Porous metal-based composite material based on cold spraying and selective corrosion and preparation method of porous metal-based composite material

Abstract

The invention provides a porous metal-based composite material based on cold spraying and selective corrosion and a preparation method thereof. Comprising the steps that a composite coating composed of pore-forming components and framework components is deposited on the surface of a base body through low-pressure cold spraying; placing the substrate with the coating in an alkaline solution containing a corrosion inhibitor for one-time chemical corrosion, selectively dissolving the pore-forming component to form a porous structure, and cleaning and drying to obtain a final product. A moderately loose coating structure is formed through low-pressure cold spraying, precise selective corrosion is achieved in combination with the specific corrosion inhibitor, the process is simple and efficient, and the method is suitable for industrial batch production. The porous metal-based composite material has a continuous three-dimensional network structure dominated by skeleton components, is high in porosity, good in connectivity and large in specific surface area, has good mechanical strength and corrosion resistance, and has application potential in the fields of structured catalysis and reaction engineering, thermal management technology and the like.

Description

Technical Field

[0001] This invention belongs to the field of porous material preparation technology, specifically relating to a porous metal matrix composite material based on cold spraying and selective corrosion and its preparation method. Background Technology

[0002] Porous metal matrix composites, due to their high specific surface area, tunable pore structure, and excellent mechanical and functional properties, have wide applications in fields such as catalyst supports, filtration and separation, electromagnetic shielding, and energy storage. However, these materials are limited by their insufficient oxidation resistance and poor thermal shock resistance. Under high-temperature environments, their highly active surfaces are prone to accelerated corrosion and oxidation, leading to structural failure. This significantly restricts their practical application in certain special scenarios, especially in oxidizing conditions.

[0003] Currently, the technological pathways to improve the high-temperature service performance of porous materials mainly revolve around two aspects: composite material composition design and controllable preparation methods for porous structures. However, traditional porous material preparation technologies struggle to meet both requirements simultaneously. For example, powder sintering requires high-temperature processing, resulting in high energy consumption and difficulty in composite low-melting-point metal or ceramic phases; foaming methods rely on chemical foaming agents, making it difficult to control pore uniformity and connectivity; while 3D printing technology can customize complex structures, its high equipment cost and limited material systems restrict its application. Chemical etching creates pores by selectively dissolving pre-placed sacrificial phases, simplifying the process to some extent, but still requires the pre-introduction of pore-forming agents or the design of biphase alloys, leading to uneven distribution of sacrificial phases, numerous residual impurities, and difficulty in achieving synergistic control of macropore-micropore multi-level structures. Furthermore, existing methods, when composited with ceramic reinforcing phases (such as Al2O3 and SiC), often limit the application of materials in extreme environments such as high temperatures and corrosion due to poor interfacial bonding or high-temperature degradation.

[0004] Cold spraying, as an emerging solid-state deposition process, enables the rapid formation of metals, ceramics, and their composite coatings through supersonic powder particle impaction. Since there is no phase change or oxidation during cold spraying, it is particularly suitable for preparing composite coatings with uniform composition and low oxygen content. However, research on cold sprayed coatings is typically driven by high density, with few reports on its direct application to the preparation of porous materials. Furthermore, there is a lack of systematic schemes for synergistically controlling pore structure through material composition design and corrosion processes.

[0005] Therefore, there is an urgent need to develop an efficient, low-cost, and scalable method for preparing porous materials that can utilize the rapid composite advantages of cold spraying and achieve precise control of porosity, pore size distribution, and functional phases through selective corrosion. This will effectively ensure the high-temperature oxidation resistance and mechanical properties of the materials, thus meeting the urgent need for multifunctional integrated surface technology in key components of high-end equipment. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for preparing porous metal matrix composites based on cold spraying and selective corrosion, which aims to solve the problems of complex preparation processes for existing porous materials, difficulty in achieving both high porosity and high structural strength, and insufficient temperature and corrosion resistance.

[0007] The second objective of this invention is to provide a porous metal matrix composite material based on cold spraying and selective corrosion prepared by the above method. This material has a continuous three-dimensional network structure dominated by skeleton components, a uniform and controllable pore structure, and features excellent mechanical properties and environmental stability.

[0008] One of the technical solutions adopted by this invention to achieve its objective is to provide a method for preparing porous metal matrix composite materials based on cold spraying and selective corrosion, comprising the following steps: A composite coating is deposited on the substrate surface by low-pressure cold spraying. The composite coating consists of pore-forming components and framework components. The substrate with the composite coating is placed in an alkaline solution containing a corrosion inhibitor for chemical corrosion treatment to selectively dissolve the pore-forming components and form a porous structure. After cleaning and drying, a porous metal matrix composite material is obtained. The composite coating, by weight percentage of raw materials, comprises: 60%-80% pore-forming components, including 15wt.%-50wt.% Al, 25wt.%-50wt.% Zn, and 0-35wt.% Al2O3; and 20%-40% framework components, including 60wt.%-100wt.% Ni, 0-40wt.% Cu, and 0-20wt.% Zn.

[0009] The overall concept and inventive principle of this invention are as follows: This invention proposes a method for preparing porous metal matrix composites based on cold spraying and selective corrosion. This method couples the advantages of cold spraying solid-state deposition with the precise control of selective corrosion, aiming to prepare porous metal matrix composites efficiently, at low cost, and on a scalable scale.

[0010] This invention employs low-pressure cold spraying technology, using supersonic gas to accelerate the deposition of composite powder onto the substrate surface. The powder particles undergo intense plastic deformation in a solid state, mechanically interlocking to form a multi-component composite coating. This process is non-melting, effectively avoiding material phase transformation and oxidation, and providing a compositionally stable reaction interface for subsequent corrosion. The uniform particle distribution within the coating, without significant aggregation, ensures the stability of the selective corrosion reaction interface, thereby guaranteeing the uniformity and controllability of the pore structure. Furthermore, during high-speed impact, the intense plastic deformation and localized temperature rise facilitate the in-situ generation of thermodynamically stable intermetallic compounds such as Ni-Al at the interface between the pore-forming and framework components. Together with the residual compressive stress introduced by the cold spraying process, this contributes to improving the high-temperature resistance, corrosion resistance, and thermal shock resistance of the final porous material. Subsequently, an alkaline solution containing corrosion inhibitors is used to selectively corrode the pore-forming components in the composite coating, directionally removing them from the composite coating and forming interconnected channels. Because the skeleton components do not undergo high-temperature oxidation or phase transformation during the cold spraying process, their surfaces are clean and their intrinsic corrosion resistance is superior. Combined with corrosion inhibitors, their corrosion is further suppressed, forming a high-strength porous skeleton.

[0011] Furthermore, in the composite coating raw material of the present invention, the skeleton component accounts for 20%-40% by weight, and the main component Ni content is 60wt.%-100wt.%, which has excellent resistance to alkaline corrosion, ensuring structural integrity during corrosion and guaranteeing the overall corrosion resistance of the material. Optionally, the introduction of Cu is mainly based on the need to adjust the comprehensive properties of the skeleton, such as plasticity and conductivity. The introduction of Zn into the skeleton component is based on its good plasticity and low yield strength, which helps to promote particle bonding and ensure coating density during cold spraying. At the same time, it can also act as a sacrificial anode in corrosive environments, providing a certain electrochemical protection for the skeleton. The pore-forming component accounts for 60%-80%, mainly composed of Al and Zn, aiming to reserve sufficient mass space for the formation of a three-dimensional porous structure with high porosity and high connectivity. At the same time, the trace amounts of intermetallic compounds or solid solutions that may remain during corrosion can also play a certain supplementary and strengthening role for the skeleton. Optionally, by adding Al2O3 to the pore-forming component, it not only plays a compacting role in the cold spraying process, ensuring the stable deposition of the coating during low-pressure cold spraying, but also, after selective corrosion, its residual particles can be dispersed in the skeleton, playing a second-phase strengthening role, significantly improving the room temperature and high temperature strength, wear resistance and structural stability of the porous material.

[0012] Furthermore, the substrate includes one of carbon steel, aluminum alloy, magnesium alloy, or titanium alloy. In this invention, the composite coating is completely coated onto the substrate surface using a cold spraying process, effectively isolating the alkaline solution from direct contact with the substrate. Simultaneously, by precisely controlling parameters such as chemical corrosion time, temperature, and corrosion inhibitor concentration, it can be ensured that the corrosion reaction occurs only in the composite coating, thus guaranteeing the broad compatibility of this preparation method with various substrates.

[0013] Furthermore, the process parameters for the low-pressure cold spraying include: gas pressure of 0.5-1.0 MPa, gas temperature of 300-600℃, and spraying distance of 10-30 mm. The working gas for the low-pressure cold spraying technology includes one of compressed air, nitrogen, and helium, preferably compressed air. This invention controls the gas pressure of the low-pressure cold spraying to 0.5-1.0 MPa, which, while achieving coating deposition and ensuring coating bonding strength, forms a relatively looser or non-dense structure with micropores at the microscale. This provides channels for the subsequent penetration and diffusion of the corrosive liquid, allowing the corrosion reaction to initiate simultaneously from within the coating, thereby generating a more interconnected and uniformly distributed porous morphology. If a higher gas pressure (e.g., 2 MPa) is used, the particle impact kinetic energy will be too large, leading to an overly dense coating, which will hinder the uniform penetration of the pore-forming process, easily resulting in surface sealing, poor pore connectivity, and reduced production efficiency.

[0014] Furthermore, the particle size of each metal powder in the composite coating raw material is 5-40 μm. Before cold spraying, the metal powders of the skeleton component and the pore-forming component are thoroughly mixed by ball milling. Preferably, stainless steel grinding balls with particle sizes of 10 mm and 5 mm are used for ball milling, and the milling time is set to 2-5 hours.

[0015] Furthermore, the thickness of the composite coating is 0.5-2 mm.

[0016] Furthermore, the pore-forming component includes Al2O3, and the mass ratio of Al2O3 to Al is (0.1-2.5):1. Al2O3 serves as both a pore-forming agent and a reinforcing phase. This invention includes Al2O3 as a pore-forming component based on its solubility in alkaline corrosive solutions, allowing it to participate in the pore-forming process. However, compared to metal components such as Al and Zn, Al2O3 dissolves relatively slowly under corrosive conditions, and its degree of dissolution is influenced by multiple factors including particle size, encapsulation state, and corrosion conditions. Therefore, some Al2O3 particles fail to completely dissolve during corrosion, remaining as second-phase particles and dispersing within the final porous metal framework. By controlling the mass ratio of Al2O3 to Al within the aforementioned range, its partial dissolution can participate in the formation and influence the morphology and connectivity of pores; its partial residue can also significantly strengthen the Ni / Cu metal framework through dispersion, improving the strength, hardness, and wear resistance of the porous material at room temperature and high temperatures, and enhancing its structural stability.

[0017] Furthermore, the framework component contains Zn, and the mass ratio of Zn in the framework component to Zn in the pore-forming component is (0.05-0.4):1. In this invention, the introduction of Zn serves two purposes: firstly, as a pore-forming component, it is designed to be efficiently dissolved by alkaline solution to form pores; secondly, it is pre-alloyed and placed in the framework component, where its corrosion rate is relatively slow, allowing it to remain within the framework after selective corrosion. By controlling the mass ratio of Zn in the framework component to Zn in the pore-forming component within the aforementioned range, the formation process and final morphology of the pore structure can be precisely controlled; furthermore, the Zn retained in the framework is used to strengthen the Ni-Cu matrix with a second phase, and to optimize the material's overall properties such as toughness, corrosion resistance, and high-temperature stability, making the material more suitable for high-temperature applications.

[0018] Furthermore, the alkaline solution is a sodium hydroxide solution with a mass concentration of 20%-40%. When the concentration is below 20%, the alkaline solution dissolves pore-forming components such as aluminum and zinc too slowly, resulting in excessively long corrosion time and difficulty in ensuring their complete removal. When the concentration is above 40%, although the reaction can be accelerated, the solution viscosity increases significantly, which is not conducive to penetration and mass transfer into the coating and may exacerbate the risk of chemical corrosion of non-target framework components, while also leading to higher safety and waste liquid treatment costs.

[0019] Furthermore, the chemical etching treatment time is 0.5-5 hours, aiming to achieve a balance between the full development of the pore structure and the prevention of over-corrosion. If the time is too short, the dissolution reaction of the pore-forming components will be insufficient, resulting in low porosity and poor pore connectivity; while if the time is too long, it will not only waste energy and time, but may also lead to excessive erosion of the framework components, causing the framework to become thinner, its strength to decrease, or even causing the collapse of the porous structure.

[0020] Furthermore, the corrosion inhibitor is sodium silicate or sodium phosphate. In an alkaline environment, the addition of the corrosion inhibitor can form a dense, stable, and strongly adherent passivation film on the metal surface of the framework components, improving corrosion resistance while ensuring the overall mechanical integrity of the material. In addition, the silicate / phosphate protective film generated by the corrosion inhibitor grows in situ on the material surface and is tightly bonded to the substrate, further enhancing the corrosion resistance of the porous framework in subsequent use environments, such as high-temperature oxidation or electrochemical environments.

[0021] Further research revealed that when the corrosion inhibitor concentration is too low, the resulting protective film is incomplete and has low coverage, failing to effectively inhibit the corrosion of the framework components and easily leading to increased weight loss of the framework, thus affecting the overall strength of the material. Conversely, excessively high concentrations can not only result in an overly thick protective film, leading to poor corrosion performance and reduced overall porosity, but also easily cause side reactions such as complexation in the solution, affecting the stability of the preparation process. Therefore, this invention controls the amount of corrosion inhibitor added in the alkaline solution to be 0.1 wt.%-2 wt.%.

[0022] Furthermore, the chemical etching treatment is performed under ultrasonic assistance, with the ultrasonic frequency being 20-40 kHz. In this invention, the ultrasonic waves generate a cavitation effect through high-frequency vibration, causing the etching solution to form microjets on the material surface and within the pores. This effectively washes away the initial pores, simultaneously addressing mass transfer and product removal, ensuring uniformity of etching along the coating thickness direction, and preventing pore blockage.

[0023] After etching, the main component of the resulting porous coating material is a continuous Ni framework. Most of the pore-forming components (Al and Zn) have been effectively removed through selective dissolution reactions, thus ensuring the porosity and connectivity of the porous material. It is worth emphasizing that during the low-pressure cold spray solid-state deposition process, some Al and Zn undergo strong mechanical alloying with Ni, potentially forming intermetallic compounds such as Ni-Al and Ni-Zn, which exist in a composite form within the deposited layer. These phases, tightly bound to the Ni matrix, dissolve slowly in the alkaline etching solution, thus allowing them to exist as dispersed second phases within the framework, further enhancing the overall strength, hardness, and other properties of the porous framework.

[0024] Furthermore, the preparation method also includes: ultrasonically cleaning the corroded material with an ultrasonic frequency range of 20-40 kHz and a cleaning time of 5-15 minutes, followed by vacuum drying at 60-100℃ for 1-3 hours to avoid oxidation of the skeleton components.

[0025] The preparation method provided by this invention achieves synergistic effects in the low-pressure cold spray deposition, selective corrosion, and framework protection stages by controlling process parameters such as the composition of pore-forming components and framework components in the composite coating, the concentration and dosage of NaOH etching solution and corrosion inhibitor, corrosion time, and ultrasonic-assisted conditions, thereby obtaining a porous framework with complete structure and stable performance. Furthermore, compared with existing methods, the porous metal matrix composite material prepared by this invention achieves significant improvements in high-temperature resistance and corrosion resistance. This is mainly due to the synergistic optimization of material design and preparation process: First, using nickel as the main framework and introducing Al2O3 ceramic reinforcing phase lays the foundation for the material's high-temperature strength and oxidation resistance from a compositional perspective; second, the cold spray solid-state deposition process achieves a strong composite between Al2O3 and the metal matrix while avoiding high-temperature phase transformation and generating beneficial residual compressive stress at the interface, thus significantly improving the coating's thermal shock resistance; finally, through a selective corrosion process containing specific corrosion inhibitors, a dense silicate / phosphate protective film is formed in situ on the framework surface while obtaining a pure, interconnected porous structure, ensuring the material's excellent chemical corrosion resistance. The combination of the above features enables the composite material prepared by the present invention to meet the requirements for long-term service under harsh environments such as high temperature and corrosiveness.

[0026] The second objective of this invention is to provide a porous metal matrix composite material based on cold spraying and selective corrosion, which is prepared by the preparation method described in one of the objectives of this invention.

[0027] The porous metal matrix composite material comprises a matrix and a porous metal layer formed on the surface of the matrix; the porous metal layer has a porosity of 19.55%-31.20%, an average pore size of 2.85-6.78 μm, and a specific surface area of ​​23.7-36.8 m². 2 / g.

[0028] Based on the unique preparation process and the resulting structure, the porous metal matrix composite material provided by this invention exhibits significant comprehensive performance advantages. In an integrated matrix-coating manner, the composite material prepared by this invention not only ensures high bonding strength between the porous layer and the matrix, but also fully utilizes the excellent thermal and electrical conductivity of the metal skeleton and the high specific surface area of ​​the three-dimensional interconnected porous structure. Therefore, this material has promising applications in several technical fields: Preferably, in the field of structured catalysis and chemical engineering, this material can be directly prepared on the inner wall of a reactor, the surface of a honeycomb or corrugated metal component, and used as a structured catalyst support or structured packing with high mechanical strength and excellent mass and heat transfer performance. It is suitable for gas-solid or liquid-solid phase catalytic processes that require long-term stable operation.

[0029] Preferably, in the field of thermal management technology, the porous metal layer prepared on the surface of the heat dissipation substrate can serve as a wetting framework or high-efficiency capillary wick for high-performance phase change materials, thereby significantly improving the temperature uniformity and heat flux of heat dissipation devices and providing solutions for thermal control systems of high power density electronic devices and aerospace equipment.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a method for preparing a porous metal matrix composite material based on cold spraying and selective corrosion. The low-pressure cold spraying process accelerates the component materials to supersonic speeds to impact the substrate under solid conditions, forming a dense and uniformly composed composite coating. This process avoids the phase transformation, oxidation, and component segregation problems caused by high-temperature melting in traditional thermal spraying or powder metallurgy, thereby ensuring the chemical activity and selectivity of the subsequent corrosion reaction. By adjusting the component ratio of the component materials and the low-pressure cold spraying parameters, the thickness and component distribution uniformity of the coating can be precisely controlled, providing a stable and controllable reaction interface for selective corrosion.

[0031] (2) The present invention provides a method for preparing porous metal matrix composites based on cold spraying and selective corrosion. In the corrosion stage, alkaline solution is used as the main corrosive agent, supplemented by corrosion inhibitors to protect the framework components, thereby achieving efficient dissolution of pore-forming components such as Al and Zn, while protecting framework components such as Ni and Cu from corrosion. Sodium silicate forms a dense silicate protective film in an alkaline environment, which greatly reduces the dissolution rate of the framework components. Ultrasonic assistance further enhances the corrosion uniformity. The ultrasonic cavitation effect not only accelerates the mass transfer of the corrosive solution in the micropores, but also removes the reaction products in time. The microjets generated by ultrasonic cavitation can flush the primary pores, solve the mass transfer and product removal problems at the same time, ensure the uniformity of corrosion in the coating thickness direction, and avoid pore blockage.

[0032] (3) The preparation method provided by this invention is environmentally friendly, has a simple process, and is suitable for large-scale production. The alkaline corrosion solution used can be safely discharged after simple neutralization, avoiding the risk of heavy metal pollution that may be caused by traditional acid corrosion processes. At the same time, the connection between cold spray solid deposition and subsequent liquid phase corrosion is smooth, and the entire system is fully adapted to the needs of continuous industrial production. The porous metal matrix composite material prepared by the above method has the excellent mechanical strength, thermal and electrical conductivity of the metal skeleton, and the high specific surface area of ​​the three-dimensional interconnected porous structure. Moreover, its unique "matrix-coating" integrated form ensures high bonding strength and reliability between the functional coating and the complex-shaped load-bearing components. This makes it show application potential and competitive advantages in the fields of structured catalysis and reaction engineering, thermal management technology, etc. Attached Figure Description

[0033] Figure 1The image shows the XRD pattern of the composite coating formed by cold spraying in Embodiment 1 of the present invention. Figure 2 This is a SEM image of the surface of the porous metal matrix composite material obtained in Example 1 of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention provides a method for preparing porous metal matrix composite materials based on cold spraying and selective corrosion, comprising the following steps: Step 1: Substrate Pretreatment and Powder Preparation. Remove the contaminant layer from the surface of the substrate material, clean and dry it for later use. Prepare the raw material powder required for cold spraying, consisting of pore-forming components and framework components; by mass percentage of raw materials: pore-forming components account for 60%-80%, including 15wt.%-50wt.% Al, 25wt.%-50wt.% Zn, and 0-35wt.% Al2O3; framework components account for 20%-40%, including 60wt.%-100wt.% Ni, 0-40wt.% Cu, and 0-20wt.% Zn. Pour the above powder into a ball mill jar, add stainless steel grinding balls, and ball mill to mix and obtain a uniform composite spraying powder.

[0036] Step 2: Preparation of low-pressure cold spray composite coating. Compressed air, nitrogen, or argon is used as the working gas for low-pressure cold spraying, with a gas pressure set to 0.5-1 MPa and a preheating temperature controlled at 300-600℃. During spraying, the spraying distance between the nozzle and the substrate is maintained at 10-30 mm, and the powder feeding rate is kept stable at 20-30 g / min, forming a uniform composite coating with a thickness of 0.5-2 mm on the substrate surface.

[0037] Step 3: Selective etching treatment. The substrate with the composite coating deposited is placed in an alkaline solution containing a corrosion inhibitor for chemical etching treatment to selectively dissolve the pore-forming components and form a porous structure. The alkaline solution is a 20%-40% sodium hydroxide solution, and the corrosion inhibitor is sodium silicate or sodium phosphate, added at an amount of 0.1wt.%-2wt.%. The chemical etching treatment is carried out under ultrasonic assistance at a frequency of 20-40 kHz for 0.5-5 hours.

[0038] Step 4: Post-etching treatment of the composite coating. The etched sample is first ultrasonically cleaned at 20-40 kHz for 5-10 minutes to thoroughly remove residual etching solution and reaction products from the surface. After cleaning, the sample is placed in a vacuum drying oven at 60-100℃ for 1-4 hours to ensure the coating structure is stable and free of moisture residue, ultimately obtaining a clean, porous metal-based composite material.

[0039] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0040] The main parameters and variables of embodiments 1-3 of the present invention are shown in Table 1 below.

[0041] Table 1

[0042] Example 1 This embodiment provides a method for preparing porous metal matrix composite materials based on cold spraying and selective corrosion, including the following steps: Step 1: Substrate Pretreatment and Composite Powder Preparation. A Q235 carbon steel plate with dimensions of 50 mm × 50 mm × 2 mm was used as the substrate. The surface oxide layer was removed using an angle grinder, followed by ultrasonic cleaning with anhydrous ethanol for 10 minutes to remove oil stains. The plate was then dried for later use. The raw material powders were weighed according to the following proportions: Al powder 35 g, Zn powder 35 g, Ni powder 30 g, totaling 100 g. The weighed powders were placed in a ball mill jar, and 10 mm and 5 mm stainless steel grinding balls (ball-to-powder mass ratio 5:1) were added. The mixture was ball-milled at 200 rpm for 3 hours to obtain a uniformly composed composite spray powder.

[0043] Step 2: Low-pressure cold spray deposition of the composite coating. Compressed air is used as the working gas for low-pressure cold spraying. The process parameters are set as follows: gas pressure 0.7 MPa, substrate preheating temperature 450 ℃, nozzle-to-substrate surface distance (spraying distance) 15 mm, and powder feed rate 25 g / min. Using these parameters, a uniform composite coating with a thickness of approximately 0.8 mm is deposited on the pretreated substrate surface.

[0044] Step 3: Selective Chemical Etching. Preparation of the etching solution: Use a 30% (w / w) sodium hydroxide (NaOH) aqueous solution as the base etching solution, and add 0.5% (w / w) sodium phosphate (Na3PO4) as a corrosion inhibitor, stirring until completely dissolved. Completely immerse the substrate with the composite coating in the etching solution and perform etching at a constant temperature of 50 °C, simultaneously applying ultrasonic assistance at a frequency of 25 kHz. The etching treatment lasts for 2 hours.

[0045] Step 4: Post-treatment. After the etching process, the sample was removed and immediately placed in deionized water. It was then ultrasonically cleaned for 8 minutes using a frequency of 25 kHz to thoroughly remove residual etching solution and reaction products from the surface and pores. The cleaned sample was then dried in a vacuum drying oven at 70 ℃ for 1.5 hours to finally obtain the porous metal matrix composite material.

[0046] Figure 1 The XRD pattern of the composite coating formed by low-pressure cold spray deposition in Example 1 shows diffraction peaks of Al, Zn, and Ni, verifying the relevant analysis of the aforementioned coating components. Figure 2 The image shows a SEM image of the porous metal matrix composite material obtained by selective chemical etching in Example 1. The image clearly shows a uniformly distributed, three-dimensionally connected porous morphology with an intact pore structure and no obvious blockage. This indicates that the selective etching process of the present invention can effectively remove the pore-forming components and precisely control the pore structure.

[0047] Example 2 This embodiment provides a method for preparing porous metal matrix composite materials based on cold spraying and selective corrosion, including the following steps: Step 1: Substrate Pretreatment and Composite Powder Preparation. A 6061 aluminum alloy plate with dimensions of 50 mm × 50 mm × 2 mm was used as the substrate. The substrate was pretreated (including grinding, cleaning, and drying) to ensure a clean surface and good activity. 100 g of composite spraying powder was prepared according to the following proportions: 80 wt% of the pore-forming component and 20 wt% of the framework component. In the pore-forming component, Al powder accounted for 50 wt%, Zn powder for 25 wt%, and Al2O3 powder for 25 wt% (Al2O3 to Al mass ratio was 0.5:1); in the framework component, Ni powder accounted for 60 wt% and Cu powder for 40 wt%. The weighed powders were mixed using the same ball milling process as in Example 1 to obtain a uniformly composed composite spraying powder.

[0048] Step 2: Low-pressure cold spray deposition of composite coating. Compressed air is used as the working gas for low-pressure cold spraying. The process parameters are set as follows: gas pressure 0.5 MPa, substrate preheating temperature 300 ℃, spraying distance 10 mm, and powder feed rate 20 g / min. Using these parameters, a uniform composite coating with a thickness of approximately 0.5 mm is deposited on the pretreated substrate surface.

[0049] Step 3: Selective Chemical Etching. Preparation of the etching solution: A 40% (w / w) sodium hydroxide (NaOH) aqueous solution was used as the base etching solution, and 0.1% (w / w) sodium silicate (Na₂SiO₃) was added as a corrosion inhibitor. The solution was stirred until completely dissolved. The substrate with the composite coating was completely immersed in the etching solution, and etching was performed at a constant temperature of 20 °C, simultaneously assisted by ultrasonic waves at a frequency of 20 kHz. The etching process lasted for 0.5 hours.

[0050] Step 4: Post-treatment. After the etching process, the sample was removed and immediately placed in deionized water. It was then ultrasonically cleaned for 5 minutes using a frequency of 40 kHz to thoroughly remove residual etching solution and reaction products from the surface and pores. The cleaned sample was then dried in a vacuum drying oven at 70 ℃ for 1.5 hours to finally obtain the porous metal matrix composite material.

[0051] Example 3 This embodiment provides a method for preparing porous metal matrix composite materials based on cold spraying and selective corrosion, including the following steps: Step 1: Substrate Pretreatment and Composite Powder Preparation. A TC4 titanium alloy plate with dimensions of 50 mm × 50 mm × 2 mm was used as the substrate. The substrate was pretreated (including grinding, cleaning, and drying) to ensure a clean surface and good activity. 100 g of composite spray powder was prepared according to the following proportions: the pore-forming component accounted for 60 wt% of the total raw materials, and the framework component accounted for 40 wt%. In the pore-forming component, Al powder accounted for 15 wt%, Zn powder for 50 wt%, and Al₂O₃ powder for 35 wt% (the mass ratio of Al₂O₃ to Al was 2.33:1); in the framework component, Ni powder accounted for 80 wt% and Zn powder for 20 wt% (the mass ratio of Zn in the framework component to Zn in the pore-forming component was approximately 0.27:1). The weighed powder was mixed using the same ball milling process as in Example 1 to obtain a uniformly composed composite spray powder.

[0052] Step 2: Low-pressure cold spray deposition of composite coating. Compressed air is used as the working gas for low-pressure cold spraying. The process parameters are set as follows: gas pressure 1.0 MPa, substrate preheating temperature 600 ℃, spraying distance 30 mm, and powder feed rate 30 g / min. Using these parameters, a uniform composite coating with a thickness of approximately 2.0 mm is deposited on the pretreated substrate surface.

[0053] Step 3: Selective Chemical Etching. Preparation of the etching solution: Use a 20% (w / w) sodium hydroxide (NaOH) aqueous solution as the base etching solution, and add 2.0% (w / w) sodium phosphate (Na3PO4) as a corrosion inhibitor, stirring until completely dissolved. Completely immerse the substrate with the composite coating in the etching solution and perform etching at a constant temperature of 80 °C, simultaneously applying ultrasonic assistance at a frequency of 40 kHz. The etching treatment lasts for 5 hours.

[0054] Step 4: Post-treatment. After the etching process, the sample was removed and immediately placed in deionized water. It was then ultrasonically cleaned at a frequency of 20 kHz for 15 minutes to thoroughly remove residual etching solution and reaction products from the surface and pores. The cleaned sample was then dried in a vacuum drying oven at 70 ℃ for 1.5 hours to finally obtain the porous metal matrix composite material.

[0055] Comparative Example 1 (High-Pressure Cold Spraying Process) This comparative example uses a high-pressure cold spraying process to verify the importance of low-pressure cold spraying parameters in forming a uniform porous structure in this invention.

[0056] Step 1: Matrix pretreatment and composite powder preparation. The matrix, powder type, ratio, and mixing process are exactly the same as in Example 1.

[0057] Step 2: High-pressure cold spray deposition of composite coating. Nitrogen was used as the working gas for high-pressure cold spraying. The process parameters were set as follows: gas pressure 4.0 MPa, substrate preheating temperature 450 ℃, spraying distance 15 mm, and powder feed rate 25 g / min. Using these parameters, a composite coating with a thickness of approximately 0.8 mm was deposited on the pretreated substrate surface.

[0058] Step 3: Selective chemical etching treatment and post-treatment. The etching solution formulation, etching conditions (temperature, time, ultrasound), cleaning and drying processes are exactly the same as in Example 1.

[0059] After undergoing the same etching treatment, the material obtained in Comparative Example 1 showed sparse and unevenly distributed pores on its surface, poor internal pore connectivity, and a large number of un-etched areas visible in cross-section. Its porosity, specific surface area, and other indicators were significantly lower than those in Example 1. This indicates that excessively high spraying pressure leads to an overly dense coating, which hinders the uniform penetration and mass transfer of the etching solution, preventing the formation of the uniform, interconnected porous structure achieved by this invention.

[0060] Comparative Example 2 (without corrosion inhibitor added) No corrosion inhibitor was added in the chemical etching treatment of this comparative example, which was used to verify the necessity of adding a specific corrosion inhibitor to the etching solution in this invention to protect the framework components and obtain a pure porous structure.

[0061] Step 1: Matrix pretreatment and composite powder preparation. The matrix, powder type, ratio, and mixing process are exactly the same as in Example 1.

[0062] Step 2: Low-pressure cold spray deposition of composite coating. The cold spray process parameters (gas, pressure, temperature, distance, powder feed rate) and the resulting coating thickness are exactly the same as in Example 1.

[0063] Step 3: Selective chemical etching and post-treatment. Preparation of the etching solution: Only a 30% (w / w) aqueous solution of sodium hydroxide (NaOH) was used; no corrosion inhibitors were added. The etching conditions (temperature, time, ultrasound) were the same as in Example 1. The subsequent cleaning and drying processes were also exactly the same as in Example 1.

[0064] After etching, the resulting material exhibits a rough surface, a weakened peak intensity corresponding to Ni in the XRD pattern, a reduced Ni content in the surface framework, and noticeable corrosion pits. The overall strength of the material decreases, and the pores contain numerous unexpected corrosion products. This indicates that without the protection of a corrosion inhibitor, the etching solution, while dissolving the pore-forming components, also severely erodes the target framework components, failing to achieve the selective etching effect of this invention. Consequently, the chemical purity, structural integrity, and mechanical properties of the final porous material are compromised.

[0065] Performance testing The porous metal matrix composites prepared in Examples 1-3 and Comparative Examples 1 and 2 were tested, mainly for their porosity, average pore size and specific surface area. The results are shown in Table 2.

[0066] Table 2

[0067] It can be seen from Table 2 above that This invention provides a method for preparing porous metal matrix composite materials based on cold spraying and selective corrosion. The method involves depositing a composite coating of specific components on a substrate by low-pressure cold spraying and then performing one-step selective corrosion using an alkaline solution containing a specific corrosion inhibitor. This method successfully achieves synergistic control of key structural parameters such as porosity, pore size, and specific surface area.

[0068] The material prepared by this invention possesses a unique structure with a continuous metal framework, three-dimensionally interconnected pores, and strong bonding with the matrix. The experimental results in Table 2 show that the materials prepared in Examples 1-3 have significantly better porosity and specific surface area than those in Comparative Example 1 using the traditional high-pressure process. Furthermore, compared to Comparative Example 2 using a process without corrosion inhibitors, they exhibit superior framework integrity and structural controllability. Therefore, this invention demonstrates clear application potential in fields requiring materials with high strength, high specific surface area, and excellent durability, such as structured catalyst supports and thermal management technologies.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for producing a porous metal matrix composite based on cold spraying and selective etching, characterized in that, The method comprises the following steps: A composite coating is deposited on the surface of a substrate by low-pressure cold spraying, the composite coating being composed of a pore-forming component and a skeleton component; the substrate with the deposited composite coating is placed in an alkaline solution containing a corrosion inhibitor for chemical etching treatment to selectively dissolve the pore-forming component and form a porous structure; and after cleaning and drying, a porous metal matrix composite material is obtained. The composite coating contains, by mass percentage of raw material, 60-80% of the pore-forming component, including 15-50wt.% of Al, 25-50wt.% of Zn and 0-35wt.% of Al2O3; and 20-40% of the skeleton component, including 60-100wt.% of Ni, 0-40wt.% of Cu and 0-20wt.% of Zn.

2. The production method according to claim 1, characterized by, The process parameters of the low-pressure cold spraying include a gas pressure of 0.5-1Mpa, a gas temperature of 300-600℃ and a spraying distance of 10-30mm.

3. The preparation method according to claim 1, characterized in that, The thickness of the composite coating is 0.5-2mm.

4. The method of claim 1, wherein, The pore-forming component contains Al2O3, and the mass ratio of Al2O3 to Al is (0.1-2.5):

1.

5. The preparation method according to claim 1, characterized in that, The skeleton component contains Zn, and the mass ratio of Zn in the skeleton component to Zn in the pore-forming component is (0.05-0.4):

1.

6. The method of claim 1, wherein, The alkaline solution is a sodium hydroxide solution with a mass concentration of 20-40%.

7. The preparation method according to claim 1, characterized in that, The chemical etching treatment is performed for 0.5-5h.

8. The method of claim 1, wherein, The corrosion inhibitor is sodium silicate or sodium phosphate, and the addition amount of the corrosion inhibitor in the alkaline solution is 0.1-2wt.%.

9. The production method according to claim 1, characterized by, The chemical etching treatment is performed under the condition of ultrasonic assistance, and the frequency of the ultrasonic is 20-40 kHz. 10.A porous metal matrix composite material based on cold spraying and selective etching, prepared by the preparation method according to any one of claims 1-9. The porous metal matrix composite comprises a matrix and a porous metal layer formed on the surface of the matrix; the porosity of the porous metal layer is 19.55%-31.20%, the average pore diameter is 2.85-6.78μm, and the specific surface area is 23.7-36.8 m 2 / g.

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