A copper-based powder metallurgy friction material containing pretreated MAX phase and its application

Abstract

The present invention specifically relates to a copper-based powder metallurgy friction material containing a pretreated MAX phase and its application. The raw materials used in the present invention include pre-burned powder, copper powder, nickel powder, iron powder, tungsten powder, graphite powder, boron carbide powder, and zirconium oxide powder. The raw materials used in the pre-burned powder are composed of copper powder A and Ti2AlN in a mass ratio of copper powder A:Ti2AlN = 1-6:1. The material is prepared by a process of ball milling followed by pre-burning, wherein the ball milling speed is 100-200 r / min and the time is 12-28 hours; the pre-burning temperature is 500-900°C and the time is 140-160 minutes. The preparation method of the product of the present invention includes the preparation of pre-burned powder, mixing, pressing and sintering. The resulting product has high hardness, friction coefficient, friction stability coefficient, compressive strength, and shear strength, and has a low wear rate on the brake disc. The components of the present invention are rationally designed, the process is simple and controllable, and the resulting product has excellent performance and is easy to industrialize and apply.

Description

Technical Field

[0001] The present invention relates to the field of powder metallurgy friction material preparation, and in particular to a copper-based powder metallurgy material containing MAX phase ceramics, and a preparation method and application thereof. Background Art

[0002] Copper-based materials are widely used in braking and transmission applications such as automotive, high-speed rail, and aerospace due to their excellent mechanical properties, good ductility, and exceptional thermal conductivity and heat resistance. In addition to the matrix component copper, the reinforcing components iron, tungsten, and nickel, and the lubricating component graphite, the friction components are the primary factors that have the greatest impact on the friction performance of copper-based friction materials. Currently, single or composite ceramic components such as SiO2, Al2O3, TiC, SiC, and TiB2 are being introduced into copper-based materials to enhance their mechanical and frictional properties. Patent application publication number CN107012358A discloses a powder metallurgy friction material and preparation process for brake pads. This invention utilizes a composite ceramic friction component of zirconium oxide and silicon carbide to produce a friction material with high friction stability, but does not mention the product's performance parameters. Patent CN116377279A discloses a copper-based powder metallurgy brake pad containing multiple ceramic components and its preparation method. This patent utilizes the size coupling effect of ceramic particles and the synergistic enhancement between components. It is the first attempt to combine ceramic powders B4C and TiC with hexagonal boron nitride powder to enhance the friction coefficient and high temperature stability of copper-based materials. The wear loss is between 0.05 and 0.15 cm 3 / MJ, with a friction stability coefficient of 0.74-0.86 for copper-based brake pads. However, due to the poor wettability between the copper substrate and the friction components, excessive ceramic components often destroy the integrity of the copper substrate structure, resulting in performance degradation.

[0003] Now, a new approach is to introduce the ternary compound MAX phase as a solid lubricant into the copper matrix, which provides an opportunity to develop high-performance copper-based composite materials. The MAX phase is a thermodynamically stable nano-laminated material with hexagonal layers that exhibits a combination of performance characteristics that balance the ductility of metals with the brittleness of ceramics. Patent application CN103302283A and patent CN107460362A both disclose a bronze-based brake pad material containing a MAX phase Ti3AlC2 reinforced with the same and a method for preparing the same. The main difference between the two is the use of the preparation process to control the decomposition of the Ti3AlC2 material. The above patents all indicate that a stable friction coefficient has been achieved, but the interface between the MAX phase and the matrix is ​​difficult to further optimize. Summary of the Invention

[0004] Based on patent applications CN116377279A and CN103302283A, the present invention attempts for the first time to use an appropriate amount of MAX phase Ti2AlN ceramic in combination with zirconium oxide and boron carbide to form a three-ceramic component in order to further enhance the room temperature-high temperature friction stability and mechanical strength of the brake pad, thereby synergistically enhancing the friction performance of the copper-based material. At the same time, in order to strengthen the interface effect between the MAX phase and the Cu matrix, the MAX phase and the appropriate amount of Cu matrix are ball milled and pre-sintered. This not only achieves efficient and stable braking of the copper-based brake pad at high speeds, but also ensures that the resulting copper-based brake pad has high mechanical strength.

[0005] The powder metallurgy copper-based brake pad material disclosed in this invention leverages the high ductility of copper, the self-lubricating properties of Ti2AlN, and the high frictional properties of zirconium oxide and boron carbide. By adjusting the compositional ratios of the components, the copper-based brake pad achieves enhanced friction-lubrication coupling, particularly friction stability under high-speed wear. This improves the friction coefficient of the copper-based brake pad while significantly reducing the wear rate of the mating brake disc.

[0006] In response to the problems of poor wettability between components and the matrix, weak friction stability of the material, etc. in the existing multi-component ceramic reinforced copper-based powder metallurgy brake pad materials, the present invention designs a three-ceramic component synergistic modified copper-based powder metallurgy material containing a nitride MAX phase and a preparation method thereof. The high hardness and strength brought by the ceramic properties of Ti2AlN are used to improve the friction coefficient of the copper-based brake pad, its metallic properties are used to enhance the bonding strength between the ceramic component and the matrix, and its special layered structure is used to achieve self-lubrication of the brake pad material at high temperatures. Combining the above advantages, Ti2AlN is used in combination with high-hardness zirconium oxide and boron carbide to achieve a comprehensive improvement in the comprehensive performance of the copper-based brake pad, especially the friction ability.

[0007] The present invention provides a copper-based powder metallurgy friction material containing a pretreated MAX phase, wherein the proportions of the raw materials are calculated by weight and mainly include the following components:

[0008] Pre-calcined powder 8~40%, preferably 10~35%;

[0009] Electrolytic copper powder B 19-52%, preferably 19-45%;

[0010] Electrolytic nickel powder 1-7%, preferably 2-5%;

[0011] Reduced iron powder 10-20%, preferably 11-16%;

[0012] Tungsten powder 1~6%;

[0013] Graphite powder 8-15%, preferably 10-14%;

[0014] Boron carbide powder 1~5%;

[0015] Zirconia ceramic powder is 1-7%, preferably 1-3%;

[0016] The raw materials used for the calcined powder are composed of copper powder A and Ti2AlN in a mass ratio of copper powder A:Ti2AlN = 1-6:1. The preparation method comprises: weighing copper powder A and Ti2AlN powder according to the component ratio, mixing the two powders, and then placing them in a ball mill. Using an organic solvent, the mixture is ball milled at a high-energy ball mill speed of 100-200 r / min for 12-28 hours. The calcined powder is then pre-calcined at 500-900°C, preferably 500-705°C, for 140-160 minutes to obtain the calcined powder. The organic solvent is preferably ethanol.

[0017] The particle size of the copper powder A is 30-75 microns, the particle size of the Ti2AlN powder is 12-14 microns, and the particle size of the copper powder B is 20-70 microns.

[0018] In the present invention, the Ti2AlN powder is MAX phase Ti2AlN powder.

[0019] As one of the preferred solutions, the present invention provides a copper-based powder metallurgy friction material containing a pretreated MAX phase. The raw materials used in the material are composed of the following components by mass percentage: 10-15% pre-calcined powder, 40-45% electrolytic copper powder B, 5-7% electrolytic nickel powder, 11-16% reduced iron powder, 4-6% tungsten powder, 10-14% graphite powder, 2-4% boron carbide powder, and 2-4% zirconium oxide ceramic powder; the raw materials of the pre-calcined powder are composed of copper powder A and Ti2AlN in a mass ratio of 1-1.2:1.

[0020] As one preferred embodiment, the present invention provides a copper-based powder metallurgy friction material containing a pretreated MAX phase. The raw materials used are composed, by mass percentage, of the following components: 30-35% pre-calcined powder, 19-25% electrolytic copper powder B, 5-7% electrolytic nickel powder, 14-16% reduced iron powder, 4-6% tungsten powder, 10-14% graphite powder, 2-4% boron carbide powder, and 2-4% zirconium oxide ceramic powder. The pre-calcined powder is composed of copper powder A and Ti2AlN in a mass ratio of 5.8-6:1. This solution maintains a stable friction coefficient of 0.36 while minimizing wear on the brake disc.

[0021] As a further preferred embodiment, the present invention provides a copper-based powder metallurgy friction material containing a pretreated MAX phase. The raw materials used are composed, by mass percentage, of the following components: 10-11% pre-calcined powder, 44-45% electrolytic copper powder B, 5-7% electrolytic nickel powder, 11-16% reduced iron powder, 4-6% tungsten powder, 10-14% graphite powder, 2-4% boron carbide powder, and 2-4% zirconium oxide ceramic powder. The raw materials for the pre-calcined powder are composed of copper powder A and Ti2AlN in a 1:1 mass ratio. This solution leverages the frictional properties of zirconium oxide and boron carbide, synergistically with the self-lubricating effect of Ti2AlN, achieving synergistic friction and lubrication enhancement for powder metallurgy brake pads. This improves the friction coefficient and friction stability coefficient of the brake pad while minimizing wear on the brake pad and disc.

[0022] On the basis of the above further preferred scheme, controlling the sintering temperature of the pre-fired powder to 695~705 ℃ and the pre-fired time to 140~145 min can further improve the hardness of the product, the friction coefficient and friction coefficient stability coefficient of the product, the compressive strength and shear strength of the product and effectively reduce the wear rate of the product on the brake disc.

[0023] The present invention discloses a copper-based powder metallurgy friction material containing a pretreated MAX phase. Electrolytic copper powders A and B serve as the main components of the material. Copper powder A has a particle size of 70-75 microns, and copper powder B has a particle size of 60-70 microns. The reduced iron powder has a particle size of 60-80 microns, preferably 65-75 microns. The electrolytic nickel powder and tungsten powder have particle sizes of 60-80 microns, preferably 65-75 microns. The graphite powder is preferably flaky graphite powder. As a lubricating component, flaky graphite powder primarily promotes tribofilm formation, thereby reducing friction. The particle size is 120-180 microns, preferably 130-170 microns.

[0024] In the present invention, the particle size of zirconium oxide is 3-5 microns, more preferably 4-5 microns. The particle size of boron carbide is 2-8 microns, more preferably 4-6 microns.

[0025] Compared to existing copper-based friction materials, this invention strengthens the interface between the MAX phase and the Cu matrix through a pre-treatment process of ball milling and sintering the Ti2AlN and Cu matrix, resulting in a combined improvement in both the friction coefficient and friction stability. Especially under the unique conditions of high-speed emergency braking, the copper-based powder metallurgy brake pad containing MAX phase ceramics designed and prepared in this invention exhibits a high friction coefficient and strong stability, while also achieving low wear rate and mating component damage rate.

[0026] The present invention provides a copper-based powder metallurgy friction material containing a pretreated MAX phase, the preparation of which comprises the following steps:

[0027] Step 1: Preparation of calcined powder

[0028] Copper powder A and Ti2AlN powder are prepared as raw materials in a mass ratio of 1-6:1. The mixture is then uniformly mixed in a ball mill and milled at a high-energy speed of 100-200 r / min using an organic solvent for 12-28 hours, preferably 18-22 hours. The mixture is then pre-calcined at 500-900°C, preferably 500-705°C, for 140-160 minutes to obtain a calcined powder. The organic solvent is preferably ethanol.

[0029] Step 2: Mixing

[0030] The raw materials are dispensed according to the designed composition, and the dispensed raw material powders are mixed with the pre-treated powder to obtain a uniformly mixed powder; during mixing, the powders are first mixed by stirring, and then mixed using a V-type mixer; during mixing, aviation kerosene is added at 2-3% by weight of the raw material powders, and the speed of the V-type mixer is controlled to be 80-120 rpm and the mixing time is 45 minutes to 5 hours;

[0031] Step 3: Pressing

[0032] The uniformly mixed powder is added to a mold and pressed to obtain a pressed green body, wherein the process parameters of the pressing process are: pressure 500-600 MPa, holding time 20-30 seconds;

[0033] Step 4: Sintering

[0034] The green body is placed in a pressurized furnace and sintered in three stages under an argon atmosphere to obtain the product;

[0035] The parameters of the first stage sintering are: sintering pressure 1.5-2.5MPa, temperature 500~600℃, heat and pressure holding for 1~2 hours,

[0036] The parameters of the second stage sintering are: sintering pressure 2.5-3.5MPa, temperature 600~700℃, heat and pressure holding for 1~3 hours,

[0037] The parameters of the third stage sintering are: sintering pressure 3.5-5MPa, temperature 700~940℃, and heat and pressure holding for 2~3 hours.

[0038] To further strengthen the interfacial bonding between the Ti2AlN and Cu matrix, the present invention pre-treats the Ti2AlN and Cu by ball milling and sintering. Ball milling helps refine the grain size of both materials and increases surface activity. The subsequent sintering step effectively promotes atomic diffusion between the two, strengthening the interfacial bonding. Selecting an appropriate rotational speed of 100-200 rpm during the ball milling process significantly reduces the particle size of the Ti2AlN and Cu powders and increases surface activity, which facilitates subsequent diffusion. Too low a rotational speed results in insignificant enhancement. Too high a rotational speed results in too small Ti2AlN particles, potentially preventing them from exerting a frictional effect. The sintering temperature directly influences the interfacial behavior between the Ti2AlN and Cu. Samples sintered at approximately 700°C achieve optimal interface stability. Too low a sintering temperature results in insufficient atomic diffusion energy between the Ti2AlN and Cu, resulting in poor diffusion interface stability. Too high a sintering temperature can cause Ti2AlN to decompose, resulting in loss of its layered structure and lubrication properties.

[0039] The application of the copper-based powder metallurgy friction material containing a pretreated MAX phase of the present invention includes brake pads for automobiles, trains and high-speed railways.

[0040] Beneficial effects

[0041] The present invention utilizes copper as the matrix component and elements such as iron, tungsten, and nickel as reinforcing components, fully ensuring the ductility and mechanical strength of the matrix material. Graphite is used as a lubricating component to prevent excessive wear of the copper matrix during wear. Ti2AlN, zirconium oxide, and titanium carbide are used as friction components to enhance the friction performance of the copper-based brake pad. The boron carbide component, with its high hardness and strength, significantly improves the material's coefficient of friction. Furthermore, it oxidizes at high temperatures to form a boron oxide tribofilm, improving the surface smoothness of the matrix. While zirconium oxide particles have high hardness, they have poor wettability with the copper matrix and are prone to falling off during friction, damaging the copper-based brake pad and causing uneven friction. Therefore, the present invention selects Ti2AlN ceramic particles, a self-lubricating MAX phase ceramic material, which combines the unique properties of ceramics and metals. On the one hand, they have high wettability with the matrix and strong bonding, effectively improving the friction coefficient. On the other hand, their internal layered structure allows them to act as a solid lubricant, providing lubrication for the matrix. Finally, the amorphous aluminum oxide formed after the Ti2AlN grinding chips are oxidized can play a synergistic role in friction-lubrication enhancement. However, the interface bonding between Ti2AlN and the copper matrix is ​​still an important factor that restricts the further improvement of the friction performance of copper-based composite materials. Therefore, the present invention starts from the actual working conditions of high temperature generated by emergency braking of the brake pad, controls the ratio of MAX phase ceramics, zirconium oxide and titanium carbide, and utilizes the synergistic enhancement effect between ceramic components to improve the friction instability problem existing when a single or double ceramic component reinforces the matrix. At the same time, ball milling and high-temperature pretreatment are used to further strengthen the interface effect between Ti2AlN and the Cu matrix, which is conducive to improving the mechanical properties of the Cu-based composite material. The stronger mechanical properties give the material a stronger ability to resist wear, and at the same time, it is conducive to the better preservation of Ti2AlN particles on the friction surface, thereby forming a friction film with lubricating properties in the subsequent friction process, thereby enhancing the friction and wear performance of the copper-based brake pad under extreme working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 : XRD pattern of MAX phase Ti2AlN ceramics used in the examples;

[0043] Figure 2 This is a microscopic morphology of the product obtained in Example 4;

[0044] Figure 3 This is a microscopic morphology of the large-particle MAX phase in the product obtained in Example 4;

[0045] Figure 4 The friction curve of the fifth braking test of the product obtained in Example 1 is shown in FIG.

[0046] Figure 5 A graph showing a change in the friction stability coefficient of the product obtained in Example 1;

[0047] Figure 6 The friction curve of the 5th braking test of the product obtained in Example 2 is shown in FIG.

[0048] Figure 7 This is a graph showing the change in friction stability coefficient of the product obtained in Example 3;

[0049] Figure 8 This is a friction curve diagram of the 5th braking test of the product obtained in Example 3;

[0050] Figure 9 This is a graph showing the change in friction stability coefficient of the product obtained in Example 3;

[0051] Figure 10 This is a friction curve diagram of the fifth braking test of the product obtained in Example 4;

[0052] Figure 11 This is a graph showing the change in friction stability coefficient of the product obtained in Example 4.

[0053] from Figure 1 It can be seen that the MAX phase Ti2AlN crystal form is simple and stable, without too many impurity peaks, indicating that its properties are relatively stable.

[0054] from Figure 2 It can be seen that the graphite, zirconium oxide, and boron carbide in the product obtained in Example 4 do not chemically react with the copper matrix, and are simply mechanically bonded. The reinforcing elements such as nickel and tungsten are evenly dispersed in the matrix to strengthen it.

[0055] from Figure 3 It can be seen that a diffusion reaction occurs between the MAX phase ceramic and the copper matrix. The copper element diffuses into the Ti2AlN particles along the grain boundaries, forming a chemical diffusion bond. This bonding method can greatly enhance the interaction between the matrix and the MAX phase ceramic particles.

[0056] from Figure 4 It can be seen that the friction coefficient of the product obtained in Example 1 is around 0.41, and the friction stability coefficient is around 0.61. This is mainly due to the low ball milling speed and sintering temperature, which lead to poor interface bonding between Ti2AlN and Cu, which is not conducive to the subsequent lubrication effect.

[0057] from Figure 5 It can be seen that the friction stability coefficient of the product obtained in Example 1 is low and fluctuates greatly.

[0058] from Figure 6It can be seen that the product obtained in Example 2, prepared at the optimal ball milling speed of 200 rpm and sintering temperature of 700°C, exhibits the highest average friction coefficient of 0.45. The strong bond between Ti2AlN and the Cu matrix helps Ti2AlN remain in the friction interface during the friction process and exerts a lubricating effect.

[0059] from Figure 7 It can be seen that the friction stability coefficient of the product obtained in Example 2 is higher and the fluctuation range is smaller.

[0060] from Figure 8 It can be seen that excessively high ball milling speed and sintering temperature will lead to a decrease in the friction coefficient of Example 3. This is because excessively high ball milling speed will result in the Ti2AlN particles being too small, which is not conducive to their friction properties.

[0061] from Figure 9 It can be seen that the friction stability coefficient of Example 3 decreases under high-temperature sintering, which may be because the high temperature causes the decomposition of Ti2AlN and the destruction of the layered structure.

[0062] from Figure 10 It can be seen that adding excessive Cu powder during the pretreatment process causes the friction coefficient of Example 4 to decrease to 0.36. This is because excessive Cu agglomerates during sintering, causing the integrity of the material to be destroyed, thereby resulting in a decrease in friction performance.

[0063] from Figure 11 It can be seen that the change in the friction stability coefficient of the product obtained in Example 4 is that the average friction stability coefficient of the 10 test results is about 0.82. DETAILED DESCRIPTION

[0064] The average friction coefficient and friction stability coefficient of the products obtained in the Examples and Comparative Examples were obtained by conducting braking tests using an MM-3000 scaled-down testing machine with carbon-ceramic discs forming a friction pair. The experimental parameters were: a braking pressure of 0.5 MPa, a braking inertia of 0.45 kg·m², and a rotational speed of 24 m / s. Each experimental data was averaged after 10 repetitions of the braking test.

[0065] In the present invention, the friction stability coefficient (SC) is calculated as follows: SC=μ / μmax; wherein μ represents the average friction coefficient, and μmax represents the maximum friction coefficient.

[0066] Example 1

[0067] Step 1: Prepare Ti2AlN powder and electrolytic copper powder in a mass ratio of Ti2AlN powder to Cu powder of 1:1. Mix the prepared Ti2AlN powder and Cu powder evenly and place them in a ball mill. Use ethanol as the solvent and high-energy ball mill at a speed of 100 r / min for 20 hours. Sieve the fully mixed powder, place it in a corundum crucible, cover it, and pre-calculate it at 500°C for 140 minutes to obtain a calcined powder.

[0068] Among them: the particle size of electrolytic copper powder is 70~75 microns, and the particle size of Ti2AlN powder ceramic particles is 12~14 microns.

[0069] Step 2: Weigh the raw materials. According to the formula weight percentage, weigh 45% electrolytic copper powder, 15% reduced iron powder, 6% electrolytic nickel powder, 5% tungsten powder, 14% graphite powder, 2% boron carbide powder, 3% zirconium oxide powder, and 10% of the pre-calcined powder obtained in step 1 (i.e., the pre-treated mixed powder of Ti2AlN and Cu).

[0070] Among them: the particle size of electrolytic copper powder is 60~70 microns, the particle size of reduced iron powder is 60~70 microns, the particle size of electrolytic nickel is 65~70 microns, the particle size of tungsten powder is 60~70 microns, the particle size of graphite powder is 120~150 microns, the particle size of boron carbide particles is 2~4 microns, the particle size of zirconia ceramic particles is 3~4 microns, and the particle size of pre-calcined powder is 10~12 microns.

[0071] Step 3: Mix evenly. Add 3% by mass of aviation kerosene to the raw material powder and then add it to a V-shaped blender and stir at 100 rpm for 1 hour.

[0072] Step 4: Green body molding: Pour the raw materials into a ring mold and press at a pressure of 500 MPa for 15 seconds to produce a green body sample.

[0073] Step 5: Pressure Sintering. The green body is placed in a pressure sintering furnace and sintered in a multi-step process under an argon atmosphere to produce the finished product. The sintering process includes the following: the first stage: sintering pressure of 2 MPa, temperature of 600°C, and holding temperature for 1 hour; the second stage: sintering pressure of 3 MPa, temperature of 700°C, and holding temperature for 1 hour; and the third stage: sintering pressure of 5 MPa, temperature of 940°C, and holding temperature for 3 hours. The resulting product properties are shown in Table 1.

[0074] Example 2

[0075] Step 1: Prepare Ti2AlN powder and electrolytic copper powder in a mass ratio of Ti2AlN powder to Cu powder of 1:1. Mix the prepared Ti2AlN powder and Cu powder evenly and place them in a ball mill. Use ethanol as the solvent and high-energy ball mill at a speed of 200 r / min for 20 hours. Sieve the fully mixed powder, place it in a corundum crucible, cover it, and pre-calculate it at 700°C for 140 minutes to obtain a calcined powder.

[0076] Among them: the particle size of electrolytic copper powder is 70~75 microns, and the particle size of Ti2AlN powder ceramic particles is 12~14 microns.

[0077] Step 2: Weigh the raw materials. According to the formula's mass percentages, weigh 45% electrolytic copper powder, 15% reduced iron powder, 6% electrolytic nickel powder, 5% tungsten powder, 14% graphite powder, 2% boron carbide powder, and 3% zirconium oxide powder. The pre-calcined powder obtained in Step 1 (i.e., the pre-treated mixed powder of Ti2AlN and Cu) is 10% of the raw materials. The particle size of the electrolytic copper powder is 65-70 microns, the particle size of the reduced iron powder is 65-70 microns, the particle size of the electrolytic nickel powder is 65-70 microns, the particle size of the tungsten powder is 65-70 microns, the particle size of the graphite powder is 130-150 microns, the particle size of the boron carbide particles is 2-5 microns, and the particle size of the zirconium oxide ceramic particles is 3-5 microns. The particle size of the pre-calcined powder obtained in Step 1 is 10-15 microns.

[0078] Step 2: Mix evenly. Add 3% by mass of aviation kerosene to the raw material powder and then add it to a V-shaped blender and stir at 200 rpm for 2 hours.

[0079] Step 3: Green body molding: Pour the raw materials into a ring mold and press at a pressure of 500 MPa for 30 seconds to produce a green body sample.

[0080] Step 4: Pressure Sintering. The green body is placed in a pressure sintering furnace and sintered in a multi-step process under an argon atmosphere to produce the finished product. The sintering process includes the following: the first stage: sintering pressure of 3 MPa, temperature of 600°C, and holding temperature for 2 hours; the second stage: sintering pressure of 4 MPa, temperature of 800°C, and holding temperature for 2 hours; and the third stage: sintering pressure of 5 MPa, temperature of 980°C, and holding temperature for 4 hours. The resulting product properties are shown in Table 1.

[0081] Example 3

[0082] Step 1: 5 wt% Ti2AlN powder and 5 wt% Cu powder were evenly mixed and placed in a ball mill. The mixture was then ball milled at a high-energy ball mill speed of 300 r / min for 20 h using organic matter as a solvent. The fully mixed powder was sieved and placed in a corundum crucible, which was covered and pre-calcined at 900°C for 140 min to obtain a calcined powder.

[0083] Among them: the particle size of electrolytic copper powder is 70~75 microns, and the particle size of Ti2AlN powder ceramic particles is 12~14 microns.

[0084] Step 2: Weigh the raw materials. According to the formula's mass percentages, weigh 45% electrolytic copper powder, 15% reduced iron powder, 6% electrolytic nickel powder, 5% tungsten powder, 14% graphite powder, 2% boron carbide powder, 3% zirconium oxide powder, and 10% Ti2AlN and Cu pretreated mixed powder. The particle size of the electrolytic copper powder is 70-75 microns, the particle size of the reduced iron powder is 70-75 microns, the particle size of the electrolytic nickel powder is 70-75 microns, the particle size of the tungsten powder is 70-75 microns, the particle size of the graphite powder is 140-150 microns, the particle size of the boron carbide particles is 4-6 microns, the particle size of the zirconium oxide ceramic particles is 4-5 microns, and the particle size of the Ti2AlN ceramic powder is 12-14 microns.

[0085] Step 3: Mix evenly. Add 3% by mass of aviation kerosene to the raw material powder and then add it to a V-shaped blender and stir at 200 rpm for 5 hours.

[0086] Step 4: Green body molding: Pour the raw materials into a ring mold and press at a pressure of 500 MPa for 60 seconds to produce a molded green body sample.

[0087] Step 5: Pressure Sintering. The green body is placed in a pressure sintering furnace and sintered in a multi-step process under an argon atmosphere to produce the finished product. The sintering process includes the following: the first stage: sintering pressure of 3 MPa, temperature of 600°C, and holding temperature for 4 hours; the second stage: sintering pressure of 4 MPa, temperature of 800°C, and holding temperature for 4 hours; and the third stage: sintering pressure of 5 MPa, temperature of 980°C, and holding temperature for 6 hours. The resulting product properties are shown in Table 1.

[0088] Example 4

[0089] The preparation method and experimental parameters are basically the same as those in Example 2, except that:

[0090] During the first step of powder pretreatment, the Cu powder was weighed at 30% and the Ti2AlN powder was weighed at 5%;

[0091] The second step is to weigh the raw materials according to the formula: 20% electrolytic copper powder, 15% reduced iron powder, 6% electrolytic nickel powder, 5% tungsten powder, 14% graphite powder, 2% boron carbide powder, 3% zirconium oxide powder, and 35% Ti2AlN and Cu pretreated mixed powder.

[0092] The properties of the obtained product are shown in Table 1.

[0093] Comparative Example 1

[0094] The preparation method and experimental parameters were essentially the same as those in Example 1, except that Ti2AlN ceramic powder was not added as a friction component in this example. Instead, 50% electrolytic copper powder, 15% reduced iron powder, 6% electrolytic nickel powder, 5% tungsten powder, 14% graphite powder, 2% boron carbide powder, and 8% zirconium oxide powder were weighed in a single batch according to the formula's mass percentages. The resulting product properties are shown in Table 1.

[0095] Comparative Example 2

[0096] The preparation method and experimental parameters were essentially the same as those in Example 2, except that zirconium oxide ceramic powder was omitted as a friction component. Instead, 56% electrolytic copper powder, 13% reduced iron powder, 3% electrolytic nickel powder, 4% tungsten powder, 12% graphite powder, 4% boron carbide powder, and 8% Ti2AlN powder were weighed in a single batch according to the formula's mass percentages. The resulting product properties are shown in Tables 1 and 2.

[0097] Comparative Example 3

[0098] The preparation method and experimental parameters are basically the same as those in Example 2, except that no copper powder is added during the pretreatment process in this example, and only 5% Ti2AlN is pretreated separately. The properties of the obtained product are shown in Tables 1 and 2.

[0099] Comparative Example 4

[0100] Other conditions were the same as those in Example 2, except that the Ti2AlN powder in this example did not undergo ball milling during the pretreatment process. The properties of the obtained product are shown in Tables 1 and 2.

[0101] Comparative Example 5

[0102] Other conditions were the same as those in Example 4, except that the Cu powder and Ti2AlN powder were not pre-sintered during the pretreatment process. The properties of the obtained products are shown in Tables 1 and 2.

[0103] The products obtained in the Examples and Comparative Examples were paired with carbon-ceramic discs and subjected to simulated friction tests in an MM-3000 friction and wear tester. The test parameters were: braking speed: 6000 rpm, braking pressure: 0.6 MPa, and braking inertia: 0.35 kg·m². Under these test parameters, the temperature of the friction surface during high-speed friction reached approximately 900°C.

[0104]

[0105] As shown in Table 1, the average friction coefficient of all examples exceeds the national standard of 0.35. In Example 2, the material exhibits the highest friction coefficient, the lowest friction stability coefficient and wear rate; this is due to the optimal pretreatment of Cu and Ti2AlN powders at 200 rpm and sintering at 700°C. At this time, the interface bonding ability between Cu powder and Ti2AlN is the strongest. Stronger interface bonding gives the composite material better mechanical properties such as hardness and shear strength. Therefore, it exhibits better resistance to friction during the friction process. Moreover, the stronger interface bonding force of Ti2AlN helps it remain on the friction surface during the friction process, providing a lubricating effect. In Example 1, due to the lower ball milling speed and sintering temperature, incomplete atomic diffusion leads to weaker interface bonding force, resulting in weakened friction performance. In Example 3, the ball milling speed and sintering temperature are too high. Excessively high sintering temperature may lead to the decomposition of Ti2AlN and the destruction of the layered structure, which will cause it to lose its original lubricating properties. In Example 4, the content of Cu powder in the pretreatment is much greater than that of Ti2AlN. Excessive Cu will cause agglomeration during the sintering process, destroying the overall performance of the composite material, which will lead to deterioration of friction performance.

[0106] In Comparative Example 1, there are no Ti2AlN ceramic particles, and therefore, there is no layered MAX phase lubrication effect, its average friction coefficient is high, and the friction stability is insufficient. This leads to a higher wear rate in Comparative Example 1. In Comparative Example 2, there are no zirconia ceramic particles, and there is no zirconia to provide an abrasive wear effect. The average friction coefficient of Comparative Example 2 is only 0.2, which is far below the national standard. In Comparative Example 3, no Cu powder is added during the pretreatment process, which is not conducive to the element diffusion between Ti2AlN and Cu, and its interface bonding performance is poor. Therefore, the friction stability coefficient of Comparative Example 3 is lower than that of Example 2. In Comparative Example 4, the ball milling process is not performed during the pretreatment process of Ti2AlN powder. Therefore, although the friction coefficient of Comparative Example 4 is high, the friction stability is extremely poor. This may be because the surface activity of the powder that has not undergone the ball milling process is low, and the element diffusion difficulty is high, which is not conducive to its lubrication performance in the subsequent friction process. The difference between Comparative Example 5 and Example 2 is that no sintering step is performed during the pretreatment process, and there is no obvious diffusion bonding between Ti2AlN and Cu powder, which is not conducive to their retention during the friction process and it is difficult to exert the friction-lubrication properties. Therefore, the friction coefficient and friction stability coefficient are both low.

[0107]

[0108] As shown in Table 2, Example 2, prepared at the optimal ball milling speed and sintering temperature, exhibited the best hardness, compressive strength, and shear strength. This strengthening comes from the stronger interface bonding effect brought about by the element diffusion behavior of Ti2AlN and Cu powder during the pretreatment process. This bonding can effectively resist the expansion of external cracks generated in the material under the action of external forces, which is beneficial to the strengthening of the mechanical properties of the composite material. The ball milling speed and sintering temperature of the embodiment are too low, which is not conducive to the diffusion of elements. The sintering temperature of Example 3 is too high, resulting in excessive growth of Ti2AlN grains. The oversized grains destroy the internal balance of the material, and microcracks are easily generated around the large particles when subjected to external forces. The excessive Cu in Example 4 agglomerates during the sintering process, which is not conducive to subsequent molding. Therefore, the mechanical properties of the composite material are damaged. Comparative Example 1 and Comparative Example 2 show that Comparative Example 2 is greater than Comparative Example 1 because Ti2AlN enhances the mechanical properties of the Cu material better than ZrO2. The mechanical properties of Comparative Example 3 were inferior to those of Example 2 because no Cu powder was added during pretreatment, resulting in poor interfacial bonding. Comparative Example 4 was due to the poor surface activity of the unmilled powder. Comparative Example 5 was due to the weak diffusion bonding between the unsintered Cu powder and Ti2AlN, making it difficult to resist the growth of microcracks during deformation.

Claims

1. A copper-based powder metallurgy friction material containing a pretreated MAX phase, characterized in that: The proportions of the raw materials are calculated by weight percentage and include the following components: Pre-burned powder 8~40%; Electrolytic copper powder B 19~52%; Electrolytic nickel powder 1~7%; Reduced iron powder 10~20%; Tungsten powder 1~6%; Graphite powder 8~15%; Boron carbide powder 1~5%; Zirconia ceramic powder is 1~7%; The raw materials used for the pre-calcined powder are composed of copper powder A and Ti2AlN in a mass ratio of copper powder A:Ti2AlN=1-6:

1. The preparation method is as follows: copper powder A and Ti2AlN powder are weighed respectively according to the component ratio, the two are evenly mixed, and then placed in a ball milling equipment, using organic matter as a solvent, and ball milling the mixed powder with a high-energy ball mill at a rotation speed of 100-200 r / min for 12-28 hours, and then pre-calcining at 500-900°C for 140-160 minutes to obtain the pre-calcined powder.

2. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 1, characterized in that: The particle size of the copper powder A is 30-75 microns, the particle size of the Ti2AlN ceramic powder is 12-14 microns, and the particle size of the copper powder B is 20-70 microns.

3. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 1, characterized in that: The raw materials used are composed of the following components by mass percentage: The pre-calcined powder comprises 10-15%, electrolytic copper powder B 40-45%, electrolytic nickel powder 5-7%, reduced iron powder 11-16%, tungsten powder 4-6%, graphite powder 10-14%, boron carbide powder 2-4%, and zirconium oxide ceramic powder 2-4%. The raw materials of the pre-calcined powder are composed of copper powder A and Ti2AlN in a mass ratio of 1-1.2:

1.

4. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 1, characterized in that: The raw materials used are composed of the following components by mass percentage: 30-35% of pre-calcined powder, 19-25% of electrolytic copper powder B, 5-7% of electrolytic nickel powder, 14-16% of reduced iron powder, 4-6% of tungsten powder, 10-14% of graphite powder, 2-4% of boron carbide powder, and 2-4% of zirconium oxide ceramic powder; the raw materials of the pre-calcined powder are composed of copper powder A and Ti2AlN in a mass ratio of 5.8-6:

1.

5. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 3, characterized in that: The raw materials used are composed of the following components by mass percentage: 10-11% pre-calcined powder, 44-45% electrolytic copper powder B, 5-7% electrolytic nickel powder, 11-16% reduced iron powder, 4-6% tungsten powder, 10-14% graphite powder, 2-4% boron carbide powder, and 2-4% zirconium oxide ceramic powder; the raw materials of the pre-calcined powder are composed of copper powder A and Ti2AlN in a mass ratio of 1:

1.

6. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 5, characterized in that: The sintering temperature of the pre-fired powder is controlled to be 695~705℃ and the pre-fired time is 140~145 min.

7. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 1, characterized in that: The particle size of the reduced iron powder is 60~80 microns, the particle size of the electrolytic nickel powder and the tungsten powder is 60~80 microns, the graphite powder is flaky graphite powder, and its particle size is 120~180 microns; the zirconium oxide particle size is 3~5 microns, and the boron carbide particle size is 2~8 microns.

8. A copper-based powder metallurgy friction material containing a pretreated MAX phase according to any one of claims 1 to 7, characterized in that: Its preparation comprises the following steps: Step 1: Preparation of calcined powder Copper powder A and Ti2AlN powder are prepared as raw materials in a mass ratio of copper powder A:Ti2AlN=1-6:

1. The two are evenly mixed and placed in a ball mill. The mixture is ball milled for 12-28 hours using an organic solvent at a high-energy ball mill speed of 100-200 r / min, and then pre-calcined at 500-900°C for 140-160 minutes to obtain a calcined powder. Step 2: Mixing The raw materials are dispensed according to the designed composition, and the dispensed raw material powders are mixed with the pre-treated powder to obtain a uniformly mixed powder; during mixing, the powders are first mixed by stirring, and then mixed using a V-type mixer; during mixing, aviation kerosene is added at 2-3% by weight of the raw material powders, and the speed of the V-type mixer is controlled to be 80-120 rpm and the mixing time is 45 minutes to 5 hours; Step 3: Pressing The uniformly mixed powder is added to a mold and pressed to obtain a pressed green body, wherein the process parameters of the pressing process are: pressure 500-600 MPa, holding time 20-30 seconds; Step 4: Sintering The green body is placed in a pressurized furnace and sintered in three stages under an argon atmosphere to obtain the product; The parameters of the first stage sintering are: sintering pressure 1.5~2.5MPa, temperature 500~600℃, heat and pressure holding for 1~2 hours, The parameters of the second stage sintering are: sintering pressure 2.5~3.5MPa, temperature 600~700℃, heat and pressure holding for 1~3 hours, The parameters of the third stage sintering are: sintering pressure 3.5~5MPa, temperature 700~940℃, and heat and pressure holding for 2~3 hours.

9. The copper-based powder metallurgy friction material containing a pretreated MAX phase according to claim 8, characterized in that: In step 1, the high-energy ball milling time is 18-22 hours, and the pre-sintering temperature is 500-705°C.

10. Use of the copper-based powder metallurgy friction material containing a pretreated MAX phase according to any one of claims 1 to 7, characterized in that: The application includes use as a brake pad for at least one of automobiles, trains, and high-speed railways.

Images