Porous self-lubricating aluminum matrix composite material, and preparation method and application thereof

Abstract

The present application relates to a kind of porous self-lubricating aluminum matrix composite material and its preparation method and application, and the porous aluminum matrix composite material obtained by higher purity raw material powder through powder metallurgy has better comprehensive mechanical properties and wear resistance, the composition distribution of the obtained material is uniform, porosity is controllable, and after oil immersion, it has excellent self-lubricating characteristics.

Description

Technical Field

[0001] This invention relates to the field of metal-based self-lubricating composite materials and their preparation, and more particularly to a porous self-lubricating aluminum-based composite material and its preparation method. Background Technology

[0002] Nickel-aluminum alloys, due to their excellent properties such as low density, high strength, high specific modulus, and good high-temperature oxidation resistance, have become ideal lightweight structural materials with the greatest development prospects in high-tech fields such as aerospace and nuclear power engineering. However, nickel-aluminum alloys exhibit a high coefficient of friction and wear under dry sliding friction conditions, which significantly limits their widespread application in high-tech fields.

[0003] To address this technical challenge, researchers both domestically and internationally have developed nickel-aluminum-based self-lubricating composite materials by adding solid lubricants such as WS2, Ag, ZnO, CaF2, and graphene to nickel-aluminum alloys. Compared to nickel-aluminum alloys, these materials exhibit significantly improved tribological properties. This represents a promising direction for the development of next-generation lightweight structural materials, making the research and development of novel solid lubricants a highly valuable endeavor.

[0004] However, traditional solid lubricants have defects and limitations: solid lubricants usually improve the tribological properties of materials at the expense of the strength of the base material; solid lubricants usually only have a lubricating effect in a narrow temperature range, and exceeding the operating temperature range will lead to lubrication failure or even serious accidents.

[0005] Furthermore, silicon carbide, as a high-strength wear-resistant material, possesses high hardness and thermal conductivity. Its application in ceramic matrix composites can significantly improve the flexural strength and operating temperature of the material, and greatly enhance its wear resistance. However, silicon carbide is difficult to disperse uniformly in the ceramic matrix, and its wettability with metal lubricating phase components is not very good, which will significantly affect the mechanical properties of the composite material.

[0006] Solid lubricating phase components are added to metallurgical powder of porous sintered bodies for mixing and sintering. During the sintering process, the solid lubricating phase components are prone to oxidation and burn-off, resulting in partial loss of their lubricity and thus affecting their friction performance.

[0007] Self-lubricating materials are an important component for ensuring the normal operation of oil-free lubricated mechanical structures. Currently, the development direction of self-lubricating materials mainly focuses on pollution-free, low-wear, and self-healing properties. Material composites are an important means of achieving self-lubricating composite materials.

[0008] Currently, the development of lubricant-containing composite materials is rapid. For example, composite materials containing lubricating oil achieve lubrication by allowing lubricating grease to seep into the joints during structural operation. Composite materials containing solid lubricants achieve lubrication by extruding the solid lubricant onto the material surface during operation, forming a lubricating film. However, these types of composite materials often suffer from insufficient strength due to oil content and porosity, or insufficient lubricant strength, ultimately severely limiting their application range. Summary of the Invention

[0009] (a) Technical problems to be solved

[0010] To address the aforementioned problems in the prior art, this invention provides a porous self-lubricating aluminum-based composite material and its preparation method.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0013] A porous self-lubricating aluminum-based composite material, wherein the composite material comprises, by weight, 125-145 parts aluminum powder, 3-5 parts copper powder, 1-5 parts nickel powder, 3-6 parts silicon powder, and 3-6 parts nano-titanium diboride powder; wherein the mass ratio of copper powder to nickel powder is 3-5:1.

[0014] Furthermore, the aluminum powder has an average particle size of 2-8 μm; the copper powder has an average particle size of 3-5 μm; the nickel powder has an average particle size of 5-8 μm; the silicon powder has an average particle size of 5-10 μm; and the nano-titanium diboride powder has an average particle size of 40-60 nm.

[0015] Furthermore, the second phase in the composite material comprises Al3CuNi phase and Al7Cu4Ni phase; the content of Al7Cu4Ni phase is higher than that of Al3CuNi phase.

[0016] Furthermore, the composite material has an open porosity of 12-38%, a friction coefficient of less than or equal to 0.16 after oil immersion, and a hardness of 97-130 HV.

[0017] A method for preparing a porous self-lubricating aluminum-based composite material includes the following steps:

[0018] S1: Mix 90-100 parts by weight of aluminum powder, 3-5 parts by weight of copper powder, and 1-5 parts by weight of nickel powder, and then ball mill once to obtain powder A;

[0019] S2: Add 35-45 parts by weight of aluminum powder, 3-6 parts by weight of silicon powder, and 3-6 parts by weight of nano titanium diboride powder to powder A and perform secondary ball milling to obtain powder B.

[0020] S3: Place powder B into a mold and press it at a pressure of 220-260 MPa. The sintering temperature is 520-580℃, and the holding time is 20-30 minutes. The vacuum degree is <10. -1 Pa;

[0021] S4: The porous aluminum alloy matrix obtained by sintering is first washed with alkali, then etched in an acidic solution and then immersed in a stearic acid ethanol solution for modification. After the surface is treated with hydrophobic and oleophilic methods, a composite material is obtained.

[0022] Furthermore, the ball-to-material ratio for the first ball milling is 8-12:1, the rotation speed is 400-600 r / min, and the milling time is 30-50 h; the ball-to-material ratio for the second ball milling is 6-9:1, the rotation speed is 200-400 r / min, and the milling time is 4-12 h.

[0023] Furthermore, the alkaline washing process involves immersing the sample in a mixed solution at a temperature of 50-60°C for 3-5 minutes, followed by rinsing with deionized water; the mixed solution contains 20-40 g / L sodium hydroxide, 10-25 g / L sodium carbonate, and 2-4 g / L sodium gluconate.

[0024] Furthermore, the etching process involves etching with a mixed solution containing 5-15 g / L oxalic acid and 150-220 g / L hydrochloric acid for 8-12 hours, followed by rinsing with deionized water after etching.

[0025] Furthermore, the modification process involves immersing the etched composite material in a 1%-2% stearic acid ethanol solution for 20-40 minutes, followed by natural air drying in an atmospheric environment.

[0026] Application of a porous self-lubricating aluminum-based composite material in sliding bearings.

[0027] (III) Beneficial Effects

[0028] The beneficial effects of this invention are:

[0029] 1. This invention utilizes high-purity raw material powders to obtain porous aluminum-based composite materials through powder metallurgy. These materials exhibit excellent comprehensive mechanical properties and wear resistance. The resulting material has a uniform composition distribution, controllable porosity, and superior self-lubricating properties after oil impregnation. The aluminum powder used has a purity of ≥99.9%, copper powder ≥99.99%, nickel powder ≥99.9%, silicon powder ≥99.99%, and nano-titanium diboride powder ≥99.9%.

[0030] 2. By controlling the Cu:Ni element mass ratio between 3 and 5, the second phase in the alloy is mainly composed of two wear-resistant phases: Al3CuNi and Al7Cu4Ni. Among them, the fine wear-resistant Al7Cu4Ni is more abundant, which can effectively improve the wear resistance and thermal stability of the alloy.

[0031] 3. The first ball milling time of 30-50 hours is to obtain a pre-formed powder with a composition close to Al95-Cu4-Ni1. The second ball milling time of 4-12 hours is to mix the pre-formed Al95-Cu4-Ni1 powder with aluminum powder, silicon powder, and nano-titanium diboride powder evenly. The purpose of the first mixing is to ensure a high Cu:Ni mass ratio, thereby fully reacting to generate more Al7Cu4Ni phase, thus improving the wear resistance of the alloy.

[0032] 4. By controlling different pressing pressures and sintering temperatures, porous aluminum-based bearing materials with different open porosities can be obtained.

[0033] 5. In this invention, alkaline washing of porous aluminum alloy bearing material is used to remove the oxide film on the surface of the pores of the porous aluminum alloy substrate.

[0034] 6. In this invention, oxalic acid and hydrochloric acid etching are used to create a rough surface inside the pores, increasing the internal porosity and surface area, thereby improving the oil absorption rate of the composite material. Besides the number of pores, the characteristic state of the pores is also a crucial factor affecting the properties of the material. The pore characteristics of a material are whether the pores are closed inside the material or connected to the outside on the surface. The former are closed pores, and the latter are open pores. Some pores are divided into independent segments inside the material, while others are interconnected. Furthermore, the size of the pores and the uniformity of their distribution within the material are characteristic features of the pores. Acid etching can open the closed pores, transforming them into open pores, thereby significantly increasing the open porosity and making the internal pores as interconnected as possible to achieve greater oil absorption and a longer self-lubricating effect during use. Simultaneously, the etching step of this invention can eliminate impurities. After sintering, the second phase in the composite material of this invention mainly consists of two wear-resistant phases: Al3CuNi and Al7Cu4Ni, with a higher proportion of fine, wear-resistant Al7Cu4Ni. These phases also exhibit strong corrosion resistance. Furthermore, the mechanical alloying achieved through primary ball milling and the uniform mixing achieved through secondary ball milling effectively provide the necessary conditions for internal metallographic homogenization and the abundant formation of the second phase. This causes the distribution and connection of impurities within the material to tend towards the periphery, allowing them to be removed from the pores during acid etching.

[0035] 7. In this invention, the modification in the low surface energy stearic acid ethanol solution is to make the pores more oleophilic.

[0036] In summary, the porous self-lubricating aluminum-based sliding bearing material prepared by this invention has good comprehensive mechanical properties and wear resistance. The aluminum matrix has a uniform pore distribution with a pore size of about 0.2~0.4mm and an open porosity of 12~38%. After oil immersion, it exhibits excellent self-lubricating properties with a friction coefficient of less than 0.16. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart of the implementation steps of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, 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. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. 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.

[0040] Example 1:

[0041] (1) Aluminum powder, copper powder and nickel powder are mixed in a mass ratio of 96:3:1 and put into a ball mill jar for ball milling. The ball-to-material ratio for the first ball milling is 12:1, the ball mill speed is 400 r / min, and the ball milling time is 30 h to obtain powder A.

[0042] (2) Then add 41% aluminum powder, 6% silicon powder and 3% nano titanium diboride powder according to the total mass fraction of powder A for secondary ball milling. The ball-to-material ratio of the secondary ball milling is 6:1, the ball milling speed is 400 r / min and the time is 4 h. After the ball milling is completed, fill the mixed powder into the mold and press it into shape at 220 MPa.

[0043] (3) Then the mold is placed in a vacuum sintering furnace for sintering at a temperature of 520℃ for 20 minutes, with a vacuum degree <10. -1 Pa, to obtain a porous aluminum alloy matrix;

[0044] (4) The porous aluminum alloy substrate obtained by sintering is immersed in a mixed solution containing 40 g / L sodium hydroxide, 15 g / L sodium carbonate and 2 g / L sodium gluconate at a solution temperature of 60°C for 3 min, and then the oxide film on the surface of the porous aluminum alloy is removed and washed with deionized water.

[0045] Then, the etching was carried out in a solution containing 5 g / L oxalic acid and 150 g / L hydrochloric acid for 8 hours, and then rinsed with deionized water.

[0046] The etched aluminum-based sliding bearing material was immersed in a 1% stearic acid ethanol solution for 40 minutes to perform hydrophobic and oleophilic treatment, and then placed in an atmospheric environment to air dry naturally.

[0047] (5) The modified porous aluminum alloy matrix is ​​subjected to oil immersion treatment to obtain a porous self-lubricating aluminum-based sliding bearing material.

[0048] The porous self-lubricating aluminum-based sliding bearing material prepared in this embodiment was tested below. The porosity of the density aluminum alloy matrix was measured by the drainage method. After immersion in oil, tribological tests were performed on it using a friction and wear testing machine. The test results are shown in Table 1.

[0049] Example 2

[0050] (1) Aluminum powder, copper powder and nickel powder are mixed in a mass ratio of 95:4:1 and put into a ball mill jar for one ball milling. The ball-to-material ratio for one ball milling is 10:1, the ball mill speed is 500 r / min, and the ball milling time is 40 h to obtain powder A.

[0051] (2) Then add 41% aluminum powder, 6% silicon powder and 5% nano titanium diboride powder according to the total mass fraction of powder A for secondary ball milling. The ball-to-material ratio of the secondary ball milling is 9:1, the ball milling speed is 400 r / min and the time is 8 h. After the ball milling is completed, fill the mixed powder into the mold and press it into shape at 240 MPa.

[0052] (3) Then the mold is placed in a vacuum sintering furnace for sintering at a temperature of 550℃ for 30 minutes, with a vacuum degree of <10. -1 Pa, to obtain a porous aluminum alloy matrix;

[0053] (4) The porous aluminum alloy substrate obtained by sintering is immersed in a mixed solution containing 30 g / L sodium hydroxide, 10 g / L sodium carbonate and 2 g / L sodium gluconate at a solution temperature of 50°C for 5 min, and then the oxide film on the surface of the porous aluminum alloy is removed and washed with deionized water.

[0054] Then, the etching was carried out in a solution containing 10 g / L oxalic acid and 180 g / L hydrochloric acid for 8 hours, and then rinsed with deionized water.

[0055] The etched aluminum-based sliding bearing material was immersed in a 1% stearic acid ethanol solution for 30 minutes to perform hydrophobic and oleophilic treatment, and then placed in an atmospheric environment to air dry naturally.

[0056] (5) The modified porous aluminum alloy matrix is ​​subjected to oil immersion treatment to obtain a porous self-lubricating aluminum-based sliding bearing material.

[0057] The porous self-lubricating aluminum-based sliding bearing material prepared in this embodiment was observed and tested, and the results are shown in Table 1.

[0058] Example 3

[0059] (1) Aluminum powder, copper powder and nickel powder are mixed in a mass ratio of 94:5:1 and put into a ball mill jar for ball milling. The ball-to-material ratio for the first ball milling is 8:1, the ball mill speed is 600 r / min, and the ball milling time is 50 h to obtain powder A.

[0060] (2) Then add 41% aluminum powder, 6% silicon powder and 6% nano titanium diboride powder according to the total mass fraction of powder A for secondary ball milling. The ball-to-material ratio of the secondary ball milling is 7:1, the ball milling speed is 200 r / min and the time is 12 h. After the ball milling is completed, fill the mixed powder into the mold and press it into shape at 260 MPa.

[0061] (3) Then the mold is placed in a vacuum sintering furnace for sintering at a temperature of 580℃ for 30 minutes, with a vacuum degree of <10. -1 Pa, to obtain a porous aluminum alloy matrix;

[0062] (4) The porous aluminum alloy substrate obtained by sintering is immersed in a mixed solution containing 20 g / L sodium hydroxide, 25 g / L sodium carbonate and 4 g / L sodium gluconate at a solution temperature of 50°C for 5 min, and then the oxide film on the surface of the porous aluminum alloy is removed and washed with deionized water.

[0063] Then, the mixture was etched for 12 hours in a solution containing 15 g / L oxalic acid and 220 g / L hydrochloric acid, and then rinsed with deionized water.

[0064] The etched aluminum-based sliding bearing material was immersed in a 2% stearic acid ethanol solution for 20 minutes to perform hydrophobic and oleophilic treatment, and then placed in an atmospheric environment to air dry naturally.

[0065] (5) The modified porous aluminum alloy matrix is ​​subjected to oil immersion treatment to obtain a porous self-lubricating aluminum-based sliding bearing material.

[0066] The porous self-lubricating aluminum-based sliding bearing material prepared in this embodiment was observed and tested, and the results are shown in Table 1.

[0067] Table 1. Properties of materials obtained in each embodiment

[0068] Example Hardness (HV) of composite materials Porosity (%) of composite material coefficient of friction after oil immersion Example 1 97 38.3 0.13 Example 2 121 22.5 0.11 Example 3 130 12.1 0.15

[0069] With increasing sintering temperature and nano-titanium diboride content, the hardness of the porous aluminum-based bearing material obtained after sintering gradually increases, while the porosity gradually decreases. However, after oil impregnation, the porous self-lubricating aluminum-based bearing material obtained in Example 2 exhibits the lowest coefficient of friction, and the coefficients of friction in Examples 1 and 3 are both below 0.16, demonstrating excellent self-lubricating properties. Considering both economic cost and friction characteristics, Example 2 is the optimal implementation scheme among the examples.

[0070] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A porous self-lubricating aluminum-based composite material, characterized in that: The composite material comprises, by weight, 125-145 parts aluminum powder, 3-5 parts copper powder, 1-5 parts nickel powder, 3-6 parts silicon powder, and 3-6 parts nano-titanium diboride powder; the mass ratio of copper powder to nickel powder is 3-5:

1. The preparation method of the porous self-lubricating aluminum-based composite material includes the following steps: S1: Mix 90-100 parts by weight of aluminum powder, 3-5 parts by weight of copper powder, and 1-5 parts by weight of nickel powder, and then ball mill once to obtain powder A; S2: Add 35-45 parts by weight of aluminum powder, 3-6 parts by weight of silicon powder, and 3-6 parts by weight of nano titanium diboride powder to powder A for secondary ball milling, and obtain powder B after completion; S3: Place powder B into a mold and press it at a pressure of 220-260 MPa. The sintering temperature is 520-580℃, and the holding time is 20-30 minutes. The vacuum degree is <10. -1 Pa; S4: The porous aluminum alloy matrix obtained by sintering is first washed with alkali, then etched in an acidic solution and then immersed in a stearic acid ethanol solution for modification. After the surface is treated with hydrophobic and oleophilic methods, a composite material is obtained.

2. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The aluminum powder has an average particle size of 2-8 μm; the copper powder has an average particle size of 3-5 μm; the nickel powder has an average particle size of 5-8 μm; the silicon powder has an average particle size of 5-10 μm; and the nano-titanium diboride powder has an average particle size of 40-60 nm.

3. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The second phase in the composite material comprises Al3CuNi phase and Al7Cu4Ni phase; the content of Al7Cu4Ni phase is higher than that of Al3CuNi phase.

4. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The composite material has an open porosity of 12-38%, a friction coefficient of less than or equal to 0.16 after oil immersion, and a hardness of 97-130 HV.

5. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The ball-to-material ratio for the first ball milling is 8-12:1, the rotation speed is 400-600 r / min, and the milling time is 30-50 h; the ball-to-material ratio for the second ball milling is 6-9:1, the rotation speed is 200-400 r / min, and the milling time is 4-12 h.

6. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The alkaline washing process involves immersing the sample in a mixed solution at a temperature of 50-60°C for 3-5 minutes, followed by rinsing with deionized water. The mixed solution contains 20-40 g / L sodium hydroxide, 10-25 g / L sodium carbonate, and 2-4 g / L sodium gluconate.

7. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The etching process involves etching with a mixed solution containing 5-15 g / L oxalic acid and 150-220 g / L hydrochloric acid for 8-12 hours, followed by rinsing with deionized water after etching.

8. The porous self-lubricating aluminum-based composite material according to claim 1, characterized in that: The modification process involves immersing the etched composite material in a 1%-2% stearic acid ethanol solution for 20-40 minutes, followed by natural air drying in the atmosphere.

9. The application of a porous self-lubricating aluminum-based composite material as described in any one of claims 1-4 in sliding bearings.

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