CN117620158A - Nitride-containing copper-based powder metallurgy friction material and preparation method thereof - Google Patents
Nitride-containing copper-based powder metallurgy friction material and preparation method thereof Download PDFInfo
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 121
- 239000002783 friction material Substances 0.000 title claims abstract description 74
- 239000010949 copper Substances 0.000 title claims abstract description 58
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 56
- 238000004663 powder metallurgy Methods 0.000 title claims abstract description 40
- 150000004767 nitrides Chemical class 0.000 title claims abstract description 25
- 238000002360 preparation method Methods 0.000 title abstract description 13
- 239000000843 powder Substances 0.000 claims abstract description 93
- 239000002131 composite material Substances 0.000 claims abstract description 40
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 23
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 23
- 239000000956 alloy Substances 0.000 claims abstract description 23
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 23
- 239000010439 graphite Substances 0.000 claims abstract description 23
- 238000000498 ball milling Methods 0.000 claims abstract description 22
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims abstract description 22
- 229910000604 Ferrochrome Inorganic materials 0.000 claims abstract description 21
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims abstract description 20
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000002245 particle Substances 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 13
- 238000004519 manufacturing process Methods 0.000 claims abstract description 8
- 238000005245 sintering Methods 0.000 claims description 23
- 238000002156 mixing Methods 0.000 claims description 16
- 238000003825 pressing Methods 0.000 claims description 15
- 239000002994 raw material Substances 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 229910000831 Steel Inorganic materials 0.000 claims description 7
- 239000010959 steel Substances 0.000 claims description 7
- 238000000465 moulding Methods 0.000 claims description 6
- 239000011812 mixed powder Substances 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 239000012300 argon atmosphere Substances 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 2
- 229910052593 corundum Inorganic materials 0.000 claims description 2
- 230000007935 neutral effect Effects 0.000 claims description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 2
- 230000017525 heat dissipation Effects 0.000 abstract description 2
- 239000011159 matrix material Substances 0.000 description 24
- 239000000463 material Substances 0.000 description 21
- 238000012360 testing method Methods 0.000 description 16
- 239000000306 component Substances 0.000 description 14
- 238000005299 abrasion Methods 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
- 230000003014 reinforcing effect Effects 0.000 description 7
- 239000000919 ceramic Substances 0.000 description 5
- 230000001050 lubricating effect Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 3
- 238000005461 lubrication Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- 238000005411 Van der Waals force Methods 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910052582 BN Inorganic materials 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229910019589 Cr—Fe Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 150000001879 copper Chemical class 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010892 electric spark Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000011174 green composite Substances 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 238000007373 indentation Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000012779 reinforcing material Substances 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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- Powder Metallurgy (AREA)
Abstract
The invention discloses a nitride-containing copper-based powder metallurgy friction material and a preparation method thereof, wherein the nitride-containing copper-based powder metallurgy friction material comprises composite copper powder, iron powder, tin powder, crystalline flake graphite, hexagonal boron nitride powder, aluminum nitride powder and ferrochrome powder, the composite copper powder is obtained by ball milling a copper powder and reinforced particle powder with the mass ratio of 100:1-3 in a planetary high-energy ball mill, and the reinforced particle powder is high-entropy alloy powder or oxide powder. Compared with the prior art, the friction material has stable friction coefficient, wear resistance and working stability in the braking process, has the characteristics of high hardness, high strength, good heat dissipation and the like, and is more suitable for manufacturing high-speed train brake pads.
Description
Technical Field
The invention belongs to the field of powder metallurgy friction materials, and particularly relates to a nitride-containing copper-based powder metallurgy friction material and a preparation method thereof, in particular to a material for manufacturing a high-speed train brake pad.
The invention belongs to a green composite material for 3.3.3.3 other high-performance composite material rail transit in the important direction of 3.3 high-performance composite material industry in the 3 new material industry of strategic novel industry catalogue.
Background
Among various friction materials, copper-based powder metallurgy friction materials are the most reliable and widely applied high-speed train brake pad materials due to excellent mechanical properties, heat conduction capability and wear resistance. The copper-based powder metallurgy friction material can fully exert the advantages of the copper matrix, the friction component and the lubrication component and the synergistic effect of the copper matrix, the friction component and the lubrication component, and the final forming is realized by directly utilizing the powder metallurgy technology production, so that the copper-based powder metallurgy brake pad is widely used in the aspect of high-speed motor train unit braking with the speed of 350 km/h. The copper matrix dominates the overall properties of the material such as strength, toughness, thermal conductivity and the like; the friction-increasing phase plays a role in increasing friction, has high hardness and strength, can increase friction coefficient, and prevents the matrix from falling off during braking; the lubricating phase plays a role in lubricating, can stabilize the friction coefficient, improves the working stability and wear resistance of the friction material, is beneficial to reducing the wear of the dual material and ensures that the friction pair works stably. With the continuous improvement of the running speed of the motor train unit, the heat generated by friction braking is higher and higher, the instantaneous temperature of a friction surface can reach more than 900 ℃, and higher requirements are provided for the high-temperature stability and high-temperature oxidation resistance of a friction material. As a core component of a high-speed train braking system, the advantages and disadvantages of the performance of the friction material used for the brake pads directly affect the running speed of the train and the safety and stability of the braking process. The conventional copper-based friction material is easy to generate the problems of unstable friction coefficient, large abrasion loss and the like under the service condition, and development of a new friction material is needed to make up for the defects of the conventional friction material.
There have been reports of some related patents on copper-based powder metallurgy friction materials. The Chinese patent with publication number of CN115612947A discloses a powder metallurgy friction block and a preparation method thereof, wherein the friction block comprises the following components in mass fraction: 45-60% of atomized copper powder, 2-4% of Sn, 2-4% of Ni, 5-15% of copper-clad iron powder, 4-10% of high-carbon Cr-Fe powder, 1-3% of short carbon fiber and TiB 2 3 to 5 percent, 7 to 9 percent of NbC, 4.5 to 9 percent of artificial graphite, 0.5 to 1 percent of natural graphite and MoS 2 1-5% but the friction block has an average friction coefficient of 0.369-0.378 at a brake speed of 350km/h, which is relatively low. The Chinese patent publication No. CN114210966A discloses a high-stability friction coefficient copper-based powder metallurgy friction material which is composed of 48-52% of electrolytic copper powder, 18-24% of reduced iron powder, 12-16% of graphite, 3-6% of ferrochrome, 2-4% of aluminum oxide, 2-4% of molybdenum powder, 2-5% of precipitated barium sulfate and 3-6% of polyvinyl alcohol powder, and can stabilize the frictionThe coefficient of friction, but the volatile organic matters in sintering are not friendly to the environment due to the polyvinyl alcohol powder contained in the components. The Chinese patent with publication number of CN110923498A discloses a copper-based powder metallurgy friction material containing metal carbide and metal oxide composite ceramic friction components and a preparation method thereof, wherein the friction coefficient of the copper-based friction material is improved by adding metal carbide and metal oxide composite ceramic as friction components, but the method uses pure copper powder as a matrix, so that the friction material has poor mechanical properties at high temperature, and the mechanical strength of pure copper is lower, and the pure copper is easy to soften at high temperature, so that the current use requirement cannot be met, and the traditional ceramic reinforcing phase has large difference of thermal expansion coefficients of the pure copper matrix, the wettability between the ceramic reinforcing phase and the pure copper matrix is poor, defects are easy to generate at interfaces, and the performance of the composite material is influenced. Therefore, how to ensure that the friction material has excellent friction and wear properties, the strength of the matrix is improved, and the matrix and other components keep high bonding strength so as to meet the use of high-speed heavy-load conditions is a target which is commonly pursued by researchers.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a nitride-containing copper-based powder metallurgy friction material capable of improving the strength of a copper matrix, improving the friction coefficient stability of the friction material and reducing the abrasion loss and a preparation method thereof.
The object of the invention is achieved in the following way:
the nitride-containing copper-based powder metallurgy friction material comprises, by mass, 56-65% of composite copper powder, 12-16% of iron powder, 1-4% of tin powder, 9% of flake graphite, 1-3% of hexagonal boron nitride powder, 3-9% of aluminum nitride powder and 3-9% of ferrochrome powder, wherein the total amount of the aluminum nitride powder and the ferrochrome powder is not higher than 12%; the composite copper powder is obtained by ball milling the copper powder and reinforced particle powder with the mass ratio of 100:1-3 in a planetary high-energy ball mill, wherein the reinforced particle powder is high-entropy alloy powder or oxide powder.
The grain size of the high-entropy alloy powder is 400 meshes and is one of FeCoNiCrAl, feCoNiCrAlCu, feCoNiCrTi.
The oxide powder has a particle size of 100-200 nm and is one of Al2O3, siO2 and ZrO 2.
The rotating speed of the ball mill is 200-350 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2-4 h.
The copper powder is electrolytic copper powder with 200 meshes, the iron powder is reduced iron powder with 200 meshes, the ferrochrome alloy powder and the tin powder are 100 meshes, the crystalline flake graphite is 80 meshes, the hexagonal boron nitride powder is 200 meshes, and the aluminum nitride powder is 400 meshes.
The preparation method of the nitride-containing copper-based powder metallurgy friction material comprises the following steps:
(1) Preparing composite copper powder: ball milling is carried out on copper powder and reinforced particle powder according to the mass ratio of 100:1-3 in a planetary high-energy ball mill, the rotating speed of the ball mill is 200-350 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2-4 h;
(2) Mixing: putting the composite copper powder prepared in the step (1) and iron powder, tin powder, aluminum nitride powder and ferrochrome powder into a V-shaped mixer for mixing 2-4 h, and adding flake graphite and hexagonal boron nitride powder 10-20min before mixing is finished;
(3) Cold pressing: placing the mixed powder in the step (2) into a cold pressing mold, adopting a vertical hydraulic press for cold pressing molding, wherein the pressure is 400-600 Mpa, and the pressure maintaining time is 40-60 s;
(4) Sintering: and (3) placing the sample after cold press molding into a high-temperature high-vacuum hot press sintering furnace for sintering, wherein the sintering temperature is 900-1000 ℃, and preserving the heat for 2-3h under vacuum or argon atmosphere.
The rotating speed of the V-shaped mixer in the step (2) is 10-20 r/min.
The falling rate of the neutral hydraulic machine in the step (3) is 10-15 mm/min.
The temperature profile of the sintering process in step (4) is set as follows: heating from room temperature to 200deg.C for 10-20min, and maintaining for 5-10min; heating from 200deg.C to 800deg.C for 40-60min, and maintaining for 10-20min; heating from 800 deg.C to 900-1000 deg.C for 10-30min, incubating the sample for 2-3h, cooling to below 100deg.C with water, and cooling to room temperature with furnace.
Compared with the prior art, the friction material has stable friction coefficient, wear resistance and working stability in the braking process, has the characteristics of high hardness, high strength, good heat dissipation and the like, and is more suitable for manufacturing high-speed train brake pads.
Drawings
FIG. 1 is a graph of average friction coefficient versus comparative friction materials for examples and comparative examples.
FIG. 2 is a graph showing the abrasion loss of the friction materials of the examples and the comparative examples.
FIG. 3 is a microstructure of a copper-based powder metallurgy friction material sample prepared in example 1.
Detailed Description
The nitride-containing copper-based powder metallurgy friction material comprises, by mass, 56-65% of composite copper powder, 12-16% of iron powder, 1-4% of tin powder, 9% of flake graphite, 1-3% of hexagonal boron nitride powder, 3-12% of aluminum nitride powder and 3-12% of ferrochrome powder, wherein the total amount of the aluminum nitride powder and the ferrochrome powder is not higher than 12%; the composite copper powder is obtained by ball milling the copper powder and reinforced particle powder with the mass ratio of 100:1-3 in a planetary high-energy ball mill, wherein the reinforced particle powder is high-entropy alloy powder or oxide powder. The preparation process of the composite copper powder is preferably carried out at the rotating speed of a ball mill of 200-350 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2-4 h.
Further preferred, the high entropy alloy powder has a particle size of 400 mesh FeCoNiCrAl, feCoNiCrAlCu, feCoNiCrTi; the particle size of the oxide powder is 100-200 nm of Al 2 O 3 、SiO 2 、ZrO 2 One of them.
The preferable scheme of the raw materials is that the copper powder is electrolytic copper powder with 200 meshes, the iron powder is reduced iron powder with 200 meshes, the ferrochrome alloy powder and the tin powder are 100 meshes, the crystalline flake graphite is 80 meshes, the hexagonal boron nitride powder is 200 meshes, and the aluminum nitride powder is 400 meshes.
The high-entropy alloy has higher strength, good wear resistance, high work hardening, high-temperature softening resistance, high-temperature oxidation resistance, corrosion resistance and other excellent performances, and meanwhile, compared with a ceramic reinforcing body, the high-entropy alloy and a copper matrix show good interface bonding and excellent compatibility in physical metallurgy, so the high-entropy alloy is an ideal matrix reinforcing material for copper-based friction materials. The high-entropy alloy powder is used for reinforcing the copper matrix, so that the strength hardness and high-temperature softening resistance of the Cu matrix can be improved, the softening of the Cu matrix at high temperature is avoided, the friction coefficient stability of the friction material is improved, and the abrasion loss is reduced.
The hexagonal boron nitride used in the invention is white powder with a hexagonal crystal structure, has a similar lamellar structure with common lubricating component graphite, hBN atoms in the same layer are connected through covalent bonds, layers are combined together through Van der Waals force, when the hBN is subjected to shearing force, the layers connected through Van der Waals force are fragile, slipping phenomenon is easy to occur, an hBN lubricating film is further generated, and the abrasion degree of friction materials can be reduced. The hBN has excellent high temperature resistance and corrosion resistance, has higher thermal stability compared with graphite, can maintain excellent lubricity even if the temperature is increased to 900 ℃, and can reduce the abrasion loss of the material at high temperature and stabilize the friction coefficient by adding the hBN as a lubricating phase. The hBN has good stability at high temperature, can still keep stable during high-speed braking, provides excellent lubricity, ensures that the friction coefficient of the material is kept relatively stable during high-speed braking, and ensures that the material can be kept stable under the conditions of low speed and high speed by the matched use of the crystalline flake graphite and the hBN.
Aluminum nitride not only has very high hardness, but also has much higher thermal conductivity than the commonly used friction components, which is close to that of pure copper; alN also has the advantages of small density, low thermal expansion coefficient, high-temperature strength and the like, and is an ideal material for reinforcing the copper-based powder metallurgy friction material. The AlN is added to improve the strength and hardness of the material, so that the friction material still keeps high friction coefficient at high temperature, in addition, the high heat conduction characteristic of aluminum nitride is exerted, heat generated during high-speed friction is timely dissipated, the influence of the heat on the friction material is reduced, and the abrasion loss is reduced.
The formula of the copper-based powder metallurgy friction material does not contain metals harmful to the environment such as zinc, lead and the like, and does not contain organic materials, thereby meeting the environmental protection requirement.
A preparation method of a nitride-containing copper-based powder metallurgy friction material comprises the following steps:
(1) Preparing composite copper powder: ball milling is carried out on copper powder and reinforced particle powder according to the mass ratio of 100:1-3 in a planetary high-energy ball mill, the rotating speed of the ball mill is 200-350 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2-4 h. The high-entropy alloy powder or nano oxide particles are used as the reinforcing phase of the electrolytic copper matrix, and the reinforcing particles with high hardness and high wear resistance are dispersed and distributed in the copper matrix in a mechanical ball milling mode to play a role in dispersion strengthening, so that the strength hardness and high-temperature softening resistance of the copper matrix are improved, the softening of the copper matrix at high temperature is avoided, the friction coefficient stability of the friction material is improved, and the wear amount is reduced.
(2) Mixing: putting the composite copper powder prepared in the step (1) and iron powder, tin powder, aluminum nitride powder and ferrochrome powder into a V-shaped mixer for mixing 2-4 h, and adding flake graphite and hexagonal boron nitride powder 10-20min before mixing is finished, wherein the optimal rotating speed of the V-shaped mixer is 10-20 r/min;
(3) Cold pressing: placing the mixed powder in the step (2) into a cold pressing mold, adopting a vertical hydraulic press for cold pressing molding, wherein the pressure is 400-600 Mpa, the pressure maintaining time is 40-60s, and the optimal descending rate of the vertical hydraulic press during working is 10-15 mm/min;
(4) Sintering: and (3) placing the sample after cold press molding into a high-temperature high-vacuum hot press sintering furnace for sintering, wherein the sintering temperature is 900-1000 ℃, and preserving the heat for 2-3h under vacuum or argon atmosphere. The optimum temperature profile for the sintering process is set as: heating from room temperature to 200deg.C for 10-20min, and maintaining for 5-10min; heating from 200deg.C to 800deg.C for 40-60min, and maintaining for 10-20min; raising the temperature from 800 ℃ to 900-1000 ℃ for 10-30 min; the sample is kept for 2-3h, then cooled to below 100 ℃ by water, and cooled to room temperature along with the furnace.
The invention adopts unique material proportion, pressing parameters and sintering parameters, prepares the powder metallurgy friction material meeting the use conditions by a powder metallurgy technology, has simple preparation process and reliable performance, and is suitable for industrial production.
Example 1
A nitride-containing copper-based powder metallurgy friction material comprises the following raw materials in percentage by mass: 59% of composite copper powder, 15% of iron powder, 4% of tin powder, 9% of crystalline flake graphite, 1% of hexagonal boron nitride powder, 3% of aluminum nitride powder and 9% of ferrochrome powder; wherein, the copper powder is 200 meshes of electrolytic copper powder, the iron powder is 200 meshes of reduced iron powder, the high-purity ferrochrome powder and the tin powder are 100 meshes, the crystalline flake graphite is 80 meshes, the hexagonal boron nitride powder is 200 meshes, and the aluminum nitride powder is 400 meshes; the composite copper powder is obtained by ball milling copper powder and high-entropy alloy powder FeCoNiCrAl in a planetary high-energy ball mill according to the mass ratio of 100:1.
A preparation method of a nitride-containing copper-based powder metallurgy friction material comprises the following steps:
first, a composite copper powder is prepared: the electrolytic copper powder and the high-entropy alloy powder FeCoNiCrAl are subjected to ball milling in a planetary high-energy ball mill according to the mass ratio of 100:1, the rotating speed of the ball mill is 200 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2h. Then, the prepared composite copper powder, iron powder, tin powder, aluminum nitride powder and ferrochrome powder are put into a V-shaped mixer to be mixed for 2 hours, and flake graphite and hexagonal boron nitride powder are added 10 minutes before the mixing is finished. And then placing the mixed powder into a mould, and adopting 600MPa pressure for cold pressing to prepare a blank. And finally, placing the blank formed by cold pressing into a high-temperature high-vacuum hot-pressing sintering furnace, vacuumizing, introducing argon, sintering at 950 ℃ and preserving heat for 3 hours, then cooling to below 100 ℃ by water, cooling to room temperature along with the furnace, and taking out the sintered friction material.
Sintered friction material with a density of 5.21g/cm was examined 3 The hardness was 25.91HB. The friction coefficients of the friction and wear testing machines are respectively 0.419, 0.405, 0.403, 0.398 and 0.393, and the wear amounts are respectively 18.1mg, 32.5 mg, 47.7 mg, 82.2 mg and 147.7 mg, which are respectively measured by adopting a Siankantong MM3000 type friction and wear testing machine and respectively using braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350 km/h.
Example 2
A nitride-containing copper-based powder metallurgy friction material comprises the following raw materials in percentage by mass: 56% of composite copper powder, 16% of iron powder, 4% of tin powder, 9% of crystalline flake graphite, 3% of hexagonal boron nitride powder, 5% of aluminum nitride powder and 7% of ferrochrome powder. The mass ratio of copper powder to high-entropy alloy powder FeCoNiCrAl in the composite copper powder is 100:3, and the ball milling time is 4 h. Mixing in a V-shaped mixer for 3h, and adding flake graphite and hexagonal boron nitride powder 15min before mixing; the cold pressing pressure was 500MPa and the rest of the preparation method was copper example 1.
Sintered friction material density of 5.17g/cm 3 The hardness was 27.15HB. The friction coefficients of 0.423, 0.421, 0.409, 0.392 and 0.388, respectively, and the abrasion amounts of 16.3 mg, 26.6 mg, 50.9 mg, 79.4 mg and 140.1 mg, respectively, were measured by using a Siankantong MM3000 type friction abrasion tester at brake speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350km/h, respectively.
Example 3
A nitride-containing copper-based powder metallurgy friction material comprises the following raw materials in percentage by mass: 65% of composite copper powder, 12% of iron powder, 1% of tin powder, 9% of crystalline flake graphite, 2% of hexagonal boron nitride powder, 8% of aluminum nitride powder and 3% of ferrochrome powder. The mass ratio of copper powder to high-entropy alloy powder FeCoNiCrAlCu in the composite copper powder is 100:2, the rotating speed of a ball mill is 300r/min, and the ball milling time is 3h. Mixing in a V-shaped mixer for 4 hours, and adding flake graphite and hexagonal boron nitride powder 20 minutes before mixing; sintering at 980 ℃ and preserving heat for 2 hours. Other process conditions were the same as in example 1.
Sintered friction material having a density of 5.19g/cm 3 The hardness was 29.83HB. The friction coefficients of the friction and wear testing machines of the Siankantong MM3000 type are respectively 0.412, 0.409, 0.392, 0.394 and 0.383 by using the braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350km/h to carry out braking experiments, and the wear amounts are respectively 19.8 mg, 25.7 mg, 29 mg, 69.7 mg and 118.4 mg.
Example 4
A nitride-containing copper-based powder metallurgy friction material comprises the following raw materials in percentage by mass: 58% of composite copper powder, 15% of iron powder, 3% of tin powder, 9% of crystalline flake graphite, 3% of hexagonal boron nitride powder, 9% of aluminum nitride powder and 3% of ferrochrome powder. The mass ratio of copper powder in the composite copper powder to FeCoNiCrTi powder is 100:2, the rotating speed of a ball mill is 250/min, the ball milling time is 4h, the mixing in a V-shaped mixer is 4h,400MPa of cold pressing pressure is adopted, and the sintering is carried out at 1000 ℃ and the heat preservation is carried out for 3h. Other process conditions were the same as in example 1.
Sintered friction material having a density of 5.22g/cm 3 The hardness was 30.47HB. The friction coefficients of the friction and wear testing machines are respectively 0.428, 0.421, 0.419, 0.411 and 0.402, and the wear amounts are respectively 21.1 mg, 23.1 mg, 34.6 mg, 57 mg and 91.1 mg, which are respectively measured by adopting a Siankantong MM3000 type friction and wear testing machine and respectively using braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350 km/h.
Example 5
A nitride-containing copper-based powder metallurgy friction material comprises the following raw materials in percentage by mass: 60% of composite copper powder, 15% of iron powder, 2% of tin powder, 9% of crystalline flake graphite, 2% of hexagonal boron nitride powder, 6% of aluminum nitride powder and 6% of ferrochrome powder. Copper powder and 200 mesh Al in composite copper powder 2 O 3 The mass ratio of the powder is 100:2, the rotating speed of the ball mill is 350/min, the mixing in the V-shaped mixer is 4h, the cold pressing pressure is 450MPa, and the sintering is carried out at 900 ℃ and the heat preservation is carried out for 2h. Other process conditions were the same as in example 1.
Sintered friction material having a density of 4.75g/cm 3 The hardness was 30.83HB. The friction coefficients of the friction and wear testing machine with the Xishanntong MM3000 type friction and wear testing machine are respectively 0.424, 0.402, 0.397, 0.382 and 0.374 by using the braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350km/h, and the wear amounts are respectively 23.2 mg, 25.9 mg, 31.6 mg, 44 mg and 88.9 mg.
Comparative example 1
The difference from example 4 is that the composite copper powder was replaced with an equivalent amount of electrolytic copper powder.
Sintered friction material having a density of 5.19g/cm 3 The hardness was 25.17HB. The friction coefficients of the friction and wear testing machines of the Siankantong MM3000 type are respectively 0.378, 0.356, 0.335, 0.317 and 0.309 by using the braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350km/h to carry out braking experiments, and the wear amounts are respectively 23.1 mg, 35.6 mg, 47.1 mg, 114.6 mg and 219.1 mg.
Compared with the example 4, after the composite copper powder is replaced by the equivalent electrolytic copper powder, the density and hardness of the friction material are reduced, the friction coefficient of the material is smaller and the abrasion loss is large in the braking speed range from 150km/h to 350km/h, the friction coefficient is greatly reduced along with the increase of the braking speed, and the stability is poor. The high-entropy alloy powder FeCoNiCrTi is added into the electrolytic copper powder in a mechanical ball milling mode to form composite copper powder, so that the strength, hardness and high-temperature softening resistance of the copper matrix are improved. Compared with electrolytic copper powder, the composite copper powder has high hardness, wear resistance and high-temperature softening resistance, and the friction coefficient of the material can be improved, the wear rate can be reduced and the composite copper powder has better friction coefficient stability by using the composite copper powder as a matrix of the friction material. In addition, the microscopic morphology of the electrolytic copper powder is changed after mechanical ball milling, the dendritic morphology is broken, and the pressed density of the material is increased in the forming process.
Comparative example 2
The difference from example 3 is that the electrolytic copper powder was 63%, the high entropy alloy powder FeCoNiCrAlCu 2%, and the two were not made into composite copper powder, but were directly mixed with other raw materials.
Sintered friction material having a density of 5.02g/cm 3 The hardness was 27.83HB. The friction coefficients of the friction and wear testing machines of the Siankantong MM3000 type are respectively 0.391, 0.379, 0.352, 0.334 and 0.313, and the wear amounts are respectively 27.8 mg, 45.7 mg, 69.2 mg, 138.7 mg and 308.4 mg by adopting the friction and wear testing machines of the Siankantong MM3000 type to carry out braking experiments at braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350 km/h.
In comparison with example 3, the high-entropy alloy powder FeCoNiCrAlCu was directly mixed with other raw materials, and the high-entropy alloy powder FeCoNiCrAlCu was present as a friction component, failing to strengthen the electrolytic copper matrix. Compared with the composite copper powder, the electrolytic copper powder has poorer mechanical property and high-temperature softening resistance as a matrix, so that the hardness of the friction material is reduced, the friction coefficient is lower and the abrasion amount is increased.
The above examples and comparative examples were each subjected to a frictional wear test on a Siemens-Runner MM3000 type frictional wear tester. Cutting the material by using a DK7720 electric spark numerical control wire cutting machine after the sintering of the material is completed, wherein the size of the cut material is 20mm multiplied by 10mm, and 3 pieces of each piece of material are required to be cut; the frictional wear test was performed on an MM3000 frictional wear tester and measured with a thermocouple in real time, and the test contained five different braking speeds of 150km/h, 200km/h, 250km/h, 300km/h and 350km/h, ten times in total, and the data were averaged. Cooling the sample by air cooling after each braking test is finished, taking down the friction material after the temperature is lower than 60 ℃, measuring by adopting a high-precision electronic balance with the precision of 0.001 g, obtaining the wear rate of the friction material after calculation, then assembling the friction material in a friction and wear testing machine again, selecting another group of braking speeds according to the sequentially increasing sequence, repeating the testing steps to obtain the friction coefficient and the wear rate at different speeds, and pushing the friction coefficient and the wear rate of the friction material at five braking speeds until the friction coefficient and the wear rate of the friction material at five braking speeds are tested; the hardness of the material is tested by adopting a 320HBS-3000 Brinell hardness tester, the diameter of a pressure head is 10mm, the load is 500N, the pressure maintaining time is 30 s, the diameter of an indentation is taken to calculate the hardness value, each sample is tested 5 times, and the average value of the hardness is obtained; and detecting the density of the sintered material by adopting an Archimedes drainage method.
The average friction coefficients and the amounts of wear of the friction materials prepared in examples 1 to 5 and comparative examples 1 to 2 are shown in FIGS. 1 and 2, respectively. As can be seen from the figures, examples 1 to 5 have both higher friction coefficient, lower wear amount and more stable friction coefficient, and have excellent comprehensive frictional wear performance, compared with comparative examples 1 and 2.
Fig. 3 is a microstructure diagram of a copper-based powder metallurgy friction material sample prepared in example 1, and it can be seen from fig. 3 that the combination effect of the matrix, the friction component and the lubrication component is good, the distribution is relatively uniform, and the stable structure ensures the excellent performance.
The above examples and comparative examples illustrate the basic principles and features of the present invention, but the above description merely illustrates preferred embodiments of the present invention and is not limited by the embodiments. Many modifications and variations may be made by one of ordinary skill in the art, given the benefit of this disclosure, without departing from the spirit of the invention and the scope of the claims.
Claims (9)
1. A nitride-containing copper-based powder metallurgy friction material, characterized in that: comprises the following raw materials, by mass, 56-65% of composite copper powder, 12-16% of iron powder, 1-4% of tin powder, 9% of crystalline flake graphite, 1-3% of hexagonal boron nitride powder, 3-9% of aluminum nitride powder and 3-9% of ferrochrome powder, wherein the total amount of the aluminum nitride powder and the ferrochrome powder is not higher than 12%; the composite copper powder is obtained by ball milling the copper powder and reinforced particle powder with the mass ratio of 100:1-3 in a planetary high-energy ball mill, wherein the reinforced particle powder is high-entropy alloy powder or oxide powder.
2. A nitride-containing copper-based powder metallurgy friction material according to claim 1, wherein: the grain size of the high-entropy alloy powder is 400 meshes and is one of FeCoNiCrAl, feCoNiCrAlCu, feCoNiCrTi.
3. A nitride-containing copper-based powder metallurgy friction material according to claim 1, wherein: the oxide powder has a particle size of 100-200 nm and is one of Al2O3, siO2 and ZrO 2.
4. A nitride-containing copper-based powder metallurgy friction material according to claim 1, wherein: the rotating speed of the ball mill is 200-350 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2-4 h.
5. A nitride-containing copper-based powder metallurgy friction material according to claim 1, wherein: the copper powder is electrolytic copper powder with 200 meshes, the iron powder is reduced iron powder with 200 meshes, the ferrochrome alloy powder and the tin powder are 100 meshes, the crystalline flake graphite is 80 meshes, the hexagonal boron nitride powder is 200 meshes, and the aluminum nitride powder is 400 meshes.
6. The method for producing a nitride-containing copper-based powder metallurgy friction material according to any one of claims 1 to 5, characterized in that: the method comprises the following steps:
(1) Preparing composite copper powder: ball milling is carried out on copper powder and reinforced particle powder according to the mass ratio of 100:1-3 in a planetary high-energy ball mill, the rotating speed of the ball mill is 200-350 r/min, the weight ratio of steel balls to powder in the ball mill is 5:1, and the ball milling time is 2-4 h;
(2) Mixing: putting the composite copper powder prepared in the step (1) and iron powder, tin powder, aluminum nitride powder and ferrochrome powder into a V-shaped mixer for mixing 2-4 h, and adding flake graphite and hexagonal boron nitride powder 10-20min before mixing is finished;
(3) Cold pressing: placing the mixed powder in the step (2) into a cold pressing mold, adopting a vertical hydraulic press for cold pressing molding, wherein the pressure is 400-600 Mpa, and the pressure maintaining time is 40-60 s;
(4) Sintering: and (3) placing the sample after cold press molding into a high-temperature high-vacuum hot press sintering furnace for sintering, wherein the sintering temperature is 900-1000 ℃, and preserving the heat for 2-3h under vacuum or argon atmosphere.
7. The method for producing a nitride-containing copper-based powder metallurgy friction material according to claim 6, wherein: the rotating speed of the V-shaped mixer in the step (2) is 10-20 r/min.
8. The method for producing a nitride-containing copper-based powder metallurgy friction material according to claim 6, wherein: the falling rate of the neutral hydraulic machine in the step (3) is 10-15 mm/min.
9. The method for producing a nitride-containing copper-based powder metallurgy friction material according to claim 1, wherein: the temperature profile of the sintering process in step (4) is set as follows: heating from room temperature to 200deg.C for 10-20min, and maintaining for 5-10min; heating from 200deg.C to 800deg.C for 40-60min, and maintaining for 10-20min; heating from 800 deg.C to 900-1000 deg.C for 10-30min, incubating the sample for 2-3h, cooling to below 100deg.C with water, and cooling to room temperature with furnace.
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