A valve core valve sleeve surface double-layer composite nano structure protective layer and a construction method thereof

Abstract

This invention belongs to the field of valve core and valve sleeve surface treatment technology, specifically disclosing a double-layer composite nanostructure protective layer for valve core and valve sleeve surfaces and its construction method. The construction method includes: S1: depositing a titanium thin film precursor with a thickness of 0.5–5 μm on the surface of the valve core or valve sleeve substrate; S2: performing controlled-depth irradiation in a helium-containing plasma environment, causing self-organized reconstruction of only the surface layer of the precursor, resulting in in-situ growth of a villous fuzz nanostructure layer, while the bottom layer remains dense, forming a double-layer composite structure; S3: passivation treatment to generate a TiO2 passivation film on the surface of the fuzz layer. This invention, through "partial thickness reconstruction," for the first time constructs a functionally layered double-layer protection system. The surface layer provides high specific surface area passivation and micro-motion buffering, while the bottom dense titanium-based thin film acts as an intrinsic barrier providing backup protection, solving the problem of protection failure after wear. This protective layer is integrated with the substrate, interface-free, and possesses excellent corrosion resistance, wear resistance, structural stability, and dimensional compatibility.

Description

Technical Field

[0001] This invention relates to the field of valve core and valve sleeve surface treatment technology, specifically to a double-layer composite nanostructure protective layer for the surface of valve core and valve sleeve and its construction method. Background Technology

[0002] In precision hydraulic and pneumatic control systems, the kinematic pair consisting of the valve core and valve sleeve is a core component, and their mating clearance is often strictly controlled at the micrometer level (e.g., 2 μm to 8 μm). In harsh environments such as aerospace and marine engineering, this tiny clearance is extremely susceptible to jamming, leakage, and even functional failure due to surface corrosion and wear.

[0003] To improve the surface protection performance of such components, existing technologies often employ electroplating, electroless plating, and physical / chemical vapor deposition to prepare external coatings on the substrate surface, such as chromium plating, nickel plating, TiN, or Al2O3 ceramic coatings. However, these external coatings have fundamental defects: there is a clear physical or chemical interface between the coating and the substrate, which is prone to crack initiation and propagation under the influence of friction, vibration, and thermal cycling during long-term service, ultimately leading to coating peeling and failure; it is difficult to avoid intrinsic defects such as micropores and microcracks during coating preparation, which become rapid channels for corrosive media to penetrate into the substrate, reducing the long-term protective effect; at the same time, the thickness of traditional coatings is usually on the order of several micrometers to tens of micrometers, which significantly changes the original fitting accuracy of precision valve cores and sleeves with a fitting clearance of only a few micrometers, affecting the sealing performance and operational stability of the system.

[0004] In recent years, the technology of inducing the formation of nanostructures by irradiating titanium surfaces with helium plasma has attracted attention. Studies have shown that under appropriate ion energy and temperature conditions, helium plasma irradiation can induce various surface morphologies on titanium surfaces, such as nanocones and nanoporous structures. Furthermore, introducing titanium components during the irradiation process can further enhance the growth rate of nanostructures. However, the aforementioned existing technologies all involve direct irradiation of pure bulk titanium materials, resulting in a single-layer nanostructure or damaged area extending downwards from the surface. While this structure increases surface roughness and specific surface area to some extent, its nanomorphological control is limited, and its mechanical and barrier properties depend on the substrate itself. Under the harsh conditions of corrosion protection and friction-wear coupling, the overall performance of such single-layer structures is insufficient, especially after long-term wear. Once the surface nanostructure is worn through, the substrate is directly exposed to the corrosive environment, leading to a complete loss of protective function.

[0005] Therefore, there is an urgent need to develop a surface protection method that can construct a valve core and valve sleeve surface with excellent corrosion resistance, high interfacial bonding strength, good wear resistance and backup protection capability, while simultaneously meeting precision dimensional requirements. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a double-layer composite nanostructure protective layer on the surface of valve core and valve sleeve and its construction method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for constructing a double-layer composite nanostructure protective layer on the surface of a valve core and valve sleeve, comprising the following steps: Step S1: Deposit a titanium thin film precursor on the surface of the valve core or valve sleeve substrate under a protective gas plasma atmosphere, controlling its thickness to be 0.5 μm to 5 μm; Step S2: The substrate on which the titanium thin film precursor is deposited is placed in a helium-containing plasma environment for irradiation treatment, and the irradiation parameters are controlled so that the titanium thin film precursor undergoes self-organization and reconstruction only in a certain depth range in its thickness direction, thereby growing a villous fuzz nanostructure layer in situ on its surface, while its bottom part remains in an unirradiated dense state, thus forming a bilayer composite structure composed of a surface fuzz nanostructure layer and a bottom dense titanium-based thin film layer. Step S3: The irradiated valve core or sleeve undergoes surface passivation treatment, generating a passivated oxide film on the surface of the fuzz nanostructure layer, forming the final nanostructure protective layer. Through step S1 (depositing a titanium thin film precursor), step S2 (controlled-depth irradiation causing self-organized reconstruction only at the surface depth), and step S3 (passivation treatment), a dual-layer composite protective structure of "surface fuzz nanostructure layer + bottom dense titanium-based thin film layer" is achieved. The surface layer provides high specific surface area passivation and micro-motion buffering, while the bottom dense film acts as an intrinsic barrier providing backup protection, solving the problem of complete loss of protective function after wear of existing single-layer nanostructures. Simultaneously, the total thickness of the protective layer is in the nanometer to submicrometer range, adaptable to the precise fit clearance requirements of the valve core and sleeve.

[0008] In some embodiments, in step S2, the irradiation parameters are controlled to make the substrate surface temperature reach 1000 K to 2000 K, the incident ion energy greater than 30 eV, and the ion flux reach 10². 5 m - On the order of magnitude 2. By limiting the irradiation temperature, ion energy, and ion flux parameters, it is ensured that the surface of the titanium thin film precursor can undergo self-organized reconstruction under stable and controllable conditions to form a uniform and dense fuzz nanostructure, providing a process guarantee for the reliable preparation of bilayer composite structures.

[0009] In some embodiments, by controlling the irradiation time to be in the range of 10 minutes to 120 minutes and / or the ion flux to be 10² 5 m - ² to 10² 6 m -Within a certain range, the thickness of the fuzz nanostructure layer is 10% to 80% of the thickness of the titanium thin film precursor. By controlling the irradiation time and / or ion flux, the thickness of the fuzz nanostructure layer is precisely controlled between 10% and 80% of the precursor thickness, enabling flexible adjustment of the thickness ratio of the functional layer to the backup layer in the bilayer structure to meet the protection performance requirements of different service conditions.

[0010] In some embodiments, the thickness of the titanium thin film precursor is controlled to be 1 μm to 3 μm, and the thickness of the fuzz nanostructure layer is controlled to be 100 nm to 800 nm. The precursor thickness of 1 μm to 3 μm and the fuzz layer thickness of 100 nm to 800 nm ensure that the underlying dense film has sufficient backup protective thickness while making the total protective layer size much smaller than the valve core-valve sleeve mating clearance, thus ensuring that the fitting accuracy of the precision moving parts is not affected.

[0011] In some embodiments, the deposition of the titanium thin film precursor in step S1 and the irradiation treatment in step S2 are carried out continuously in the same vacuum chamber. Continuous deposition and irradiation within the same vacuum chamber avoids the risks of surface contamination and oxidation caused by transferring the workpiece between different chambers, simplifies the process flow, improves preparation efficiency, and ensures the interface cleanliness between the titanium thin film precursor and the subsequent irradiation treatment.

[0012] In some embodiments, in steps S1 and / or S2, the titanium thin film precursor or fuzz nanostructure layer is uniformly formed on the cylindrical or complex curved surface of the valve core or valve sleeve by rotating the workpiece and / or using multi-angle plasma irradiation. By rotating the workpiece and / or using multi-angle plasma irradiation, the problem of uniform processing on the cylindrical and complex curved surfaces of the valve core or valve sleeve is solved, ensuring the uniform formation of the titanium thin film precursor and fuzz nanostructure layer on non-planar workpieces, and improving the applicability of this method to actual engineering components.

[0013] In some embodiments, the valve core or valve sleeve substrate is made of titanium alloy. The selection of titanium alloy as the substrate material allows for a stable bond between the titanium alloy and the titanium film precursor due to the good affinity between titanium and titanium-like metals, further enhancing the structural stability of the entire double-layer composite protection system.

[0014] This invention provides a valve core or valve sleeve with a double-layer composite nanostructure protective layer on its surface. The protective layer consists of a top fuzz nanostructure layer and a bottom dense titanium-based thin film layer. The fuzz nanostructure layer comprises a titanium nanofiber framework and a TiO2 passivation film covering its surface. The dense titanium-based thin film layer is a portion of the titanium thin film precursor that remains in a non-irradiated, dense state. Furthermore, the dense titanium-based thin film layer and the substrate, as well as the dense titanium-based thin film layer and the fuzz nanostructure layer, are all integral structures with no discernible separation interfaces. This protective layer evolves from the same titanium thin film precursor, and the integral structure between each layer and the substrate, without separation interfaces, fundamentally eliminates the defects of traditional coatings that are prone to peeling, and also possesses excellent corrosion resistance, wear resistance, and structural stability.

[0015] In some embodiments, the thickness of the fuzz nanostructure layer is 100 nm to 800 nm, the thickness of the dense titanium-based thin film layer is 0.2 μm to 2.9 μm, and the thickness of the fuzz nanostructure layer is 10% to 80% of the total thickness of the titanium thin film precursor. By limiting the specific thickness range and proportional relationship of each layer in the product, it is ensured that the product has significant protective performance while the total thickness is controlled at the nanometer to submicrometer level, without changing the original fitting accuracy of the valve core and valve sleeve, thus guaranteeing the sealing performance and motion accuracy of precision hydraulic or pneumatic systems.

[0016] The beneficial effects of this invention are: First, by controlling the irradiation depth, the titanium thin film precursor undergoes only "partial thickness reconstruction," thus forming a two-layer composite protective structure consisting of a "surface fuzz nanostructure layer + a bottom dense titanium-based thin film layer." By pre-depositing a titanium thin film precursor of a specific thickness and precisely controlling the irradiation to only affect a portion of its surface depth, a functionally layered composite system is constructed. The bottom dense titanium-based thin film layer possesses excellent inherent corrosion resistance, acting as an "intrinsic barrier" to effectively block any possible penetration paths of corrosive media into the fuzz nanostructure layer, forming a two-tiered protection. When the surface fuzz layer is damaged due to extreme wear, the bottom dense film still provides reliable backup protection, significantly improving the system's fault tolerance and long-term reliability—something that existing single-layer structures cannot achieve.

[0017] Secondly, since the fuzz nanostructure layer is grown in situ from the titanium thin film precursor itself, and the underlying dense titanium-based thin film layer is also a retained portion of the precursor, there is no interface between the surface fuzz layer and the underlying dense film—they originate from the same thin film, differing only in structural morphology, without any material boundary. Simultaneously, when the substrate is a titanium alloy, a stable bond is formed between the titanium thin film precursor and the substrate due to the excellent affinity between titanium and titanium as similar metals. This fundamentally eliminates any possibility of interlayer delamination, and its structural stability far exceeds that of traditional double-layer coating systems formed through two deposition processes, and is also superior to the gradient damage transition zone between the nanostructure and the substrate in existing technologies.

[0018] Third, by adjusting the initial thickness of the titanium thin film precursor and irradiation parameters (irradiation time, ion flux, etc.), the thickness of the dense layer and the fuzz layer can be controlled independently and precisely. This allows for the design of the total thickness of the entire protection system at the nanometer level, ensuring that it is much smaller than the fitting clearance of the valve core and valve sleeve. This provides strong protection without changing the original dimensions and tolerances of the parts.

[0019] Fourth, the fuzz nanostructure layer formed on the surface after irradiation is passivated to form a TiO2 passivation film, which retains the excellent repassivation ability of titanium and can achieve self-healing of local damage. At the same time, the porous elastic structure of the fuzz nanofiber network can effectively absorb energy and buffer stress during fretting friction, exhibiting excellent wear resistance and structural stability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0021] Figure 1 This is a process flow diagram of an embodiment of the present invention; Figure 2 This is a scanning electron microscope (SEM) image of the fuzzy nanostructure formed on the surface of titanium material after treatment by the method of this invention in an embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the principle of the application of the present invention to valve core surface treatment in an embodiment of the invention; Figure 4 The image shows a transmission electron microscope (TEM) image (left) and a schematic diagram of the growth process (right) of the fuzz nanostructure as the ion flux increases, representing an embodiment of the present invention. Figure 5This is a schematic diagram of the cross-sectional structure of the double-layer composite nanostructure protective layer according to an embodiment of the present invention. Detailed Implementation

[0022] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] 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 drawings, are intended to cover non-exclusive inclusion.

[0024] The directional and positional terms used in this invention, such as up, down, front, back, left, right, inside, outside, top, bottom, side, etc., are merely for reference to the accompanying drawings. Therefore, the directional and positional terms used are for illustrating and understanding this invention, and not for limiting the scope of protection of this invention.

[0025] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments: Example 1 This embodiment provides a method for constructing a double-layer composite nanostructure protective layer on the surface of a valve core and valve sleeve. Surface treatment of hydraulic valve core / sleeve, such as Figure 1 As shown, this embodiment includes the following steps: Pretreatment: The titanium alloy (TC4) valve core / sleeve to be treated is ultrasonically cleaned and dried, then placed in the plasma treatment chamber. The chamber is evacuated to a background vacuum of 1×10⁻⁶. -4 Pa.

[0026] Step S1: Depositing the titanium thin film precursor: Argon gas with a purity of 99.99% was introduced at a flow rate of 15 sccm, maintaining a chamber pressure of approximately 1 Pa. Argon plasma was initiated for magnetron sputtering at a sputtering power of 100 W and substrate room temperature. A constant-speed rotation mechanism was used for the valve core / sleeve to ensure uniform deposition of a dense titanium thin film precursor with a thickness of approximately 2 μm on its cylindrical surface.

[0027] Figure 3 A schematic diagram illustrating the principle of this invention applied to valve core surface treatment is shown. Figure 3 A constant-speed rotation mechanism is used for the valve core / sleeve, combined with multi-angle plasma irradiation, to ensure that a dense titanium thin film precursor with a thickness of about 2 μm is uniformly deposited on its cylindrical surface.

[0028] Step S2: Controlled-depth induced fuzz nanostructure growth: Argon gas flow was stopped, and 99.999% pure helium gas was introduced into the cavity to excite plasma. By adjusting the power and bias voltage, the workpiece surface temperature was made to reach approximately 1200 K, the incident ion energy to approximately 50 eV, and the ion flux to approximately 5 × 10². 5 m - ². Under these conditions, the titanium film precursor was irradiated for 45 minutes. By controlling the irradiation time, helium ions were directed to act only on the surface layer of the titanium film precursor, inducing self-organized reconstruction. After irradiation, a villous fuzz nanostructure was formed on the surface layer of the titanium film precursor at a depth of approximately 500 nm, while the underlying titanium film at a depth of approximately 1.5 μm remained in its original dense state, thus forming a bilayer composite structure of "surface fuzz nanostructure (approximately 500 nm) + underlying dense titanium-based film (approximately 1.5 μm)".

[0029] Figure 4 The image shows a transmission electron microscope (TEM) image (left) illustrating the increase in thickness of the fuzz nanostructure with increasing ion flux, and a schematic diagram (right) illustrating the growth process of the fuzz nanostructure. (See reference) Figure 4 With increasing irradiation time (equivalent to the accumulation of ion flux), helium ion implantation leads to self-organized reconstruction of the titanium film precursor surface, and the nanostructure gradually transforms from initial nucleation to dense growth, with a corresponding increase in structural height and coverage. By precisely controlling the irradiation time to 45 minutes, helium ions act only on the surface layer of the titanium film precursor within a depth of approximately 500 nm, inducing its growth into a villous fuzz nanostructure, while the underlying titanium film of approximately 1.5 μm retains its original dense state.

[0030] Figure 2 A scanning electron microscope (SEM) image of the fuzzy nanostructure formed on the surface of titanium material after treatment by the method of the present invention is shown. (Refer to...) Figure 1 Fuzz nanostructures are composed of a large number of tiny nanofibers, exhibiting a complex three-dimensional microstructure and having a very large specific surface area.

[0031] Step S3: Passivation Treatment: After the treatment is completed and the workpiece has cooled to room temperature, it is removed from the vacuum chamber and exposed to clean air for 2 hours. The fuzz nanofibers, with their extremely high specific surface area, rapidly react with oxygen, forming a dense TiO2 passivation film with a thickness of approximately 5–10 nm on their surface in situ, thus obtaining the finished product. The total protective layer thickness is approximately 2 μm, of which the fuzz + TiO2 layer accounts for approximately 25%, and the dense titanium-based thin film layer accounts for approximately 75%.

[0032] Figure 5A schematic cross-sectional view of the bilayer composite nanostructure protective layer formed by the present invention is shown. (Refer to...) Figure 5 The resulting protective layer consists of a surface fuzz nanostructure layer 30 and a bottom dense titanium-based thin film layer 20. The fuzz nanostructure layer 30 comprises a titanium nanofiber framework 31 and a TiO2 passivation film 32 covering its surface (approximately 5–10 nm thick). The dense titanium-based thin film layer 20 is a portion of the titanium thin film precursor that remains in a dense, unirradiated state. The dense titanium-based thin film layer 20 and the substrate 10, as well as the dense titanium-based thin film layer 20 and the fuzz nanostructure layer 30, are integrated structures with no discernible separation interfaces.

[0033] Example 2: Comparative Experiment on Adjusting Fuzz Layer Thickness The same basic steps as in Example 1 were used, except that the irradiation time was shortened to 20 minutes. The results showed that the total thickness of the titanium thin film precursor was approximately 2 μm, and after irradiation, a fuzz nanostructure layer with a thickness of approximately 200 nm was formed on the surface, with a dense titanium-based thin film layer retained below it for approximately 1.8 μm.

[0034] The same basic steps as in Example 1 were used, except that the irradiation time was extended to 90 minutes. The results showed that the total thickness of the titanium thin film precursor was approximately 2 μm, and after irradiation, a fuzz nanostructure layer with a thickness of approximately 1.1 μm was formed on the surface, with a dense titanium-based thin film layer remaining below it for approximately 0.9 μm.

[0035] The above results demonstrate that by simply adjusting the irradiation time, the thickness ratio of the fuzz nanostructure layer to the dense titanium-based thin film layer can be precisely controlled over a wide range, enabling flexible design of the entire double-layer composite protective structure.

[0036] Performance Testing and Comparison To verify the effectiveness of the present invention, the following samples were tested respectively: Comparative Example 1: Untreated titanium alloy valve core / valve sleeve substrate (corresponding to "untreated sample").

[0037] Comparative Example 2: Workpiece with only a 2 μm titanium film deposited and without helium irradiation (corresponding to "Ti film sample").

[0038] Comparative Example 3: The surface of a titanium alloy substrate (without a pre-deposited titanium film) was directly irradiated with the same helium irradiation parameters as in Example 1 to form a single-layer nanostructure region.

[0039] Example 1 of the present invention: It has a bilayer composite structure of "fuzz nanostructure layer + dense titanium-based thin film layer" (corresponding to "sample of the present invention (fuzz+TiO2)").

[0040] (1) Salt spray corrosion test Exposure tests of different durations were conducted on each sample under 5% NaCl neutral salt spray conditions, and the results are shown in Tables 1, 2, and 3.

[0041] Comparison of corrosion resistance of valve core / sleeve under different operating conditions Table 1: Table 2: Table 3: As shown in Tables 1, 2, and 3, the salt spray failure time of Example 1 of this invention exceeds 120 hours, significantly better than Comparative Example 1 (48 hours), Comparative Example 2 (72 hours), and Comparative Example 3 (96 hours). Regarding corrosion current density, Example 1 of this invention reduces it to 0.8 μA / cm², approximately an order of magnitude lower than Comparative Example 1 (8.2 μA / cm²). Of particular note is that even after artificially scratching the surface fuzz nanostructure layer to simulate extreme wear damage in the later stages of the experiment, the corrosion current density of Example 1 of this invention remained at around 1.5 μA / cm², without the sharp increase in corrosion current density observed in Comparative Example 3 after substrate exposure. This indicates that the underlying dense titanium-based thin film layer, acting as a backup barrier, plays a substantial and effective protective role, endowing this invention with a "fault tolerance" capability not possessed by other samples.

[0042] In alternating temperature cycling and high humidity environment tests, Example 1 of the present invention also showed the best stability. After 100 temperature cycles, the surface remained basically unchanged, and after 72 hours of high humidity exposure, there was no obvious corrosion. This is due to the dual synergistic effect of the continuous dense characteristics of the fuzz nanostructure and the underlying dense titanium-based thin film layer.

[0043] (2) Reciprocating friction and wear test Under reciprocating friction conditions of 5 N load, 5 Hz frequency, and 5 mm stroke, the samples were tested for different numbers of cycles. The results are shown in Tables 4, 5, and 6.

[0044] Comparison of structural stability of different samples under reciprocating friction conditions Table 4: Table 5: Table 6: As can be seen from Tables 4, 5, and 6, Embodiment 1 of the present invention has a 10 4 After one cycle, the structural integrity remained above 95%, with a wear volume of only 1.8 × 10⁻⁶.- 3 mm³, far lower than Comparative Example 1 (8.5 × 10⁻⁶ mm³). - ³ mm³), Comparative Example 2 (5.2 × 10⁻⁶ mm³) - ³ mm³) and Comparative Example 3 (3.1 × 10⁻⁶ mm³) - ³ mm³). In 5×10 4 After several cycles, the friction coefficient of Comparative Example 1 continued to increase to 0.75, that of Comparative Example 2 increased slightly to 0.60, and that of Comparative Example 3 gradually increased to 0.52, while the friction coefficient of Example 1 of the present invention remained basically stable at a lower level of 0.32 to 0.38. In 10 5 After several cycles, Comparative Example 1 and Comparative Example 3 both showed substrate exposure or local failure, Comparative Example 2 showed large-area peeling, while Example 1 of the present invention only showed local compaction, still maintaining continuous coverage and effective protection.

[0045] Comparing Comparative Example 3 with Example 1 of the present invention, it can be seen that although both have fuzz nanostructures on their surfaces, Comparative Example 3, after undergoing 10... 5 After several cycles, the fuzz layer was worn through, the substrate was exposed, and the protection partially failed. However, in Embodiment 1 of this invention, after the surface fuzz layer was partially compacted, the underlying dense titanium-based thin film layer continued to provide effective protection, demonstrating that the service reliability and service life of the bilayer composite structure are significantly superior to those of the single-layer structure. The surface fuzz nanofiber network effectively buffers frictional stress, while the underlying dense titanium-based thin film layer provides durable structural support and a backup protective barrier.

[0046] (3) Overall performance comparison To fully illustrate the technical advantages of the present invention, a systematic comparison was made between Embodiment 1 of the present invention and commonly used existing chromium plating technology and simple Ti film technology, and the results are shown in Table 7.

[0047] Table 7 Performance comparison of this invention with chromium plating technology and pure Ti film As clearly shown in Table 7, traditional chromium plating is an externally thickened coating (5–20 μm), which is prone to microcracks and faces the risk of cracking and peeling during long-term use. Furthermore, its large thickness negatively impacts the micron-level fit clearance between the valve core and valve sleeve. Additionally, the chromium plating process involves harmful substances such as hexavalent chromium, resulting in poor environmental friendliness. While pure titanium films are environmentally friendly, their surface hardness and wear resistance are generally poor, and they contain microporous defects. More importantly, they lack backup protection; once the film is damaged, the substrate is exposed to a corrosive environment.

[0048] The bilayer composite structure of "fuzz nanostructure layer + dense titanium-based thin film layer" formed in Example 1 of this invention exhibits significant advantages in multiple dimensions, including corrosion resistance (salt spray >120 h, corrosion current density 0.8 μA / cm²), friction performance (friction coefficient 0.30–0.38), structural stability, temperature cycling adaptability, and dimensional compatibility. In particular, the unique bilayer composite design of this invention endows the system with "backup protection capability"—even if the surface fuzz structure wears or is damaged under extreme service conditions, the underlying dense titanium-based thin film layer can still independently assume the corrosion protection function, continuously protecting the valve core and sleeve substrate from corrosive media erosion. This is a key advantage that chromium plating and simple Ti films do not possess, and it has significant engineering implications for precision hydraulic systems with long-term service.

[0049] (4) Precision Dimension Influence Test The key dimensions of the valve core / valve sleeve before and after treatment were detected using a coordinate measuring machine. The dimensional change before and after treatment in Embodiment 1 of the present invention is less than 0.2 μm, which is much smaller than the 2-8 μm fitting clearance requirement of the valve core / valve sleeve. This proves that while providing excellent protective performance, it does not affect the fitting accuracy and motion stability of the precision moving pair.

[0050] Alternative implementation methods It should be understood that those skilled in the art can conceive of various alternative solutions to achieve the same inventive objective based on the concept of this invention. For example: In step S1, the deposition of titanium thin films can be carried out using various physical vapor deposition methods such as magnetron sputtering, arc ion plating, and electron beam evaporation, or chemical vapor deposition using titanium-containing precursors.

[0051] In step S2, a small amount of other inert or reactive gases can be mixed into the helium-containing plasma. The key is to control the irradiation energy and time so that only the titanium thin film precursor undergoes partial depth reconstruction.

[0052] In step S3, passivation treatment can be performed by natural oxidation, thermal oxidation (heating to 100-400°C in an oxygen-containing atmosphere), oxygen-containing plasma oxidation, or anodic oxidation.

[0053] In addition to titanium alloys, the substrate can also be other metal materials such as stainless steel and hard alloys. By pre-depositing a titanium thin film precursor and implementing controlled-depth irradiation, the double-layer composite protective structure can also be constructed on its surface.

[0054] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this invention; the scope of protection of this invention is defined by the claims in the claims, and all equivalent changes and modifications made in accordance with this invention are within the scope of protection of this patent.

Claims

1. A method for constructing a valve core valve sleeve surface double-layer composite nanostructure protective layer, characterized in that: Includes the following steps: Step S1: Deposit a titanium thin film precursor on the surface of the valve core or valve sleeve substrate under a protective gas plasma atmosphere, controlling its thickness to be 0.5 μm to 5 μm; Step S2: The substrate on which the titanium thin film precursor is deposited is placed in a helium-containing plasma environment for irradiation treatment, and the irradiation parameters are controlled so that the titanium thin film precursor undergoes self-organization and reconstruction only in a certain depth range in its thickness direction, thereby growing a villous fuzz nanostructure layer in situ on its surface, while its bottom part remains in an unirradiated dense state, thus forming a bilayer composite structure composed of a surface fuzz nanostructure layer and a bottom dense titanium-based thin film layer. Step S3: Perform surface passivation treatment on the irradiated valve core or valve sleeve to generate a passivation oxide film on the surface of the fuzz nanostructure layer, forming the final nanostructure protective layer.

2. The method for constructing the dual-layer composite nanostructure protective layer on the surface of the valve core and valve sleeve according to claim 1, characterized in that: In step S2, the substrate surface temperature is brought to 1000 K to 2000 K by controlling the irradiation parameters, the incident ion energy is greater than 30 eV, and the ion flux reaches the order of 10 5 m - ².

3. The method for constructing a double-layer composite nanostructure protective layer on the surface of the valve core and valve sleeve according to claim 2, characterized in that: by controlling the irradiation time in the range of 10 minutes to 120 minutes and / or the ion flux in the range of 10 5 m - ² to 10 6 m - ². The thickness of the fuzz nanostructure layer is 10% to 80% of the thickness of the titanium thin film precursor.

4. The method for constructing a double-layer composite nanostructure protective layer on the surface of the valve core and valve sleeve according to claim 3, characterized in that: The thickness of the titanium thin film precursor is controlled to be 1 μm to 3 μm, and the thickness of the fuzz nanostructure layer is controlled to be 100 nm to 800 nm.

5. The method for constructing a double-layer composite nanostructure protective layer on the surface of the valve core and valve sleeve according to claim 1, characterized in that: The deposition of titanium thin film precursor in step S1 and the irradiation treatment in step S2 are carried out continuously in the same vacuum chamber.

6. The method of claim 1, wherein the method further comprises: In step S1 and / or step S2, the titanium thin film precursor or fuzz nanostructure layer is uniformly formed on the cylindrical or complex curved surface of the valve core or valve sleeve by rotating the workpiece and / or by using multi-angle plasma irradiation.

7. The method of constructing a spool-valve-can surface bi-layer composite nanostructure protective layer according to any one of claims 1 to 6, wherein: The valve core or valve sleeve base is made of titanium alloy.

8. A valve core or valve cup, characterized by: Its surface has a double-layer composite nanostructure protective layer, which consists of a surface fuzz nanostructure layer and a bottom dense titanium-based thin film layer. The fuzz nanostructure layer consists of a titanium nanofiber skeleton and a TiO2 passivation film covering its surface. The dense titanium-based thin film layer is a partial titanium thin film precursor that maintains an unirradiated dense state. Moreover, the dense titanium-based thin film layer and the substrate, as well as the dense titanium-based thin film layer and the fuzz nanostructure layer, are all integrated structures with no discernible separation interfaces.

9. The valve core or valve sleeve according to claim 8, characterized in that: The thickness of the fuzz nanostructure layer is 100 nm to 800 nm, the thickness of the dense titanium-based thin film layer is 0.2 μm to 2.9 μm, and the thickness of the fuzz nanostructure layer is 10% to 80% of the total thickness of the titanium thin film precursor.

Images