Nano-diamond reinforced powder metallurgy brake pad friction body material and preparation method thereof

Abstract

The invention discloses a nano-diamond reinforced powder metallurgy brake pad friction body material and a preparation method thereof, and relates to a brake pad friction body material and a preparation method thereof. The problem that in the prior art, the stability of a braking system of a train at a high running speed cannot be achieved is solved. The friction body material comprises a matrix component, a lubricating component, a friction component and a basic reinforcing component, wherein the sum of the mass percentages of the matrix component, the lubricating component, the friction component and the basic reinforcing component is 100%; wherein the mass percent of the copper powder in the matrix component is 50%-70%, and the mass percent of the iron powder in the matrix component is 10%-30%; the mass percent of the lubricating component is 10%-20%; the mass percent of the friction component is 1%-5%; the mass percent of the nano-diamond in the enhanced component is 0.1%-1%; the friction component is composed of one or more of silicon dioxide, aluminum oxide, titanium carbide, tungsten carbide, silicon carbide powder and zirconium oxide powder; the lubricating component is composed of one or more of graphite, carbon nanotubes and molybdenum disulfide. Belongs to the technical field of powder metallurgy.

Description

Technical Field

[0001] The invention relates to a brake piece friction body material and a preparation method thereof, belonging to the technical field of powder metallurgy. Background Art

[0002] With rapid economic development and increasing travel demands, rail transit is also moving towards higher speeds. On September 21, 2017, the Fuxing China Standard EMU CR400 train entered service on the Beijing-Shanghai High-Speed ​​Railway, setting a new benchmark for high-speed rail operation at a speed of 350 kilometers per hour. China has become the country with the highest commercial high-speed rail speed in the world. From June 28 to 29, 2023, China Railway Corporation conducted performance verification of a series of new technological components at higher operating speeds on the Fuqing to Quanzhou section of the Fuzhou-Xiamen High-Speed ​​Railway. On the Meizhou Bay Cross-sea Bridge, the test train operated at a single-train speed of 453 kilometers per hour and a relative passing speed of 891 kilometers per hour; in the Haiwei Tunnel, the test train operated at a single-train speed of 420 kilometers per hour and a relative passing speed of 840 kilometers per hour. A total of 57 scientific research tests were completed during the verification process, with all indicators performing well. In 2024, China Railway Corporation will lead the production of the CR450 prototype and conduct type testing. High-speed rail speed increases are not simply a matter of acceleration; many factors are involved. Besides greater power and lighter weight, the most critical technology is braking performance. When the initial braking speed reaches 400 km / h, an emergency stop can generate temperatures of nearly 1,000 degrees Celsius on the friction surface of the brake disc and pad. Conventional powder metallurgy brake pads reach their performance limits at these temperatures. The resulting high temperatures soften the friction matrix, causing added components to fall off, increasing wear and degrading the pad's braking performance. Therefore, improving the high-temperature resistance and reducing wear of powder metallurgy friction materials, ensuring adequate interface lubrication, and stabilizing the friction coefficient are key to improving high-speed braking performance.

[0003] Nanodiamond is a type of non-metallic carbon material formed by carbon atoms in an sp3 hybrid manner. It is a diamond powder with an average particle size of nanometers. It combines the dual characteristics of nanoparticles and superhard materials, with a huge specific surface area, a large number of structural defects and surface oxygen-containing functional groups, etc., which makes it have great potential in the development of new materials with special properties.

[0004] Has the following properties:

[0005] 1. Structural Characteristics: Usually spherical or spherical in shape, composed of several nanometer-sized diamond particles. Its crystal structure is similar to that of macroscopic diamond, where carbon atoms form a tetrahedral structure in an sp3 hybridized manner.

[0006] 2. Mechanical properties: It has high strength and extremely high hardness. It is one of the hardest known materials and is harder than traditional micron-level diamonds.

[0007] Application areas: Due to its high hardness and wear resistance, it is widely used in surface coating materials such as cutting tools, bearings, drill bits and cutting tools. It is added as an additive to composite materials, coatings and paints to improve the mechanical properties, thermal conductivity and wear resistance of the materials. Nanodiamonds are added to intermetallic compounds. Copper, tin, and zinc intermetallic compounds containing nanodiamonds can be used as friction parts under very harsh working conditions, when plastic and liquid lubricating materials are often squeezed out. Nanodiamonds are ideal component materials for copper-zinc or copper-tin alloys. Based on the above excellent properties of nanodiamonds, the present invention adds them as a reinforcing component to the friction body material to improve the high temperature resistance of the friction body, reduce wear, and stabilize the friction coefficient.

[0008] An invention patent with publication number CN114833339A and application date May 6, 2022, discloses a high-temperature-resistant powder metallurgy friction material and heat-resistant brake pad, as well as their preparation methods and applications. The raw materials for this high-temperature-resistant powder metallurgy friction material include: 40-50% nickel-coated copper powder, 10-30% iron powder, 5-10% ferrochrome powder, 6-8% molybdenum disulfide, 5-10% nickel-coated graphite, and 1-3% silicon carbide. The nickel plating layer of the nickel-coated copper powder has a thickness of 2-5 μm, and the nickel plating layer of the nickel-coated graphite has a thickness of 5-10 μm. Heat-resistant brake pads made from this high-temperature-resistant powder metallurgy friction material exhibit strong heat resistance and maintain stable friction and wear performance during high-speed braking, making them suitable for use as heat-resistant brake pads for high-speed EMUs operating at speeds of 350 km / h to 400 km / h.

[0009] The invention patent with publication number CN113565907B and application date July 23, 2021 discloses a friction material for brake pads, which is used to solve the problem that brake pads can only be used at speeds below 350 km / h, and at higher speeds will cause defects such as decreased brake pad strength and attenuation of friction coefficient. The friction material for brake pads provided by the present invention comprises the following raw material components in parts by weight: 52 to 66 parts of a matrix component, 4 to 7 parts of a friction component, 15 to 28 parts of a reinforcing component and 19 to 32 parts of a lubricating component; wherein the matrix component comprises copper-clad iron powder, the friction component comprises tungsten carbide, and the reinforcing component comprises transition metal alloy powder; the lubricating component comprises any one or more of graphene and silicon carbide whiskers. The present invention effectively improves the heat resistance and matrix strength of the friction material, reduces thermal decay, and reduces its own wear rate. The present invention also provides a method for preparing a friction material and a brake pad for a motor vehicle.

[0010] Patent publication number CN116372163A, filed on December 5, 2022, discloses a high-speed train brake pad material containing fluidized, high-efficiency oxidized fibrous copper-based powder. This invention belongs to the field of brake material development technology. The raw materials used include, by mass percentage, the following components: 35-58% copper powder, 10-20% iron powder, 2-8% zirconium dioxide, 5-15% ferrochrome powder, 15-20% graphite, and 1-5% molybdenum disulfide. The copper powder contains fibrous copper powder at least 45%. The particle size distribution of the fibrous copper powder is as follows: 5-6% by weight for copper powder with a particle size of 5μm or less; 59-65% by weight for copper powder with a particle size of 5-20μm; and 30-33% by weight for particles greater than 20μm and less than or equal to 45μm. The material can be produced using conventional powder metallurgy methods. The product obtained by the present invention has high hardness, high shear strength, high compressive strength, more stable friction coefficient and lower wear under high-energy braking conditions. The present invention has reasonable component design and simple and controllable preparation process, which is convenient for large-scale industrial application.

[0011] The invention patent with publication number CN 115415515A and application date of December 2, 2022 discloses a friction body, which relates to the technical field of high-speed train brake pads. The friction body, in terms of mass percentage, includes the following components: 60wt% to 70wt% of a matrix component, 12wt% to 30wt% of a friction component, and 10wt% to 18wt% of a lubricating component; wherein the matrix component is a copper-tin-zinc alloy powder, and the friction component is a high-chromium, high-carbon ferrochrome powder. By adopting the above technical solution, the hardness and strength of the friction body formed are greatly improved, thereby further improving the friction performance and wear resistance of the friction body, and the mechanical properties and friction performance of the friction body are stable. The present invention also provides a method for preparing a friction body, a friction component, and a powder metallurgy brake pad.

[0012] The invention patent, with publication number CN110238380A and application date September 17, 2019, discloses a graphene-enhanced high-speed train brake pad material and its preparation method. This invention belongs to the field of powder metallurgy friction materials technology and addresses the technical problem of high-speed train brake pad material strength, wear resistance, and high-temperature resistance requirements. The solution is as follows: its raw materials consist of a matrix component, a matrix reinforcement component, a friction component, and a lubricating component, the sum of the mass percentages of each component being 100%. Specifically, it consists of copper powder, graphene or graphene oxide, iron powder, chromium oxide, zirconium oxide, graphite, and molybdenum disulfide. The preparation process includes four process stages: ball milling, mixing, molding, and sintering. The graphene-enhanced high-speed train brake pad prepared by the present invention has the characteristics of high strength, good temperature resistance, and wear resistance, and can fully meet the braking requirements of high-speed trains with speeds of 350 km / h and above.

[0013] The invention patent with publication number CN111779781A and application date July 8, 2020 discloses a brake pad and a method for manufacturing the same, which relates to the field of train braking technology to solve the problems of brake pads often occurring during the braking process of heavy-loaded locomotives, such as edge loss, corner loss, block loss, metal inlay, and abnormal wear. The brake pad includes a steel back and a friction body, and the steel back and the friction body are an integrated structure. The friction body includes a base component, a lubricating component, and a friction component. A groove matching the shape of the friction body is provided on the steel back. The brake pad includes the above-mentioned technical solution. The present invention provides a brake pad and a method for manufacturing the same for improving the service life of the brake pad.

[0014] However, the above technologies still cannot solve the stability problem of the train's braking system at higher operating speeds. Summary of the Invention

[0015] In order to solve the problem that the existing technology cannot solve the stability of the train braking system at high speed, the present invention proposes a nano-diamond reinforced powder metallurgy brake pad friction body material and a preparation method thereof.

[0016] The technical solution adopted by the present invention to solve the above problems is as follows: the nano-diamond reinforced powder metallurgy brake pad friction material of the present invention includes a matrix component, a lubricating component, a friction component and a basic reinforcing component, and the sum of the mass percentages of the matrix component, the lubricating component, the friction component and the basic reinforcing component is 100%;

[0017] The mass percentage of copper powder in the matrix component is 50% to 70%, and the mass percentage of iron powder is 10% to 30%.

[0018] The mass percentage of the lubricating component is 10%-20%;

[0019] The mass percentage of the friction component is 1% to 5%;

[0020] The mass percentage of nano-diamond in the reinforcing component is 0.1% to 1%;

[0021] The friction component is composed of one or more of silicon dioxide, aluminum oxide, titanium carbide, tungsten carbide, silicon carbide powder and zirconium oxide powder;

[0022] The lubricating component is composed of one or more of graphite, carbon nanotubes and molybdenum disulfide;

[0023] The particle size of nanodiamonds ranges from 70 to 150 nanometers.

[0024] Furthermore, the copper powder in the matrix component refers to electrolytic copper powder, and the iron powder in the matrix component refers to reduced iron powder.

[0025] The steps of the method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material of the present invention are as follows:

[0026] Step 1: using ultrasound to disperse nanodiamonds to form a nanodiamond dispersion, and testing the nanodiamond dispersion after the dispersion is completed;

[0027] Step 2: Pour the qualified nano-diamond dispersion into the copper powder, stir thoroughly and then dry;

[0028] Step 3, mixing iron powder, graphite, molybdenum disulfide, silicon carbide and zirconium oxide to obtain a mixture;

[0029] Step 4: batching the copper powder mixed with nanodiamonds and the mixture obtained in step 3 to form a powder;

[0030] Step 5: cold pressing the powder obtained in step 4 to obtain a green compact;

[0031] Step 6: Sintering the compact under a protective atmosphere to obtain the powder metallurgy brake pad friction body material.

[0032] Furthermore, in step 1, the dispersion liquid is distilled water, the ultrasonic dispersion time is 45-90 minutes, the inspection method is microscopic observation, the inspection standard is triangular sampling, and the acceptance standard is that the nano-diamond powder has no agglomeration when visually observed under a microscope.

[0033] Furthermore, the stirring time in step 2 is 20 to 60 minutes, the drying temperature is 80 to 180° C., and the drying time is 6 to 18 hours.

[0034] Furthermore, in step 5, the pressing pressure is 300-500 MPa, and the holding time is 5-15 seconds.

[0035] Furthermore, in step 6, the sintering temperature is 800-1000° C., the holding time is 0.5-2 hours, and the protective gas is hydrogen.

[0036] The beneficial effects of this invention are as follows: Nanodiamond-reinforced powder metallurgy brake pad friction material offers significant advantages. Its ultra-high strength and excellent thermal conductivity significantly enhance the material's overall hardness and wear resistance, effectively withstanding high braking pressures and friction. It also facilitates heat dissipation, lowers the friction interface temperature, and reduces thermal decay. Nanodiamonds exhibit excellent chemical stability, enhancing the material's corrosion resistance and adaptability to harsh environments. Furthermore, their low coefficient of friction helps optimize friction performance, maintaining a stable coefficient under varying braking conditions, and improving braking reliability and safety, fully meeting the braking requirements of high-speed trains operating at speeds of 350 km / h and above. DETAILED DESCRIPTION

[0037] Specific embodiment 1: A nano-diamond reinforced powder metallurgy brake pad friction body material includes a matrix component, a lubricating component, a friction component and a basic reinforcement component, and the sum of the mass percentages of the matrix component, the lubricating component, the friction component and the basic reinforcement component is 100%;

[0038] The mass percentage of copper powder in the matrix component is 50% to 70%, and the mass percentage of iron powder is 10% to 30%.

[0039] The mass percentage of the lubricating component is 10%-20%;

[0040] The mass percentage of the friction component is 1% to 5%;

[0041] The mass percentage of nano-diamond in the reinforcing component is 0.1% to 1%;

[0042] The friction component is composed of one or more of silicon dioxide, aluminum oxide, titanium carbide, tungsten carbide, silicon carbide powder and zirconium oxide powder;

[0043] The lubricating component is composed of one or more of graphite, carbon nanotubes and molybdenum disulfide;

[0044] The particle size of nanodiamonds ranges from 70 to 150 nanometers.

[0045] The copper powder in the matrix component refers to electrolytic copper powder, and the iron powder in the matrix component refers to reduced iron powder.

[0046] Among them, the nano-diamond reinforced powder metallurgy brake pad friction body material is composed of electrolytic copper powder, iron powder, graphite, molybdenum disulfide, silicon carbide, zirconium oxide and nano-diamond, wherein the mass percentage of each component is 50-70% electrolytic copper powder, 10-30% iron powder, 5-15% graphite, 3-10% molybdenum disulfide, 1-5% silicon carbide, 1-5% zirconium oxide and 0.1-1% nano-diamond.

[0047] Specific embodiment 2: A method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material, the specific steps include:

[0048] Step 1: using ultrasound to disperse nanodiamonds to form a nanodiamond dispersion, and testing the nanodiamond dispersion after the dispersion is completed;

[0049] Step 2: Pour the qualified nano-diamond dispersion into the copper powder, stir thoroughly and then dry;

[0050] Step 3, mixing iron powder, graphite, molybdenum disulfide, silicon carbide and zirconium oxide to obtain a mixture;

[0051] Step 4: batching the copper powder mixed with nanodiamonds and the mixture obtained in step 3 to form a powder;

[0052] Step 5: cold pressing the powder obtained in step 4 to obtain a green compact;

[0053] Step 6: Sintering the compact under a protective atmosphere to obtain the powder metallurgy brake pad friction body material.

[0054] Among them, the dispersion liquid in step 1 is distilled water, the ultrasonic dispersion time is 45-90 minutes, the inspection method is microscopic observation, the inspection standard is triangular sampling, and the qualified standard is that the nano-diamond powder has no agglomeration when visually observed under a microscope.

[0055] The stirring time in step 2 is 20 to 60 minutes, the drying temperature is 80 to 180° C., and the drying time is 6 to 18 hours.

[0056] In step 5, the pressing pressure is 300-500 MPa, and the holding time is 5-15 seconds.

[0057] In step 6, the sintering temperature is 800-1000° C., the holding time is 0.5-2 hours, and the protective gas is hydrogen.

[0058] Example

[0059] Example 1

[0060] Weigh 0.2 parts of nanodiamond powder, add distilled water, and disperse in an ultrasonic disperser for one hour. Pour the dispersed solution into 55 parts of electrolytic copper powder and stir. The mixed powder is then dried in a vacuum oven. Add 55 parts of electrolytic copper powder and 0.2 parts of nanodiamond into a mixer, along with 30 parts of reduced iron powder, 4 parts of silicon carbide powder, 1 part of zirconium oxide powder, 6 parts of graphite powder, and 7 parts of molybdenum disulfide. After mixing thoroughly, place the mixture in a mold and compression-mold it at a pressure of 500 MPa. Then, sinter it in a sintering furnace at 950°C in a hydrogen atmosphere for two hours to produce the nanodiamond-reinforced powder metallurgy brake pad friction material.

[0061] Example 2

[0062] 0.5 parts of nanodiamond powder were weighed, added to distilled water, and dispersed in an ultrasonic disperser for one hour. The dispersed solution was then poured into 60 parts of electrolytic copper powder and stirred. The mixed powder was then dried in a vacuum oven. The 60 parts of electrolytic copper powder and 0.5 parts of nanodiamond were then placed in a mixer. 20 parts of reduced iron powder, 3 parts of silicon carbide powder, 2 parts of zirconium oxide powder, 8 parts of graphite powder, and 5 parts of molybdenum disulfide were also added and mixed. After uniform mixing, the mixture was placed in a mold and compression-molded at a pressure of 500 MPa. The mixture was then sintered in a sintering furnace at 950°C in a hydrogen atmosphere for two hours to produce a nanodiamond-reinforced powder metallurgy friction material.

[0063] Example 3

[0064] 0.8 parts of nanodiamond powder were weighed, added to distilled water, and dispersed in an ultrasonic disperser for one hour. The dispersed solution was then poured into 65 parts of electrolytic copper powder and stirred. The mixed powder was then dried in a vacuum oven. The 65 parts of electrolytic copper powder and 0.8 parts of nanodiamond were then placed in a mixer. 10 parts of reduced iron powder, 2 parts of silicon carbide powder, 2 parts of zirconium oxide powder, 10 parts of graphite powder, and 3 parts of molybdenum disulfide were also added and mixed. After uniform mixing, the mixture was placed in a mold and compression-molded at a pressure of 500 MPa. The mixture was then sintered in a sintering furnace at 950°C in a hydrogen atmosphere for two hours to produce a nanodiamond-reinforced powder metallurgy friction material.

[0065] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A nano-diamond reinforced powder metallurgy brake pad friction material, characterized in that: The invention comprises a matrix component, a lubricating component, a friction component and a basic reinforcement component, wherein the sum of the mass percentages of the matrix component, the lubricating component, the friction component and the basic reinforcement component is 100%; The mass percentage of copper powder in the matrix component is 50% to 70%, and the mass percentage of iron powder is 10% to 30%. The mass percentage of the lubricating component is 10%-20%; The mass percentage of the friction component is 1% to 5%; The mass percentage of nano-diamond in the reinforcing component is 0.1% to 1%; The friction component is composed of one or more of silicon dioxide, aluminum oxide, titanium carbide, tungsten carbide, silicon carbide powder and zirconium oxide powder; The lubricating component is composed of one or more of graphite, carbon nanotubes and molybdenum disulfide; The particle size of nanodiamonds ranges from 70 to 150 nanometers.

2. The nano-diamond reinforced powder metallurgy brake pad friction material according to claim 1, characterized in that: The copper powder in the matrix component refers to electrolytic copper powder, and the iron powder in the matrix component refers to reduced iron powder.

3. A method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material, characterized in that: The specific steps include: Step 1: using ultrasound to disperse nanodiamonds to form a nanodiamond dispersion, and testing the nanodiamond dispersion after the dispersion is completed; Step 2: Pour the qualified nano-diamond dispersion into the copper powder, stir thoroughly and then dry; Step 3, mixing iron powder, graphite, molybdenum disulfide, silicon carbide and zirconium oxide to obtain a mixture; Step 4: batching the copper powder mixed with nanodiamonds and the mixture obtained in step 3 to form a powder; Step 5: cold pressing the powder obtained in step 4 to obtain a green compact; Step 6: Sintering the compact under a protective atmosphere to obtain the powder metallurgy brake pad friction body material.

4. The method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material according to claim 3, characterized in that: In step 1, the dispersion liquid is distilled water, the ultrasonic dispersion time is 45-90 minutes, the inspection method is microscopic observation, the inspection standard is triangular sampling, and the acceptance standard is that the nano-diamond powder has no agglomeration when visually observed under a microscope.

5. The method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material according to claim 3, characterized in that: The stirring time in step 2 is 20 to 60 minutes, the drying temperature is 80 to 180° C., and the drying time is 6 to 18 hours.

6. The method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material according to claim 3, characterized in that: In step 5, the pressing pressure is 300-500 MPa, and the holding time is 5-15 seconds.

7. The method for preparing a nano-diamond reinforced powder metallurgy brake pad friction material according to claim 3, characterized in that: In step 6, the sintering temperature is 800-1000° C., the holding time is 0.5-2 hours, and the protective gas is hydrogen.