A copper-based powder metallurgy brake pad containing multiple ceramic components and its preparation method

Abstract

The present invention relates to a copper-based powder metallurgy brake pad containing multiple ceramic components and a preparation method thereof. The copper-based powder metallurgy brake pad containing multiple ceramic components, the raw materials used include, by mass percentage: 50-60% of electrolytic copper powder; 10-18% of reduced iron powder; 2-4% of electrolytic nickel powder; 2-4% of atomized tin powder; 2-5% of tungsten powder; 8-14% of natural flaky graphite powder; 2-4% of hexagonal boron nitride powder; 2-6% of boron carbide powder; 2-6% of titanium carbide powder. The preparation method includes mixing materials, pressing to obtain a green body, treating the steel back, and then obtaining the product through hot press sintering. The product obtained by the present invention has a wear amount of 0.04-0.15 cm<supgt;3< / supgt; / MJ and a friction stability coefficient of 0.72-0.86 under a braking pressure of 0.6 MPa and a braking inertia of 0.35 kg·m<supgt;2< / supgt>. The component design of the present invention is reasonable, the preparation process is simple and controllable, and the obtained product has excellent performance and is convenient for industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of copper-based powder metallurgy brake pads, and particularly relates to a copper-based powder metallurgy brake pad containing multiple ceramic components and a preparation method thereof. Background Art

[0002] The braking system is a key system for the safety guarantee and emergency of transportation tools. The basic braking composed of the friction pair material plays a decisive role in the braking system. It can be said that without a safe and reliable friction pair material for the braking system, it is impossible to achieve the high-speed operation of transportation tools.

[0003] Most of the braking systems used in high-speed trains currently adopt disc braking devices. The friction pair is composed of a brake disc and a brake pad, and the deceleration or stopping is achieved by using the frictional force generated between the two. Therefore, there is an urgent need to develop high-temperature-resistant, low-wear and high-performance brake pads.

[0004] Chinese Patent Document CN114542632A discloses a high-speed train brake pad applying a composite wear-resistant material and a preparation method thereof. The used composite wear-resistant material is composed of metal powder and inorganic non-metallic powder. This method improves the wear resistance and strength of the high-speed train brake pad.

[0005] Chinese Patent Document CN102102720B discloses a ceramic / metal double continuous phase composite material brake pad, which relates to silicon carbide foam ceramics. The produced brake pad can cooperate with the brake disc, has a suitable and stable friction coefficient, low manufacturing cost and long service life.

[0006] Chinese Patent Document CN113550993B discloses a reinforced high-speed train brake pad material and a preparation method thereof. The strengthening component used is MoAl-Si-B powder to prepare a brake pad with a relatively high friction coefficient, low wear amount and small damage to the brake disc.

[0007] As can be seen from the above, due to its excellent properties such as high strength, stable chemical properties, excellent corrosion resistance and high temperature resistance, ceramic powder plays a very good role in stabilizing the friction performance at high temperatures. However, so far, there are few reports on using the double ceramic powders B4C-TiC in combination with hexagonal boron nitride powder and a metal matrix to improve the friction stability and heat resistance of brake pads. Summary of the Invention

[0008] Based on improving the heat resistance of copper-based powder metallurgy brake pads, the present invention uses the characteristic parameters of various reinforcing phases to synergistically enhance, gives full play to the advantages and coupling effects of each component, and obtains a copper-based composite material with excellent comprehensive performance. The present invention makes a first attempt to use the double ceramic powders B4C-TiC in combination with hexagonal boron nitride powder and a metal matrix to improve the friction stability and heat resistance of brake pads.

[0009] The copper-based powder metallurgy brake pad of the present invention containing multiple ceramic components, the raw materials used include, by mass percentage:

[0010] Electrolytic copper powder 50 - 60%, preferably 52 - 58%;

[0011] Reduced iron powder 10 - 18%, preferably 14 - 16%;

[0012] Electrolytic nickel powder 2 - 4%, preferably 2 - 3%;

[0013] Atomized tin powder 2 - 4%, preferably 2 - 2.5%;

[0014] Tungsten powder 2 - 5%, preferably 2 - 4%, further preferably 2%;

[0015] Natural flaky graphite powder 8 - 14%, preferably 10 - 14%, further preferably 10%;

[0016] Hexagonal boron nitride powder 2 - 4%, preferably 2%;

[0017] Boron carbide powder 2 - 6%, preferably 2 - 4%;

[0018] Titanium carbide powder 2 - 6%, preferably 5 - 6%.

[0019] As a further preferred scheme; when the components are within the defined range, when the content of boron carbide powder is 3% and the content of titanium carbide powder is 5%, the friction stability of the product will be further improved.

[0020] As an even more preferred scheme: electrolytic copper powder 58%, reduced iron powder 16%, electrolytic nickel 2%, atomized tin powder 2%, tungsten powder 2%, natural flaky graphite powder 10%, hexagonal boron nitride powder 2%, boron carbide powder 3%, titanium carbide powder 5%.

[0021] Compared with the existing copper-based powder metallurgy friction materials reinforced with a single ceramic powder, the present invention utilizes the characteristic parameters of boron carbide, titanium carbide, and hexagonal boron nitride to synergistically enhance, giving full play to the advantages and coupling effects of the three components. During the braking process, boron carbide powder will form a boron oxide ceramic film on the friction surface, improving the stability of friction performance at high temperatures. Titanium carbide powder will adhere to the copper matrix, reducing the loss of the matrix and increasing wear resistance. The synergistic effect of the two ceramic powders enables the copper-based powder metallurgy brake pad to have both good high-temperature resistance and less wear. When an appropriate amount of boron carbide powder and titanium carbide powder are combined with hexagonal boron nitride powder and the metal matrix, a direct mixing method can be used to prepare a copper-based powder metallurgy friction material with relatively excellent performance. Of course, if the prepared ceramic powders (such as hexagonal boron nitride powder, boron carbide powder, titanium carbide powder) are first subjected to high-energy ball milling, the performance of the product will be further improved.

[0022] The electrolytic copper powder is the matrix component, serving as the main body to bear the load and conduct heat, and being the main channel for the dissipation of frictional heat. The particle size is 60 - 80 microns.

[0023] The reduced iron powder is the matrix strengthening component, with low solubility and good wettability. As the second phase in the copper powder, it makes the friction and wear performance of the material better. The particle size is 60 - 80 microns.

[0024] The electrolytic nickel powder is the matrix strengthening component, which is infinitely soluble in the copper matrix and can increase the melting point and high-temperature strength of the matrix. The particle size is 60 - 80 microns.

[0025] The atomized tin powder is the matrix strengthening component, which will generate an instantaneous liquid phase during the sintering process, promoting the densification of sintering. The particle size is not higher than 60 - 80 microns.

[0026] The tungsten powder is the matrix strengthening component, which can increase the specific heat capacity of the matrix and ensure excellent thermal conductivity. The particle size is 60 - 80 microns.

[0027] The natural flaky graphite powder is the matrix lubricating component, used to eliminate jamming, reduce noise, adjust the friction coefficient, and reduce the wear of the brake disc. The particle size is 150 - 200 microns.

[0028] The hexagonal boron nitride powder is the matrix lubricating component, which improves the high-temperature friction stability. The particle size is 60 - 80 microns.

[0029] The boron carbide powder is the matrix friction component, which can prevent the matrix from losing as micro-protrusions at high temperatures and increase the wear resistance. The particle size is 60 - 80 microns.

[0030] The titanium carbide powder is the matrix friction component, which adjusts the friction factor, eliminates the adhesion deposits and oxides on the surface of the brake disc to improve the high-temperature friction stability. The particle size is 60 - 80 microns.

[0031] A preparation method of a copper-based powder metallurgy brake pad containing multiple ceramic components according to the present invention includes the following steps:

[0032] The first step:

[0033] Weigh the electrolytic copper powder, reduced iron powder, electrolytic nickel powder, atomized tin powder, tungsten powder, natural flaky graphite powder, hexagonal boron nitride powder, boron carbide powder, and titanium carbide powder according to the designed components. Add the prepared powders into a V-type mixer, and supplement 2.5 - 3.5% of the total mass of the powders with aviation kerosene. Control the rotation speed at 90 - 100 r / min and mix at room temperature for 10 - 12 hours to obtain uniformly mixed powders;

[0034] The second step:

[0035] Pour the well - mixed powder into a mold and press it into shape. When pressing, control the pressing pressure at 450 - 550 MPa and the pressure - holding time at 15 - 25 s;

[0036] Step 3: Shot peening of the steel back

[0037] Conduct surface pretreatment on the required steel back, shot - peen and polish it smoothly, then clean and dry it;

[0038] Step 4: Sintering and forming

[0039] Place the obtained green body on the steel back and sinter it using a pressure - sintering furnace, adopting a technology combining stepped heating and segmented pressurization; Specific process: Under the condition of a sintering pressure of 1 - 1.5 MPa, heat up to 600 °C; then raise the sintering pressure to 2 - 2.5 MPa and heat up to the sintering temperature of 910 - 940 °C; then raise the sintering pressure to 3 - 5 MPa and hold for 2 - 3 hours at the sintering temperature. Use H2 and N2 as the full - process protective atmosphere; obtain a copper - based powder metallurgy brake pad containing multiple ceramic components.

[0040] When applied industrially, the prepared hexagonal boron nitride powder, boron carbide powder, and titanium carbide powder can be first placed in a high - energy ball mill, add 50 ml of ethanol, and adopt a ball - to - material ratio of 50 - 100:1, preferably 50:1. Control the rotation speed at 350 - 450 r / min, preferably 400 - 450:1. The ball - milling time is 10 - 50 hours, preferably 40 - 55 hours. The composite ceramic powder after high - energy ball milling is not only well - mixed, but also has a small particle size and high activity, which is beneficial to the densification of the green body sintering.

[0041] Conduct surface pretreatment on the required steel back, shot - peen and polish it smoothly, then clean and dry it; Measure its surface roughness to be 0.8 - 1.6.

[0042] When sintering and forming, the protective gas used is composed of H2 and N2 in a volume ratio of 1 - 2:1 - 2.

[0043] The copper - based powder metallurgy brake pad containing multiple ceramic components designed and prepared by the present invention; its density is 4.2 - 5.2 g / cm 3 , and the porosity is 2 - 10%.

[0044] The copper - based powder metallurgy brake pad containing multiple ceramic components designed and prepared by the present invention; under a braking pressure of 0.6 MPa and a braking inertia of 0.35 kg·m 2 , using an MM - 3000 scaled - down test machine, paired with a carbon - ceramic disc, conduct 10 repeated brakings under dry conditions, set the braking speed at 24 m / s, and pair with a self - made carbon - ceramic disc (density 2.32 g / cm 3, the wear amount is 0.05 - 0.15 cm when paired with a hardness of 121.2 HRL 3 / MJ, preferably 0.05 - 0.08 cm 3 / MJ, and the friction stability coefficient is 0.74 - 0.86, preferably 0.82 - 0.86.

[0045] The copper - based powder metallurgy brake pad containing multiple ceramic components designed and prepared by the present invention; under a braking pressure of 0.6 MPa and a braking inertia of 0.35 kg·m 2 when using an MM - 3000 scaled - down test machine and paired with a 30CrMnSi steel brake disc (Daye Special Steel Co., Ltd.), the wear amount is 0.04 - 0.13 cm 3 / MJ, preferably 0.04 - 0.08 cm 3 / / MJ, and the friction stability coefficient is 0.72 - 0.85, preferably 0.81 - 0.85.

[0046] Certainly, the copper - based powder metallurgy brake pad containing multiple ceramic components involved and prepared by the present invention can be paired with existing carbon - ceramic discs or metal brake discs for use.

[0047] Beneficial effects

[0048] In terms of material design of the present invention, electrolytic copper powder is used as the matrix component, which serves as the main body for bearing loads and heat conduction and is the main channel for frictional heat dissipation. Reduced iron powder is introduced as the second phase to enhance the friction and wear performance of the material. Electrolytic nickel powder is introduced to infinitely solid - solve with the copper matrix to increase the melting point and high - temperature strength of the matrix. Atomized tin powder and tungsten powder are introduced to promote sintering densification and increase the specific heat capacity of the matrix. Appropriate amounts of natural flaky graphite powder and hexagonal boron nitride powder are introduced to adjust the friction coefficient and improve high - temperature friction stability. Appropriate amounts of boron carbide powder and titanium carbide powder are introduced to synergistically enhance the high - temperature resistance and friction stability of the copper - based powder metallurgy brake pad. Among them, boron carbide improves the stability of frictional performance at high temperatures by generating a boron oxide ceramic film on the friction surface. Titanium carbide powder adheres to the copper matrix, reducing the loss of the matrix and increasing wear resistance. The increase in the content of ceramic powder in the copper - based powder metallurgy brake pad is beneficial to the improvement of high - temperature friction stability, and the optimization of the introduction ratio of boron carbide powder and titanium carbide powder also increases the friction stability of the brake pad.

[0049] When the copper - based powder metallurgy brake pad provided by the present invention acts on a carbon - ceramic brake disc, not only is the wear low, but also the high - temperature friction stability is good. There are no defects in both the brake pad itself and the brake disc, and the matching is good. The brake pad with a high content and suitable ratio of ceramic powder introduced (3% boron carbide - 5% titanium carbide - 2% hexagonal boron nitride) has both good high - temperature friction stability and mechanical strength, and also maintains less wear. At the same time, the brake pad does not use asbestos, lead and their compounds. Description of the drawings

[0050] Figure 1 These are the friction braking curves of the embodiments and comparative examples of the present invention.

[0051] Figure 2 These are the friction stability coefficients of the embodiments and Comparative Example 1 of the present invention under 10 repeated high-energy brakings.

[0052] Figure 3 These are the wear rates of the embodiments and comparative examples of the present invention after 10 repeated high-energy brakings and the corresponding wear rates of the carbon-ceramic discs.

[0053] Figure 4 This is the friction surface diagram of Embodiment 4 of the present invention after the braking experiment.

[0054] It can be seen from Figure 1 Figure 2 It can be seen that: The smoothness of the braking curve and the friction stability coefficient of the embodiments are better than those of the comparative examples, and the synergistic strengthening effect of the composite ceramic powder is beneficial to the improvement of the friction performance. Embodiment 1 is better than Embodiments 2 and 3, and the optimization of the proportion of the composite ceramic powder is beneficial to the improvement of the friction performance. Embodiment 4 is better than Embodiment 1, and the composite ceramic powder after high-energy ball milling is beneficial to the improvement of the friction performance. Embodiment 4 is better than Embodiment 6, and the optimization of the high-energy ball milling conditions is beneficial to the improvement of the friction performance. Embodiment 4 is better than Embodiment 7, and the prepared copper-based powder metallurgy brake pads have better adaptability to the carbon-ceramic disc.

[0055] It can be seen from Figure 3 It can be seen that: The wear rate of the embodiments after high-energy braking is less than that of the comparative examples, and the damage to the carbon-ceramic disc is lower, the friction performance is better, and the synergistic strengthening effect of the composite ceramic powder is beneficial to the improvement of the friction performance.

[0056] It can be seen from Figure 4 It can be seen that: The friction surface of Embodiment 4 has a smooth film, no obvious defects, and little wear. Detailed implementation manners

[0057] A copper-based powder metallurgy brake pad prepared by applying a dual-ceramic powder system according to the present invention comprises the following steps:

[0058] Embodiment 1:

[0059] The first step: Raw material weighing

[0060] Weigh electrolytic copper powder 58%, reduced iron powder 16%, electrolytic nickel 2%, atomized tin powder 2%, tungsten powder 2%, natural flaky graphite powder 10%, hexagonal boron nitride powder 2%, boron carbide powder 3%, and titanium carbide powder 5% in ascending order of mass percentage. For each added raw material, stir with a crucible for 3 minutes, and finally add aviation kerosene accounting for 3% of the total mass of the powder to the manually pre-mixed raw materials.

[0061] The second step: Raw material mixing

[0062] Put the manually pre-mixed raw materials into a V-type mixer that has been cleaned with ethanol and dried, with a rotation speed of 100 r / min. After mixing at room temperature for 10 hours, store them in a vacuum-sealed bag.

[0063] Step 3: Green body pressing

[0064] Pour the stored powder into a mold and press out a hollow circle with an outer diameter of 74 mm and an inner diameter of 53 mm and a cube with a side length of 25 mm at room temperature. The pressing pressure is 550 MPa and the pressure holding time is 25 s.

[0065] Step 4: Shot peening of the steel back

[0066] Conduct surface pretreatment on the required steel back. After shot peening and polishing it smoothly, clean and dry it. Its surface roughness is 1.1.

[0067] Step 5: Sintering and forming

[0068] Place the obtained green body on the steel back and sinter it using a bell-type pressurized sintering furnace, adopting a technology that combines stepped heating and segmented pressurization. Specific process: Under the condition of a sintering pressure of 1.5 MPa, heat up to 600 °C; under the condition of a sintering pressure of 2 MPa, heat up to the sintering temperature of 920 °C; under the condition of a sintering pressure of 4 MPa, hold the temperature at the sintering temperature for 2 hours. A mixed gas composed of H2 and N2 in a volume ratio of 1:2 is used as the full-process protective atmosphere.

[0069] Step 6: Surface treatment

[0070] Let the sintered and formed blank cool naturally to room temperature. After polishing its surface smoothly, clean and dry it for standby.

[0071] Step 7: High-energy braking test

[0072] Use an MM-3000 scaled-down test machine, a hollow circle with an outer diameter of 74 mm and an inner diameter of 53 mm, and a self-made carbon-ceramic disc from Central South University Powder Metallurgy Research Institute as the counter part, with a braking energy density of 3200 J / cm 2 and the average value of 10 brakings; the test results are shown in Figure 1 、 Figure 2 . During high-energy braking, the average friction stability coefficient of the copper-based powder metallurgy brake pad is 0.82, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are respectively 3 / MJ and 0.01 cm 3 / MJ.

[0073] Average friction stability coefficient = average friction coefficient / maximum friction coefficient in the braking curve.

[0074] Example 2:

[0075] Step 1: Weighing of raw materials

[0076] Weigh electrolytic copper powder 54%, reduced iron powder 14%, electrolytic nickel 4%, atomized tin powder 4%, tungsten powder 2%, natural flaky graphite powder 12%, hexagonal boron nitride powder 2%, boron carbide powder 2%, and titanium carbide powder 6% in ascending order of mass percentage. For each raw material added, stir with a crucible for 3 minutes. Finally, add aviation kerosene accounting for 3% of the total mass of the powder to the manually pre-mixed raw materials.

[0077] Step 2: Mixing of raw materials

[0078] Put the manually pre-mixed raw materials into a V-type mixer that has been cleaned with ethanol and dried. The rotation speed is 100 r / min. After mixing at room temperature for 9 hours, store it in a vacuum-sealed bag.

[0079] Step 3: Compression of green compacts

[0080] Pour the stored powder into a mold, and press out a hollow circle with an outer diameter of 74 mm and an inner diameter of 53 mm and a cube with a side length of 25 mm at room temperature. The pressing pressure is 550 MPa, and the pressure holding time is 20 s.

[0081] Step 4: Shot peening of steel back

[0082] Conduct surface pretreatment on the required steel back. After shot peening and polishing it smooth, wash and dry it. Its surface roughness is 1.0.

[0083] Step 5: Sintering and forming

[0084] Place the obtained green compact on the steel back and use a bell-type pressure sintering furnace for sintering, adopting a technology that combines stepwise heating and segmented pressurization. Specific process: Under the condition of a sintering pressure of 1 MPa, heat up to 600 °C; under the condition of a sintering pressure of 2.5 MPa, heat up to the sintering temperature of 930 °C; under the condition of a sintering pressure of 4.5 MPa, keep the sintering temperature for 3 hours. A mixed gas composed of H2 and N2 in a volume ratio of 1:2 is used as the whole-process protective atmosphere.

[0085] Step 6: Surface treatment

[0086] Let the sintered and formed blank cool naturally to room temperature. Polish its surface smooth, then wash and dry it for standby.

[0087] Step 7: High-energy braking test

[0088] Using an MM-3000 scaled-down test machine, a hollow circle with a size of 74 mm (outer diameter) × 53 mm (inner diameter), and a self-made carbon-ceramic disc from Central South University Powder Metallurgy Research Institute as the counterpiece, the braking energy density is 3200 J / cm 2 , and the average value of 10 brakings; the test results are shown in Figure 1 、 Figure 2 . During high-energy braking, the average friction stability coefficient of the copper-based powder metallurgy brake pad is 0.75, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are 0.12 cm 3 / MJ and 0.02 cm 3 / MJ.

[0089] Example 3:

[0090] The first step: weighing raw materials

[0091] Weigh 52% of electrolytic copper powder, 16% of reduced iron powder, 3% of electrolytic nickel, 3% of atomized tin powder, 4% of tungsten powder, 14% of natural flaky graphite powder, 2% of hexagonal boron nitride powder, 4% of boron carbide powder, and 2% of titanium carbide powder in ascending order of mass percentage. For each added raw material, stir with a crucible for 3 minutes, and finally add 3% of aviation kerosene based on the total powder amount to the manually pre-mixed raw materials.

[0092] The second step: mixing raw materials

[0093] Put the manually pre-mixed raw materials into a V-type mixer that has been cleaned with ethanol and dried. The rotation speed is 100 r / min, and mix at room temperature for 9 hours, then put it into a vacuum-sealed bag for storage.

[0094] The third step: green compact pressing

[0095] Pour the stored powder into a mold, and press out a hollow circle with a size of 74 mm (outer diameter) × 53 mm (inner diameter) and a cube with a size of 25 mm at room temperature. The pressing pressure is 550 MPa, and the pressure holding time is 20 s.

[0096] The fourth step: steel back shot peening

[0097] Perform surface pretreatment on the required steel back. After shot peening and polishing to be smooth, clean and dry it, and its surface roughness is 0.8.

[0098] The fifth step: sintering and forming

[0099] The obtained green body is placed on the steel back and sintered using a bell-jar type pressure sintering furnace, adopting a technology that combines stepped heating and segmented pressurization. Specific process: Under the condition of a sintering pressure of 1 MPa, heat up to 600 °C; under the condition of a sintering pressure of 2.5 MPa, heat up to the sintering temperature of 930 °C; under the condition of a sintering pressure of 4.5 MPa, hold for 3 hours at the sintering temperature, and a mixed gas composed of H2 and N2 in a volume ratio of 1:1 is used as the full-process protective atmosphere.

[0100] Step 6: Surface treatment

[0101] The sintered and formed blank is naturally cooled to room temperature, its surface is polished smooth and then cleaned and dried for standby.

[0102] Step 7: High-energy braking test

[0103] Use an MM-3000 scaled-down test machine, a hollow circle with a size of 74 mm (outer diameter) × 53 mm (inner diameter), a self-made carbon-ceramic disc by Central South University Powder Metallurgy Research Institute as the counter part, and a braking energy density of 3200 J / cm 2 , the average value of 10 brakings; the test results are shown in Figure 1 , Figure 2 . During high-energy braking, the average friction stability coefficient of the copper-based powder metallurgy brake pad is 0.74, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are respectively and 0.11 cm 3 / MJ and 0.018 cm 3 / MJ.

[0104] Example 4

[0105] Other conditions are the same as those in Example 1, the difference is that the as-prepared hexagonal boron nitride powder, boron carbide powder, and titanium carbide powder are first placed in a high-energy ball mill with a ball-to-material ratio of 50:1, a rotation speed of 450 r / min, and ball milled for 40 hours. After ball milling, through drying treatment, activated and uniformly mixed ceramic powder is obtained; then the activated and uniformly mixed ceramic powder is mixed with the as-prepared electrolytic copper powder 58%, reduced iron powder 16%, electrolytic nickel 2%, atomized tin powder 2%, tungsten powder 2%, and natural flaky graphite powder 10% in the manner of Example 1. The performance of the obtained product is that the average friction stability coefficient is 0.86, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are respectively and 0.05 cm 3 / MJ and 0.005 cm 3 / MJ.

[0106] Example 5

[0107] Other conditions are the same as in Example 4, except for the change in the proportion of composite ceramic powder. 4% hexagonal boron nitride powder, 2% boron carbide powder, and 4% titanium carbide powder are added. The performance of the obtained product is that the average friction stability coefficient is 0.77, and the wear amounts of the copper-based powder metallurgy brake pad and carbon-ceramic are 0.08 cm 3 / MJ and 0.01 cm 3 / MJ.

[0108] Example 6

[0109] Other conditions are the same as in Example 4, except for the change in the ball milling conditions. The ball-to-material ratio is 100:1, the rotation speed is 350 r / min, and the ball milling is carried out for 20 hours. The performance of the obtained product is that the average friction stability coefficient is 0.83, and the wear amounts of the copper-based powder metallurgy brake pad and carbon-ceramic are 0.06 cm 3 / MJ and 0.012 cm 3 / MJ.

[0110] Example 7. Other conditions are the same as in Example 4, except for the change in the mating disk. An MM-3000 scaled-down test machine is used, with a hollow circle having a size of 74 mm (outer diameter) × 53 mm (inner diameter), and a 30CrMnSi steel brake disk as the counter part, with a braking energy density of 3200 J / cm 2 and the average value of 10 brakings. The average friction stability coefficient of the copper-based powder metallurgy brake pad is 0.85, and the wear amounts of the copper-based powder metallurgy brake pad and carbon-ceramic are 0.04 cm 3 / MJ and 0.003 cm 3 / MJ.

[0111] Example 8. Other conditions are the same as in Example 1, except for the change in the mating disk. An MM-3000 scaled-down test machine is used, with a hollow circle having a size of 74 mm (outer diameter) × 53 mm (inner diameter), and a 30CrMnSi steel brake disk as the counter part, with a braking energy density of 3200 J / cm 2 and the average value of 10 brakings. The average friction stability coefficient of the copper-based powder metallurgy brake pad is 0.81, and the wear amounts of the copper-based powder metallurgy brake pad and carbon-ceramic are 0.08 cm 3 / MJ and 0.005 cm 3 / MJ.

[0112] Comparative Example 1:

[0113] Step 1: Weighing of raw materials

[0114] Weigh electrolytic copper powder 58%, reduced iron powder 11%, electrolytic nickel 2%, atomized tin powder 3%, tungsten powder 2%, natural flaky graphite powder 10%, hexagonal boron nitride powder 4%, boron carbide powder 5%, and titanium carbide powder 5% in ascending order by mass percentage. For each raw material added, stir with a crucible for 3 minutes. Finally, add 3% aviation kerosene of the total powder amount to the manually pre-mixed raw materials.

[0115] Step 2: Raw material mixing

[0116] Put the manually pre-mixed raw materials into a V-type mixer that has been cleaned with ethanol and dried. The rotation speed is 100 r / min. Mix at room temperature for 9 hours, and then store in a vacuum-sealed bag.

[0117] Step 3: Green compact pressing

[0118] Pour the stored powder into a mold, and press out a hollow circle with an outer diameter of 74 mm and an inner diameter of 53 mm and a cube with a side length of 25 mm at room temperature. The pressing pressure is 550 MPa, and the pressure holding time is 20 s.

[0119] Step 4: Steel back shot peening

[0120] Perform surface pretreatment on the required steel back. After shot peening and polishing it smoothly, clean and dry it. Its surface roughness is 1.0.

[0121] Step 5: Sintering and forming

[0122] Place the obtained green compact on the steel back and sinter it using a bell-type pressurized sintering furnace, adopting a technology that combines stepwise heating and segmented pressurization. Specific process: Under the condition of a sintering pressure of 1 MPa, heat up to 600 °C; under the condition of a sintering pressure of 2.5 MPa, heat up to the sintering temperature of 930 °C; under the condition of a sintering pressure of 4.5 MPa, hold at the sintering temperature for 3 hours. A mixed gas composed of H2 and N2 in a volume ratio of 1:2 is used as the full-process protective atmosphere.

[0123] Step 6: Surface treatment

[0124] Let the sintered and formed blank cool naturally to room temperature. Polish its surface smoothly, then clean and dry it for standby.

[0125] Step 7: High-energy braking test

[0126] Use an MM-3000 scaled-down test machine, a hollow circle with an outer diameter of 74 mm and an inner diameter of 53 mm, and a self-made carbon-ceramic disk from Central South University Powder Metallurgy Research Institute as the counter part. The braking energy density is 3200 J / cm 2 , and the average value of 10 brakings; the test results are shown in Figure 1 、 Figure 2. During high-energy braking, the average friction stability coefficient of the copper-based powder metallurgy brake pad is 0.61, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are 0.14 cm 3 / MJ and 0.04 cm 3 / MJ.

[0127] Comparative Example 2

[0128] Other conditions are the same as those in Example 1, except for the change in the proportion of the composite ceramic powder. 4% hexagonal boron nitride powder, 8% boron carbide powder, and 0% titanium carbide powder are added. The performance of the obtained product is that the average friction stability coefficient is 0.55, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are 0.18 cm 3 / MJ and 0.10 cm 3 / MJ.

[0129] Comparative Example 3

[0130] Other conditions are the same as those in Example 1, except for the change in the proportion of the composite ceramic powder. 4% hexagonal boron nitride powder, 0% boron carbide powder, and 8% titanium carbide powder are added. The performance of the obtained product is that the average friction stability coefficient is 0.56, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are 0.17 cm 3 / MJ and 0.09 cm 3 / MJ.

[0131] Comparative Example 4

[0132] Other conditions are the same as those in Example 1, except for the change in the proportion of the composite ceramic powder. 0% hexagonal boron nitride powder, 4% boron carbide powder, and 6% titanium carbide powder are added. The performance of the obtained product is that the average friction stability coefficient is 0.58, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are 0.16 cm 3 / MJ and 0.08 cm 3 / MJ.

[0133] Comparative Example 5

[0134] Other conditions are the same as those in Example 1, except for the change in the raw material proportion. 50% electrolytic copper powder, 20% reduced iron powder, 3% electrolytic nickel, 3% atomized tin powder, 4% tungsten powder, 14% natural flaky graphite powder, 2% hexagonal boron nitride powder, 2% boron carbide powder, and 2% titanium carbide powder. The performance of the obtained product is that the average friction stability coefficient is 0.51, and the wear amounts of the copper-based powder metallurgy brake pad and the carbon-ceramic are 0.20 cm 3 / MJ and 0.12 cm 3 / MJ.

[0135] Comparative Example 6

[0136] Other conditions are the same as those in Example 3, except for the change in the raw material ratio. The raw materials include 58% electrolytic copper powder, 18% reduced iron powder, 4% electrolytic nickel, 3% atomized tin powder, 4% tungsten powder, 6% natural flaky graphite powder, 2% hexagonal boron nitride powder, 1% boron carbide powder, and 4% titanium carbide powder. The performance of the obtained product is that the average friction stability coefficient is 0.57, and the wear amounts of the copper-based powder metallurgy brake pads and carbon ceramics are 0.15 cm 3 / MJ and 0.06 cm 3 / MJ.

[0137] Comparative Example 7

[0138] Other conditions are the same as those in Comparative Example 2, except for the change in the mating disk. An MM-3000 scaled-down test machine is used, with a hollow circle having a size of 74 mm (outer diameter) × 53 mm (inner diameter), and a 30CrMnSi steel brake disk as the mating part, with a braking energy density of 3200 J / cm 2 and the average value of 10 brakings. The average friction stability coefficient of the copper-based powder metallurgy brake pads is 0.54, and the wear amounts of the copper-based powder metallurgy brake pads and carbon ceramics are 0.16 cm 3 / MJ and 0.08 cm 3 / MJ.

[0139] Comparative Example 8

[0140] Other conditions are the same as those in Comparative Example 4, except for the change in the mating disk. An MM-3000 scaled-down test machine is used, with a hollow circle having a size of 74 mm (outer diameter) × 53 mm (inner diameter), and a 30CrMnSi steel brake disk as the mating part, with a braking energy density of 3200 J / cm 2 and the average value of 10 brakings. The average friction stability coefficient of the copper-based powder metallurgy brake pads is 0.57, and the wear amounts of the copper-based powder metallurgy brake pads and carbon ceramics are 0.13 cm 3 / MJ and 0.05 cm 3 / MJ.

Claims

1. A copper-based powder metallurgy brake pad containing multiple ceramic components, characterized in that; The raw materials used include, by mass percentage: Electrolytic copper powder: 52 - 58%; Reduced iron powder: 14 - 16%; Electrolytic nickel powder: 2 - 3%; Atomized tin powder: 2 - 2.5%; Tungsten powder: 2 - 4%; Natural flaky graphite powder: 10 - 14%; Hexagonal boron nitride powder: 2%; Boron carbide powder: 2 - 4%; Titanium carbide powder: 5 - 6%; Its preparation method includes the following steps: The first step: Weigh electrolytic copper powder, reduced iron powder, electrolytic nickel powder, atomized tin powder, tungsten powder, natural flaky graphite powder, hexagonal boron nitride powder, boron carbide powder, and titanium carbide powder according to the designed components. First, place the prepared hexagonal boron nitride powder, boron carbide powder, and titanium carbide powder into a high-energy ball mill, add 50 ml of ethanol, use a ball-to-material ratio of 50 - 100:1, control the rotation speed at 350 - 450 r / min; the ball milling time is 10 - 50 hours; then add it to a V-type mixer together with other prepared powders, and supplement 2.5 - 3.5% of the total mass of the powders with aviation kerosene, control the rotation speed at 90 - 100 r / min, and mix at room temperature for 10 - 12 hours to obtain a uniformly mixed powder; The second step: Pour the uniformly mixed powder into a mold and press it into shape. When pressing into shape, control the pressing pressure at 450 - 550 MPa and the pressure holding time at 15 - 25 s; The third step: Shot peening of the steel back Perform surface pretreatment on the required steel back, shot peen and polish it until smooth, then clean and dry it; The fourth step: Sintering and forming Place the obtained green compact on the steel back and sinter it using a pressure sintering furnace, adopting a technology combining stepwise heating and segmented pressurization; specific process: Under the condition of a sintering pressure of 1 - 1.5 MPa, heat up to 600 °C; then raise the sintering pressure to 2 - 2.5 MPa and heat up to the sintering temperature of 910 - 940 °C; then raise the sintering pressure to 3 - 5 MPa and hold at the sintering temperature for 2 - 3 hours, with H2 and N2 as the whole-process protective atmosphere; obtain a copper-based powder metallurgy brake pad containing multiple ceramic components.

2. The copper-based powder metallurgy brake pad containing multiple ceramic components according to claim 1, characterized in that: Among the raw materials used, the content of boron carbide powder is 3 wt% and the content of titanium carbide powder is 5 wt%.

3. A copper-based powder metallurgy brake pad containing multiple ceramic components according to claim 1, characterized in that; The raw materials used include, by mass percentage: Electrolytic copper powder: 58%, reduced iron powder: 16%, electrolytic nickel: 2%, atomized tin powder: 2%, tungsten powder: 2%, natural flaky graphite powder: 10%, hexagonal boron nitride powder: 2%, boron carbide powder: 3%, titanium carbide powder: 5%.

4. A copper-based powder metallurgy brake pad containing multiple ceramic components according to claim 1, characterized in that: The particle size of the electrolytic copper powder is 60 - 80 microns; The particle size of the reduced iron powder is 60 - 80 microns; The particle size of the electrolytic nickel powder is 60 - 80 microns; The particle size of the atomized tin powder is not higher than 80 microns; The particle size of the tungsten powder is 60 - 80 microns; The particle size of the natural flaky graphite powder is 150 - 200 microns; The particle size of the hexagonal boron nitride powder is 60 - 80 microns; The particle size of the boron carbide powder is 60 - 80 microns; The particle size of the titanium carbide powder is 60 - 80 microns.

5. A copper-based powder metallurgy brake pad containing multiple ceramic components according to claim 1, characterized in that: Perform surface pretreatment on the required steel back, clean and dry it after shot peening and polishing it smoothly; measure its surface roughness to be 0.8 - 1.6; When sintering and forming, the protective gas used is composed of H2 and N2 in a volume ratio of 1 - 2:1 - 2.

6. The copper-based powder metallurgy brake pad containing multiple ceramic components according to claim 1, wherein: The prepared copper-based powder metallurgy brake pads containing multiple ceramic components; the density thereof is 4.2-5.2 g / cm 3 , and the porosity is 2-10%.

7. A copper-based powder metallurgy brake pad containing multiple ceramic components according to claim 1, characterized in that: At a braking pressure of 0.6 MPa and a braking inertia of 0.35 kg·m 2 Under these conditions, using an MM-3000 scaled-down test rig, paired with a carbon-ceramic disc, 10 repeated brakings were carried out under dry conditions. The braking speed was set at 24 m / s, and the wear amount was in the range of 0.05 - 0.08 cm 3 / MJ, and the friction stability coefficient was 0.82 - 0.86; At a braking pressure of 0.6 MPa and a braking inertia of 0.35 kg·m 2 Under this condition, using the MM-3000 scaled-down test rig, paired with a 30CrMnSi steel brake disc, 10 repeated brakings are carried out under dry conditions. The braking speed is set at 24 m / s, and the wear amount is between 0.04 and 0.08 cm 3 / / MJ, and the friction stability coefficient is 0.81 - 0.85.

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