A cvd-based surface strengthening process for aluminum strips

Abstract

The present application belongs to the technical field of aluminum strip surface treatment, and particularly relates to an aluminum strip surface strengthening process based on CVD. The present application aims to solve the problem that the existing aluminum strip surface strengthening method is difficult to improve the durability of the aluminum strip in a high-salt-mist environment. The present application first performs straightening and activation treatment on the aluminum strip, and after the treatment is completed, the aluminum strip is sent into a deposition chamber for magnetron sputtering deposition, specifically including a metal injection stage, a nitriding support stage and a composite deposition stage. Subsequently, the aluminum strip is sent into a deposition workshop for a pulse CVD process, and after the process is completed, functional modification is performed, and the surface of the aluminum strip after the surface strengthening process exists in sequence a Ti-Si diffusion layer, a TiSiN diffusion layer, a Ti-Si-C-N composite layer, a multilayer corrosion-resistant layer and a fluorine-containing layer. The surface strengthening process provided by the present application can effectively guarantee the use durability of the aluminum strip in a high-salt-mist environment, and has excellent surface hardness and structural stability.

Description

Technical Field

[0001] This invention belongs to the field of aluminum strip surface treatment technology, specifically relating to a CVD-based aluminum strip surface strengthening process. Background Technology

[0002] Aluminum alloys, with their excellent specific strength and processing performance, have become a key material for lightweighting vehicle body structural components and power battery packs. Especially in the application of core components such as battery pack underbody plates, control arms and subframes, aluminum strips not only need to bear the function of structural support, but also need to directly face extreme service environments, such as high salt spray coastal environments or complex road conditions, which puts forward higher requirements for the surface performance of aluminum strips.

[0003] Aluminum alloys are widely used, but their chemically reactive nature and the loose oxide film that naturally forms on their surface make them difficult to provide long-term protection. Currently, various surface strengthening methods exist for aluminum alloys. For high-strength aluminum used in automobiles and other equipment, PVD and CVD deposition are common treatments, but all have limitations. With the increasing size of battery packs, the processing width of aluminum strips has reached over 2100mm. Depositing nanoscale coatings on such wide surfaces places extremely high demands on the flatness of the substrate, thus presenting more challenges for the surface treatment of high-width aluminum strips. Currently, the industry needs a treatment method that can effectively strengthen the surface of high-width aluminum strips without softening the aluminum substrate.

[0004] To address the problem that existing aluminum strip surface strengthening methods are insufficient to improve the durability of aluminum strips in high salt spray environments, a CVD-based aluminum strip surface strengthening process is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a CVD-based surface strengthening process for aluminum strips. First, the aluminum strip undergoes a straightening and activation treatment. After this treatment, the aluminum strip is sent to a deposition chamber for magnetron sputtering deposition, specifically including a metal implantation stage, a nitriding support stage, and a composite deposition stage. Subsequently, the aluminum strip is sent to a deposition workshop for pulsed CVD processing. After completion, functionalization modification is performed. The surface of the aluminum strip after the surface strengthening process sequentially contains a Ti-Si diffusion layer, a TiSiN diffusion layer, a Ti-Si-CN composite layer, a multilayer corrosion-resistant layer, and a fluorine-containing layer.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A CVD-based surface strengthening process for aluminum strip includes the following steps:

[0008] The aluminum strip moves at a speed of 1.0 m / min throughout the entire production line section.

[0009] The aluminum strip undergoes a straightening and activation treatment, specifically: the aluminum strip is kept under a tension of 15-25 MPa, and a mixture of argon and hydrogen is introduced at a working pressure of 1.0 Pa for 60 seconds. The pulse bias voltage is -1000 V, the frequency is 40 kHz, the argon flow rate is 1000 sccm, and the hydrogen flow rate is 150 sccm. After treatment, the aluminum strip is fed into the deposition chamber.

[0010] The aluminum ribbon entering the deposition chamber undergoes magnetron sputtering deposition, specifically divided into a metal implantation stage, a nitriding support stage, and a composite deposition stage. Specifically, in the metal implantation stage, argon gas at 1000 sccm is introduced, maintaining a peak power density of 1.5 kW / cm³. 2 The magnetron sputtering deposition process employed HiPIMS technology. The target material was a TiSi alloy target with a Ti:Si molar ratio of 80:20, a frequency of 500-800Hz, and a substrate bias of -500V. The Ti-Si diffusion layer thickness was 50-100nm. In the nitriding support stage, the nitrogen flow rate was linearly increased to 300sccm within 2 minutes, maintaining an operating pressure of 0.5Pa, a duty cycle of 5%, and keeping the target material constant. The TiSiN diffusion layer thickness was 300-500nm. In the composite deposition stage, an argon flow rate of 1000sccm and a nitrogen flow rate of 300sccm were maintained, while 100sccm of acetylene gas was introduced. The operating pressure was maintained at 0.5Pa, the duty cycle at 4%, and the target material constant. The Ti-Si-CN composite layer thickness was 800-1000nm.

[0011] Aluminum strips deposited by magnetron sputtering are fed into the deposition workshop, where a multilayer corrosion-resistant layer is formed using a pulsed CVD process. The pulsed CVD process specifically involves adjusting the RF power supply frequency to 13.56MHz, the pulse frequency to 5-10kHz, the duty cycle to 25%, and controlling the aluminum strip substrate temperature to 150-180℃. Reactive gases are alternately introduced. Specifically, the reactive gases are a first mixture and a second mixture. The first mixture consists of 500 sccm of SiH4 and 300 sccm of NH3; the second mixture consists of 500 sccm of SiH4 and 200 sccm of CH4. The first mixture is introduced for 5 seconds, followed by the second mixture for 4 seconds, completing one switching cycle. A total of 125-150 cycles are performed. The operating pressure is maintained at 100Pa, and the spray head spacing is 400mm. When processing aluminum strips with a width of 2100mm, 5 sets of spray heads are used. The total thickness of the target multilayer corrosion-resistant layer is 1.5-2.5μm.

[0012] In the deposition workshop, after the aluminum strip completes the pulsed CVD process, it undergoes functionalization modification. The functionalization modification process specifically involves adjusting the bias voltage of the pulsed CVD-treated aluminum strip to -300V, introducing 100 sccm of C4F8 gas and 400 sccm of CH4 gas, and treating for 2-4 minutes to obtain a fluorine-containing layer. This fluorine-containing layer is obtained by modifying a multilayer corrosion-resistant layer, with a target thickness of 100-200 nm.

[0013] After the aluminum strip surface strengthening process is completed, the aluminum strip surface sequentially contains a Ti-Si diffusion layer, a TiSiN diffusion layer, a Ti-Si-CN composite layer, a multi-layer corrosion-resistant layer, and a fluorine-containing layer.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1. A straightening and activation treatment is performed before the deposition chamber to control the shape error of the aluminum strip. Simultaneously, a plasma mixture of argon and hydrogen is used to treat the surface of the aluminum strip. Under mechanical tension, the aluminum strip exhibits lattice distortion on its surface. The argon and hydrogen plasma treatment effectively removes the oxide layer on the aluminum strip surface and forms metastable aluminum-hydrogen chemical bonds. This provides a good active anchor point for the chemical bonding in subsequent deposition processes, ensuring a stable distance between the aluminum strip and the electrode in the deposition chamber while effectively improving deposition efficiency.

[0016] 2. A magnetron sputtering deposition method is employed, where a specific ratio of Ti and Si elements are deposited on the shallow surface of an aluminum strip under argon protection. Subsequently, nitrogen and acetylene gases are sequentially introduced while maintaining the sputtering power, achieving a gradient multilayer deposition. First, high-energy Ti and Si elements bombard and inject into the aluminum substrate surface, forming a Ti-Si diffusion layer, ensuring basic adhesion. When nitrogen gas is introduced, a TiSiN diffusion layer gradually forms, serving as a high-hardness support layer, and the growth of TiN columnar crystals is suppressed by the Si. When acetylene gas is introduced, on the basis of the TiSiN diffusion layer, Ti elements form TiCN nanocrystals, and Si elements form an amorphous SiCN structure. Due to their thermodynamic incompatibility, the amorphous phase automatically precipitates and encapsulates the nanocrystals, forming a Ti-Si-CN composite layer. This gradient-formed protective layer solves the problem of mismatched thermal expansion coefficients between different coating layers and improves the surface hardness of the aluminum strip by utilizing the precipitation characteristics of the amorphous phase.

[0017] 3. Through pulsed CVD technology, multiple spray heads are used for simultaneous air intake. The working frequency and duty cycle are adjusted to ensure that the substrate temperature of the aluminum strip is below 200℃. The reactive gas ratio is periodically switched to form an amorphous multilayer corrosion-resistant layer on the aluminum strip surface. This improves the uniformity of the thermal field in the deposition workshop and prevents the deposition effect from deteriorating at the edges of wide aluminum strips. This multilayer corrosion-resistant layer has high density, and its amorphous structure effectively prevents dislocation slip by utilizing the superlattice effect, thereby improving the hardness and toughness of the corrosion-resistant structure.

[0018] 4. Following the pulsed CVD process, functional modification is performed. A specific proportion of fluorine-containing precursor is mixed into the carbon source gas, and the bias voltage of the aluminum strip substrate is adjusted at the end of the deposition process. This forms a nanoscale micro-rough structure on the surface of the multi-layer corrosion-resistant layer, which is the fluorine-containing layer. This fluorine-containing rough structure greatly reduces the surface energy of the aluminum strip, giving it good hydrophobicity and reducing the risk of salt spray corrosion. At the same time, the fluorine-containing surface layer endows the aluminum strip with excellent dry friction self-lubricating properties, allowing the aluminum strip to effectively maintain its surface properties during short-term high-intensity friction, meeting the requirements of chassis components for resistance to mud and sand erosion. Attached Figure Description

[0019] Figure 1 This is a flowchart of the CVD-based aluminum strip surface strengthening process in this invention. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below through some embodiments and experimental examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Reference Figure 1 The process flow diagram shown illustrates that this invention provides a CVD-based aluminum strip surface strengthening process, the technical solution of which is as follows:

[0022] Example 1

[0023] The aluminum strip moves at a speed of 1.0 m / min throughout the production line. The width of the processed aluminum strip is 2100 mm, and the aluminum alloy grade is 6063.

[0024] The aluminum strip underwent straightening and activation treatment, specifically as follows: The aluminum strip was subjected to a tension of 15 MPa, and a mixture of argon and hydrogen gas was introduced at a working pressure of 1.0 Pa for 60 seconds. The pulse bias voltage was -1000 V, the frequency was 40 kHz, the argon flow rate was 1000 sccm, and the hydrogen flow rate was 150 sccm. After treatment, the aluminum strip was fed into the deposition chamber.

[0025] The aluminum ribbon entering the deposition chamber undergoes magnetron sputtering deposition, specifically divided into a metal implantation stage, a nitriding support stage, and a composite deposition stage. Specifically, in the metal implantation stage, argon gas at 1000 sccm is introduced, maintaining a peak power density of 1.5 kW / cm³. 2 The process involves several stages: a 2% duty cycle, a TiSi alloy target with a Ti:Si molar ratio of 80:20, a 500Hz frequency, a -500V substrate bias, and a Ti-Si diffusion layer thickness of 50-100nm. The nitriding support stage involves linearly increasing the nitrogen flow rate to 300sccm within 2 minutes, maintaining an operating pressure of 0.5Pa, a duty cycle of 5%, and keeping the target material constant. The TiSiN diffusion layer thickness is 300-500nm. The composite deposition stage involves maintaining an argon flow rate of 1000sccm and a nitrogen flow rate of 300sccm, introducing 100sccm of acetylene gas, maintaining an operating pressure of 0.5Pa, a duty cycle of 4%, and keeping the target material constant. The Ti-Si-CN composite layer thickness is 800-1000nm.

[0026] Aluminum strips deposited by magnetron sputtering are fed into the deposition workshop, where a multilayer corrosion-resistant layer is formed using a pulsed CVD process. The pulsed CVD process specifically involves adjusting the RF power supply frequency to 13.56MHz, the pulse frequency to 5kHz, the duty cycle to 25%, and controlling the aluminum strip substrate temperature to 150℃, while alternately introducing reactive gases. Specifically, the reactive gases are a first mixture and a second mixture. The first mixture consists of 500 sccm of SiH4 and 300 sccm of NH3; the second mixture consists of 500 sccm of SiH4 and 200 sccm of CH4. The first mixture is introduced for 5 seconds, followed by the second mixture for 4 seconds, completing one switching cycle, for a total of 125 cycles. The operating pressure is maintained at 100Pa, and the spray head spacing is 400mm. When processing aluminum strips with a width of 2100mm, 5 sets of spray heads are used. The total thickness of the target multilayer corrosion-resistant layer is 1.5-2.5μm.

[0027] In the deposition workshop, after the aluminum strip completes the pulsed CVD process, it undergoes functionalization modification. The functionalization modification process specifically involves adjusting the bias voltage of the pulsed CVD-treated aluminum strip to -300V, introducing 100 sccm of C4F8 gas and 400 sccm of CH4 gas, and treating for 2 minutes to obtain a fluorine-containing layer. This fluorine-containing layer is obtained by modifying a multilayer corrosion-resistant layer, with a target thickness of 100-200 nm.

[0028] After the aluminum strip surface strengthening process is completed, the aluminum strip surface sequentially contains a Ti-Si diffusion layer, a TiSiN diffusion layer, a Ti-Si-CN composite layer, a multi-layer corrosion-resistant layer, and a fluorine-containing layer.

[0029] Examples 2-16 differ from Example 1 in operating parameters, but the other process steps and the range of raw material selection are the same.

[0030] The specific changes in operating parameters are summarized in Table 1.

[0031] Table 1. Changes in operating parameters in Examples 1-16

[0032]

[0033] Comparative Example 1

[0034] Unlike Example 1, in the straightening and activation process, the pressure of the aluminum strip was controlled at 2 MPa to maintain its movement and prevent it from developing a micro-yield effect. All other process parameters were the same.

[0035] Comparative Example 2

[0036] Unlike Example 1, hydrogen gas was not introduced during the straightening and activation process, but all other process parameters remained the same.

[0037] Comparative Example 3

[0038] Unlike Example 5, pure Ti was used as the target material in the magnetron sputtering deposition process, instead of TiSi alloy target material, while other process parameters remained the same.

[0039] Comparative Example 4

[0040] Unlike Example 5, the magnetron sputtering deposition process does not include the metal implantation stage and the nitriding support stage; instead, it directly proceeds to the composite deposition stage, while all other process parameters remain the same.

[0041] Comparative Example 5

[0042] Unlike Example 5, in the nitriding support stage of magnetron sputtering deposition, the nitrogen flow rate is not linearly adjusted; instead, nitrogen is introduced directly at a flow rate of 300 sccm at the beginning, while other process parameters remain the same.

[0043] Comparative Example 6

[0044] Unlike Example 9, in the pulsed CVD process, only the first mixed gas is used for deposition, while other process parameters are the same.

[0045] Comparative Example 7

[0046] Unlike Example 9, in the pulsed CVD process, the temperature of the aluminum strip substrate was adjusted to 220°C by adjusting the duty cycle, while other process parameters remained the same.

[0047] Comparative Example 8

[0048] Unlike Example 9, in the pulsed CVD process, only one spray head is activated, while all other process parameters remain the same.

[0049] Comparative Example 9

[0050] Unlike Example 13, C4F8 gas was not introduced during the functionalization modification process, while all other process parameters remained the same.

[0051] Comparative Example 10

[0052] Unlike Example 13, the bias voltage of the aluminum strip was adjusted to -50V during the functionalization modification process, while other process parameters remained the same.

[0053] Experimental Example 1

[0054] The coating thickness uniformity and film adhesion of the aluminum strips treated in Examples 1-4 and Comparative Examples 1-2 were tested, and the relevant results are summarized in Table 2.

[0055] The test method for coating thickness uniformity is as follows: 10 test points are taken at equal intervals in the transverse direction of the aluminum strip to measure the coating thickness, and the maximum thickness difference (μm) is recorded. The thickness deviation (%) is then calculated as follows: Maximum thickness difference / Average coating thickness = Thickness deviation (%). The smaller the thickness deviation, the better the coating thickness uniformity.

[0056] The test method for film adhesion refers to the relevant test methods in GB / T 30707-2014 standard. The test methods for ceramic coatings are also fully applicable to aluminum strip coatings. The initial failure load L of the treated aluminum strip is measured. C1 (N) and spalling load L C2 (N), the pressure head loading rate is 100N / min, the scratch length is 10mm, and the scratch rate is 10mm / min.

[0057] Table 2. Coating thickness uniformity and film adhesion of aluminum strips treated in Examples 1-4 and Comparative Examples 1-2

[0058]

[0059] As shown in Table 2, Examples 1 to 4 are significantly better than Comparative Examples 1 and 2 in terms of coating thickness deviation, initial failure load, and peeling load, indicating that the straightening and activation process adopted in this invention has obvious advantages in improving the uniformity of aluminum strip coating and film-substrate adhesion.

[0060] Comparative Example 1 reduced the aluminum strip tension during the straightening and activation treatment, maintaining the strip movement without producing a micro-yield effect. This resulted in a significant increase in coating thickness deviation and a decrease in film adhesion. This was because the lack of sufficient mechanical tension could not effectively eliminate plate shape errors, making it difficult for the aluminum strip to maintain a stable distance from the electrode in the deposition chamber. Consequently, this led to uneven deposition efficiency and thickness distribution. Insufficient surface lattice distortion also affected the activation effect. Comparative Example 2 removed hydrogen in the treatment atmosphere, resulting in a significant reduction in initial failure load and peeling load. Its film adhesion was the lowest among all groups. This was attributed to the fact that although simple argon physical bombardment could remove part of the oxide layer, the lack of hydrogen to participate in the chemical reduction reaction prevented the formation of key metastable aluminum-hydrogen chemical bonds on the aluminum strip surface. Consequently, subsequent deposition treatment lacked sufficient chemical bonding active anchor points.

[0061] In summary, this invention introduces a straightening and activation treatment before deposition, combining mechanical tension control with argon-hydrogen mixed plasma cleaning technology. These two techniques produce a significant synergistic effect: the specific mechanical tension corrects aluminum strip shape errors, ensuring geometric stability during deposition to improve coating uniformity, and induces microscopic distortions in the surface lattice to aid activation; combined with the chemical action of hydrogen plasma, highly active aluminum-hydrogen chemical bond anchors are constructed in situ while effectively removing the surface oxide layer. This dual synergistic mechanism of physical straightening and chemical activation ensures the high uniformity of the ultra-wide aluminum strip coating while significantly enhancing the bonding strength between the substrate and the coating at the microscopic interface, laying a solid foundation for subsequent high-quality thin film deposition.

[0062] Experimental Example 2

[0063] The thermal shock resistance and neutral salt spray resistance of the aluminum strips treated in Examples 5-8 and Comparative Examples 3-5 were tested, and the relevant results are summarized in Table 3.

[0064] The test method for thermal shock resistance is as follows: heat the aluminum strip to 150°C and then cool it rapidly with water at 10°C. After 10 cycles, check the peeling of the coating on the aluminum strip surface.

[0065] The test method for neutral salt spray resistance refers to the relevant test method of ASTM B117-2011 standard. A 5% sodium chloride solution is used as the salt spray, and the aluminum strip is subjected to corrosion test at 35°C. The time (in hours) when the first visible corrosion point appears in the central area of ​​the aluminum strip is recorded. The longer this time, the better the neutral salt spray resistance of the aluminum strip.

[0066] Table 3. Thermal shock resistance and neutral salt spray resistance of the aluminum strips treated in Examples 5-8 and Comparative Examples 3-5.

[0067]

[0068] As shown in Table 3, Examples 5 to 8 all maintained surface integrity without peeling in the thermal shock resistance test, and their tolerance time in the neutral salt spray corrosion test was significantly better than that of Comparative Examples 3, 4 and 5, indicating that the gradient multilayer deposition layer prepared in the examples has obvious advantages in terms of thermal stress shock resistance and corrosion protection.

[0069] Comparative Example 3 used a pure titanium target instead of a titanium-silicon alloy target during magnetron sputtering deposition. Lacking the synergistic effect of silicon, it could not utilize silicon to suppress the growth of columnar titanium nitride crystals, nor could it form a dense structure of amorphous silicon carbonitride encapsulating nanocrystals. This resulted in easy penetration of corrosive media along grain boundaries, significantly reducing its resistance to neutral salt spray. Comparative Example 4 omitted the metal implantation and nitriding support stages and directly performed composite deposition. This lack of a titanium-silicon diffusion layer to ensure adhesion and a gradient transition layer to mitigate thermal expansion mismatch led to rapid, large-area peeling of the coating during thermal shock cycling due to excessive internal stress, further deteriorating its corrosion resistance. Comparative Example 5 did not use linear nitrogen flow rate adjustment during the nitriding support stage, resulting in abrupt changes in the internal composition of the coating and failure to form a continuous gradient structure. This made it prone to cracking and peeling during thermal shock cycling, thus affecting its long-term corrosion resistance.

[0070] In summary, this invention employs magnetron sputtering deposition, utilizing a specific ratio of titanium-silicon alloy target material and a gradient introduction process of reactive gases to construct a composite protective system with gradually changing physicochemical properties. The diffusion layer formed by high-energy titanium-silicon element implantation establishes excellent interfacial adhesion. Subsequent linear introduction of nitrogen constructs a high-hardness support layer and optimizes the grain structure using silicon. Finally, the introduction of acetylene forms a composite structure where an amorphous phase automatically precipitates and encapsulates nanocrystals. This compositional gradient change achieved through linear adjustment of gas flow effectively solves the problem of thermal expansion coefficient mismatch between the hard coating and the aluminum substrate. Simultaneously, the silicon-induced amorphous nanocomposite structure cuts off corrosion channels, synergistically achieving structural stability and excellent corrosion resistance of the aluminum strip surface under extreme hot and cold environments.

[0071] Experimental Example 3

[0072] The tensile strength of the aluminum strips treated in Examples 9-12 and Comparative Examples 6-8 was tested and compared with that of untreated aluminum strips, and the tensile strength retention rate was calculated. Simultaneously, the surface nanohardness and edge resistance to neutral salt spray of the treated aluminum strips were tested. The relevant results are summarized in Table 4.

[0073] The surface nanohardness test method is as follows: referring to the relevant test method of ASTM E2546-15 (2023) standard, the indentation depth is controlled to be ≤200nm, the load holding time is 10s, and the indenter loading rate is 0.05s. -1The indenter was a triangular pyramidal diamond indenter with a face angle of 65.3°. After testing, the nanohardness (GPa) of the aluminum strip surface was calculated.

[0074] The test method for the edge resistance to neutral salt spray is the same as in Experiment 2, but the time (in hours) for the first visible corrosion spot to appear in the edge area is observed.

[0075] Table 4. Relevant performance parameters of the aluminum strips treated in Examples 9-12 and Comparative Examples 6-8

[0076]

[0077] As shown in Tables 3 and 4, Examples 9 to 12 are significantly better than Comparative Examples 6, 7 and 8 in terms of tensile strength retention, surface nanohardness and edge resistance to neutral salt spray. This indicates that the pulsed CVD process used in this invention has significant advantages in protecting the mechanical properties of the substrate, improving the hardness of the coating and ensuring the uniformity of wide-width processing.

[0078] Comparative Example 6 used only a single gas during deposition without periodic switching, failing to form a multilayered structure with alternating amorphous and crystalline states. This lack of a crucial mechanism to prevent dislocation slip using the superlattice effect resulted in a significant reduction in surface nanohardness and a marked impact on corrosion resistance. Comparative Example 7 increased the aluminum strip substrate temperature by adjusting the duty cycle, achieving deposition, but this caused the aluminum substrate to soften due to overheating, leading to a substantial decrease in tensile strength retention and severely impairing the mechanical properties of the aluminum strip as a structural component. Comparative Example 8 only activated a single spray head for gas supply. For a wide aluminum strip, this failed to guarantee the uniformity of the thermal field and reactive gas distribution within the deposition workshop, resulting in poorer deposition at the aluminum strip edges and a precipitous drop in edge corrosion resistance. Meanwhile, the edge salt spray resistance of Examples 9-12 showed no significant difference compared to the center salt spray resistance of Examples 5-8, indicating that the multi-spray head design ensured uniformity of salt spray resistance between the center and edge regions of the aluminum strip surface.

[0079] In summary, this invention introduces a multi-spray head air intake system through pulsed CVD technology, coupled with the periodic switching of the reactive gas ratio. These two elements produce a significant synergistic effect: the multi-spray head design ensures the uniformity of the thermal and airflow fields within the deposition workshop over a wide range, effectively preventing edge deposition quality degradation; strict control of the substrate temperature within a specific range avoids thermal damage to the aluminum substrate, maintaining its high tensile strength; simultaneously, the periodic switching of the reactive gas successfully constructs an amorphous multilayer corrosion-resistant structure, utilizing the superlattice effect to achieve a dual improvement in hardness and toughness, synergistically ensuring that the ultra-wide aluminum strip achieves consistent high hardness and high corrosion resistance across its entire width while maintaining the strength of the substrate.

[0080] Experiment Example 4

[0081] The water contact angle, surface friction coefficient, and salt spray resistance after mud and sand impact of the aluminum strips treated in Examples 13-16 and Comparative Examples 9-10 were tested. The relevant results are summarized in Table 5.

[0082] The surface friction coefficient was tested according to the ASTM G99-23 standard. A 6mm diameter GCr15 bearing steel ball was used as the grinding pair, the normal load was 5N, the sliding speed was 10cm / s, and the surface friction coefficient under steady state was recorded.

[0083] The test method for salt spray resistance is the same as in Experiment Example 2. The specific method for mud and sand impact is as follows: refer to the relevant test method of ASTM D3170-2022 standard, use standard basalt crushed stone with a particle size of 9.5-16mm, a projection pressure of 483kPa, a projection amount of 500g, and an impact angle of 45°, and then conduct salt spray resistance test.

[0084] The water contact angle was measured using a 0.1 mL water droplet.

[0085] Table 5. Surface friction coefficient and salt spray resistance after mud and sand impact of aluminum strips treated in Examples 13-16 and Comparative Examples 9-10.

[0086]

[0087] As shown in Tables 3 and 5, Examples 13 to 16 are significantly better than Comparative Examples 9 and 10 in terms of surface friction coefficient and salt spray resistance after mud and sand impact, indicating that the fluorine-containing functionalized surface layer prepared by the present invention has obvious advantages in dry friction self-lubrication and anti-mechanical erosion protection.

[0088] Comparative Example 9 did not introduce a fluorine-containing precursor during the functionalization modification process, resulting in the absence of the crucial fluorine element on the surface. This prevented the aluminum strip from acquiring low surface energy characteristics and self-lubricating properties, leading to a significant increase in the coefficient of friction. Under the mechanical impact of mud and gravel, the hard coating was prone to brittle fracture and peeling, resulting in a sharp decline in corrosion resistance. Comparative Example 10 reduced the bias voltage of the aluminum strip during the modification process, failing to provide sufficient ion bombardment energy. This prevented the effective formation of a nanoscale micro-rough structure on the surface, weakening the hydrophobic effect and failing to provide sufficient structural support for the lubrication layer. Consequently, the friction performance deteriorated, and the protection of the substrate was insufficient in the mud and gravel impact test. Compared to Examples 5-8, Examples 13-16 maintained better salt spray resistance after mud and gravel impact, demonstrating that the complete functionalization modification process significantly improves the mud and gravel impact resistance of the aluminum strip surface.

[0089] In summary, this invention introduces a fluorine-containing precursor into the carbon source gas after the pulsed CVD process, and combines this with a process operation that increases the operating voltage at the end of deposition. These two actions produce a significant synergistic effect: the introduction of fluorine endows the material with extremely low surface energy and self-lubricating properties, while high-voltage ion bombardment induces the formation of a nanoscale micro-rough structure on the surface. This specific fluorine-containing rough structure achieves excellent hydrophobicity to reduce the risk of corrosive media adhesion, and ensures that the aluminum strip can maintain its surface performance through effective lubrication under high-intensity friction and impact, thus synergistically meeting the stringent requirements of chassis components for resistance to mud and sand erosion and long-term corrosion protection.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A CVD based surface strengthening process of aluminum ribbon characterized in that: The surface strengthening process specifically comprises: The aluminum strip is subjected to straightening activation treatment, and after the treatment is completed, the aluminum strip is sent into a deposition chamber; In the deposition chamber, the aluminum strip is subjected to magnetron sputtering deposition; The magnetron sputtering deposition process comprises a metal injection stage, a nitriding support stage and a composite deposition stage in sequence; The aluminum strip subjected to the magnetron sputtering deposition is sent into a deposition workshop to perform a pulse CVD process; In the deposition workshop, after the aluminum strip completes the pulse CVD process, functional modification is performed; After the surface strengthening process of the aluminum strip is completed, the surface of the aluminum strip sequentially comprises a Ti-Si diffusion layer, a TiSiN diffusion layer, a Ti-Si-C-N composite layer, a multilayer corrosion-resistant layer and a fluorine-containing layer; The metal injection stage uses a TiSi alloy target, and the Ti-Si diffusion layer is obtained by treatment; the nitrogen flow is linearly increased to 300 sccm within 2 min in the nitriding support stage, and the TiSiN diffusion layer is obtained by treatment; the composite deposition stage uses a composite atmosphere of argon, nitrogen and acetylene, and the Ti-Si-C-N composite layer is obtained by treatment.

2. A CVD based surface strengthening process for aluminum strips as claimed in claim 1, wherein: In the pulse CVD process, the reaction gas comprises a first mixed gas and a second mixed gas; the first mixed gas is kept flowing for 5 s, and then switched to the second mixed gas flowing for 4 s to complete one switching cycle, a total of 125-150 cycles are performed, and the multilayer corrosion-resistant layer is obtained by treatment.

3. A CVD based surface strengthening process for aluminum ribbon as claimed in claim 2 wherein: The first mixed gas comprises 500 sccm of SiH4 and 300 sccm of NH3, and the second mixed gas comprises 500 sccm of SiH4 and 200 sccm of CH4.

4. A CVD based surface strengthening process for aluminum strips as claimed in claim 1, wherein: In the straightening activation treatment process, the tension of the aluminum strip is controlled at 15-25 MPa, and the treatment atmosphere is a mixed atmosphere of argon and hydrogen.

5. A CVD based surface strengthening process for aluminum strips as claimed in claim 1, wherein: In the functional modification process, the treatment atmosphere is 100 sccm of C4F8 gas and 400 sccm of CH4 gas, and the fluorine-containing layer is obtained by treatment.

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