the corrosion current decreased by nearly three orders of magnitude, dropping to 10. -8 A / cm 2 The corrosion potential shifted positively at the same level. This indicates that the inert PAO physically seals the open pores, providing a major barrier against the migration of corrosive ions.

[0075] Furthermore, experimental results show that the friction coefficient of the AT3-PAO-0.5wt.%DDSA coating prepared in Example 2, as shown in Figure 13, is stable at around 0.12, which is superior to the AT3-PAO of Comparative Example 2 (approximately 0.13) and close to the level of Example 1. Figure 12 As shown, the corrosion current of the AT3-PAO-0.5wt.%DDSA coating prepared in Example 2 increases to nearly 10. -9 A / cm 2 The corrosion resistance of the coating in Example 2 is slightly lower than that of the AT3-ARO coating in Example 1. This is mainly because the lower DDSA content makes it difficult to form a stable and dense boundary film, which cannot completely block the penetration of water and chloride ions.

[0076] As shown in Figure 13, the coefficient of friction of the AT3-PAO-1.0wt.%DDSA coating prepared in Example 3 was further reduced to approximately 0.11. Meanwhile, as shown in Figure 12, its corrosion resistance is close to that of the AT3-ARO coating in Example 1. However, considering that the coating will induce continuous mechanical shearing and boundary film consumption under dynamic sliding conditions, the stability of the 1wt.%DDSA coating during extremely long-term service is slightly inferior to that of Example 1. This is mainly because the excess DDSA molecules in the AT3-ARO coating (5.0wt.%DDSA) of Example 1 form reverse micelles in the nonpolar PAO and construct "micro-oil reservoirs," which can more quickly replenish the depleted active molecules, thereby maintaining the continuity of in-situ tribochemical reactions during ultra-long-term friction.

[0077] like Figure 14As shown, the coatings prepared by adding sodium petroleum sulfonate (SPS) in Comparative Examples 3 and 4 exhibit significantly weaker corrosion resistance than those prepared by DDSA, and their corrosion current density is greater than that of the AT3-PAO coating in Comparative Example 2, and the coatings in Examples 1 and 3. As a surfactant, sodium petroleum sulfonate has a certain degree of hydrophilicity, and its hydrophilic groups may form "channels" within the pores, which could accelerate the penetration of corrosive media, reduce charge transfer resistance, and lead to a decline in electrochemical performance.

[0078] In summary, this invention provides a ceramic-based self-lubricating composite coating and its preparation method based on PAO / DDSA rust-preventive oil impregnation modification, relating to the fields of composite coating preparation and surface modification technology. Utilizing the inherent defect structure of the micro / nanopore network within the thermally sprayed ceramic coating as a micro-reservoir for the liquid rust-preventive oil, a liquid composite rust-preventive oil with deep penetration, adaptive dynamic lubrication capability, and active chemical corrosion inhibition and rust prevention functions is introduced. This forms a self-replenishing lubricating film at the friction interface while endowing the coating with long-lasting and active corrosion resistance. Under marine friction conditions, the PAO / DDSA liquid composite rust-preventive oil dynamically overflows to the surface through capillary action and frictional stress mechanical extrusion. PAO provides fluid lubrication, while DDSA reacts in situ to generate a bidirectional metal-carboxylate chemical boundary protective film, achieving a synergistic effect of low friction, wear resistance, and active seawater corrosion resistance. This fundamentally solves the problems of difficulty in simultaneously achieving lubrication and corrosion prevention, and poor long-term effectiveness in traditional technologies, making it particularly suitable for surface protection of moving friction components in marine equipment such as ships, seawater pumps and valves, and offshore platforms.

[0079] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A PAO / DDSA rust-preventive oil impregnated modified ceramic-based self-lubricating composite coating, characterized in that, include: The thermally sprayed ceramic coating substrate has an intrinsic defect structure at the micro / nano scale; Liquid composite rust-preventive oil filling the intrinsic defect structure of the thermally sprayed ceramic coating substrate; The liquid composite rust inhibitor remains liquid at room temperature and contains synthetic base oil and corrosion inhibitors that can chemically adsorb and / or undergo in-situ tribochemical reactions with metal surfaces. When subjected to frictional loads, the liquid composite rust-preventive oil can be continuously released from the intrinsic defect structure to the friction interface, forming a two-way boundary lubrication film, while providing active chemical corrosion protection to the thermally sprayed ceramic coating substrate.

2. The PAO / DDSA rust-preventive oil-impregnated modified ceramic-based self-lubricating composite coating according to claim 1, characterized in that, The synthetic base oil is a polyalphaolefin, and the corrosion inhibitor is dodecenyl succinic anhydride; the mass fraction of the corrosion inhibitor in the liquid composite rust-preventive oil is 0.5% to 5.0%.

3. The PAO / DDSA rust-preventive oil-impregnated modified ceramic-based self-lubricating composite coating according to claim 2, characterized in that, The intrinsic defect structure includes pores, microcracks, and unbonded areas between layers. The liquid composite rust-preventive oil penetrates through a vacuum impregnation process and is stably retained within the intrinsic defect structure by capillary action at the micro / nano scale, forming a micro-oil reservoir. Furthermore, frictional stress triggers exudation, dynamically replenishing the bidirectional boundary lubrication film. The kinematic viscosity of the liquid composite rust-preventive oil at 40°C is 350~450 mmHg. 2 / s.

4. The PAO / DDSA rust-preventive oil impregnation modified ceramic-based self-lubricating composite coating according to claim 2, characterized in that, The bidirectional boundary lubricating film is a bidirectional metal-carboxylate boundary lubricating film, which is formed by the in-situ tribochemical reaction between the corrosion inhibitor and the coating surface and the friction pair surface.

5. The PAO / DDSA rust-preventive oil-impregnated modified ceramic-based self-lubricating composite coating according to claim 1, characterized in that, In the thermally sprayed ceramic coating substrate, the ceramic coating is any one of oxide ceramic coating, carbide ceramic coating, and nitride ceramic coating, with a thickness of 100~300μm.

6. A method for preparing a PAO / DDSA rust-preventive oil impregnated modified ceramic-based self-lubricating composite coating, used to prepare the PAO / DDSA rust-preventive oil impregnated modified ceramic-based self-lubricating composite coating according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1, using a thermal spraying process, a ceramic coating is sprayed onto a metal substrate to obtain a thermally sprayed ceramic coating substrate with micro / nano-scale intrinsic defect structures; S2, heating the liquid composite rust-preventive oil containing synthetic base oil and corrosion inhibitor to a preset temperature; S3, the thermally sprayed ceramic coating substrate is completely immersed in the liquid composite rust-preventive oil heated in step S2, and vacuum impregnation is performed to allow the rust-preventive oil to penetrate into the intrinsic defect structure of the thermally sprayed ceramic coating substrate. S4. Cool to room temperature to restore the liquid composite rust-preventive oil to a stable liquid state and remove excess rust-preventive oil from the surface of the thermally sprayed ceramic coating substrate to obtain a PAO / DDSA rust-preventive oil impregnated and modified ceramic-based self-lubricating composite coating.

7. The method for preparing the PAO / DDSA rust-preventive oil-impregnated modified ceramic-based self-lubricating composite coating according to claim 6, characterized in that, In step S1, the thermal spraying process adopts atmospheric plasma spraying, and the process parameters include: plasma spray gun current of 450~650A, argon flow rate of 30~45L / min, hydrogen flow rate of 4~12L / min, spray distance of 90~140mm, and powder feeding rate of 20~60g / min.

8. The method for preparing the PAO / DDSA rust-preventive oil impregnation modified ceramic-based self-lubricating composite coating according to claim 6, characterized in that, In step S2, the heating temperature is 50~70℃.

9. The method for preparing the PAO / DDSA rust-preventive oil impregnation modified ceramic-based self-lubricating composite coating according to claim 6, characterized in that, In step S3, the conditions for vacuum impregnation are: pressure of -0.040 to -0.085 MPa and impregnation time of 40 to 60 min.

10. The application of the PAO / DDSA rust-preventive oil impregnation-modified ceramic-based self-lubricating composite coating according to any one of claims 1 to 5, characterized in that, Applications in the fields of friction reduction, wear resistance, and corrosion resistance.

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