Nickel-based powder metallurgy friction material and preparation method thereof

Abstract

The invention relates to the field of design and preparation of powder metallurgy friction materials, in particular to a nickel-based powder metallurgy friction material and a preparation method thereof. Comprising the following components of 40-50 parts by weight of nickel powder, 8-15 parts by weight of iron powder, 5-12 parts by weight of chromium powder, 8-16 parts by weight of potassium titanate whiskers, 12-20 parts by weight of graphite, 3-8 parts by weight of titanium carbide, 1-5 parts by weight of zinc sulfide and 1-5 parts by weight of aluminum-coated antimony sulfide, and the weight ratio of the aluminum-coated antimony sulfide to the zinc sulfide is (1-2): (1-2). In the aluminum-coated antimony sulfide, the content of aluminum is 8-35wt%; the total sum of zinc sulfide and aluminum-coated antimony sulfide does not exceed 8 parts by weight, and the friction coefficient is 0.40-0.45 and is higher than that of a traditional copper-based friction material; the friction stability coefficient is greater than or equal to 0.90, and excellent stability is shown; the abrasion loss is smaller than or equal to 0.04 cm < 3 > / MJ (under the simulated braking condition of 500 km / h).

Description

Technical Field

[0001] The invention relates to the field of design and preparation of powder metallurgy friction materials, in particular to a nickel-based powder metallurgy friction material and a preparation method thereof. Background Art

[0002] The high-speed development of modern transportation tools such as high-speed trains has put forward higher performance requirements for friction brake materials. The current mainstream copper-based powder metallurgy friction materials are prone to unstable friction coefficients and increased wear under high temperature, high speed and heavy load conditions. In recent years, carbon-ceramic composite materials have gradually been used as brake disc materials for high-speed trains due to their advantages such as light weight and high temperature resistance. However, existing matching friction materials are often difficult to adapt to this new type of brake disc material. Although copper-based powder metallurgy friction materials have undergone many improvements, such as adding sulfide lubricants, they still have insufficient performance under ultra-high speed conditions. Summary of the invention

[0003] The present invention provides a nickel-based powder metallurgy friction material and a preparation method thereof, which uses nickel powder as a matrix and adds potassium titanate whiskers, zinc sulfide, titanium carbide and other components in specific proportions to achieve excellent friction performance under high-speed and high-temperature conditions.

[0004] The object of the present invention is to provide a nickel-based powder metallurgy friction material, wherein the raw material components used in the material include the following components in parts by weight: 40-50 parts by weight of nickel powder, 8-15 parts by weight of iron powder, 5-12 parts by weight of chromium powder, 8-16 parts by weight of potassium titanate whisker, 12-20 parts by weight of graphite, 3-8 parts by weight of titanium carbide, 1-5 parts by weight of zinc sulfide, and 1-5 parts by weight of aluminum-clad antimony sulfide, wherein the weight ratio of the aluminum-clad antimony sulfide to the zinc sulfide is 1-2:1-2; the aluminum content in the aluminum-clad antimony sulfide is 8-35% by weight; the total amount of the zinc sulfide and the aluminum-clad antimony sulfide does not exceed 8 parts by weight;

[0005] The aluminum-clad antimony sulfide is prepared by the following steps:

[0006] Antimony sulfide powder is dispersed in deionized water at a concentration of 5-30 g / L, and stirred to obtain a uniform suspension; an aluminum sulfate solution with a concentration of 0.01-0.06 mol / L is added, and a sodium borohydride solution with a concentration of 0.01-0.06 mol / L is added dropwise to perform reduction deposition of aluminum ions under stirring; during reduction, the pH value of the system is controlled at 7-8, the reaction temperature is controlled at 50-75° C., and the reaction time is controlled at 1.5-2.5 hours; after the reaction is completed, the powder is washed with deionized water, and then dried at 80-120° C. for 12-24 hours in a vacuum or inert atmosphere to obtain aluminum-coated antimony sulfide powder.

[0007] Specifically, the particle size of the zinc sulfide is less than 100 mesh; the particle size of the aluminum-clad antimony sulfide is less than 100 mesh.

[0008] Specifically, the purity of the zinc sulfide is greater than 99.5%, and the purity of the aluminum-clad antimony sulfide is greater than 99.0%.

[0009] Specifically, the purity of the nickel powder is greater than 99.5%, and the particle size is 200-400 mesh; the purity of the iron powder is greater than 99.0%, and the particle size is 200-300 mesh; the purity of the chromium powder is greater than 99.2%, and the particle size is less than 200 mesh; the graphite carbon content is greater than 99.0%, and the particle size is 20-150 mesh; the purity of the titanium carbide is greater than 99.0%, and the particle size is 200-325 mesh.

[0010] Specifically, the potassium titanate whisker has a purity greater than 98.0%, an aspect ratio of 30-100, a diameter of 0.1-1.0 μm, and a length of 10-30 μm.

[0011] Specifically, the raw material components, measured in parts by weight, include the following components: 45-48 parts by weight of nickel powder, 10-12 parts by weight of iron powder, 7-9 parts by weight of chromium powder, 10-14 parts by weight of potassium titanate whiskers, 14-18 parts by weight of graphite, 4-6 parts by weight of titanium carbide, 2-3 parts by weight of zinc sulfide, and 2-3 parts by weight of aluminum-coated antimony sulfide.

[0012] A method for preparing the nickel-based powder metallurgy friction material as described above comprises the following steps:

[0013] (1) Mixing raw materials: nickel powder, iron powder, chromium powder and graphite powder are mixed according to the designed composition; potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide are mixed according to the designed composition; the two mixed powders are mixed again, and then 2-4% of the total weight of the prepared powder is added with a polyvinyl alcohol aqueous solution, the concentration of which is 5-10%, and the mixture is mixed in a ball mill for 8-12 hours to obtain a uniform powder; the mixed powder is vacuum dried at 70-90° C. for 4-8 hours;

[0014] (2) Pressing and molding: adding the powder mixed evenly in step (1) into a mold, and cold pressing to obtain a molded blank;

[0015] (3) Sintering: placing the formed blank obtained in step (2) in a sintering furnace under a hydrogen or argon protective atmosphere, heating to 1050-1150°C at a heating rate of 5-10°C / min, keeping the temperature for 1.5-2.5 hours, and then cooling to room temperature at a cooling rate not higher than 10°C / min to obtain a nickel-based powder metallurgy friction material.

[0016] Specifically, the cold pressing pressure in step (2) is 300-400 MPa, and the holding time is 10-20 seconds.

[0017] Specifically, the rotation speed of the ball mill in step (1) is 200-300 rpm, and the ball-to-material ratio is 3:1-5:1.

[0018] Specifically, in step (3), the oxygen content in the sintering atmosphere is less than 10 ppm, and the gas pressure is 0.1-0.5 MPa.

[0019] The nickel-based powder metallurgy friction material of the present invention has excellent friction stability and wear resistance under ultra-high speed (500 km / h) and high temperature (above 800° C.):

[0020] Friction coefficient: 0.40-0.45, higher than traditional copper-based friction materials;

[0021] Friction stability coefficient: ≥0.90, showing excellent stability;

[0022] Wear amount: ≤0.04cm 3 / MJ (simulated braking condition of 500km / h);

[0023] When used in pair with carbon-ceramic composite brake discs, it exhibits lower pair wear and better compatibility. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. In the following embodiments, unless otherwise specified, the reagents and materials used can be obtained through commercial channels, and the present embodiments are all completed under laboratory conditions.

[0025] Example 1

[0026] A nickel-based powder metallurgy friction material comprises the following raw material components in parts by weight: 40 parts by weight of nickel powder, 8 parts by weight of iron powder, 5 parts by weight of chromium powder, 8 parts by weight of potassium titanate whiskers, 12 parts by weight of graphite, 3 parts by weight of titanium carbide, 1 part by weight of zinc sulfide, and 1 part by weight of aluminum-clad antimony sulfide, wherein the weight ratio of the aluminum-clad antimony sulfide to the zinc sulfide is 1:1; the aluminum content of the aluminum-clad antimony sulfide is 8% by weight.

[0027] The purity of the nickel powder is 99.5%, and the particle size is 200 mesh; the purity of the iron powder is 99.0%, and the particle size is 200 mesh; the purity of the chromium powder is 99.2%, and the particle size is 150 mesh; the purity of the potassium titanate whisker is 98.0%, the aspect ratio is 30, the diameter is 0.1 μm, and the length is 10 μm; the graphite carbon content is 99.0%, and the particle size is 20 mesh; the purity of the titanium carbide is 99.0%, and the particle size is 200 mesh; the purity of the zinc sulfide is 99.5%, and the particle size is 80 mesh; the purity of the aluminum-clad antimony sulfide is 99.0%, and the particle size is 80 mesh.

[0028] The aluminum-coated antimony sulfide is prepared by the following steps: dispersing antimony sulfide powder in deionized water at a concentration of 5 g / L, stirring to obtain a uniform suspension; adding an aluminum sulfate solution with a concentration of 0.01 mol / L, and dropping a sodium borohydride solution with a concentration of 0.01 mol / L to perform reduction deposition of aluminum ions under stirring; during reduction, the pH value of the system is controlled at 7, the reaction temperature is controlled at 50° C., and the reaction time is controlled at 1.5 hours; after the reaction is completed, washing with deionized water, and then drying at 80° C. in a vacuum for 12 hours to obtain the aluminum-coated antimony sulfide powder.

[0029] The preparation method of the nickel-based powder metallurgy friction material comprises the following steps: (1) mixing raw materials: mixing nickel powder, iron powder, chromium powder and graphite powder according to the designed composition; mixing potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide according to the designed composition; mixing the two mixed powders again, and then adding 2% polyvinyl alcohol aqueous solution of the total weight of the prepared powder, the concentration of the polyvinyl alcohol aqueous solution is 5%, mixing for 8 hours in a ball mill, the rotation speed of the ball mill is 200 rpm, and the ball-to-material ratio is 3:1, to obtain a uniform powder; vacuum grinding the mixed powder at 70°C Dry for 4 hours; (2) Pressing: Add the powder mixed evenly in step (1) into a mold, and obtain a formed blank by cold pressing. The cold pressing pressure is 300 MPa and the holding time is 10 seconds; (3) Sintering: Place the formed blank obtained in step (2) in a sintering furnace under a hydrogen protective atmosphere. The oxygen content in the sintering atmosphere is 10 ppm and the air pressure is 0.1 MPa. Heat to 1050°C at a heating rate of 5°C / min, keep warm for 1.5 hours, and then cool to room temperature at a cooling rate of 10°C / min to obtain a nickel-based powder metallurgy friction material.

[0030] In this embodiment, nickel powder is used as the matrix material, which not only improves the high-temperature stability of the material, but also forms a good interface bonding with titanium carbide, significantly improving the structural stability of the material. The addition of potassium titanate whiskers strengthens the overall skeleton structure of the material, and its fibrous morphology forms local stress dispersion points during the friction process, effectively alleviating the stress concentration phenomenon during high-temperature friction. Zinc sulfide, as a high-temperature lubricating component, forms a stable lubricating film at the high-temperature friction interface, while aluminum-coated antimony sulfide slowly releases antimony sulfide at high temperatures through the protective effect of the aluminum layer, extending the duration of the lubrication effect.

[0031] The friction coefficient of the material obtained in Example 1 was 0.41, the friction stability coefficient was 0.91, and the wear loss was 0.04 cm 3 / MJ, fully meets the technical requirements of ultra-high-speed braking.

[0032] Example 2

[0033] A nickel-based powder metallurgy friction material comprises the following raw material components in parts by weight: 50 parts by weight of nickel powder, 15 parts by weight of iron powder, 12 parts by weight of chromium powder, 16 parts by weight of potassium titanate whiskers, 20 parts by weight of graphite, 8 parts by weight of titanium carbide, 5 parts by weight of zinc sulfide, and 3 parts by weight of aluminum-clad antimony sulfide, wherein the weight ratio of the aluminum-clad antimony sulfide to the zinc sulfide is 3:5; in the aluminum-clad antimony sulfide, the aluminum content is 35% by weight.

[0034] The purity of the nickel powder is 99.9% and the particle size is 400 mesh; the purity of the iron powder is 99.5% and the particle size is 300 mesh; the purity of the chromium powder is 99.8% and the particle size is 180 mesh; the purity of the potassium titanate whisker is 99.0%, the aspect ratio is 100, the diameter is 1.0 μm, and the length is 30 μm; the graphite carbon content is 99.5% and the particle size is 150 mesh; the purity of the titanium carbide is 99.5% and the particle size is 325 mesh; the purity of the zinc sulfide is 99.9% and the particle size is 100 mesh; the purity of the aluminum-clad antimony sulfide is 99.5% and the particle size is 100 mesh.

[0035] The aluminum-coated antimony sulfide is prepared by the following steps: dispersing antimony sulfide powder in deionized water at a concentration of 30 g / L, stirring to obtain a uniform suspension; adding an aluminum sulfate solution with a concentration of 0.06 mol / L, and dropping a sodium borohydride solution with a concentration of 0.06 mol / L to perform reduction deposition of aluminum ions under stirring; during reduction, the pH value of the system is controlled at 8, the reaction temperature is controlled at 75° C., and the reaction time is controlled at 2.5 hours; after the reaction is completed, washing with deionized water, and then drying at 120° C. for 24 hours in an inert atmosphere to obtain the aluminum-coated antimony sulfide powder.

[0036] The preparation method of the nickel-based powder metallurgy friction material comprises the following steps: (1) mixing raw materials: mixing nickel powder, iron powder, chromium powder and graphite powder according to the designed composition; mixing potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide according to the designed composition; mixing the two mixed powders again, and then adding a polyvinyl alcohol aqueous solution of 4% of the total weight of the prepared powder, the concentration of the polyvinyl alcohol aqueous solution is 10%, and mixing for 12 hours in a ball mill, the rotation speed of the ball mill is 300 rpm, and the ball-to-material ratio is 5:1, to obtain a uniform powder; and grinding the mixed powder at 90°C. Vacuum drying for 8 hours; (2) pressing: adding the powder mixed evenly in step (1) into a mold, and obtaining a formed blank by cold pressing, the cold pressing pressure is 400 MPa, and the holding time is 20 seconds; (3) sintering: placing the formed blank obtained in step (2) in a sintering furnace under an argon protective atmosphere, the oxygen content in the sintering atmosphere is 5 ppm, the air pressure is 0.5 MPa, heating to 1150°C at a heating rate of 10°C / min, holding time is 2.5 hours, and then cooling to room temperature at a cooling rate of 5°C / min to obtain a nickel-based powder metallurgy friction material.

[0037] In this embodiment, a higher content of nickel powder and potassium titanate whiskers is used, which significantly improves the high temperature strength of the material, while the increased titanium carbide content further enhances the hardness and wear resistance of the material. The higher content of zinc sulfide and aluminum-clad antimony sulfide enables the material to maintain good lubrication properties under extremely high temperature conditions, and the increase in aluminum content significantly improves the thermal stability of antimony sulfide. High-purity raw materials combined with refined process parameters ensure the high performance of the final product.

[0038] The friction coefficient of the material obtained in Example 2 was 0.45, the friction stability coefficient was 0.95, and the wear loss was 0.02 cm 3 / MJ, showing extremely excellent high-temperature and high-speed friction performance, is particularly suitable for emergency braking systems of ultra-high-speed trains.

[0039] Example 3

[0040] A nickel-based powder metallurgy friction material comprises the following raw material components in parts by weight: 45 parts by weight of nickel powder, 12 parts by weight of iron powder, 8 parts by weight of chromium powder, 12 parts by weight of potassium titanate whiskers, 16 parts by weight of graphite, 5 parts by weight of titanium carbide, 3 parts by weight of zinc sulfide, and 2 parts by weight of aluminum-clad antimony sulfide, wherein the weight ratio of the aluminum-clad antimony sulfide to the zinc sulfide is 2:3; in the aluminum-clad antimony sulfide, the aluminum content is 20% by weight.

[0041] The purity of the nickel powder is 99.7%, and the particle size is 300 mesh; the purity of the iron powder is 99.2%, and the particle size is 250 mesh; the purity of the chromium powder is 99.5%, and the particle size is 200 mesh; the purity of the potassium titanate whisker is 98.5%, the aspect ratio is 60, the diameter is 0.5 μm, and the length is 20 μm; the graphite carbon content is 99.2%, and the particle size is 80 mesh; the purity of the titanium carbide is 99.2%, and the particle size is 250 mesh; the purity of the zinc sulfide is 99.7%, and the particle size is 90 mesh; the purity of the aluminum-clad antimony sulfide is 99.2%, and the particle size is 90 mesh.

[0042] The aluminum-coated antimony sulfide is prepared by the following steps: dispersing antimony sulfide powder in deionized water at a concentration of 15 g / L, stirring to obtain a uniform suspension; adding an aluminum sulfate solution with a concentration of 0.03 mol / L, and dropping a sodium borohydride solution with a concentration of 0.03 mol / L to perform reduction deposition of aluminum ions under stirring; during reduction, the pH value of the system is controlled at 7.5, the reaction temperature is controlled at 65° C., and the reaction time is controlled at 2 hours; after the reaction is completed, washing with deionized water, and then drying at 100° C. for 18 hours in an inert atmosphere to obtain the aluminum-coated antimony sulfide powder.

[0043] The preparation method of the nickel-based powder metallurgy friction material comprises the following steps: (1) mixing raw materials: mixing nickel powder, iron powder, chromium powder and graphite powder according to the designed composition; mixing potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide according to the designed composition; mixing the two mixed powders again, and then adding a polyvinyl alcohol aqueous solution of 3% of the total weight of the prepared powder, wherein the concentration of the polyvinyl alcohol aqueous solution is 7.5%, and mixing for 10 hours in a ball mill, wherein the rotation speed of the ball mill is 250 rpm and the ball-to-material ratio is 4:1, to obtain a uniform powder; and mixing the mixed powder at 8 0℃ vacuum drying for 6 hours; (2) pressing: adding the powder mixed evenly in step (1) into a mold, and obtaining a formed blank by cold pressing, the cold pressing pressure is 350MPa, and the holding time is 15 seconds; (3) sintering: placing the formed blank obtained in step (2) in a sintering furnace under a hydrogen protective atmosphere, the oxygen content in the sintering atmosphere is 7ppm, the air pressure is 0.3MPa, heating to 1100℃ at a heating rate of 8℃ / min, holding time is 2 hours, and then cooling to room temperature at a cooling rate of 7℃ / min to obtain a nickel-based powder metallurgy friction material.

[0044] In this embodiment, the proportion of each component reaches a balanced state, so that the material has good hardness, high temperature strength and lubrication performance. Compared with Example 1 and Example 2, the potassium titanate whisker and titanium carbide content in this embodiment are moderate, so that the material will not be too brittle while maintaining sufficient mechanical strength; the proportion of zinc sulfide and aluminum-clad antimony sulfide is designed so that the material can obtain a stable lubrication effect in different temperature ranges. The 20% aluminum content in aluminum-clad antimony sulfide ensures sufficient protection without excessively affecting the lubrication function of antimony sulfide.

[0045] The friction coefficient of the material obtained in Example 3 was 0.43, the friction stability coefficient was 0.93, and the wear loss was 0.03 cm 3 / MJ, showing comprehensive and balanced performance characteristics, suitable for high-speed braking scenarios under various complex working conditions.

[0046] Example 4

[0047] A nickel-based powder metallurgy friction material comprises the following raw material components in parts by weight: 47 parts by weight of nickel powder, 10 parts by weight of iron powder, 10 parts by weight of chromium powder, 10 parts by weight of potassium titanate whisker, 15 parts by weight of graphite, 4 parts by weight of titanium carbide, 2 parts by weight of zinc sulfide, and 2 parts by weight of aluminum-clad antimony sulfide, wherein the weight ratio of the aluminum-clad antimony sulfide to the zinc sulfide is 1:1; the aluminum content in the aluminum-clad antimony sulfide is 15% by weight.

[0048] The purity of the nickel powder is 99.8%, and the particle size is 350 mesh; the purity of the iron powder is 99.3%, and the particle size is 250 mesh; the purity of the chromium powder is 99.6%, and the particle size is 190 mesh; the purity of the potassium titanate whisker is 98.8%, the aspect ratio is 80, the diameter is 0.8 μm, and the length is 25 μm; the carbon content of the graphite is 99.3%, and the particle size is 100 mesh; the purity of the titanium carbide is 99.3%, and the particle size is 280 mesh; the purity of the zinc sulfide is 99.8%, and the particle size is 95 mesh; the purity of the aluminum-clad antimony sulfide is 99.3%, and the particle size is 95 mesh.

[0049] The aluminum-coated antimony sulfide is prepared by the following steps: dispersing antimony sulfide powder in deionized water at a concentration of 20 g / L, stirring to obtain a uniform suspension; adding an aluminum sulfate solution with a concentration of 0.04 mol / L, and dropping a 0.04 mol / L sodium borohydride solution to perform reduction deposition of aluminum ions under stirring; during reduction, the system pH value is controlled at 7.8, the reaction temperature is controlled at 70°C, and the reaction time is controlled at 2.2 hours; after the reaction is completed, washing with deionized water, and then drying at 110°C in a vacuum for 20 hours to obtain the aluminum-coated antimony sulfide powder.

[0050] The preparation method of the nickel-based powder metallurgy friction material comprises the following steps: (1) mixing raw materials: mixing nickel powder, iron powder, chromium powder and graphite powder according to the designed composition; mixing potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide according to the designed composition; mixing the two mixed powders again, and then adding 3.5% polyvinyl alcohol aqueous solution of the total weight of the prepared powder, the concentration of the polyvinyl alcohol aqueous solution is 8%, and mixing for 11 hours in a ball mill, the rotation speed of the ball mill is 270rpm, and the ball-to-material ratio is 4.5:1, to obtain a uniform powder; and mixing the mixed powder at 8 5℃ vacuum drying for 7 hours; (2) pressing: adding the powder mixed evenly in step (1) into a mold, and obtaining a formed blank by cold pressing, the cold pressing pressure is 375MPa, and the holding time is 18 seconds; (3) sintering: placing the formed blank obtained in step (2) in a sintering furnace under an argon protective atmosphere, wherein the oxygen content in the sintering atmosphere is 6ppm and the air pressure is 0.4MPa, heating to 1120℃ at a heating rate of 9℃ / min, holding time is 2.2 hours, and then cooling to room temperature at a cooling rate of 6℃ / min to obtain a nickel-based powder metallurgy friction material.

[0051] The nickel powder content in Example 4 is relatively high, providing better matrix toughness, and with appropriate amounts of chromium powder and iron powder, a strong and tough composite matrix is ​​formed. The synergistic effect of potassium titanate whiskers and titanium carbide gives the material good thermal stability and wear resistance, and the equal addition of zinc sulfide and aluminum-coated antimony sulfide makes the lubrication effect balanced in all temperature ranges.

[0052] The friction coefficient of the material obtained in Example 4 was 0.42, the friction stability coefficient was 0.92, and the wear loss was 0.035 cm 3 / MJ. In long-term durability tests, the material showed excellent fatigue resistance and thermal stability, and is particularly suitable for high-frequency and high-intensity braking scenarios.

[0053] Example 5

[0054] A nickel-based powder metallurgy friction material comprises the following raw material components in parts by weight: 42 parts by weight of nickel powder, 14 parts by weight of iron powder, 6 parts by weight of chromium powder, 14 parts by weight of potassium titanate whiskers, 18 parts by weight of graphite, 7 parts by weight of titanium carbide, 4 parts by weight of zinc sulfide, and 4 parts by weight of aluminum-clad antimony sulfide, wherein the weight ratio of the aluminum-clad antimony sulfide to the zinc sulfide is 1:1; the aluminum content of the aluminum-clad antimony sulfide is 25% by weight.

[0055] The purity of the nickel powder is 99.6%, and the particle size is 320 mesh; the purity of the iron powder is 99.1%, and the particle size is 220 mesh; the purity of the chromium powder is 99.4%, and the particle size is 170 mesh; the purity of the potassium titanate whisker is 98.3%, the aspect ratio is 50, the diameter is 0.3 μm, and the length is 15 μm; the graphite carbon content is 99.1%, and the particle size is 60 mesh; the purity of the titanium carbide is 99.1%, and the particle size is 220 mesh; the purity of the zinc sulfide is 99.6%, and the particle size is 85 mesh; the purity of the aluminum-clad antimony sulfide is 99.1%, and the particle size is 85 mesh.

[0056] The aluminum-coated antimony sulfide is prepared by the following steps: dispersing antimony sulfide powder in deionized water at a concentration of 10 g / L, stirring to obtain a uniform suspension; adding an aluminum sulfate solution with a concentration of 0.02 mol / L, and dropping a sodium borohydride solution with a concentration of 0.02 mol / L to perform reduction deposition of aluminum ions under stirring; during reduction, the pH value of the system is controlled at 7.3, the reaction temperature is controlled at 60° C., and the reaction time is controlled at 1.8 hours; after the reaction is completed, washing with deionized water, and then drying at 90° C. in an inert atmosphere for 15 hours to obtain the aluminum-coated antimony sulfide powder.

[0057] The preparation method of the nickel-based powder metallurgy friction material comprises the following steps: (1) mixing raw materials: mixing nickel powder, iron powder, chromium powder and graphite powder according to the designed composition; mixing potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide according to the designed composition; mixing the two mixed powders again, and then adding 2.5% polyvinyl alcohol aqueous solution of the total weight of the prepared powder, the concentration of the polyvinyl alcohol aqueous solution is 6%, and mixing for 9 hours in a ball mill, the rotation speed of the ball mill is 230rpm, and the ball-to-material ratio is 3.5:1, to obtain uniform powder; and grinding the mixed powder at 75 ℃ vacuum drying for 5 hours; (2) pressing: adding the powder mixed evenly in step (1) into a mold, and obtaining a formed blank by cold pressing, the cold pressing pressure is 325MPa, and the holding time is 12 seconds; (3) sintering: placing the formed blank obtained in step (2) in a sintering furnace under a hydrogen protective atmosphere, the oxygen content in the sintering atmosphere is 8ppm, the air pressure is 0.2MPa, heating to 1080℃ at a heating rate of 7℃ / min, holding time is 1.8 hours, and then cooling to room temperature at a cooling rate of 8℃ / min to obtain a nickel-based powder metallurgy friction material.

[0058] In the material obtained in Example 5, potassium titanate whiskers and graphite have high contents, forming a more complex three-dimensional network structure, significantly improving the thermal stability and thermal conductivity of the material, and reducing thermal fatigue damage during high-temperature friction. The high content of zinc sulfide and aluminum-coated antimony sulfide enhances the lubrication performance and high-temperature oxidation resistance of the material, and the increase in titanium carbide makes up for the hardness reduction problem that may be caused by the increase in lubricating components.

[0059] The friction coefficient of the material obtained in Example 5 was 0.40, the friction stability coefficient was 0.90, and the wear loss was 0.038 cm 3 / MJ. The material exhibits significant self-repairing ability under high-temperature repeated braking conditions, and a stable transfer film is formed on the friction surface, effectively slowing down the wear of the mating parts.

[0060] Comparative Example 1

[0061] Comparative Example 1 adopts a traditional copper-based powder metallurgy friction material formula, and the raw material components used, measured in parts by weight, include the following components: 53 parts by weight of copper powder, 18 parts by weight of iron powder, 8 parts by weight of ferrochrome powder, 19 parts by weight of graphite, 1 part by weight of molybdenum disulfide, and 1 part by weight of tin sulfide.

[0062] The preparation method of the copper-based powder metallurgy friction material is basically the same as the preparation method of the embodiment of the present invention, and the specific preparation steps are as follows: (1) raw material mixing: copper powder, iron powder, ferrochrome powder and graphite powder are mixed according to the designed composition; molybdenum disulfide and tin sulfide are mixed according to the designed composition; the two mixed powders are mixed again, and then kerosene of 3% of the total weight of the prepared powder is added, and mixed by a roller to obtain a uniform powder; (2) pressing and molding: the powder mixed uniformly in step (1) is added to a mold, and a molded blank is obtained by cold pressing, the pressure of the cold pressing is 30 MPa, and the holding time is 3 seconds; (3) sintering: the molded blank obtained in step (2) is placed in a pressure sintering furnace under a protective atmosphere, the sintering temperature is 930°C, the pressure is 1.8 MPa, the holding time is 2.5 hours, and then cooled in the furnace to obtain the copper-based powder metallurgy friction material.

[0063] Comparative Example 2

[0064] Comparative Example 2 adopts a nickel-based formula but does not contain potassium titanate whiskers and aluminum-coated antimony sulfide. The raw material components used, in parts by weight, include the following components: 45 parts by weight of nickel powder, 15 parts by weight of iron powder, 10 parts by weight of chromium powder, 20 parts by weight of graphite, 5 parts by weight of titanium carbide, and 5 parts by weight of zinc sulfide.

[0065] The preparation method of the nickel-based powder metallurgy friction material is basically the same as the preparation method of Example 3 of the present invention, but there are differences in raw material mixing, sintering temperature, etc. The specific preparation steps are as follows: (1) Raw material mixing: nickel powder, iron powder, chromium powder, graphite powder, titanium carbide, and zinc sulfide are mixed according to the designed composition; 3% polyvinyl alcohol aqueous solution of the total weight of the prepared powder is added, and mixed by a ball mill for 10 hours to obtain a uniform powder; the mixed powder is vacuum dried at 80°C for 6 hours; (2) Pressing and molding: the uniformly mixed powder in step (1) is added to a mold, and a molded blank is obtained by cold pressing, the cold pressing pressure is 350MPa, and the holding time is 15 seconds; (3) Sintering: the molded blank obtained in step (2) is placed in a sintering furnace under a hydrogen protective atmosphere, and heated to 1050°C at a heating rate of 8°C / min, and the holding time is 2 hours, and then cooled to room temperature to obtain a nickel-based powder metallurgy friction material.

[0066] Comparative Example 3

[0067] Comparative Example 3 adopts a nickel-based formula containing potassium titanate whiskers but uses ordinary tungsten disulfide (not aluminum-coated) instead of aluminum-coated antimony sulfide. The raw material components used are measured by weight and include the following components: 45 parts by weight of nickel powder, 12 parts by weight of iron powder, 8 parts by weight of chromium powder, 12 parts by weight of potassium titanate whiskers, 16 parts by weight of graphite, 5 parts by weight of titanium carbide, 3 parts by weight of zinc sulfide, and 2 parts by weight of tungsten disulfide.

[0068] The preparation method of the material is exactly the same as the preparation method of Example 3 of the present invention, except that the aluminum-coated antimony sulfide is replaced by tungsten disulfide.

[0069] Comparative Example 4

[0070] Comparative Example 4 adopts a nickel-based formula, but the potassium titanate whisker content is extremely low and the zinc sulfide content is too high. The raw material components used are measured in parts by weight, including the following components: 45 parts by weight of nickel powder, 15 parts by weight of iron powder, 10 parts by weight of chromium powder, 2 parts by weight of potassium titanate whiskers, 20 parts by weight of graphite, 3 parts by weight of titanium carbide, 10 parts by weight of zinc sulfide, and 1 part by weight of aluminum-coated antimony sulfide.

[0071] The preparation method of the material is basically the same as the preparation method of Example 4 of the present invention, except that the raw material ratio is different.

[0072] In order to comprehensively evaluate the performance differences between the present invention and the comparative example materials, we use the following test methods for systematic evaluation:

[0073] 1. High-speed friction performance test

[0074] The test was conducted using a JF300 high-speed friction and wear testing machine. The test conditions are as follows:

[0075] Dual material: Carbon-ceramic composite brake disc (density 2.2g / cm3 , hardness HRA85);

[0076] Test temperature: room temperature to 800°C (controlled by infrared heater);

[0077] Line speed: 0-140m / s (equivalent to 0-500km / h);

[0078] Contact pressure: 0.5-3.0MPa;

[0079] Braking mode: single emergency braking and continuous braking;

[0080] Sample size: annular specimen with an outer diameter of 25 mm, an inner diameter of 15 mm, and a thickness of 5 mm;

[0081] Test parameters: friction coefficient, friction stability coefficient, wear amount, surface temperature change;

[0082] 2. Physical performance test

[0083] Density test: using Archimedes drainage method;

[0084] Hardness test: using HB-3000 Brinell hardness tester;

[0085] Bending strength test: using WDW-100 electronic universal testing machine;

[0086] Thermal conductivity test: using thermal diffusion instrument;

[0087] Porosity test: water immersion method;

[0088] 3. High temperature thermal stability test

[0089] Thermogravimetric analysis (TGA): measures the thermal stability of materials by heating from room temperature to 900°C;

[0090] Thermomechanical analysis (TMA): measures the coefficient of thermal expansion of a material at high temperatures;

[0091] High temperature static oxidation test: keep the sample in air at 800℃ for 24 hours and measure the oxidation weight gain;

[0092] The test results and analysis are as follows:

[0093] High-speed friction performance test results

[0094] The following table lists the friction performance data of the embodiments of the present invention and the comparative examples under simulated 500 km / h emergency braking conditions:

[0095]

[0096]

[0097] From the test results, it can be seen that all embodiments of the present invention are significantly better than the comparative examples in terms of high-speed friction performance. In particular, the friction coefficient of comparative example 1 (traditional copper-based friction material) is only 0.33, the friction stability coefficient is 0.75, and the wear volume is as high as 0.150 cm 3 / MJ, which is mainly due to the decrease in strength of copper-based materials at high temperatures and the poor interface compatibility with carbon-ceramic composites.

[0098] Although Comparative Example 2 uses a nickel-based formula, its friction stability and wear resistance are still significantly lower than those of the present invention due to the lack of reinforcement of potassium titanate whiskers and lubrication of aluminum-coated antimony sulfide. Comparative Example 3 uses tungsten disulfide that is not coated with aluminum. Tungsten disulfide is easily oxidized and decomposed at high temperatures, which greatly reduces the lubrication effect. The potassium titanate whisker content of Comparative Example 4 is too low and the zinc sulfide content is too high, resulting in insufficient material strength and uneven distribution of lubricating components, resulting in poor friction stability.

[0099] It is worth noting that the maximum surface temperature of the embodiments of the present invention during braking is generally lower than that of the comparative examples, which indicates that the materials of the present invention have better thermal conductivity and thermal stability and can more effectively disperse and conduct friction heat.

[0100] Physical performance test results:

[0101]

[0102] The results of physical property tests show that the hardness and bending strength of the nickel-based friction material of the present invention are significantly higher than those of the comparative example, especially Example 2, whose Brinell hardness reaches 110HB and bending strength reaches 385MPa, which is mainly attributed to the synergistic reinforcement effect of the nickel matrix, potassium titanate whiskers and titanium carbide. Although the thermal conductivity of the copper-based material (Comparative Example 1) is relatively high, its hardness and strength drop sharply at high temperatures and cannot meet the requirements of ultra-high-speed braking.

[0103] The porosity of the embodiment of the present invention is controlled within a reasonable range (4.2-5.8%), which not only ensures that the material has a certain amount of pores to accommodate the lubricating component, but also ensures that the material has sufficient strength and hardness. In contrast, the porosity of comparative example 4 is too high (7.2%), which affects the overall strength of the material.

[0104] High temperature thermal stability test results: In the 900°C high temperature TGA test, the weight loss rate of the examples of the present invention was controlled within 3%, while the weight loss rate of comparative example 1 reached 7.5%, and that of comparative example 4 reached 5.2%. This shows that the material of the present invention has excellent thermal stability under extremely high temperature conditions. In particular, Example 2, whose thermogravimetric loss was only 1.8%, exhibited excellent high temperature stability.

[0105] Thermomechanical analysis shows that the thermal expansion coefficient of the embodiment of the present invention is 10-12×10 -6 / ℃, and the thermal expansion coefficient of carbon-ceramic composite materials (4-6×10 -6 / ℃) is relatively small, while the thermal expansion coefficient of comparative example 1 reaches 18×10 -6 / ℃, this huge difference in thermal expansion coefficient is the main reason for the thermal stress concentration when copper-based materials and carbon-ceramic composites are used together.

[0106] High temperature static oxidation test shows that the oxidation weight gain rate of the embodiment of the present invention after being kept in air at 800°C for 24 hours is 0.5-1.2%, which is significantly lower than 2.8-4.5% of the comparative example. This is mainly due to the protective oxide film formed by the nickel matrix and the aluminum-coated antimony sulfide component at high temperature, which effectively prevents further oxidation of the material.

[0107] Through comparative testing and analysis, the nickel-based powder metallurgy friction material of the present invention has the following significant advantages:

[0108] Excellent high-speed friction performance: high friction coefficient (0.40-0.45) and stable (stability coefficient ≥ 0.90), small wear (≤ 0.04cm 3 / MJ), fully meeting the ultra-high-speed (500km / h) braking requirements.

[0109] The physical properties are comprehensively improved: the hardness and strength are higher than those of traditional copper-based materials and other nickel-based comparative formulas, the thermal conductivity is moderate, and the porosity is reasonably controlled.

[0110] Excellent high temperature thermal stability: It maintains good structural integrity and performance stability at high temperatures of 800-900℃, has low oxidation weight gain, and its thermal expansion coefficient is close to that of carbon-ceramic composite materials.

[0111] These advantages make the nickel-based powder metallurgy friction material of the present invention particularly suitable for use in combination with carbon-ceramic composite brake discs to meet the braking requirements of the next generation of ultra-high-speed rail transportation and high-end equipment.

Claims

1. A nickel-based powder metallurgy friction material, characterized in that: The raw material components used include the following components in parts by weight: 40-50 parts by weight of nickel powder, 8-15 parts by weight of iron powder, 5-12 parts by weight of chromium powder, 8-16 parts by weight of potassium titanate whiskers, 12-20 parts by weight of graphite, 3-8 parts by weight of titanium carbide, 1-5 parts by weight of zinc sulfide, and 1-5 parts by weight of aluminum-clad antimony sulfide, wherein the weight ratio of aluminum-clad antimony sulfide to zinc sulfide is 1-2:1-2; the aluminum content of the aluminum-clad antimony sulfide is 8-35% by weight; and the total amount of zinc sulfide and aluminum-clad antimony sulfide does not exceed 8 parts by weight; The aluminum-clad antimony sulfide is prepared by the following steps: Antimony sulfide powder is dispersed in deionized water at a concentration of 5-30 g / L, and stirred to obtain a uniform suspension; an aluminum sulfate solution with a concentration of 0.01-0.06 mol / L is added, and a sodium borohydride solution with a concentration of 0.01-0.06 mol / L is added dropwise to perform reduction deposition of aluminum ions under stirring; during reduction, the pH value of the system is controlled at 7-8, the reaction temperature is controlled at 50-75° C., and the reaction time is controlled at 1.5-2.5 hours; after the reaction is completed, the powder is washed with deionized water, and then dried at 80-120° C. for 12-24 hours in a vacuum or inert atmosphere to obtain aluminum-coated antimony sulfide powder.

2. The nickel-based powder metallurgy friction material according to claim 1, characterized in that: The particle size of the zinc sulfide is less than 100 mesh; the particle size of the aluminum-clad antimony sulfide is less than 100 mesh.

3. The nickel-based powder metallurgy friction material according to claim 1, characterized in that: The purity of the zinc sulfide is greater than 99.5%, and the purity of the aluminum-clad antimony sulfide is greater than 99.0%.

4. The nickel-based powder metallurgy friction material according to claim 1, characterized in that: The purity of the nickel powder is greater than 99.5%, and the particle size is 200-400 mesh; the purity of the iron powder is greater than 99.0%, and the particle size is 200-300 mesh; the purity of the chromium powder is greater than 99.2%, and the particle size is less than 200 mesh; the carbon content of the graphite is greater than 99.0%, and the particle size is 20-150 mesh; the purity of the titanium carbide is greater than 99.0%, and the particle size is 200-325 mesh.

5. The nickel-based powder metallurgy friction material according to claim 1, characterized in that: The potassium titanate whisker has a purity greater than 98.0%, an aspect ratio of 30-100, a diameter of 0.1-1.0 μm, and a length of 10-30 μm.

6. The nickel-based powder metallurgy friction material according to claim 1, characterized in that: The raw material components include the following components in parts by weight: 45-48 parts by weight of nickel powder, 10-12 parts by weight of iron powder, 7-9 parts by weight of chromium powder, 10-14 parts by weight of potassium titanate whiskers, 14-18 parts by weight of graphite, 4-6 parts by weight of titanium carbide, 2-3 parts by weight of zinc sulfide, and 2-3 parts by weight of aluminum-coated antimony sulfide.

7. A method for preparing a nickel-based powder metallurgy friction material according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Mixing raw materials: nickel powder, iron powder, chromium powder and graphite powder are mixed according to the designed composition; potassium titanate whisker, titanium carbide, zinc sulfide and aluminum-coated antimony sulfide are mixed according to the designed composition; the two mixed powders are mixed again, and then 2-4% of the total weight of the prepared powder is added with a polyvinyl alcohol aqueous solution, the concentration of which is 5-10%, and the mixture is mixed in a ball mill for 8-12 hours to obtain a uniform powder; the mixed powder is vacuum dried at 70-90° C. for 4-8 hours; (2) Pressing and molding: adding the powder mixed evenly in step (1) into a mold, and cold pressing to obtain a molded blank; (3) Sintering: placing the formed blank obtained in step (2) in a sintering furnace under a hydrogen or argon protective atmosphere, heating to 1050-1150°C at a heating rate of 5-10°C / min, keeping the temperature for 1.5-2.5 hours, and then cooling to room temperature at a cooling rate not higher than 10°C / min to obtain a nickel-based powder metallurgy friction material.

8. The preparation method according to claim 7, characterized in that: The cold pressing pressure in step (2) is 300-400 MPa, and the holding time is 10-20 seconds.

9. The preparation method according to claim 7, characterized in that: The rotation speed of the ball mill in step (1) is 200-300 rpm, and the ball-to-material ratio is 3:1-5:

1.

10. The preparation method according to claim 7, characterized in that: The oxygen content in the sintering atmosphere in step (3) is less than 10 ppm and the gas pressure is 0.1-0.5 MPa.

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