High-performance brake copper alloy and method for producing the same

Abstract

The application discloses a high-performance braking copper alloy and a preparation method thereof. The copper alloy is a copper alloy with a cerium titanate / cerium silicate friction phase and a Ti3AlC2 lubricating phase. Copper alloy powder with surface-loaded cerium titanate / cerium silicate and titanium-aluminum alloy powder with surface-loaded graphene oxide are mixed by ball milling, and Ti3AlC2 lubricating phase is formed by in-situ reaction of Ti-Al-C through vacuum sintering, thereby reducing the wear rate. On the other hand, the cerium titanate / cerium silicate serves as a friction component, improves the braking friction, and the high temperature of friction promotes the formation of an oxide layer of cerium elements on the surface of the friction layer, thereby stabilizing the friction factor and effectively improving the stability of the braking process.

Description

Technical Field

[0001] This invention relates to high-performance brake copper alloys and their preparation methods, and particularly to a brake copper alloy with synergistic enhancement of in-situ lubrication phase and friction phase and its preparation method. Background Technology

[0002] High-speed train braking systems primarily employ disc brakes, relying on the friction between brake pads and the brake disc to dissipate a significant amount of train kinetic energy and achieve braking. As a crucial component of the braking system, brake pads endure the combined effects of high pressure, high temperature, high speed, and impact loads during braking friction, operating under extremely harsh conditions. Therefore, the requirements for brake pads are becoming increasingly stringent. Copper alloys are widely used due to their excellent thermal conductivity, mechanical properties, and braking performance, and have the potential to meet even higher braking demands. Common brake copper alloys generally consist of a matrix component, a friction component, and a lubrication component. The matrix component, copper, possesses excellent thermal conductivity, high-temperature stability, and friction and wear resistance. The friction component, to ensure stability during high-speed, high-temperature braking, mainly consists of high-hardness ceramic particles (carbides, oxides, etc.) that improve and stabilize the coefficient of friction. These hard ceramic phases, after being cut and crushed, form wear debris that fills the surface friction layer, stabilizing the coefficient of friction and thus stabilizing the braking performance of the brake pads at high temperatures. Lubricating components have a lubricating effect and can reduce the wear of brake pads and brake discs. Common lubricating components include layered materials such as graphite and MoS2.

[0003] As high-speed trains reach increasingly higher speeds, the significant kinetic energy dissipated during braking results in substantial frictional heat, causing a sharp rise in brake pad temperature. This places higher demands on the friction coefficient, wear resistance, and thermal stability of brake pads. Current technologies often employ h-BN and Ti3SiC2 as lubricants, and high-hardness ceramics such as c-BN and B4C as hard phases to improve the wear resistance and frictional stability of copper alloys. Other technologies utilize silicon oxide, zirconium oxide, and alumina, which exhibit good high-temperature stability, as hard phases to enhance braking stability. These technologies improve the service life and stability of brake copper alloy brake pads. However, the increasingly high speeds of high-speed trains and the resulting high temperatures during braking easily lead to material oxidation and fluctuations in the friction coefficient. Therefore, simultaneously improving the wear resistance of brake copper alloys and enhancing their high-temperature oxidation resistance has become a key technical challenge. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a high-performance brake copper alloy.

[0005] Another object of the present invention is to provide a method for preparing the high-performance brake copper alloy.

[0006] Technical solution: The high-performance braking copper alloy of the present invention is a copper alloy that is synergistically reinforced by a friction phase of cerium titanate / cerium silicate and a lubricating phase of Ti3AlC2.

[0007] Furthermore, the cerium titanate / cerium silicate friction phase is formed by stirring tetraethyl orthosilicate and tetrabutyl titanate solution evenly, then adding cerium nitrate and copper alloy powder successively, using oxalic acid as a complexing agent to form a gel, and then calcining it to synthesize a phase loaded onto the surface of copper alloy powder.

[0008] Furthermore, the Ti3AlC2 lubricating phase is formed by plasma grafting of amino groups onto the surface of titanium-aluminum alloy powder, followed by acetic acid protonation, electrostatic adsorption of graphene oxide, and induction of in-situ reaction between Ti-Al-C by high-temperature sintering.

[0009] The preparation method of the high-performance brake copper alloy of the present invention includes the following steps: (1) The titanium-aluminum alloy powder was ultrasonically cleaned in anhydrous ethanol for 10 min and then dried. Amino groups were grafted onto the surface of the titanium-aluminum alloy powder under an ammonia atmosphere using plasma for 15-20 min. The powder was then added to a 0.1-0.2 mol / L acetic acid solution for protonation for 15-30 min and dried to obtain a titanium-aluminum alloy powder with a positively charged surface. (2) Add the positively charged titanium-aluminum alloy powder from step (1) into a 0.1-0.3 mol / L graphene oxide solution, and dry it after electrostatic adsorption for 30-60 min to obtain titanium-aluminum alloy powder with graphene oxide loaded on the surface. (3) Add tetraethyl orthosilicate and tetrabutyl titanate to anhydrous ethanol at a volume ratio of 1:1 to 2:1 and stir magnetically until homogeneous. Add 0.5 to 1 mol / L of cerium nitrate aqueous solution and continue stirring for 30 to 50 min to obtain a mixed solution. (4) After adding the copper alloy powder to the mixed solution in step (3), stir for 30-40 min, then add 20-30% of the volume of the mixed solution of 0.5 mol / L oxalic acid solution and continue stirring until completely dissolved to obtain copper alloy powder with cerium titanate / cerium silicate gel on the surface. Dry at 80-100℃ to obtain powder, and then calcine at 900-950℃ for 3-4 h to obtain copper alloy powder with cerium titanate / cerium silicate on the surface. (5) The titanium-aluminum alloy powder with graphene oxide loaded on the surface in step (2) and the copper alloy powder with cerium titanate / cerium silicate coated on the surface in step (4) are ball-milled and mixed at a mass ratio of 1:10 to 1:20 to obtain composite powder. (6) The composite powder in step (5) is sintered under vacuum at 950℃~1050℃ to obtain a high-performance brake copper alloy.

[0010] Furthermore, in step (1), the ratio of titanium to aluminum atoms in the titanium-aluminum alloy is 3:1 to 2:1.

[0011] Furthermore, in step (2), the atomic ratio of carbon in graphene oxide to aluminum in titanium-aluminum alloy is 2:3 to 2.5:3.

[0012] Furthermore, in step (3), the volume ratio of tetraethyl orthosilicate, tetrabutyl titanate, anhydrous ethanol, and cerium nitrate aqueous solution is 1:1:2:2 to 2:1:2:2.

[0013] Furthermore, in step (4), the copper alloy is one or both of Cu-20Ni and Cu-15Sn, and the added mass of copper alloy powder is 40% to 60% of the mass of the mixed solution.

[0014] Furthermore, in step (5), the mass ratio of the titanium-aluminum alloy powder with graphene oxide loaded on its surface to the copper alloy powder with cerium titanate / cerium silicate coated on its surface in step (4) is 1:10 to 1:20.

[0015] Invention Principle: This invention addresses the manufacturing of high-performance brake copper alloys, specifically focusing on the synergistic improvement of wear resistance and high-temperature oxidation resistance. Leveraging the excellent self-lubricating properties of ternary carbides and the superior wear resistance of cerium titanate / cerium silicate, a sol-gel method is employed to generate a cerium titanate / cerium silicate ceramic friction phase in situ on the surface of copper alloy particles, thereby enhancing frictional stability. Simultaneously, a plasma grafting and acetic acid protonation composite process is used to electrostatically adsorb graphene oxide onto the surface of titanium-aluminum alloy particles. Vacuum high-temperature sintering induces an in-situ reaction between Ti-Al-C to form a Ti3AlC2 lubricating phase, further improving wear resistance. Furthermore, based on the strong oxygen affinity of cerium, titanium, and aluminum, and the excellent high-temperature stability of their oxides, the high temperatures generated during braking induce oxidation of these highly reactive elements, forming a dense oxide layer. This stabilizes the friction coefficient, while the dense oxide layer hinders alloy oxidation, achieving a simultaneous improvement in both wear resistance and oxidation resistance of the brake copper alloy.

[0016] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: 1. This method synthesizes a hard cerium titanate / cerium silicate composite friction phase on the surface of copper alloy powder based on the sol-gel method. Compared with the traditional direct addition method that mixes carbide and oxide friction phases with copper alloy powder through ball milling and then sintering, this process can enhance the bonding between the hard friction phase and the copper alloy matrix, obtain a good interface, and thus improve the friction braking stability of the hard friction phase. On the other hand, a plasma grafting and weak acid protonation composite process is used to electrostatically adsorb graphene oxide on the surface of titanium-aluminum alloy. During vacuum sintering, a high-temperature in-situ reaction between Ti-Al-C is induced to form a Ti3AlC2 lubricating phase, which effectively reduces the wear rate of copper alloy.

[0017] 2. This method is based on the strong oxygen affinity of cerium, titanium and aluminum and the good high-temperature stability of their oxides. It utilizes the high temperature induced by braking process to desolvate aluminum in the Ti3AlC2 lubricating phase and diffuse active cerium, which easily combines with oxygen to form an oxide layer, thereby accelerating the formation of friction oxide film, improving wear resistance and high-temperature oxidation resistance, and thus achieving a synergistic improvement in the wear resistance and oxidation resistance of copper alloys. Attached Figure Description

[0018] Figure 1 This is the phase structure spectrum of the high-performance brake copper alloy prepared in Example 1; Figure 2 The transient friction coefficients of the high-performance braking copper alloy prepared in Example 1 at braking speeds of 80 km / h and 160 km / h; Figure 3 The transient friction coefficient of the high-performance braking copper alloy prepared in Example 1 at braking speeds of 250 km / h and 300 km / h; Figure 4 This is a graph showing the average friction coefficient of the high-performance braking copper alloys prepared in Examples 1 to 5 at different braking speeds; Figure 5 The wear rate of the high-performance brake copper alloys prepared in Examples 1 to 5 at different braking speeds. Detailed Implementation

[0019] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are provided below for detailed description. Unless otherwise specified, the methods of the present invention are conventional methods in the art. Example 1

[0020] (1) The titanium-aluminum alloy powder was ultrasonically cleaned in anhydrous ethanol for 10 min and then dried. Under an ammonia atmosphere, amino groups were grafted onto the surface of the titanium-aluminum alloy powder with a titanium to aluminum atomic ratio of 3:1 for 15 min using plasma. The powder was then added to a 0.1 mol / L acetic acid solution for protonation and soaked for 15 min. After drying, a titanium-aluminum alloy powder with a positively charged surface was obtained. (2) According to the molar ratio of carbon in graphene oxide to aluminum in titanium-aluminum alloy in step (1) being 2:3, the positively charged titanium-aluminum alloy powder in step (1) was added to a 0.2 mol / L graphene oxide solution, and dried after electrostatic adsorption for 30 min to obtain titanium-aluminum alloy powder with graphene oxide loaded on the surface. (3) Add tetraethyl orthosilicate and tetrabutyl titanate to anhydrous ethanol and stir magnetically until homogeneous. Add 0.5 mol / L cerium nitrate aqueous solution. The volume ratio of tetraethyl orthosilicate, tetrabutyl titanate, anhydrous ethanol and cerium nitrate solution is 1:1:2:2. Continue stirring for 30 min to obtain a mixed solution. (4) Weigh 40% of the mass of the mixed solution in step (3) and add it to the mixed solution in step (3). Stir for 30 min, then add 0.5 mol / L oxalic acid solution with a volume of 20% of the mixed solution and continue stirring until completely dissolved to obtain copper alloy powder coated with cerium titanate / cerium silicate gel. Dry the powder at 80°C and then calcine at 900°C for 3 h to obtain Cu-Ni alloy powder coated with cerium titanate / cerium silicate. (5) The titanium-aluminum alloy powder with graphene oxide loaded on the surface in step (2) and the Cu-Ni alloy powder with cerium titanate / cerium silicate coated on the surface in step (4) are ball-milled and mixed at a mass ratio of 1:20 to obtain composite powder. (6) The composite powder in step (5) is sintered at 950°C under vacuum to obtain a high-performance brake copper alloy.

[0021] from Figure 1 The diffraction peaks of the two friction phases, cerium titanate and cerium silicate, can be found in the prepared high-performance brake copper alloy. At the same time, the diffraction peaks of the in-situ formed Ti3AlC2 lubricating phase can also be clearly observed, indicating that the preparation method has obtained a brake copper alloy with synergistic reinforcement of the two friction phases and the lubricating phase. Example 2

[0022] The difference between this embodiment and embodiment 1 is that the mass ratio of the titanium-aluminum alloy powder with graphene oxide loaded on the surface in step (5) to the copper alloy powder with cerium titanate / cerium silicate coated on the surface in step (4) is adjusted to 1:30. Example 3

[0023] The difference between this embodiment and embodiment 2 is that the mass of copper alloy powder added in step (4) is set to 60% of the mass of the mixed solution. Example 4

[0024] The difference between this embodiment and embodiment 3 is that the molar ratio of carbon in graphene oxide in step (2) to aluminum in titanium-aluminum alloy in step (1) is adjusted to 2.5:3. Example 5

[0025] The difference between this embodiment and embodiment 4 is that the volume ratio of tetraethyl orthosilicate and tetrabutyl titanate in step (3) is adjusted to 2:1.

[0026] Figure 2 and Figure 3The transient friction coefficient of the high-performance braking copper alloy prepared in Example 1 at different braking speeds (according to B.3 of TJ / CL307-2019 "Provisional Technical Conditions for Brake Pads of EMUs") was found to fluctuate within a range of less than 5% at different braking speeds. This indicates that the oxide layer induced by the highly reactive cerium element in the in-situ cerium titanate / cerium silicate friction phase promotes the formation of the friction layer during the friction process, which can stabilize the change in friction coefficient and has a more significant effect on stabilizing the friction coefficient compared to carbides. Figure 4 The average friction coefficient of the high-performance braking copper alloys prepared in Examples 1 to 5 at different braking speeds is shown. The average friction coefficient at high speed is about 0.39, which is higher than the current best friction coefficient of 0.37 for MoS2, zirconium oxide, silicon oxide and tantalum carbide reinforced copper alloys at high speeds. This indicates that the decrease in strength of the copper alloy caused by higher braking speed is reduced and the braking effect is obvious. Figure 5 The high-performance brake copper alloys prepared in Examples 1 to 5 exhibit wear rates of less than 8.9 × 10⁻⁶ under both low-speed and high-speed braking. -2 cm 3 / MJ and 9.8×10 -2 cm 3 / MJ, both are lower than the wear rate of existing brake copper alloys of 11×10. -2 cm 3 / MJ, further illustrating that the copper alloy prepared by this method can not only effectively stabilize the friction coefficient under low-speed / high-speed braking and improve braking stability, but also significantly reduce the wear rate of the brakes, thereby improving their service life.

[0027] Comparative Example 1 The specific preparation process is the same as in Example 1, except that steps (1) to (4) are not used. Instead, cerium titanate, cerium silicate, Cu-Ni alloy and Ti3AlC2 are mixed by ball milling in a mass ratio of 1.2:1:20:0.7 and then vacuum sintered.

[0028] The brake copper alloy prepared in Comparative Example 1 had average friction coefficients of 0.33 and 0.28 under low-speed and high-speed braking, respectively, and wear rates of approximately 18.2 × 10⁻⁶. -2 cm 3 / MJ and 30.6×10 -2 cm 3 The average friction coefficient and wear rate of the / MJ are significantly inferior to those of the high-performance braking copper alloy prepared by this method under low-speed / high-speed braking. In this method, the in-situ synthesis of cerium titanate / cerium silicate friction phase on the surface of copper alloy powder can enhance the interfacial bonding between the friction phase and the copper alloy and the high-temperature deformation ability during braking, thereby improving braking stability. On the other hand, the in-situ synthesis and element diffusion of the Ti3AlC2 lubricating phase during vacuum sintering can promote the interfacial bonding with the copper alloy matrix and reduce the wear rate.

[0029] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A high-performance brake copper alloy, characterized in that, It contains a cerium titanate / cerium silicate friction phase, a Ti3AlC2 lubricating phase, and a copper alloy matrix.

2. The high-performance brake copper alloy according to claim 1, characterized in that, The cerium titanate / cerium silicate friction phase is synthesized by stirring tetraethyl orthosilicate and tetrabutyl titanate solution evenly, then adding cerium nitrate and copper alloy powder successively, using oxalic acid as a complexing agent to form a gel, and then calcining it onto the surface of copper alloy powder.

3. The high-performance brake copper alloy according to claim 1, characterized in that, The Ti3AlC2 lubricating phase is formed by plasma grafting of amino groups onto the surface of titanium-aluminum alloy powder, followed by acetic acid protonation, electrostatic adsorption of graphene oxide, and induction of in-situ reaction between Ti-Al-C by high-temperature sintering.

4. A method for preparing the high-performance brake copper alloy according to claim 1, 2, or 3, characterized in that, Includes the following steps: (1) The titanium-aluminum alloy powder was ultrasonically cleaned in anhydrous ethanol for 10 min and then dried. Amino groups were grafted onto the surface of the titanium-aluminum alloy powder under an ammonia atmosphere using plasma for 15-20 min. The powder was then added to a 0.1-0.2 mol / L acetic acid solution for protonation for 15-30 min and dried to obtain a titanium-aluminum alloy powder with a positively charged surface. (2) Add the positively charged titanium-aluminum alloy powder from step (1) into a 0.1-0.3 mol / L graphene oxide solution, and dry it after electrostatic adsorption for 30-60 min to obtain titanium-aluminum alloy powder with graphene oxide loaded on the surface. (3) Add tetraethyl orthosilicate and tetrabutyl titanate to anhydrous ethanol at a volume ratio of 1:1 to 2:1 and stir magnetically until homogeneous. Add 0.5 to 1 mol / L of cerium nitrate aqueous solution and continue stirring for 30 to 50 min to obtain a mixed solution. (4) After adding the copper alloy powder to the mixed solution in step (3), stir for 30-40 min, then add 20-30% of the volume of the mixed solution of 0.5 mol / L oxalic acid solution and continue stirring until completely dissolved to obtain copper alloy powder with cerium titanate / cerium silicate gel on the surface. Dry at 80-100℃ to obtain powder, and then calcine at 900-950℃ for 3-4 h to obtain copper alloy powder with cerium titanate / cerium silicate on the surface. (5) The titanium-aluminum alloy powder with graphene oxide loaded on the surface in step (2) and the copper alloy powder with cerium titanate / cerium silicate coated on the surface in step (4) are ball-milled and mixed to obtain composite powder. (6) The composite powder in step (5) is sintered under vacuum at 950℃~1050℃ to obtain a high-performance brake copper alloy.

5. The method for preparing the high-performance brake copper alloy according to claim 4, characterized in that, In step (1), the ratio of titanium to aluminum atoms in the titanium-aluminum alloy is 3:1 to 2:

1.

6. The method for preparing the high-performance brake copper alloy according to claim 4, characterized in that, In step (2), the molar ratio of carbon in graphene oxide to aluminum in titanium-aluminum alloy is 2:3 to 2.5:

3.

7. The method for preparing the high-performance brake copper alloy according to claim 4, characterized in that, In step (3), the volume ratio of tetraethyl orthosilicate, tetrabutyl titanate, anhydrous ethanol, and cerium nitrate aqueous solution is 1:1:2:2 to 2:1:2:

2.

8. The method for preparing the high-performance brake copper alloy according to claim 4, characterized in that, In step (4), the copper alloy is one or both of Cu-Ni and Cu-Sn.

9. The method for preparing the high-performance brake copper alloy according to claim 4, characterized in that, In step (4), the mass of copper alloy powder added is 40% to 60% of the mass of the mixed solution.

10. The method for preparing the high-performance brake copper alloy according to claim 4, characterized in that, In step (5), the mass ratio of the titanium-aluminum alloy powder with graphene oxide loaded on its surface to the copper alloy powder with cerium titanate / cerium silicate coated on its surface in step (4) is 1:20 to 1:30.

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