Steel-aluminum composite material and method for manufacturing the same

Abstract

This invention relates to the field of metal composite materials technology, and more particularly to a steel-aluminum composite material and its preparation method. The invention discloses a steel-aluminum composite material comprising: a steel base layer and a coating layer covering at least a portion of the surface of the steel base layer. The coating layer, from near to far from the steel base layer, comprises: a deposition layer, an intermediate layer, and a sealing layer; wherein the chemical formula of the deposition layer is Al2O3; the intermediate layer is a rare-earth-doped ZrO2-SiC gradient ceramic coating; and the sealing layer is a graphene-corrosion inhibitor composite layer. The steel-aluminum composite material and its preparation method of this invention, by constructing a three-layer coating structure of a deposition layer, an intermediate layer, and a sealing layer on the surface of the steel base layer, achieve triple corrosion protection of the steel-aluminum composite interface, effectively solving the problem of galvanic corrosion in steel-aluminum composite materials, improving the interfacial bonding strength and long-term corrosion resistance of the material, and is environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of metal composite materials technology, and in particular to a steel-aluminum composite material and its preparation method. Background Technology

[0002] Steel-aluminum composites combine the high strength of steel with the lightweight advantages of aluminum, making them promising for high-end manufacturing fields such as automotive bodies and aerospace structural components. However, a significant electrode potential difference exists between steel and aluminum, making the steel-aluminum interface highly susceptible to galvanic corrosion in humid, salt spray, or other electrolyte-containing service environments. This corrosion weakens the interfacial bonding strength of the steel-aluminum composite, severely shortening its service life and becoming a core bottleneck restricting the large-scale industrial application of steel-aluminum composites.

[0003] To address the corrosion problem at steel-aluminum composite interfaces, various protective measures have been employed in existing technologies. Traditional phosphating or chromate conversion processes, while forming a basic protective film on the metal surface, utilize hexavalent chromium, posing a serious environmental pollution risk. Furthermore, the resulting protective film exhibits limited corrosion resistance, with a short neutral salt spray test tolerance time of less than 800 hours, failing to meet the demands of harsh operating conditions. Thermal spraying of ceramic coatings can form a high-hardness protective layer on the material surface, but the thermal stress generated during coating preparation can easily lead to microcracks in the film. These microcracks become channels for the penetration of corrosive ions such as chloride ions, ultimately causing the protective barrier to fail. Physical vapor deposition (PVD) coatings suffer from insufficient adhesion between the coating and the substrate, making them prone to peeling during subsequent processing or use. Introducing organic fillers such as polytetrafluoroethylene (PTFE) is limited by the high-temperature resistance of organic materials, making it difficult to adapt to high-temperature conditions or subsequent coating processes.

[0004] Therefore, developing a steel-aluminum composite material that is environmentally friendly, has high interfacial bonding strength, long-term corrosion resistance, and can effectively resist chloride ion corrosion has become an urgent need to break through the limitations of existing technologies and promote the development of the steel-aluminum composite material industry. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a steel-aluminum composite material and its preparation method. By constructing a three-layer coating structure consisting of a deposition layer, an intermediate layer, and a sealing layer on the surface of a steel base layer, triple corrosion protection is achieved at the steel-aluminum composite interface. This effectively solves the problem of galvanic corrosion in steel-aluminum composite materials, improves the interfacial bonding strength and long-term corrosion resistance of the material, and is also environmentally friendly.

[0006] Therefore, the first objective of the present invention is to provide a steel-aluminum composite material.

[0007] The second objective of this invention is to provide a method for preparing steel-aluminum composite materials.

[0008] To achieve the first objective of this invention, the technical solution of this invention provides a steel-aluminum composite material, comprising: a steel base layer and a coating layer covering at least a portion of the surface of the steel base layer, wherein the coating layer comprises, from near to far from the steel base layer: a deposition layer, an intermediate layer and a sealing layer; wherein the chemical formula of the deposition layer is Al2O3; the intermediate layer is a rare earth-doped ZrO2-SiC gradient ceramic coating; and the sealing layer is a graphene-corrosion inhibitor composite layer.

[0009] Compared with existing technologies, the technical effects achieved by this solution are as follows: The deposited layer is a dense Al2O3 layer, which can effectively block the interdiffusion of iron atoms in the steel substrate and aluminum atoms in the aluminum substrate, thereby reducing the risk of galvanic corrosion caused by atomic diffusion at the source. Simultaneously, this deposited layer is tightly bonded to the steel substrate, providing a stable base for the subsequent coating adhesion. The intermediate layer is a rare-earth-doped ZrO2-SiC gradient ceramic coating. The doping of rare-earth elements can stabilize the crystal structure of ZrO2, improving the toughness and crack resistance of the coating. The SiC group... The coating enhances wear resistance and hardness, while the gradient structure design further hinders the penetration of corrosive ions such as chloride ions, significantly improving the corrosion resistance and mechanical properties of the steel-aluminum composite material. The sealing layer is a graphene-corrosion inhibitor composite layer. Graphene has excellent barrier properties and mechanical strength, which can enhance the density and damage resistance of the coating. The corrosion inhibitor is embedded between the graphene layers to form a self-healing network. When the coating suffers minor damage, the corrosion inhibitor can be quickly released and form a passivation film at the damaged site, achieving self-repair and extending the service life of the composite material. The three-layer coating structure forms a triple anti-corrosion barrier system. The synergistic effect of each layer not only solves the problem of poor protection and easy failure of traditional single coatings, but also has environmental friendliness and high temperature resistance, which can meet the stringent requirements of automotive body and aerospace structural components.

[0010] In one embodiment of the present invention, the thickness of the deposited layer is 5nm-30nm.

[0011] Compared with existing technologies, the technical effects achieved by this solution are as follows: the thickness of the deposited layer is controlled within the range of 5nm-30nm, which ensures that the Al2O3 layer has sufficient density, effectively blocking the mutual diffusion of iron atoms in the steel base layer and aluminum atoms in the aluminum base layer, avoiding galvanic corrosion caused by atomic diffusion, while also preventing internal stress caused by excessive coating thickness, thus preventing cracking or peeling of the coating. At the same time, the deposited layer within this thickness range can form a good bond with the steel base layer, providing a stable and flat substrate for the subsequent coating of intermediate and sealing layers, ensuring the structural integrity and protective effect of the entire coating layer.

[0012] In one embodiment of the present invention, the thickness of the intermediate layer is 50nm-200nm; the rare earth element is selected from at least one of yttrium, lanthanum, cerium and neodymium.

[0013] Compared with existing technologies, the technical effects achieved by this solution are as follows: the thickness of the intermediate layer is controlled within the range of 50nm to 200nm, which ensures that the rare earth-doped ZrO2-SiC gradient ceramic coating has sufficient thickness to hinder the penetration of corrosive ions such as chloride ions, while preventing microcracks caused by excessive thermal stress due to excessive coating thickness. At the same time, the coating within this thickness range can form a good interfacial bond with the upper and lower layers, ensuring the structural stability of the entire coating layer. The use of at least one rare earth element from yttrium, lanthanum, cerium, and neodymium for doping can effectively stabilize the crystal phase structure of ZrO2, improve the toughness and crack resistance of the coating, and further enhance the density and corrosion resistance of the coating, thereby significantly improving the mechanical properties and corrosion resistance of the steel-aluminum composite material.

[0014] In one embodiment of the present invention, the corrosion inhibitor is selected from at least one of benzotriazole derivatives, molybdates, and tungstates.

[0015] Compared with existing technologies, the technical effects achieved by this solution are as follows: Benzotriazole derivatives molybdate and tungstate both possess excellent metal passivation properties, capable of complexing with metal ions on the surface of steel-aluminum composite materials to form a dense and stable passivation film, effectively preventing corrosive ions from contacting the metal substrate. Benzotriazole derivatives, as organic corrosion inhibitors, have good compatibility with graphene layers and can stably embed themselves between graphene layers to form a self-healing network. Molybdate and tungstate, as inorganic corrosion inhibitors, can be rapidly released and react with the metal substrate when the coating is damaged, filling the protective gaps at the damaged areas. The flexible selection of organic and inorganic corrosion inhibitors can adapt to different service environments, further enhancing the long-term corrosion resistance of composite materials. At the same time, these corrosion inhibitors do not contain toxic heavy metal components, meet environmental protection requirements, and will not cause pollution to subsequent processing and use.

[0016] To achieve the second objective of this invention, the technical solution of this invention provides a method for preparing steel-aluminum composite materials, used to prepare steel-aluminum composite materials according to any of the above technical solutions, comprising the following steps: S100, steel base pretreatment, wherein the steel base is subjected to sandblasting and argon plasma cleaning in sequence to obtain a first blank; S200, deposition layer preparation, wherein the first blank is subjected to atomic layer deposition reaction to obtain a second blank; S300, intermediate layer coating, wherein a nano-ceramic sol is sprayed onto the second blank using a spraying machine to obtain a third blank; S400, sealing layer preparation, wherein a mixture of graphene and corrosion inhibitor is coated on the surface of the third blank, and after curing, a steel-aluminum composite material is obtained.

[0017] Preferably, a high-pressure airless sprayer is selected.

[0018] Compared with existing technologies, the technical effects achieved by this solution are as follows: This preparation method achieves precise construction of the steel-aluminum composite coating layer through four steps: steel substrate pretreatment, deposition layer preparation, intermediate layer coating, and sealing layer preparation. The steps are closely linked and the process parameters are controllable, ensuring the stability and consistency of product performance. Specifically, step S100 involves sandblasting and argon plasma cleaning of the steel substrate. Sandblasting creates suitable surface roughness, improving the mechanical bonding between the subsequent deposition layer and the steel substrate. Argon plasma cleaning effectively removes the oxide layer and impurities from the steel substrate surface, reducing the surface oxygen atom concentration and providing a clean and highly active substrate for the growth of the deposition layer. Step S200 uses atomic layer deposition to prepare Al2O3 deposition. The deposition process allows for precise control of the thickness and density of the deposited layer, effectively blocking the diffusion of steel and aluminum atoms and inhibiting galvanic corrosion at its source. Step S300 involves applying a nano-ceramic sol using a sprayer, achieving uniform coverage of the intermediate layer. The resulting rare-earth-doped ZrO2-SiC gradient ceramic coating hinders the penetration of corrosive ions, enhancing the corrosion resistance and mechanical properties of the composite material. Step S400 involves coating and curing a mixture of graphene and corrosion inhibitor, forming a self-healing sealing layer on the surface of the composite material, further strengthening the anti-corrosion effect. The entire preparation method is simple, requires no raw materials containing heavy metals, meets environmentally friendly production requirements, and the process conditions in each step are mild, causing no damage to the steel and aluminum substrate, making it suitable for large-scale industrial production.

[0019] In one embodiment of the present invention, the surface roughness Ra of the first blank is 3.2 μm-4.5 μm; the surface oxygen atom concentration of the first blank is <8 at.

[0020] Compared with existing technologies, the technical effects achieved by this solution are as follows: the surface roughness Ra of the first blank is controlled within the range of 3.2μm to 4.5μm, which increases the contact area of ​​the steel base surface, enhances the mechanical bonding force between the subsequent deposition layer and the steel base, and prevents the deposition layer from peeling off during subsequent processing or use. At the same time, this roughness range will not cause stress concentration and will not affect the mechanical properties of the steel base itself. The oxygen atom concentration on the surface of the first blank is controlled below 8at%, which can effectively remove the oxide layer and residual impurities on the surface of the steel base, reduce the obstacle of the oxide layer to the growth of the deposition layer, provide a clean and highly active surface for the atomic layer deposition reaction, ensure the density and uniformity of the deposition layer, thereby improving the ability of the deposition layer to block the diffusion of steel and aluminum atoms and enhancing the anti-corrosion effect of the entire coating layer.

[0021] In one technical solution of the present invention, S200 specifically includes: S210, placing the first billet in an atomic deposition reaction chamber, introducing aluminum compound and water vapor, and performing 150-550 cycles of deposition; S220, placing the first billet treated in S210 in an electrolyte and performing staged multi-frequency pulse treatment; S230, hot rolling the first billet treated in S220 to obtain a second billet.

[0022] Preferably, a single deposition step includes, in sequence, a TMA pulse, an argon purging, a water pulse, and an argon purging.

[0023] Preferably, the film density of the first preform after S210 treatment is ≥3.2g / cm³, and the pinhole density is <0.1 pinholes / μm².

[0024] Preferably, the phased multi-frequency pulse includes: the first stage low-frequency constant current, using a 50Hz low-frequency pulse, a current density of 4A / dm², and constant current boosting to 150V; the second stage medium-frequency stepped boost, using a 200Hz pulse, boosting the voltage by 50V every 30 seconds until the pressure reaches 350V, with a duty cycle of 25%; and the third stage high-frequency constant voltage, using an 800Hz high-frequency pulse, maintaining a constant voltage of 450V (negative pulse amplitude limited to -60V), with a duty cycle of 15%.

[0025] Compared with existing technologies, the technical effects achieved by this solution are as follows: Step S200, through the coordinated operation of three sub-processes—atomic deposition, staged multi-frequency pulse processing, and hot rolling—achieves integrated construction of the deposited layer and the metallurgical bonding of the steel-aluminum interface. Step S210 places the first billet in the atomic deposition reaction chamber, introduces aluminum compounds and water vapor, and performs 150 to 550 cycles of deposition. This allows for precise control of the thickness and density of the Al2O3 deposited layer, resulting in a low pinhole density that effectively blocks the interdiffusion of steel and aluminum atoms, thus inhibiting galvanic corrosion at its source. Step S220 places the atomically deposited billet in an electrolyte for further processing. The multi-frequency pulse treatment in stages can form a porous oxide film on the surface of the aluminum substrate, increasing the contact area between the aluminum substrate and adjacent layers and improving the interfacial bonding strength. At the same time, the oxide film has a certain degree of corrosion resistance and can help block corrosive ions. S230 hot rolling composite of the pulse-treated billet can break the oxide film on the steel-aluminum surface, promote atomic diffusion at the steel-aluminum interface, achieve a strong metallurgical bond, and avoid interfacial delamination during subsequent use. The various sub-processes in the entire S200 step work together to ensure the protective performance of the deposited layer and strengthen the bonding strength of the steel-aluminum composite interface, thereby improving the overall mechanical properties and corrosion resistance reliability of the composite material.

[0026] In one technical solution of the present invention, in S210, the temperature of the atomic layer deposition reaction is 80℃-120℃; in S210, the time for a single deposition is 30s-60s; in S220, the electrolyte includes at least one of sodium silicate and potassium fluorozirconate; in S230, the temperature of hot rolling composite is 300℃-400℃; in S230, the pressure of hot rolling composite is 15MPa-25MPa; and in S230, the time of hot rolling composite is 5min-10min.

[0027] Compared with existing technologies, the technical effects achieved by this solution are as follows: In S210, by controlling the temperature and single deposition time of the atomic layer deposition reaction, the growth rate and density of the Al2O3 deposition layer can be precisely controlled, avoiding defects such as coarse grains and increased pinholes caused by excessively high temperatures or long deposition times. It also prevents uneven deposition layer thickness and insufficient bonding with the steel substrate caused by excessively low temperatures or short deposition times, ensuring the deposition layer possesses excellent atomic diffusion barrier properties. In S220, an electrolyte containing at least one of sodium silicate and potassium fluorozirconate is used, which can form a uniform oxide film with suitable porosity on the aluminum substrate surface. This oxide film can serve as a buffer layer during hot rolling composite processes, improving the steel-aluminum interface. The S230 process achieves a metallurgical bonding effect while enhancing the adhesion between the aluminum substrate and the subsequent intermediate layer. The hot-rolled composite temperature is controlled between 300℃ and 400℃, the pressure between 15MPa and 25MPa, and the time between 5min and 10min. This temperature range allows the aluminum substrate to be in a semi-solid state, significantly enhancing its plasticity. Combined with this pressure range, the oxide film on the steel-aluminum surface can be effectively broken, promoting full diffusion of interfacial atoms. This time range ensures that temperature and pressure are applied uniformly to the steel-aluminum interface, achieving a strong metallurgical bond, without causing excessive grain growth in the matrix and affecting the mechanical properties of the composite material. The synergistic effect of these parameters ensures the stability of the interfacial bonding strength and corrosion resistance of the steel-aluminum composite material.

[0028] In one embodiment of the present invention, the nano-ceramic sol is a mixture of ZrO2, Y2O3 and SiC.

[0029] Compared with existing technologies, the technical effects achieved by this solution are as follows: The nano-ceramic sol uses a mixture of ZrO2, Y2O3, and SiC. Each component can work synergistically to improve the overall performance of the coating. ZrO2 has excellent toughening effect, which can enhance the coating's crack resistance and prevent damage caused by external force or thermal stress. Y2O3, as a rare earth oxide, can stabilize the crystal structure of ZrO2 and prevent ZrO2 from undergoing crystal phase transformation during preparation or use, thus affecting the coating performance. SiC can significantly improve the coating's hardness and wear resistance, and extend its service life. The gradient ceramic coating formed by the three components has high density and can effectively hinder the penetration of corrosive ions such as chloride ions, blocking the galvanic corrosion pathway at the steel-aluminum interface. At the same time, the sol component has good compatibility with the spraying process. After coating and curing, it can form a coating that is tightly bonded to the upper and lower layers, ensuring the structural stability and protective reliability of the entire coating layer.

[0030] In one embodiment of the present invention, the amount of graphene added is 0.5wt%-2wt%; the amount of corrosion inhibitor added is 1wt%-3wt%.

[0031] Compared with existing technologies, the technical effects achieved by this solution are as follows: The graphene addition is controlled within the range of 0.5wt% to 2wt%. This utilizes graphene's excellent barrier properties and mechanical strength to enhance the density and damage resistance of the sealing layer, providing a stable load carrier for the corrosion inhibitor. Excessive addition will not cause graphene agglomeration, preventing defects in the sealing layer from affecting the protective effect. The corrosion inhibitor addition is controlled within the range of 1wt% to 3wt%, ensuring sufficient corrosion inhibitor can be loaded between the graphene layers. When the coating is damaged, this inhibitor is quickly released and forms a passivation film for self-repair. Excessive corrosion inhibitor will not cause precipitation, avoiding contamination of the steel-aluminum composite surface or affecting the adhesion between the coating and the substrate. The synergistic matching of the two substances fully leverages the carrier role of graphene and the self-repairing effect of the corrosion inhibitor, further improving the corrosion resistance of the sealing layer and ensuring the long-term protective effect of the entire coating. Detailed Implementation

[0032] The technical solutions of various embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033]

Example 1

[0034]

Example 2

[0035]

Example 3

[0036] Testing revealed that the steel-aluminum composite material prepared in this embodiment, through a three-layer coating structure design of "deposition layer-intermediate layer-sealing layer", achieves long-term corrosion resistance, with a neutral salt spray test tolerance time exceeding 1800 hours. Furthermore, the preparation process is environmentally friendly, with no heavy metal pollution, making it suitable for manufacturing high-performance steel-aluminum composite materials in the automotive, aerospace, and other fields.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects. The scope of the invention is defined by the appended claims, not by the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No markings in the claims should be construed as limiting the scope of the claims.

[0038] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A steel-aluminum composite material, characterized in that, include: A steel base layer and a covering layer covering at least a portion of the surface of the steel base layer, the covering layer comprising, from near to far from the steel base layer: a deposition layer, an intermediate layer, and a sealing layer; The chemical formula of the deposited layer is Al2O3; The intermediate layer is a rare earth-doped ZrO2-SiC gradient ceramic coating. The sealing layer is a graphene-corrosion inhibitor composite layer.

2. The steel-aluminum composite material according to claim 1, characterized in that, The thickness of the deposited layer is 5nm-30nm.

3. The steel-aluminum composite material according to claim 1, characterized in that, The thickness of the intermediate layer is 50nm-200nm; The rare earth element is selected from at least one of yttrium, lanthanum, cerium and neodymium.

4. The steel-aluminum composite material according to claim 1, characterized in that, The corrosion inhibitor is selected from at least one of benzotriazole derivatives, molybdates, and tungstates.

5. A method for preparing a steel-aluminum composite material, the method being used to prepare the steel-aluminum composite material as described in any one of claims 1-4, characterized in that, Includes the following steps: S100, Steel base pretreatment: The steel base is subjected to sandblasting and argon plasma cleaning in sequence to obtain the first blank; S200, Deposition layer preparation: The first blank is subjected to atomic layer deposition reaction to obtain the second blank; S300, intermediate layer coating, using a spraying machine to spray nano-ceramic sol onto the second green body to obtain the third green body; S400, preparation of the sealing layer: a mixture of graphene and corrosion inhibitor is coated on the surface of the third preform, and the steel-aluminum composite material is obtained after curing.

6. The method for preparing steel-aluminum composite material according to claim 5, characterized in that, The surface roughness Ra of the first blank is 3.2μm-4.5μm; The surface oxygen atom concentration of the first preform is <8 at.

7. The method for preparing steel-aluminum composite material according to claim 5, characterized in that, S200 specifically includes: S210. Place the first blank in the atomic deposition reaction chamber, introduce aluminum compound and water vapor, and perform 150-550 cycles of deposition. S220. The first blank after S210 is placed in an electrolyte and subjected to staged multi-frequency pulse treatment. S230. The first billet after S220 is hot-rolled to obtain the second billet.

8. The method for preparing steel-aluminum composite material according to claim 7, characterized in that, In S210, the temperature for atomic layer deposition is 80℃-120℃; In S210, the time for a single deposition is 30s-60s; In S220, the electrolyte includes at least one of sodium silicate and potassium fluorozirconate; In S230, the hot-rolled composite temperature is 300℃-400℃; In S230, the pressure of hot-rolled composite is 15MPa-25MPa; In S230, the hot rolling composite time is 5-10 minutes.

9. The method for preparing steel-aluminum composite material according to claim 5, characterized in that, The nano-ceramic sol is a mixture of ZrO2, Y2O3 and SiC.

10. The method for preparing steel-aluminum composite material according to claim 5, characterized in that, The amount of graphene added is 0.5wt%-2wt%; The amount of corrosion inhibitor added is 1wt%-3wt%.