Powder metallurgy friction material and preparation method thereof

Abstract

The invention belongs to the technical field of friction materials, and relates to a powder metallurgy friction material and a preparation method thereof. The powder metallurgy friction material is prepared from the following raw materials: 10 wt%-15 wt% of silicon carbide nanoparticles, 5 wt%-15 wt% of aluminum oxide nanoparticles, 5 wt%-10 wt% of molybdenum disulfide, 5 wt%-10 wt% of hexagonal boron nitride, 5 wt%-10 wt% of a microencapsulation self-repairing agent and the balance of nano copper powder. Through cooperative use of the silicon carbide nano-particles, the nano-copper powder and the microencapsulation self-repairing agent, the wear resistance and the mechanical performance of the powder metallurgy friction material are improved, and the preparation method is simple and suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of friction materials, and relates to a friction material containing silicon carbide, and in particular to a powder metallurgy friction material and a preparation method thereof. Background Art

[0002] Powder metallurgy is an industrial technology that produces metal powder or uses metal powder as raw material, and then produces metal materials, composite materials and various types of products through molding and sintering. Powder metallurgy has unique chemical composition and mechanical and physical properties that cannot be obtained by traditional melting and casting methods.

[0003] Copper-based powder metallurgy friction materials are composite materials made of copper and its alloys as the matrix, with friction components and lubricating components added, and prepared by powder metallurgy. Compared with organic friction materials, this friction material has the advantages of good heat resistance, high mechanical strength, stable friction and wear performance, etc., so it is widely used in the automotive field. However, with the development of automobiles in the direction of high speed and heavy load, traditional copper-based powder metallurgy friction materials are severely worn during use and can no longer meet the requirements of comprehensive performance of automotive brake materials. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a powder metallurgy friction material and a preparation method thereof. The present invention improves the wear resistance and mechanical properties of the powder metallurgy friction material through the coordinated use of silicon carbide nanoparticles, nano copper powder and microencapsulated self-healing agent, and the preparation method is simple and suitable for large-scale industrial production.

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a powder metallurgy friction material. The raw materials for preparing the powder metallurgy friction material include, in terms of mass percentage: 10wt%-15wt% of silicon carbide nanoparticles, 5wt%-15wt% of aluminum oxide nanoparticles, 5wt%-10wt% of molybdenum disulfide, 5wt%-10wt% of hexagonal boron nitride, 5wt%-10wt% of microencapsulated self-healing agent and the remainder of nano copper powder.

[0007] In the powder metallurgy friction material provided by the present invention, nano copper powder is a base material, which can form a copper film on the surface of the powder metallurgy friction material, increase the friction coefficient, improve the braking effect, and reduce wear and tear, thereby increasing the service life.

[0008] Silicon carbide nanoparticles are one of the reinforcing materials. They have high hardness and wear resistance, can effectively improve the overall hardness, enhance the ability to resist wear, reduce material loss during friction, and can also improve the consistency of friction performance of powder metallurgy friction materials under different working conditions. The appropriate mass percentage helps to exert the reinforcing effect of silicon carbide nanoparticles. In the present invention, the mass percentage of silicon carbide nanoparticles is 10wt%-15wt%, for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%, but is not limited to the listed values, and the remaining values ​​not listed in the numerical range are also applicable.

[0009] As one of the reinforcing materials, aluminum oxide nanoparticles have high strength and rigidity, and can significantly improve the mechanical properties of powder metallurgy friction materials. The appropriate content can also make the powder metallurgy friction materials have an ideal friction coefficient. The appropriate mass percentage helps to exert the reinforcing effect of aluminum oxide nanoparticles. In the present invention, the mass percentage of aluminum oxide nanoparticles is 5wt%-15wt%, for example, it can be 5wt%, 8wt%, 10wt%, 12wt% or 15wt%, but it is not limited to the listed values, and the remaining values ​​not listed in the numerical range are also applicable.

[0010] As one of the lubricating materials, molybdenum disulfide can effectively reduce the friction coefficient, reduce frictional heat, and help improve the thermal stability and reliability of powder metallurgy friction materials, so that they have a longer service life. The appropriate mass percentage helps to exert the lubricating effect of molybdenum disulfide. In the present invention, the mass percentage of molybdenum disulfide is 5wt%-10wt%, for example, it can be 5wt%, 6wt%, 8wt%, 9wt% or 10wt%, but it is not limited to the listed values, and the other values ​​not listed in the numerical range are also applicable.

[0011] As one of the lubricating materials, hexagonal boron nitride has a layered structure similar to graphite, maintains good lubrication performance under high temperature conditions, and improves the high temperature stability and reliability of powder metallurgy friction materials. The appropriate mass percentage helps to exert the lubrication effect of hexagonal boron nitride. In the present invention, the mass percentage of hexagonal boron nitride is 5wt%-10wt%, for example, it can be 5wt%, 6wt%, 8wt%, 9wt% or 10wt%, but it is not limited to the listed values, and the remaining values ​​not listed in the numerical range are also applicable.

[0012] The microencapsulated self-repairing agent is used as a repair and enhancement material. When cracks or damage occur in the powder metallurgy friction material during use, the microcapsule will rupture and release the internal repair agent, thereby repairing the cracks, restoring the integrity of the material, and improving the service life and reliability of the material; it can also reduce the friction coefficient and reduce friction loss. The appropriate mass percentage helps to exert the repair and enhancement effect of the microencapsulated self-repairing agent. In the present invention, the mass percentage of the microencapsulated self-repairing agent is 5wt%-10wt%, for example, it can be 5wt%, 6wt%, 8wt%, 9wt% or 10wt%, but it is not limited to the listed values, and the remaining values ​​not listed in the numerical range are also applicable.

[0013] Moreover, in the powder metallurgy friction material provided by the present invention, there is a synergistic effect between the nano copper powder, silicon carbide nanoparticles and the microencapsulated self-repairing agent. The silicon carbide nanoparticles and the nano copper powder can accelerate the rupture of the microencapsulated self-repairing agent and the release of the repairing agent during the friction process, making the repair process more rapid and effective; moreover, the silicon carbide nanoparticles can be filled in cracks and pores to improve the density, and the nano copper powder can enhance the bonding force through interaction with other components, so that the powder metallurgy friction material has good mechanical properties; the synergistic effect of the three can also make the powder metallurgy friction material have a friction coefficient that meets the process requirements.

[0014] Preferably, the average particle size of the silicon carbide nanoparticles is 50nm-200nm, for example, 50nm, 80nm, 100nm, 120nm, 150nm, 160nm, 180nm or 200nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the average particle size of the aluminum oxide nanoparticles is 20 nm-100 nm, for example, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm or 100 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] Preferably, the average particle size of the molybdenum disulfide is 50nm-500nm, for example, it can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the average particle size of the hexagonal boron nitride is 0.5 μm-5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the average particle size of the microencapsulated self-healing agent is 1 μm-20 μm, for example, it can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the average particle size of the nano copper powder is 20 nm-100 nm, for example, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm or 100 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the nano copper powder is nano copper powder surface treated with a silane coupling agent, and the silane coupling agent surface treatment comprises: the copper powder is sequentially cleaned, dried and pickled, then immersed in a silane coupling agent solution, and then dried after the immersion to obtain the nano copper powder.

[0021] As a preferred technical solution of the present invention, the surface of the copper powder is treated with a silane coupling agent, which can improve the dispersibility of the nano copper powder, make it evenly dispersed in the powder metallurgy friction material, and increase the service life of the material; at the same time, the copper powder treated with the silane coupling agent can better combine with the microencapsulated self-healing agent, improve the interface bonding force between the microencapsulated self-healing agent and the metal powder, and improve the mechanical properties of the powder metallurgy friction material.

[0022] The silane coupling agent surface treatment technical solution provided by the present invention does not impose any specific restrictions on the average particle size of the copper powder used, as long as the average particle size of the obtained nano copper powder meets the process requirements.

[0023] Optionally, when the copper powder is cleaned, an organic solvent is used to remove oil stains and impurities on the surface. Preferably, the organic solvent used to clean the copper powder includes acetone and / or ethanol.

[0024] Optionally, the acid used for pickling the copper powder includes hydrochloric acid and / or sulfuric acid.

[0025] When copper powder is exposed to the air, its surface is oxidized to copper oxide. During the pickling treatment, the surface roughness of the copper powder can be increased, thereby improving the adhesion of the silane coupling agent.

[0026] Preferably, the volume ratio of the acid used for pickling is 5%-15%, for example, it can be 5%, 8%, 10%, 12% or 15%, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0027] The "volume ratio of acid" mentioned in the present invention refers to the percentage of the volume of acid in the acid solution used for pickling to the total volume of the acid solution.

[0028] Preferably, the pickling time is 1 min-30 min, for example, 1 min, 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, during the surface treatment with the silane coupling agent, the mass concentration of the silane coupling agent solution is 0.5wt%-2wt%, for example, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt% or 2wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, during the surface treatment with silane coupling agent, the immersion time is 10 min-30 min, for example, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the silane coupling agent includes any one of KH-540, KH-550, KH-560, KH-580, A-151, A-171 or KH-590, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of KH-540 and KH-550, a combination of KH-550 and KH-560, a combination of KH-580 and KH-590, a combination of A-151 and A-171, a combination of KH-550, KH-580 and KH-590, a combination of KH-550, KH-560, KH-580 and KH-590, or a combination of KH-540, KH-550, KH-560, KH-580, A-151, A-171 and KH-590.

[0032] Preferably, the silicon carbide nanoparticles are silicon carbide nanoparticles that have been surface treated with a copper-aminosilane complex, and the copper-aminosilane complex surface treatment includes: after the silicon carbide nanoparticles are cleaned, dried and surface hydroxylated, they are immersed in a copper salt-aminosilane complex solution, and after the immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

[0033] As a preferred technical solution of the present invention, surface treatment of silicon carbide nanoparticles with a copper-aminosilane complex can improve the dispersibility of silicon carbide nanoparticles; the presence of copper ions strengthens the binding force between silicon carbide nanoparticles and nano-copper powder, further strengthens the strength of powder metallurgy friction materials, solves the problem of physical interface mixed connection between silicon carbide and copper due to large difference in material density and unstable connection, and improves product quality stability.

[0034] Preferably, the surface hydroxylation treatment is performed using hydrochloric acid, nitric acid or sodium hydroxide solution.

[0035] The present invention does not limit the specific method of surface hydroxylation treatment, as long as the silicon carbide nanoparticles are treated with hydrochloric acid, nitric acid or sodium hydroxide solution.

[0036] Preferably, the method for preparing the copper salt-aminosilane complex solution comprises:

[0037] A copper salt solution with a mass concentration of 0.1 wt% to 1 wt% and an aminosilane solution with a mass concentration of 1 wt% to 5 wt% are mixed in a volume ratio of 1:2 to 1:4 to obtain the copper salt-aminosilane complex solution.

[0038] The volume ratio of the copper salt solution to the aminosilane solution is 1:2-1:4, for example, 1:2, 1:3 or 1:4, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] The mass concentration of the copper salt solution is 0.1wt%-1wt%, for example, it can be 0.1wt%, 0.3wt%, 0.5wt%, 0.6wt%, 0.8wt% or 1wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] The mass concentration of the aminosilane solution is 1wt%-5wt%, for example, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the molten salt solution is prepared by dissolving a copper salt in deionized water; the copper salt includes copper nitrate and / or copper sulfate.

[0042] Preferably, the aminosilane solution is prepared by dissolving aminosilane in ethanol and / or deionized water.

[0043] Preferably, the aminosilane in the aminosilane solution includes any one of KH-550, KH-602, KH-792 or KH540 or a combination of at least two thereof. Typical but non-limiting combinations include a combination of KH-550 and KH-602, a combination of KH-792 and KH540, a combination of KH-550, KH602 and KH540, or a combination of KH-550, KH-602, KH-792 and KH540.

[0044] Preferably, the microencapsulated self-healing agent comprises self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.1-100:0.5, for example, it can be 100:0.1, 100:0.2, 100:0.3, 100:0.4 or 100:0.5, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0045] The present invention uses a microencapsulated self-repairing agent. The polymer in the microcapsule self-repairing agent contains a reversible chemical bond, and the catalyst microcapsule contains a catalyst. When the friction material is damaged, the microcapsule ruptures, releasing the polymer and catalyst inside to cause the reversible chemical bonds to break and recombine, flow to the damaged area, combine with the surrounding materials to produce a polymerization reaction, form a new polymer, fill the damaged area, achieve self-repair, and improve the wear resistance of the friction material.

[0046] Preferably, the preparation method of the self-healing polymer microcapsules includes: dissolving the self-healing polymer in a hydrophobic solvent to form an oil phase; dissolving the emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1 μm-20 μm; adding a diamine aqueous solution, and then dripping isocyanate to form an interfacial condensation reaction, the reaction temperature is 20°C-60°C, the reaction time is 30min-120min, and self-healing polymer microcapsules are obtained.

[0047] Preferably, the hydrophobic solvent comprises toluene and / or cyclohexane.

[0048] Preferably, the emulsifier comprises any one of Tween 80, Span 20, Span 40 or Span 80, or a combination of at least two of them. Typical but non-limiting combinations include a combination of Tween 80 and Span 20, a combination of Span 20 and Span 40, a combination of Span 20, Span 40 and Span 80, or a combination of Tween 80, Span 20, Span 40 and Span 80.

[0049] Preferably, the volume ratio of the oil phase to the water phase is 1:5-1:10, for example, 1:5, 1:6, 1:8, 1:9 or 1:10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, the molar ratio of the diamine in the diamine aqueous solution to the isocyanate is 1:(0.8-1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] Optionally, the diamine in the diamine aqueous solution includes ethylenediamine and / or hexamethylenediamine.

[0052] Optionally, the isocyanate includes any one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (PAPI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) or dicyclohexylmethane diisocyanate (HMDI), or a combination of at least two thereof. Typical but non-limiting combinations include a combination of TDI and MDI, a combination of PAPI and HDI, a combination of IPDI and HMDI, a combination of TDI, MDI, PAPI, HDI, a combination of PAPI, HDI, IPDI and HMDI, or a combination of TDI, MDI, PAPI, HDI, IPDI and HMDI.

[0053] Preferably, the total mass of the diamine in the diamine aqueous solution and the isocyanate is 5%-20% of the mass of the self-healing polymer, for example, it can be 5%, 8%, 10%, 12%, 15%, 18% or 20%, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0054] Preferably, the self-healing polymer of the self-healing polymer microcapsule comprises: hydroxy vinyl silicone resin and a disulfide bond-containing compound dissolved in a solvent; adding a first catalyst and stirring evenly; heating to react at 50°C-100°C; after the reaction is completed, filtering, washing and drying to obtain the self-healing polymer.

[0055] Optionally, the hydroxy vinyl silicone resin includes any one of methyl hydroxy vinyl silicone resin, phenyl hydroxy vinyl silicone resin or fluoro hydroxy vinyl silicone resin, or a combination of at least two thereof.

[0056] Optionally, the disulfide bond-containing compound includes dithiodibenzoic acid (DTSA), polydisulfide dipropane sulfonate sodium (PSS) or 4,4 ` - Any one or a combination of at least two of dithiodimorpholine (DTDM), typical but non-limiting combinations include a combination of DTSA and PSS, a combination of PSS and DTDM, a combination of DTSA and DTDM, or a combination of DTSA, PSS and DTDM.

[0057] Preferably, the first catalyst comprises an acidic catalyst and / or a basic catalyst.

[0058] Preferably, the acidic catalyst comprises sulfuric acid and / or hydrochloric acid.

[0059] Preferably, the alkaline catalyst includes any one of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide or triethylamine, or a combination of at least two thereof.

[0060] Preferably, the preparation method of the catalyst microcapsules comprises: dissolving the second catalyst in a hydrophobic solvent to form an oil phase; dissolving the emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1 μm-20 μm; adding a diamine aqueous solution, and then dripping isocyanate to form an interfacial polycondensation reaction, the reaction temperature is 20°C-60°C, the reaction time is 30min-120min, and the catalyst microcapsules are obtained.

[0061] Preferably, the second catalyst comprises any one of an organic tin compound, an organic titanium compound or a thiol compound, or a combination of at least two thereof.

[0062] Optionally, the organic tin compound includes any one of dibutyltin dilaurate, stannous octoate or dibutyltin didodecylsulfide, or a combination of at least two of them.

[0063] Optionally, the organic titanium compound includes any one of tetraisopropyl titanate, tetra-n-butyl titanate or tetraethyl titanate, or a combination of at least two thereof.

[0064] Optionally, the thiol compound includes any one of tert-dodecyl mercaptan, 3-mercaptopropionic acid or ethanethiol, or a combination of at least two of them.

[0065] Preferably, the hydrophobic solvent comprises toluene and / or cyclohexane.

[0066] Preferably, the emulsifier comprises any one of Tween 80, Span 20, Span 40 or Span 80, or a combination of at least two of them. Typical but non-limiting combinations include a combination of Tween 80 and Span 20, a combination of Span 20 and Span 40, a combination of Span 20, Span 40 and Span 80, or a combination of Tween 80, Span 20, Span 40 and Span 80.

[0067] Preferably, the volume ratio of the oil phase to the water phase is 1:5-1:10, for example, 1:5, 1:6, 1:8, 1:9 or 1:10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] Preferably, the molar ratio of the diamine in the diamine aqueous solution to the isocyanate is 1:(0.8-1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0069] Optionally, the diamine in the diamine aqueous solution includes ethylenediamine and / or hexamethylenediamine.

[0070] Optionally, the isocyanate includes any one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (PAPI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) or dicyclohexylmethane diisocyanate (HMDI), or a combination of at least two thereof. Typical but non-limiting combinations include a combination of TDI and MDI, a combination of PAPI and HDI, a combination of IPDI and HMDI, a combination of TDI, MDI, PAPI, HDI, a combination of PAPI, HDI, IPDI and HMDI, or a combination of TDI, MDI, PAPI, HDI, IPDI and HMDI.

[0071] Preferably, the total mass of the diamine and the isocyanate in the diamine aqueous solution is 5%-20% of the mass of the second catalyst, for example, it can be 5%, 8%, 10%, 12%, 15%, 18% or 20%, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable.

[0072] In a second aspect, the present invention provides a method for preparing a powder metallurgy friction material, the preparation method comprising: mixing nano copper powder, silicon carbide nanoparticles, aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to a formula amount to obtain a mixed powder; the mixed powder is sequentially cold pressed and sintered to obtain the powder metallurgy friction material described in the first aspect.

[0073] Preferably, the cold press forming pressure is 550MPa-650MPa, for example, 550MPa, 580MPa, 600MPa, 620MPa or 650MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0074] Preferably, the sintering is performed in a protective atmosphere, and the gas used in the protective atmosphere includes nitrogen and / or an inert gas.

[0075] Preferably, the inert gas comprises helium and / or argon.

[0076] Preferably, the sintering temperature is 800°C-1300°C, for example, 800°C, 900°C, 1000°C, 1200°C or 1300°C, but is not limited to the listed values, and other values ​​within the numerical range that are not listed are also applicable.

[0077] Preferably, the sintering time is 30 min-120 min, for example, 30 min, 50 min, 60 min, 80 min, 100 min or 120 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0078] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] In the powder metallurgy friction material provided by the present invention, there is a synergistic effect between the nano copper powder, the silicon carbide nano particles and the microencapsulated self-repairing agent. The silicon carbide nano particles and the nano copper powder can accelerate the rupture of the microencapsulated self-repairing agent and the release of the repairing agent during the friction process, making the repair process more rapid and effective; moreover, the silicon carbide nano particles can be filled in cracks and pores to improve the density, and the nano copper powder can enhance the bonding force through the interaction with other components, so that the powder metallurgy friction material has good mechanical properties; the synergistic effect of the three can also make the powder metallurgy friction material have a friction coefficient that meets the process requirements. DETAILED DESCRIPTION

[0081] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0082] Example 1

[0083] The present embodiment provides a powder metallurgy friction material. The raw materials for preparing the powder metallurgy friction material include, by mass percentage: 12wt% of silicon carbide nanoparticles, 12wt% of aluminum oxide nanoparticles, 9wt% of molybdenum disulfide, 8wt% of hexagonal boron nitride, 8wt% of microencapsulated self-healing agent and the remainder of nano copper powder.

[0084] The average particle size of the silicon carbide nanoparticles is 100nm; the average particle size of the aluminum oxide nanoparticles is 50nm; the average particle size of the molybdenum disulfide is 300nm; the average particle size of the hexagonal boron nitride is 3μm; the average particle size of the microencapsulated self-healing agent is 10μm; the average particle size of the nano copper powder is 50nm;

[0085] The microencapsulated self-healing agent includes self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.2;

[0086] The preparation method of the self-repairing polymer microcapsule comprises:

[0087] (1) Preparing a self-healing polymer: dissolving a hydroxy vinyl silicone resin (Sihai Chemical, SH5202) and a disulfide bond-containing compound (dithiodibenzoic acid) in a solvent; adding a first catalyst, sulfuric acid, and stirring evenly; heating at 80° C. for reaction; after the reaction is completed, filtering, washing, and drying to obtain the self-healing polymer;

[0088] (2) Preparation of self-healing polymer microcapsules: The self-healing polymer is dissolved in a hydrophobic solvent (toluene) to form an oil phase; the emulsifier (Tween 80) is dissolved in water to form an aqueous phase; the oil phase is dispersed in the aqueous phase to form an O / W emulsion with a particle size of 10 μm; an aqueous solution of diamine (ethylenediamine) is added, and then isocyanate (toluene diisocyanate) is added dropwise to form an interfacial polycondensation reaction, the reaction temperature is 30°C, the reaction time is 60 min, and self-healing polymer microcapsules are obtained; the volume ratio of the oil phase to the aqueous phase is 1:6; the molar ratio of the diamine to the isocyanate is 1:1; the total mass of the diamine and the isocyanate accounts for 10% of the mass of the self-healing polymer.

[0089] The preparation method of the catalyst microcapsule comprises: dissolving a second catalyst organic tin compound (dibutyltin dilaurate) in a hydrophobic solvent (cyclohexane) to form an oil phase; dissolving an emulsifier (Span 80) in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 5 μm; adding a diamine (ethylenediamine) aqueous solution, and then dripping isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction, the reaction temperature is 40° C., the reaction time is 60 min, and the catalyst microcapsule is obtained; the volume ratio of the oil phase to the aqueous phase is 1:8; the molar ratio of the diamine to the isocyanate is 1:1; the total mass of the diamine and the isocyanate accounts for 15% of the mass of the second catalyst.

[0090] The preparation method of the powder metallurgy friction material described in this embodiment includes: mixing nano copper powder, silicon carbide nanoparticles, aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to the formula amount to obtain a mixed powder; the mixed powder is first pressed into shape under a pressure of 600 MPa, and then sintered in a nitrogen atmosphere at a sintering temperature of 800° C. and a sintering time of 120 min to obtain the powder metallurgy friction material.

[0091] Example 2

[0092] The present embodiment provides a powder metallurgy friction material. The raw materials for preparing the powder metallurgy friction material include, by mass percentage: 10wt% of silicon carbide nanoparticles, 15wt% of aluminum oxide nanoparticles, 10wt% of molybdenum disulfide, 5wt% of hexagonal boron nitride, 5wt% of microencapsulated self-healing agent and the remainder of nano copper powder.

[0093] The average particle size of the silicon carbide nanoparticles is 50nm; the average particle size of the aluminum oxide nanoparticles is 20nm; the average particle size of the molybdenum disulfide is 50nm; the average particle size of the hexagonal boron nitride is 0.5μm; the average particle size of the microencapsulated self-healing agent is 1μm; the average particle size of the nano copper powder is 20nm;

[0094] The microencapsulated self-healing agent includes self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.1;

[0095] The preparation method of the self-repairing polymer microcapsule comprises:

[0096] (1) Preparing a self-healing polymer: dissolving a hydroxy vinyl silicone resin (Sihai Chemical, SH5202) and a disulfide bond-containing compound (dithiodibenzoic acid) in a solvent; adding a first catalyst, sodium hydroxide, and stirring evenly; heating at 50° C. for reaction; after the reaction is completed, filtering, washing, and drying to obtain the self-healing polymer;

[0097] (2) Preparation of self-healing polymer microcapsules: The self-healing polymer is dissolved in a hydrophobic solvent (cyclohexane) to form an oil phase; the emulsifier (Span 40) is dissolved in water to form an aqueous phase; the oil phase is dispersed in the aqueous phase to form an O / W emulsion with a particle size of 1 μm; an aqueous solution of diamine (ethylenediamine) is added, and then isocyanate (toluene diisocyanate) is added dropwise to form an interfacial polycondensation reaction, the reaction temperature is 20°C, the reaction time is 120 min, and self-healing polymer microcapsules are obtained; the volume ratio of the oil phase to the aqueous phase is 1:5; the molar ratio of the diamine to the isocyanate is 1:1; the total mass of the diamine and the isocyanate accounts for 5% of the mass of the self-healing polymer.

[0098] The preparation method of the catalyst microcapsule comprises: dissolving a second catalyst (tetraisopropyl titanate) in a hydrophobic solvent toluene to form an oil phase; dissolving an emulsifier (Span 20) in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1 μm; adding a diamine (ethylenediamine) aqueous solution, and then dripping isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction, the reaction temperature is 20° C., the reaction time is 120 min, and the catalyst microcapsule is obtained; the volume ratio of the oil phase to the aqueous phase is 1:5; the molar ratio of the diamine to the isocyanate is 1:1; the total mass of the diamine and the isocyanate accounts for 5% of the mass of the second catalyst.

[0099] The preparation method of the powder metallurgy friction material described in this embodiment includes: mixing nano copper powder, silicon carbide nanoparticles, aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to the formula amount to obtain a mixed powder; the mixed powder is first pressed into shape under a pressure of 550 MPa, and then sintered in a nitrogen atmosphere at a sintering temperature of 1300° C. and a sintering time of 30 minutes to obtain the powder metallurgy friction material.

[0100] Example 3

[0101] The present embodiment provides a powder metallurgy friction material. The raw materials for preparing the powder metallurgy friction material include, by mass percentage: 15wt% of silicon carbide nanoparticles, 5wt% of aluminum oxide nanoparticles, 5wt% of molybdenum disulfide, 5wt% of hexagonal boron nitride, 5wt% of microencapsulated self-healing agent and the remainder of nano copper powder.

[0102] The average particle size of the silicon carbide nanoparticles is 200nm; the average particle size of the aluminum oxide nanoparticles is 100nm; the average particle size of the molybdenum disulfide is 500nm; the average particle size of the hexagonal boron nitride is 5μm; the average particle size of the microencapsulated self-healing agent is 20μm; the average particle size of the nano copper powder is 100nm;

[0103] The microencapsulated self-healing agent includes self-healing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.5;

[0104] The preparation method of the self-repairing polymer microcapsule comprises:

[0105] (1) Preparing a self-healing polymer: dissolving a hydroxy vinyl silicone resin (Sihai Chemical, SH5202) and a disulfide bond-containing compound (dithiodibenzoic acid) in a solvent; adding a first catalyst, triethylamine, and stirring evenly; heating at 100° C. for reaction; after the reaction is completed, filtering, washing, and drying to obtain the self-healing polymer;

[0106] (2) Preparation of self-healing polymer microcapsules: The self-healing polymer is dissolved in a hydrophobic solvent (cyclohexane) to form an oil phase; the emulsifier (Span 80) is dissolved in water to form an aqueous phase; the oil phase is dispersed in the aqueous phase to form an O / W emulsion with a particle size of 20 μm; an aqueous solution of diamine (ethylenediamine) is added, and then isocyanate (toluene diisocyanate) is added dropwise to form an interfacial polycondensation reaction, the reaction temperature is 60°C, and the reaction time is 30 min to obtain self-healing polymer microcapsules; the volume ratio of the oil phase to the aqueous phase is 1:10; the molar ratio of the diamine to the isocyanate is 1:1; the total mass of the diamine and the isocyanate accounts for 20% of the mass of the self-healing polymer.

[0107] The preparation method of the catalyst microcapsule comprises: dissolving a second catalyst (tert-dodecyl mercaptan) in a hydrophobic solvent (cyclohexane) to form an oil phase; dissolving an emulsifier (Span 80) in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 20 μm; adding a diamine (ethylenediamine) aqueous solution, and then dripping isocyanate (toluene diisocyanate) to form an interfacial polycondensation reaction, the reaction temperature is 60° C., the reaction time is 30 min, and the catalyst microcapsule is obtained; the volume ratio of the oil phase to the aqueous phase is 1:10; the molar ratio of the diamine to the isocyanate is 1:1; the total mass of the diamine and the isocyanate accounts for 20% of the mass of the second catalyst.

[0108] The preparation method of the powder metallurgy friction material described in this embodiment includes: mixing nano copper powder, silicon carbide nanoparticles, aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to the formula amount to obtain a mixed powder; the mixed powder is first pressed into shape under a pressure of 650 MPa, and then sintered in a nitrogen atmosphere at a sintering temperature of 1000° C. and a sintering time of 60 min to obtain the powder metallurgy friction material.

[0109] Example 4

[0110] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the nano copper powder is surface treated with a silane coupling agent.

[0111] The silane coupling agent surface treatment comprises: cleaning the copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol on the surface; corroding the surface of the copper powder with hydrochloric acid (10% by volume) for 15 minutes to increase the roughness; and then soaking the copper powder with a 1wt% silane coupling agent (KH-550) solution for 15 minutes, and drying after the soaking to obtain the nano copper powder.

[0112] Example 5

[0113] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the nano copper powder is surface treated with a silane coupling agent.

[0114] The silane coupling agent surface treatment comprises: cleaning the copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol on the surface; corroding the surface of the copper powder with hydrochloric acid (5% by volume) for 30 minutes to increase the roughness; and then soaking the copper powder with a 0.5wt% silane coupling agent (KH-550) solution for 30 minutes, and drying after the soaking to obtain the nano copper powder.

[0115] Example 6

[0116] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the nano copper powder is surface treated with a silane coupling agent.

[0117] The silane coupling agent surface treatment comprises: cleaning the copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol on the surface; corroding the surface of the copper powder with hydrochloric acid (15% by volume) for 1 minute to increase the roughness; and then soaking the copper powder with a 2wt% silane coupling agent (KH-550) solution for 10 minutes, and drying after the soaking to obtain the nano copper powder.

[0118] Example 7

[0119] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the silicon carbide nanoparticles therein are silicon carbide nanoparticles surface-treated with a copper-aminosilane composite.

[0120] The surface treatment of the copper-aminosilane complex comprises: washing and drying the silicon carbide nanoparticles, treating the surface hydroxyl groups with sodium hydroxide, soaking the silicon carbide nanoparticles in a copper salt-aminosilane complex solution for 20 minutes, and washing and drying the silicon carbide nanoparticles after the soaking.

[0121] The preparation method of the copper salt-aminosilane complex solution comprises: mixing a copper nitrate solution with a mass concentration of 0.5wt% and an aminosilane (KH-550 dissolved in deionized water) solution with a mass concentration of 3wt% in a volume ratio of 1:3 to obtain the copper salt-aminosilane complex solution.

[0122] Example 8

[0123] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the silicon carbide nanoparticles therein are silicon carbide nanoparticles surface-treated with a copper-aminosilane composite.

[0124] The surface treatment of the copper-aminosilane complex comprises: washing and drying the silicon carbide nanoparticles, treating the surface hydroxyl groups with sodium hydroxide, soaking the silicon carbide nanoparticles in a copper salt-aminosilane complex solution for 10 minutes, and washing and drying the silicon carbide nanoparticles after the soaking.

[0125] The preparation method of the copper salt-aminosilane complex solution includes: mixing a copper nitrate solution with a mass concentration of 0.1wt% and an aminosilane (KH-550 dissolved in deionized water) solution with a mass concentration of 1wt% in a volume ratio of 1:2 to obtain the copper salt-aminosilane complex solution.

[0126] Example 9

[0127] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the silicon carbide nanoparticles therein are silicon carbide nanoparticles surface-treated with a copper-aminosilane composite.

[0128] The surface treatment of the copper-aminosilane complex comprises: washing and drying the silicon carbide nanoparticles, treating the surface hydroxyl groups with sodium hydroxide, soaking the silicon carbide nanoparticles in a copper salt-aminosilane complex solution for 30 minutes, and washing and drying the silicon carbide nanoparticles after the soaking.

[0129] The preparation method of the copper salt-aminosilane complex solution comprises: mixing a copper nitrate solution with a mass concentration of 1wt% and an aminosilane (KH-550 dissolved in deionized water) solution with a mass concentration of 5wt% in a volume ratio of 1:4 to obtain the copper-aminosilane complex solution.

[0130] Example 10

[0131] This embodiment provides a powder metallurgy friction material, which is the same as that of Embodiment 1 except that the nano copper powder is surface treated with a silane coupling agent and the silicon carbide nanoparticles are surface treated with a copper-aminosilane composite.

[0132] The silane coupling agent surface treatment comprises: cleaning the copper powder with ethanol to remove surface oil and impurities, and then drying to remove residual ethanol on the surface; corroding the surface of the copper powder with hydrochloric acid for 15 minutes to increase the roughness; and then soaking the copper powder with a 1wt% silane coupling agent (KH-550) solution for 15 minutes, and drying after the soaking to obtain the nano copper powder.

[0133] The surface treatment of the copper-aminosilane complex comprises: washing and drying the silicon carbide nanoparticles, treating the surface hydroxyl groups with sodium hydroxide, soaking the silicon carbide nanoparticles in a copper salt-aminosilane complex solution for 20 minutes, and washing and drying the silicon carbide nanoparticles after the soaking.

[0134] The preparation method of the copper salt-aminosilane complex solution comprises: mixing a copper nitrate solution with a mass concentration of 0.5wt% and an aminosilane (KH-550 dissolved in deionized water) solution with a mass concentration of 3wt% in a volume ratio of 1:3 to obtain the copper salt-aminosilane complex solution.

[0135] Comparative Example 1

[0136] This comparative example provides a powder metallurgy friction material, which is the same as Example 1 except that it does not contain silicon carbide nanoparticles and the ratios of aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride, microencapsulated self-healing agent and nano copper powder are the same as those in Example 1.

[0137] Comparative Example 2

[0138] This comparative example provides a powder metallurgy friction material, which is the same as Example 1 except that it does not contain a microencapsulated self-healing agent and the ratios of aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride, silicon carbide nanoparticles and nano copper powder are the same as those in Example 1.

[0139] Performance Characterization

[0140] By simulating friction tests under actual working conditions, the friction coefficient of the material under specific load and speed is measured; the wear rate is calculated by measuring the system loss of the material during the friction process.

[0141] Table 1

[0142]

[0143]

[0144] In summary, in the powder metallurgy friction material provided by the present invention, there is a synergistic effect between the nano copper powder, silicon carbide nanoparticles and the microencapsulated self-healing agent. The silicon carbide nanoparticles and the nano copper powder can accelerate the rupture of the microencapsulated self-healing agent and the release of the repairing agent during the friction process, making the repair process more rapid and effective; moreover, the silicon carbide nanoparticles can fill in cracks and pores to improve the density, and the nano copper powder can enhance the bonding force through the interaction with other components, so that the powder metallurgy friction material has good mechanical properties; the synergistic effect of the three can also make the powder metallurgy friction material have a friction coefficient that meets the process requirements.

[0145] The polymer in the microcapsule self-repairing agent contains reversible chemical bonds, and the catalyst microcapsule contains a catalyst. When the friction material is damaged, the microcapsule ruptures, releasing the polymer and catalyst inside to cause the reversible chemical bonds to break and recombine, flow to the damaged area, and react with the surrounding materials to form a new polymer, which fills the damaged area to achieve self-repair and improve the wear resistance of the friction material.

[0146] As a further preferred technical solution, the surface of the copper powder is treated with a silane coupling agent, which can improve the dispersibility of the nano copper powder, make it evenly dispersed in the powder metallurgy friction material, and increase the service life of the material; at the same time, the copper powder treated with the silane coupling agent can better combine with the microencapsulated self-healing agent, improve the interface bonding force between the microencapsulated self-healing agent and the metal powder, and improve the mechanical properties of the powder metallurgy friction material.

[0147] As a further preferred technical solution, surface treatment of silicon carbide nanoparticles with a copper-aminosilane complex can improve the dispersibility of silicon carbide nanoparticles; the presence of copper ions strengthens the bonding between silicon carbide nanoparticles and nano-copper powder, further enhancing the strength of the powder metallurgy friction material, solving the problem of physical interface mixed connection between silicon carbide and copper due to large difference in material density and unstable connection, thereby improving product quality stability.

[0148] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A powder metallurgy friction material, characterized in that: Measured in mass percentage, the raw materials for preparing the powder metallurgy friction material include: 10wt%-15wt% of silicon carbide nanoparticles, 5wt%-15wt% of aluminum oxide nanoparticles, 5wt%-10wt% of molybdenum disulfide, 5wt%-10wt% of hexagonal boron nitride, 5wt%-10wt% of microencapsulated self-healing agent and the remainder of nano copper powder.

2. The powder metallurgy friction material according to claim 1, characterized in that: The average particle size of the silicon carbide nanoparticles is 50nm-200nm; And / or, the average particle size of the aluminum oxide nanoparticles is 20nm-100nm; And / or, the average particle size of the molybdenum disulfide is 50nm-500nm; And / or, the average particle size of the hexagonal boron nitride is 0.5 μm-5 μm; And / or, the average particle size of the microencapsulated self-healing agent is 1 μm-20 μm; And / or, the average particle size of the nano copper powder is 20nm-100nm.

3. The powder metallurgy friction material according to claim 1 or 2, characterized in that: The nano copper powder is a nano copper powder that has been surface treated with a silane coupling agent, and the surface treatment with a silane coupling agent includes: The copper powder is washed, dried and pickled in sequence, then immersed in a silane coupling agent solution, and dried after the immersion to obtain the nano copper powder.

4. The powder metallurgy friction material according to claim 3, characterized in that: The silane coupling agent includes any one of KH-540, KH-560, KH-550, KH-580, KH-590, A-151 or A-171, or a combination of at least two thereof.

5. The powder metallurgy friction material according to claim 1, characterized in that: The silicon carbide nanoparticles are silicon carbide nanoparticles that have been surface treated with a copper-aminosilane complex, and the surface treatment of the copper-aminosilane complex includes: After being cleaned, dried and subjected to surface hydroxylation treatment, the silicon carbide nanoparticles are immersed in a copper salt-aminosilane complex solution, and after the immersion, they are cleaned and dried to obtain the silicon carbide nanoparticles.

6. The powder metallurgy friction material according to claim 5, characterized in that: The preparation method of the copper salt-aminosilane complex solution comprises: Mixing a copper salt solution having a mass concentration of 0.1 wt% to 1 wt% and an aminosilane solution having a mass concentration of 1 wt% to 5 wt% in a volume ratio of 1:2 to 1:4 to obtain the copper salt-aminosilane complex solution; And / or, the aminosilane in the aminosilane solution includes any one of KH-550, KH-602, KH-792 or KH-540 or a combination of at least two thereof.

7. The powder metallurgy friction material according to claim 1, characterized in that: The microencapsulated self-repairing agent comprises self-repairing polymer microcapsules and catalyst microcapsules in a mass ratio of 100:0.1-100:0.

5.

8. The powder metallurgy friction material according to claim 7, characterized in that: The preparation method of the self-healing polymer microcapsule comprises: dissolving the self-healing polymer in a hydrophobic solvent to form an oil phase; dissolving an emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1 μm-20 μm; adding a diamine aqueous solution, and then dripping isocyanate to form an interfacial polycondensation reaction, the reaction temperature is 20° C.-60° C., and the reaction time is 30 min-120 min, to obtain a self-healing polymer microcapsule; And / or, the preparation method of the self-healing polymer comprises: dissolving a hydroxy vinyl silicone resin and a disulfide bond-containing compound in a solvent; adding a first catalyst and stirring evenly; heating at 50° C.-100° C. for reaction; after the reaction is completed, filtering, washing and drying to obtain the self-healing polymer; And / or, the preparation method of the catalyst microcapsule comprises: dissolving the second catalyst in a hydrophobic solvent to form an oil phase; dissolving an emulsifier in water to form an aqueous phase; dispersing the oil phase in the aqueous phase to form an O / W emulsion with a particle size of 1 μm-20 μm; adding a diamine aqueous solution, and then dripping isocyanate to form an interfacial polycondensation reaction, the reaction temperature is 20°C-60°C, the reaction time is 30min-120min, and the catalyst microcapsule is obtained; And / or, the second catalyst includes any one of an organic tin compound, an organic titanium compound or a thiol compound, or a combination of at least two thereof.

9. A method for preparing a powder metallurgy friction material, characterized in that: The preparation method comprises: mixing nano copper powder, silicon carbide nanoparticles, aluminum oxide nanoparticles, molybdenum disulfide, hexagonal boron nitride and microencapsulated self-healing agent according to a formula to obtain a mixed powder; and cold pressing and sintering the mixed powder in sequence to obtain the powder metallurgy friction material according to any one of claims 1 to 9.

10. The preparation method according to claim 9, characterized in that: The cold pressing pressure is 550MPa-650MPa; And / or, the sintering temperature is 800°C-1300°C; And / or, the sintering time is 30 min-120 min.

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