WO2024148738A1

WO2024148738A1 - High-strength carbon/ceramic brake disk with ceramic functional layer

Info

Publication number: WO2024148738A1
Application number: PCT/CN2023/096610
Authority: WO
Inventors: 赵大明; 程皓; 李睿; 李俏; 康文杰; 程凯锋; 黄粉超; 李周
Original assignee: 西安超码科技有限公司
Priority date: 2023-02-13
Filing date: 2023-05-26
Publication date: 2024-07-18
Also published as: CN115773321B; CN115773321A

Abstract

A high-strength carbon/ceramic brake disk with a ceramic functional layer. A preparation method therefor comprises: firstly subjecting a carbon/carbon green body of a binary carbon matrix to a high-temperature graphitization treatment, then preparing the graphitized carbon/carbon green body of the binary carbon matrix into a carbon/ceramic brake disk green body by means of a liquid-phase silicon infiltration reaction, and then forming a ceramic functional layer by means of an in-situ reaction of a ceramic precursor glue solution on the surface of the carbon/ceramic brake disk green body, so as to obtain a brake disk. The brake disk has the characteristics of a high mechanical strength, a high friction coefficient, a low wear rate, good oxidation resistance and a long service life.

Description

A high-strength carbon/ceramic brake disc with a ceramic functional layer

Technical Field

The invention relates to a high-strength carbon/ceramic brake disc with a ceramic functional layer, belonging to the technical field of vehicle brake parts.

Background technique

Carbon/ceramic composite materials are carbon fiber reinforced carbon and silicon carbide ceramic matrix composite materials. They first appeared as thermal structural materials in the 1980s. They have low density, good oxidation resistance, corrosion resistance, excellent high-temperature mechanical properties and thermal physical properties. They are a new type of high-temperature structural material and functional material that can meet the requirements of 1650°C. As a brake material, carbon/ceramic composite materials have the advantages of wear resistance, high temperature resistance, low density, large heat capacity, stable wet friction performance, and no attenuation of high-temperature friction coefficient. They will become the preferred brake material for the new generation of automobiles, high-speed railways, aircraft, tanks, etc.

German patent DE 19727585 A1 discloses a combination of a chopped fiber reinforced C/SiC ceramic brake disc and a brake lining, wherein the brake disc is formed by molding chopped carbon fibers and then ceramicized, and the brake lining is formed by sintered metal material or a non-organic bonding material having a ceramic bonding phase and metal particles. Chinese patent CN 113548902 A discloses a method for preparing a carbon fiber reinforced silicon carbide brake disc, wherein the chopped carbon fibers are first heat treated, and then the chopped carbon fibers of mixed lengths are evenly mixed with resin and additives and then placed in a molding machine for molding, and then high-temperature cracking is performed under a nitrogen or inert gas protective atmosphere, and finally silicon infiltration is performed in a vacuum infiltration furnace to obtain a carbon fiber reinforced silicon carbide brake disc. The carbon/ceramic brake disc produced by the above method has insufficient mechanical strength and is prone to crack failure when hit by hard objects during use.

US Patent US7445095 "braking system having a composite-material brake disc" discloses a combination of a carbon/ceramic brake disc with a friction layer and a composite brake pad, with a friction coefficient of 0.4~0.48 and excellent friction performance. The problem is that the surface friction layer contains a large amount of chopped carbon fibers, and the friction surface temperature of the brake disc rises rapidly during braking. The carbon fibers oxidize and lose strength under high temperature conditions, resulting in increased wear rate of the brake disc and a shorter service life.

Chinese patent CN 105565839 A discloses a method for preparing a carbon/ceramic brake material and a method for preparing a carbon/ceramic brake disc. Ceramic powder is added to a phenolic resin solution to obtain a mixture, which is impregnated into a carbon fiber blank by the mixture, and a porous carbon/carbon-ceramic powder composite material is obtained after carbonization. After mechanical processing, siliconization treatment is performed in a vacuum furnace to obtain a carbon/ceramic brake disc. The existing problem is that the porous carbon/carbon-ceramic powder composite material is difficult to machine; the carbon fiber as a reinforcement lacks surface protection, and silicon will cause erosion damage to the fiber during siliconization treatment, resulting in insufficient mechanical strength of the brake disc.

Chinese patent CN 111892416 A discloses a method for preparing a carbon/ceramic brake material, which comprises placing a low-density carbon/carbon blank in a silicon powder impregnation slurry, drying the blank after impregnation, and then placing the carbon/carbon blank impregnated with silicon powder into a siliconization treatment furnace, where the silicon powder in the carbon blank reacts with the deposited carbon on the surface of the blank at high temperature to form a SiC ceramic phase. The problem is that the silicon powder of the carbon/carbon blank impregnated with the silicon powder impregnation slurry is concentrated in the outer layer, and the silicon powder content decreases from the inside to the outside, resulting in uneven brake disc material after ceramicization, too much residual silicon in the outer layer, and too low SiC ceramic content in the inner layer, which affects the braking performance.

Chinese patent CN 113277869 A discloses a carbon/ceramic brake disc with wear-resistant and anti-oxidation coating and its preparation method, which is to brush a wear-resistant slurry containing 60% SiC particles in the grooves pre-opened on the carbon/carbon blank, and then use the evaporation siliconization process to coat the silicon powder, and the silicon powder does not contact the carbon/carbon composite material disc body, and the distance between the silicon powder and the carbon/carbon composite material disc body is ≥100mm. The problem is that the coating introduced by the evaporation process is thin and cannot play a long-term wear-resistant role, but can only play an anti-oxidation role; the high proportion of SiC particles in the slurry is not generated by in-situ reaction, and the bonding force with the matrix is weak, and it is easy to fall off during the friction process. The friction surface cannot form a stable friction film, resulting in a large wear rate of the brake disc and the dual brake pad.

Chinese patent CN 108299002 A discloses a process for preparing a C/C-SiC ventilated brake disc with a silicon carbide friction functional layer. The patent uses trichloromethylsilane (CH ₃ SiCl ₃ ) vapor phase siliconization method to react silicon vapor with a carbon/carbon embryo to generate silicon carbide to obtain a carbon/ceramic composite brake disc embryo. Then, a layer of pure silicon carbide is deposited on the surface of the carbon/ceramic brake disc embryo through the CVI process to form a friction functional layer. The carbon/ceramic brake disc prepared by this method has high raw material cost, long preparation cycle, and low cost performance of the brake disc product.

Chinese patent CN 110131343 A discloses a method for preparing an automobile brake disc, which first uses an integrated molding process to prepare an automobile brake preform, then uses polynitrogen silane solution and polycarbosilane solution as ceramic precursors, obtains a ceramic matrix through repeated impregnation-high temperature pyrolysis, and finally obtains a carbon fiber reinforced carbon-based/ceramic-based composite material. This method has low preparation efficiency, high cost, and great difficulty in industrial application.

Summary of the invention

In view of the problems existing in current brake discs, the present invention provides a high-strength carbon/ceramic brake disc with a ceramic functional layer. A carbon/carbon blank with a binary carbon matrix is formed by introducing pyrolytic carbon wrapping carbon fibers and resin carbon or asphalt carbon filling pores into a carbon fiber preform. In the subsequent liquid phase siliconization process, silicon preferentially reacts with the resin carbon or asphalt carbon to generate SiC, while the pyrolytic carbon effectively protects the carbon fibers from being eroded by silicon liquid, thereby maintaining a high strength retention rate of the carbon fibers and ensuring high mechanical strength of the brake disc. The ceramic functional layer generated by the in-situ reaction has good bonding strength with the matrix and adjustable thickness, and can effectively play a comprehensive role in wear resistance, oxidation resistance, and increased friction coefficient, thereby making the brake disc have the characteristics of high mechanical strength, high friction coefficient, low wear rate, good oxidation resistance, and long service life. It can not only be used on conventional cars, airplanes, and high-speed railways, but also meet the use requirements of high-performance racing cars, heavy trucks, tanks, and other extreme braking environments.

The objectives of the present invention are achieved through the following technical solutions.

A high-strength carbon/ceramic brake disc with a ceramic functional layer, wherein a carbon/carbon blank of a binary carbon matrix is first subjected to high-temperature graphitization treatment, and then the graphitized carbon/carbon blank of the binary carbon matrix is prepared into a carbon/ceramic brake disc blank by liquid phase silicon infiltration reaction, and then a ceramic functional layer is formed by an in-situ reaction of a ceramic precursor colloid on the surface of the carbon/ceramic brake disc blank, thereby obtaining the brake disc;

The carbon/carbon blank of the dual carbon matrix is prepared by first coating the carbon fiber surface of the carbon fiber preform with pyrolytic carbon by chemical vapor deposition process, and then filling the pores of the carbon fiber preform with resin carbon or pitch carbon by impregnation carbonization process; wherein the carbon fiber preform is formed by needle-punching the carbon fiber and the carbon mesh and has a density of 0.4-0.6 g/cm ³ , and the density increases to 0.8-1.3 g/cm ³ after coating with pyrolytic carbon, and further increases to 1.0-1.5 g/cm ³ after filling with resin carbon or pitch carbon, and the density of the carbon/ceramic brake disc blank is 1.9-2.4 g/cm ³ accordingly;

The ceramic precursor glue is prepared by mixing thermosetting resin, polymethylsilane and silicon powder in a mass ratio of 30: (15-40): (30-55); wherein the thermosetting resin is preferably phenolic resin, epoxy resin or furfural resin, and the thermosetting resin, polymethylsilane and silicon powder are preferably stirred for 0.5-2 h after mixing.

The carbon fiber preform can be prepared by the following steps: spreading the carbon fiber and pre-needling the carbon mesh to form a carbon fiber-carbon mesh unit layer, laying a plurality of carbon fiber-carbon mesh unit layers layer by layer and relay needling on a flat needle punching machine to form a 2.5D carbon fiber flat felt, and cutting according to the size of the brake disc to obtain the carbon fiber preform.

The carbon fiber is preferably 12-48 K carbon fiber, wherein K represents the number of thousands of tows; during the needling process of the carbon fiber-carbon web unit layer, the layering direction is adjusted to form 0°/90° alternating layer needling, and the needling density is 16-30 needles/cm ² .

The specific preparation steps of the carbon/carbon blank of the binary carbon matrix are as follows:

A carbon fiber preform with a density of 0.4-0.6 g/cm ³ is placed in a chemical vapor deposition furnace, and a carbon source gas and a diluent gas are introduced to perform chemical vapor deposition under the conditions of a high temperature of 900-1200 °C and a vacuum degree of 500-4000 Pa, so as to form pyrolytic carbon coated with carbon fibers on the surface of the carbon fiber preform, and obtain a carbon/carbon blank with a unit carbon matrix with a density of 0.80-1.3 g/cm ³ ;

Wherein, the carbon source gas is natural gas or propylene (C ₃ H ₆ ), the diluent gas is nitrogen (N ₂ ) or hydrogen (H ₂ ), and the volume ratio of the carbon source gas to the diluent gas is (1-3):1;

The carbon/carbon blank of the unit carbon matrix is placed in a vacuum-pressure impregnation curing furnace, the impregnating agent is heated to soften, and the carbon/carbon blank of the unit carbon matrix is impregnated by a vacuum method or a pressure method, so that the impregnating agent enters the internal pores of the carbon/carbon blank of the unit carbon matrix, and the remaining impregnating agent is discharged, and then the temperature is raised to 170-220 ° C, and the temperature is kept for 1-4 hours to make the impregnating agent in the carbon/carbon blank of the unit carbon matrix undergo a curing reaction, and then it is loaded into a carbonization furnace, the carbonization treatment temperature is controlled to be 850-1000 ° C, and the carbonization time is 2-6 hours, so as to obtain a carbon/carbon blank of a binary carbon matrix with a density of 1.0-1.5 g/cm ³ ;

Wherein, the impregnating agent is furfural resin, phenolic resin or asphalt, and the pressure in the furnace is not less than 1.5 MPa during pressure impregnation.

The specific steps of high-temperature graphitization treatment of the carbon/carbon blank of the binary carbon matrix are as follows: the carbon/carbon blank of the binary carbon matrix is loaded into a high-temperature treatment furnace, and a nitrogen or inert gas protective atmosphere is introduced, and the temperature is raised to 1800~2400℃, and the temperature is kept for 1~6 hours to complete the high-temperature graphitization treatment of the carbon/carbon blank of the binary carbon matrix.

The specific preparation steps of the carbon/ceramic brake disc blank are as follows: first, the carbon/carbon blank with a binary carbon matrix after graphitization is mechanically processed according to the final product drawing to obtain a molded blank; then the molded blank is placed in a graphite crucible, and the filler amount is calculated according to the volume of the final product and silicon powder is added. After the filling is completed, the graphite crucible is placed in a high-temperature furnace, the temperature is raised to 1600~2000℃, and the temperature is kept for 1~4 hours. The vacuum degree is controlled at 200~2000 Pa to melt the solid silicon material into silicon liquid, and the silicon liquid enters the pores of the molded blank through the capillary effect. Si contacts with C and chemically reacts at the silicon-carbon contact surface to generate SiC, thereby obtaining a carbon/ceramic brake disc blank with a density of 1.9~2.4 g/ ^cm3 .

Spread the silicon powder flat on the bottom of the crucible, place 5 to 8 pads made of porous silicon carbide material in the silicon powder to support the molded body so that the silicon powder does not contact the molded body.

The specific steps of preparing the ceramic functional layer on the surface of the carbon/ceramic brake disc body by in-situ reaction are as follows:

The surface of the carbon/ceramic brake disc blank is coated with the prepared ceramic precursor glue or the carbon/ceramic brake disc blank is immersed in the prepared ceramic precursor glue, and then after drying, it is placed in a high-temperature furnace, heated to 1600-2000°C, and kept warm for 1-3 hours to form a ceramic functional layer on the surface of the carbon/ceramic brake disc blank. After grinding and assembling the required metal parts, the high-strength carbon/ceramic brake disc with a ceramic functional layer according to the present invention is obtained.

The thickness of the ceramic functional layer is preferably 0.5 to 3 mm.

Beneficial effects:

(1) The present invention adopts a carbon/carbon blank with a binary carbon matrix. By introducing pyrolytic carbon that wraps the carbon fibers and resin carbon or asphalt carbon that fills the pores into the carbon fiber preform, in the subsequent liquid phase siliconization process, silicon preferentially reacts with the resin carbon or asphalt carbon to generate SiC, while the pyrolytic carbon coated on the surface of the carbon fibers can effectively protect the carbon fibers from being eroded by the silicon liquid, thereby maximally maintaining the strength and toughness of the carbon fibers and ensuring the high mechanical strength of the brake disc.

(2) When the present invention introduces resin carbon or asphalt carbon into the carbon fiber preform, the introduced impregnating agent shrinks after carbonization to form pores, creating a channel for the subsequent silicon liquid to enter, and reserves a carbon source for the silicon-carbon reaction after the silicon liquid enters the pores, effectively reducing the proportion of residual silicon, and the mass ratio of residual silicon can be controlled within 5%. Since the melting point of Si (about 1420°C) is much lower than the melting point of SiC (about 2700°C), the present invention can greatly improve the high-temperature stability of the brake disc.

(3) In order to better play the purpose of pyrolytic carbon wrapping carbon fiber to protect carbon fiber from silicon corrosion, the thickness of the introduced pyrolytic carbon is about 1-3 μm, that is, the carbon fiber preform with a density of 0.4-0.6 g/cm ³ is densified to 0.8-1.3 g/cm ^3. In order to make the resin carbon/asphalt carbon react fully with liquid silicon, the weight ratio of the introduced resin carbon/asphalt carbon is 25-35%, that is, it is further densified to 1.0-1.5 g/cm ^3. Through the scientific ratio of the content of pyrolytic carbon and resin carbon/asphalt carbon in the binary matrix carbon, the residual silicon ratio can be effectively reduced, the strength retention rate of carbon fiber can be greatly improved, and the mechanical properties of the carbon/ceramic brake disc can be improved by 10-20%.

(4) When introducing pyrolytic carbon into the carbon fiber preform, the present invention controls the volume ratio of the carbon source gas to the dilution gas, the deposition temperature, the vacuum degree and other conditions to control the microstructure of the formed pyrolytic carbon, so that it forms a rough layer structure pyrolytic carbon and avoids isotropic layer structure pyrolytic carbon. This is because the rough layer pyrolytic carbon has the characteristics of high friction coefficient and easy graphitization and opening of pores compared with the isotropic pyrolytic carbon, which is beneficial to the later ceramicization reaction and enables the brake disc to maintain stable tribological properties.

(5) The present invention prepares a ceramic functional layer on the surface of the brake disc through an in-situ reaction, has good bonding strength with the substrate, and has an adjustable thickness. In order to better play the advantages of high friction coefficient, high hardness, and oxidation resistance of SiC ceramics, through the scientific design of the ceramic functional layer formula, the SiC mass content in the prepared ceramic functional layer is greater than 92%, which is much higher than the SiC mass content in the brake disc body (40-70%), so that the friction coefficient, wear resistance, and oxidation resistance of the brake disc are effectively improved, and the service life of the brake disc can be significantly extended.

(6) The brake disc described in the present invention has the characteristics of high mechanical strength, high friction coefficient, low wear rate, good anti-oxidation performance and long service life. It can not only be used in conventional cars, airplanes and high-speed railways, but also meet the requirements of extreme braking environments such as high-performance racing cars, heavy trucks and tanks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a scanning electron microscope (SEM) image of the rough layer structure pyrolytic carbon deposited on the surface of the carbon fiber preform in step (2) of Example 1.

FIG. 2 is a scanning electron microscope (SEM) image of the isotropically structured pyrolytic carbon deposited on the surface of the carbon fiber preform in step (2) of Comparative Example 4.

Implementation

The present invention is further described below in conjunction with specific embodiments, wherein the methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

Example 1

(1) Using SYT49S-12K carbon fiber from Zhongfu Shenying Company, pre-needling the carbon fiber and carbon mesh to form a carbon fiber-carbon mesh unit layer, and using a flat needle punching machine to lay a number of carbon fiber-carbon mesh unit layers layer by layer and relay needle punching to form a 2.5D carbon fiber flat felt, wherein the plane direction is 0°/90° alternately stacked and the needle punching density in the thickness direction is 16 needles/ ^cm2 , and then cutting according to the size of the brake disc to obtain a carbon fiber preform with an outer diameter of 390 mm, a thickness of 38 mm and a density of 0.4 g/ ^cm3 ;

(2) The carbon fiber preform obtained in step (1) is placed in a chemical vapor deposition furnace, and the furnace temperature is raised to 900°C. When the vacuum degree in the furnace reaches a stable pressure of 500 Pa, C ₃ H ₆ as a carbon source gas and N ₂ as a diluent gas are introduced in a volume ratio of 1:1. After 150 hours of chemical vapor deposition, a carbon/carbon blank with a unit carbon matrix having a density of 0.91 g/cm ³ is obtained. Observation under a polarizing microscope shows that a rough layer structure pyrolytic carbon is deposited on the surface of the carbon fiber preform, and its microscopic morphology is shown in FIG1 .

(3) placing the carbon/carbon blank of the unit carbon matrix obtained in step (2) into a vacuum-pressure impregnation curing furnace, using phenolic resin as an impregnating agent, heating the phenolic resin in the vacuum-pressure impregnation curing furnace and pressurizing it to 1.5 MPa, so that the phenolic resin enters the internal pores of the product, and the remaining phenolic resin is discharged by pressure, then slowly raising the temperature in the furnace to 180°C for curing reaction, after 3 hours of curing reaction, taking out the product and placing it into a carbonization furnace for carbonization treatment, the carbonization treatment temperature is 850°C and the carbonization treatment time is 5 hours, to obtain a carbon/carbon blank of the binary carbon matrix with a density of 1.18 g/ ^cm3 ;

(4) placing the carbon/carbon blank of the binary carbon matrix obtained in step (3) into a high-temperature treatment furnace, introducing nitrogen for protection, slowly heating to 1800° C., and keeping the temperature for 6 h, thereby completing the high-temperature graphitization treatment of the carbon/carbon blank of the binary carbon matrix;

(5) machining the carbon/carbon blank of the binary carbon matrix subjected to high-temperature graphitization treatment in step (4) according to the final product drawing, machining the inner diameter, outer diameter and thickness to the desired position, punching ventilation holes, and obtaining a molded blank;

(6) 2500 g of silicon powder is spread on the bottom of the graphite crucible, and 5 pads made of porous silicon carbide material are placed in the silicon powder. The molded body obtained in step (5) is placed on the pads so that the silicon powder does not contact the molded body. Then, the graphite crucible is placed in a high-temperature furnace, the vacuum degree is controlled to 200 Pa, and the temperature is slowly raised to 1600 ° C. The temperature is kept for 4 h. After the silicon powder is melted into silicon liquid, it enters the pores of the molded body through the capillary effect, and Si reacts with C to generate SiC, thereby obtaining a carbon/ceramic brake disc body with a density of 2.26 g/cm ³ ;

(7) Phenolic resin, polymethylsilane and silicon powder are mixed in a mass ratio of 30:15:55, and the mixture is mixed by mechanical stirring for 0.5 h to prepare a ceramic precursor glue solution; the prepared ceramic precursor glue solution is brushed on the surface of the carbon/ceramic brake disc blank prepared in step (6), and then after drying and curing, it is placed in a high-temperature furnace, and the temperature is slowly raised to 1600°C and kept at this temperature for 3 h to form a ceramic functional layer with a thickness of 0.5 mm on the surface of the carbon/ceramic brake disc blank;

(8) The carbon/ceramic brake disc blank with a ceramic functional layer on the surface obtained in step (7) is polished and assembled with required metal parts to obtain a high-strength carbon/ceramic brake disc with a ceramic functional layer.

Example 2

(1) Using SYT49S-24K carbon fiber from Zhongfu Shenying Company, pre-needling the carbon fiber and carbon mesh to form a carbon fiber-carbon mesh unit layer, and using a flat needle punching machine to lay a number of carbon fiber-carbon mesh unit layers layer by layer and relay needle punching to form a 2.5D carbon fiber flat felt, wherein the plane direction is 0°/90° alternately stacked and the needle punching density in the thickness direction is 30 needles/ ^cm2 , and then cutting according to the size of the brake disc to obtain a carbon fiber preform with an outer diameter of 390 mm, a thickness of 38 mm and a density of 0.6 g/ ^cm3 ;

(2) The carbon fiber preform obtained in step (1) is placed in a chemical vapor deposition furnace, and the furnace temperature is raised to 1200°C. When the vacuum degree in the furnace reaches a stable pressure of 4000 Pa, _CH4 as a carbon source gas and _H2 as a dilution gas are introduced, and the volume ratio of _CH4 to _H2 is 3:1. After 200 hours of chemical vapor deposition, a carbon/carbon blank with a unit carbon matrix having a density of 1.22 g/ ^cm3 is obtained; observation under a polarizing microscope shows that rough layer structure pyrolytic carbon is deposited on the surface of the carbon fiber preform.

(3) placing the carbon/carbon blank of the unit carbon matrix obtained in step (2) into a vacuum-pressure impregnation curing furnace, using furfural resin as an impregnating agent, heating and pressurizing the furfural resin to 2.5 MPa in the vacuum-pressure impregnation curing furnace, allowing the furfural resin to enter the internal pores of the product, and using pressure to discharge the remaining furfural resin, then slowly raising the temperature in the furnace to 220°C for curing reaction, taking out the product after 2 hours of curing reaction and placing it into a carbonization furnace for carbonization treatment, the carbonization treatment temperature is 1000°C and the carbonization treatment time is 4 hours, and a carbon/carbon blank of the binary carbon matrix with a density of 1.45 g/ ^cm3 is obtained;

(4) placing the carbon/carbon blank of the binary carbon matrix obtained in step (3) into a high-temperature treatment furnace, introducing nitrogen for protection, slowly heating to 2200° C., and keeping the temperature for 1 h, thereby completing the high-temperature graphitization treatment of the carbon/carbon blank of the binary carbon matrix;

(6) 2500 g of silicon powder is spread on the bottom of the graphite crucible, and 8 pads made of porous silicon carbide material are placed in the silicon powder. The molded body obtained in step (5) is placed on the pads so that the silicon powder does not contact the molded body. Then, the graphite crucible is placed in a high-temperature furnace, the vacuum degree is controlled to 2000 Pa, and the temperature is slowly raised to 2000 ° C. The temperature is kept for 1 h. After the silicon powder is melted into silicon liquid, it enters the pores of the molded body through the capillary effect, and Si reacts with C to generate SiC, thereby obtaining a carbon/ceramic brake disc body with a density of 2.09 g/ ^cm3 ;

(7) Mix furfural resin, polymethylsilane and silicon powder in a mass ratio of 30:28:42, and mix by mechanical stirring for 2 h to prepare a ceramic precursor glue; brush the prepared ceramic precursor glue on the surface of the carbon/ceramic brake disc blank prepared in step (6), and then put it into a high-temperature furnace after drying and curing, slowly raise the temperature to 2000 ° C, and keep it at this temperature for 1 h to form a ceramic functional layer with a thickness of 3 mm on the surface of the carbon/ceramic brake disc blank;

Comparative Example 1

(1) Using SYT49S-24K carbon fiber from Zhongfu Shenying Company, a non-woven fabric and a carbon mesh tire were alternately laid and needle-punched, the adjacent non-woven fabric directions were 0°/90°, the needle-punching density in the thickness direction was 20 needles/ ^cm2 , and the preform was cut to obtain a 2.5D preform with an outer diameter of 390 mm, a thickness of 40 mm, and a density of 0.50 g/ ^cm3 ;

(2) The chemical vapor deposition process is the same as step (2) of Example 2, and a carbon/carbon blank having a unit carbon matrix with a density of 1.28 g/ ^cm3 is obtained accordingly;

(3) subjecting the carbon/carbon blank of the unit carbon matrix obtained in step (2) to high temperature treatment, the implementation process is the same as step (4) of Example 2;

(4) Mechanically process the carbon/carbon blank of the unit carbon matrix subjected to high temperature treatment in step (3) according to the final product drawing, process the inner diameter, outer diameter and thickness to the required position, punch ventilation holes, and obtain a molded blank;

(5) Ceramizing the green body obtained in step (4) in the same manner as step (6) of Example 2, thereby obtaining a carbon/ceramic brake disc green body having a volume density of 2.05 g/ ^cm3 ;

(6) The carbon/ceramic brake disc blank prepared in step (5) is polished and assembled with required metal parts to obtain a carbon/ceramic brake disc without a ceramic functional layer.

Comparative Example 2

(2) The carbon fiber preform obtained in step (1) is subjected to resin impregnation carbonization treatment, and the process is the same as step (3) of Example 2. After four cycles of resin impregnation carbonization treatment, a carbon/carbon blank having a unit carbon matrix with a matrix carbon of resin carbon and a density of 1.26 g/ ^cm3 is obtained;

(5) The formed green body obtained in step (4) is subjected to a ceramicizing treatment, and the implementation process is the same as step (6) of Example 2, and a carbon/ceramic brake disc green body with a volume density of 2.07 g/ ^cm3 is obtained accordingly;

Comparative Example 3

(1) Using SYT49S-24K carbon fiber from Zhongfu Shenying Company, a non-woven fabric and a carbon mesh tire were alternately laid and needle-punched, the adjacent non-woven fabric directions were 0°/90°, the needle-punching density in the thickness direction was 20 needles/ ^cm2 , and the preform was cut to obtain a 2.5D preform with an outer diameter of 390 mm, a thickness of 40 mm, and a density of 0.60 g/ ^cm3 ;

(2) subjecting the carbon fiber preform obtained in step (1) to chemical vapor deposition, the process being the same as step (2) of Example 2, to obtain a carbon/carbon blank having a unit carbon matrix with a density of 1.49 g/ ^cm3 after 300 hours of chemical vapor deposition;

(3) subjecting the carbon/carbon blank of the unit carbon matrix obtained in step (2) to an impregnation carbonization treatment, the process being the same as step (3) of Example 2, to obtain a carbon/carbon blank of a binary carbon matrix having a density of 1.70 g/ ^cm3 ;

(4) subjecting the carbon/carbon blank of the binary carbon matrix obtained in step (3) to high temperature treatment, the implementation process is the same as step (4) of Example 2;

(5) The carbon/carbon blank of the binary carbon matrix that has been subjected to high-temperature treatment obtained in step (4) is machined according to the final product drawing, the inner diameter, outer diameter and thickness are processed to the desired position, ventilation holes are punched, and a molded blank is obtained;

(6) The formed green body obtained in step (4) is subjected to a ceramic treatment, and the implementation process is the same as step (6) of Example 2, and a carbon/ceramic brake disc green body with a volume density of 1.89 g/ ^cm3 is obtained accordingly;

(7) The carbon/ceramic brake disc blank obtained in step (6) is polished and assembled with required metal parts to obtain a carbon/ceramic brake disc without a ceramic functional layer.

Comparative Example 4

(2) The carbon fiber preform obtained in step (1) is placed in a chemical vapor deposition furnace, and the furnace temperature is raised to 1100°C. When the vacuum degree in the furnace reaches a stable pressure of 2000 Pa, _CH4 as a carbon source gas and _H2 as a dilution gas are introduced, and the volume ratio of _CH4 to _H2 is 1:2. After 200 hours of chemical vapor deposition, a carbon/carbon blank with a unit carbon matrix having a density of 1.02 g/ ^cm3 is obtained; observation under a polarizing microscope shows that the obtained pyrolytic carbon has an isotropic structure, as shown in FIG2;

(3) placing the carbon/carbon blank of the unit carbon matrix obtained in step (2) into a vacuum-pressure impregnation curing furnace, using furfural resin as an impregnating agent, heating and pressurizing the furfural resin to 2.5 MPa in the vacuum-pressure impregnation curing furnace, allowing the furfural resin to enter the internal pores of the product, and using pressure to discharge the remaining furfural resin, then slowly raising the temperature in the furnace to 220°C for curing reaction, taking out the product after 2 hours of curing reaction and placing it into a carbonization furnace for carbonization treatment, the carbonization treatment temperature is 1000°C and the carbonization treatment time is 4 hours, and a carbon/carbon blank of the binary carbon matrix with a density of 1.24 g/ ^cm3 is obtained;

(6) The formed green body obtained in step (4) is subjected to a ceramicizing treatment, and the implementation process is the same as step (6) of Example 2, and a carbon/ceramic brake disc green body with a volume density of 1.78 g/ ^cm3 is obtained accordingly;

(7) The carbon/ceramic brake disc blank prepared in step (5) is polished and assembled with required metal parts to obtain a carbon/ceramic brake disc without a ceramic functional layer.

In order to further study and evaluate the mechanical properties and friction and wear properties of the carbon/ceramic brake discs prepared in the embodiments and comparative examples, the carbon/ceramic brake discs prepared in the embodiments and comparative examples were matched with imported carbon/ceramic disc special brake pads, and ground bench tests were carried out on a LINK3000 bench test machine according to the SAE J2522-AK Master test specification. The strength and test results are compared as shown in Table 1 below.

Table 1

项目project	实施例1Example 1	实施例2Example 2	对比例1Comparative Example 1	对比例2Comparative Example 2	对比例3Comparative Example 3	对比例4Comparative Example 4
压缩强度（MPa）Compression strength (MPa)	305305	278278	239239	267267	193193	206206
弯曲强度（MPa）Bending strength (MPa)	182182	167167	145145	8989	171171	115115
摩擦系数Friction coefficient	0.470.47	0.460.46	0.360.36	0.410.41	0.330.33	0.350.35
质量磨损率（g）Mass wear rate (g)	0.110.11	0.130.13	0.480.48	0.360.36	0.570.57	0.520.52

Comparative Example 1 is a carbon/ceramic brake disc containing only a unit carbon matrix (pyrolytic carbon). Due to the lack of resin carbon that consumes Si source, the residual silicon mass ratio reaches 15.3%, the mechanical properties are reduced, and the high-temperature friction performance is adversely affected. Comparative Example 2 is a carbon/ceramic brake disc containing only a unit carbon matrix (resin carbon). Due to the lack of pyrolytic carbon protection on the surface of carbon fiber, liquid silicon causes reaction erosion on carbon fiber, resulting in a significant decrease in the bending strength of the carbon/ceramic brake disc. Although Comparative Example 3 contains a binary carbon matrix, the ratio of the two is unbalanced, and the content of matrix carbon is too high, resulting in a low open porosity of the blank and a poor silicon infiltration channel, resulting in a low SiC ceramic content in the carbon/ceramic brake disc, a low product density, and a low compression strength. Comparative Example 4 is due to unreasonable process parameters. The pyrolytic carbon microstructure fails to form a rough layer structure, and is mainly isotropic carbon, which is not conducive to high-temperature graphitization opening, and the silicon infiltration channel is not smooth, resulting in a low SiC ceramic content in the carbon/ceramic brake disc, a low product density, and poor performance. Comparative Examples 1-4 do not have a ceramic functional layer, so the friction coefficient is generally lower than that of the embodiment, and the wear rate is generally higher than that of the embodiment. It can be seen from the test results in the above table that the high-strength carbon/ceramic brake disc with a ceramic functional layer prepared by the present invention, by introducing a dual-element matrix carbon (pyrolytic carbon and resin carbon/asphalt carbon), maintains the strength and toughness of the carbon fiber to the maximum extent, effectively reduces the proportion of residual silicon, and greatly improves the mechanical strength of the material; the ceramic functional layer introduced by the in-situ reaction significantly improves the friction coefficient and reduces the wear rate.

In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

A high-strength carbon/ceramic brake disc with a ceramic functional layer, characterized in that: a carbon/carbon blank of a binary carbon matrix is first subjected to high-temperature graphitization treatment, and then the graphitized carbon/carbon blank of the binary carbon matrix is prepared into a carbon/ceramic brake disc blank by liquid phase silicon infiltration reaction, and then a ceramic precursor glue is reacted in situ on the surface of the carbon/ceramic brake disc blank to form a ceramic functional layer, so as to obtain the brake disc;

The carbon/carbon blank of the dual carbon matrix is prepared by first coating the carbon fiber surface of the carbon fiber preform with pyrolytic carbon by chemical vapor deposition process, and then filling the pores of the carbon fiber preform with resin carbon or pitch carbon by impregnation carbonization process; wherein the carbon fiber preform is formed by needle-punching the carbon fiber and the carbon mesh and has a density of 0.4-0.6 g/cm 3 , and the density increases to 0.8-1.3 g/cm 3 after coating with pyrolytic carbon, and further increases to 1.0-1.5 g/cm 3 after filling with resin carbon or pitch carbon, and the density of the carbon/ceramic brake disc blank is 1.9-2.4 g/cm 3 accordingly;

The ceramic precursor glue is prepared by mixing thermosetting resin, polymethylsilane and silicon powder in a mass ratio of 30: (15-40): (30-55).
According to claim 1, a high-strength carbon/ceramic brake disc with a ceramic functional layer is characterized in that: the carbon fiber preform is prepared by the following steps: the carbon fiber is spread and the carbon mesh is pre-needled to form a carbon fiber-carbon mesh unit layer, and a plurality of carbon fiber-carbon mesh unit layers are laid layer by layer and relay-needled on a flat-plate needle punching machine to form a 2.5D carbon fiber flat felt, which is then cut according to the size of the brake disc to obtain the carbon fiber preform.
According to claim 2, a high-strength carbon/ceramic brake disc with a ceramic functional layer is characterized in that: during the needling process of the carbon fiber-carbon mesh unit layer, the layering direction is adjusted to form 0°/90° alternating layer needling, and the needling density is 16~30 needles/ cm2 ; the carbon fiber is selected from 12~48K carbon fiber.
According to any one of claims 1 to 3, a high-strength carbon/ceramic brake disc with a ceramic functional layer is characterized in that the specific preparation steps of the carbon/carbon blank of the binary carbon matrix are as follows:

A carbon fiber preform with a density of 0.4-0.6 g/cm 3 is placed in a chemical vapor deposition furnace, and a carbon source gas and a diluent gas are introduced to perform chemical vapor deposition under the conditions of a high temperature of 900-1200 °C and a vacuum degree of 500-4000 Pa, so as to form pyrolytic carbon coated with carbon fibers on the surface of the carbon fiber preform, and obtain a carbon/carbon blank with a unit carbon matrix with a density of 0.80-1.3 g/cm 3 ;

The carbon/carbon blank of the unit carbon matrix is placed in a vacuum-pressure impregnation curing furnace, the impregnating agent is heated to soften, and the carbon/carbon blank of the unit carbon matrix is impregnated by a vacuum method or a pressure method, so that the impregnating agent enters the internal pores of the carbon/carbon blank of the unit carbon matrix, and the remaining impregnating agent is discharged, and then the temperature is raised to 170-220 ° C, and the temperature is kept for 1-4 hours to make the impregnating agent in the carbon/carbon blank of the unit carbon matrix undergo a curing reaction, and then it is loaded into a carbonization furnace, the carbonization treatment temperature is controlled to be 850-1000 ° C, and the carbonization time is 2-6 hours, so as to obtain a carbon/carbon blank of a binary carbon matrix with a density of 1.0-1.5 g/cm 3 ;

The carbon source gas is natural gas or propylene, the diluent gas is nitrogen or hydrogen, and the volume ratio of the carbon source gas to the diluent gas is (1-3):1; the impregnating agent is furfural resin, phenolic resin or asphalt, and the pressure in the furnace is not less than 1.5 MPa during pressure impregnation.
According to a high-strength carbon/ceramic brake disc with a ceramic functional layer as described in claim 1, it is characterized in that: the specific steps of performing high-temperature graphitization treatment on the carbon/carbon blank of the binary carbon matrix are as follows: the carbon/carbon blank of the binary carbon matrix is loaded into a high-temperature treatment furnace, and a nitrogen or inert gas protective atmosphere is introduced, and the temperature is raised to 1800~2400℃, and the temperature is kept for 1~6 hours to complete the high-temperature graphitization treatment of the carbon/carbon blank of the binary carbon matrix.
According to claim 1, a high-strength carbon/ceramic brake disc with a ceramic functional layer is characterized in that the specific preparation steps of the carbon/ceramic brake disc blank are as follows: first, the carbon/carbon blank with a binary carbon matrix after graphitization is mechanically processed according to the final product drawing to obtain a molded blank; then the molded blank is placed in a graphite crucible, and the filler amount is calculated according to the volume of the final product and silicon powder is added. After the filling is completed, the graphite crucible is placed in a high-temperature furnace, the temperature is raised to 1600~2000℃, and the temperature is kept for 1~4 hours. The vacuum degree is controlled to be 200~2000 Pa to obtain a carbon/ceramic brake disc blank with a density of 1.9~2.4 g/ cm3 .
According to claim 6, a high-strength carbon/ceramic brake disc with a ceramic functional layer is characterized in that silicon powder is spread flat on the bottom of the crucible, and 5 to 8 pads made of porous silicon carbide material are placed in the silicon powder to support the molded body so that the silicon powder does not contact the molded body.
The high-strength carbon/ceramic brake disc with a ceramic functional layer according to claim 1 is characterized in that the thermosetting resin in the ceramic precursor glue is phenolic resin, epoxy resin or furfural resin.
According to claim 1, a high-strength carbon/ceramic brake disc with a ceramic functional layer is characterized in that: the specific steps of preparing the ceramic functional layer on the surface of the carbon/ceramic brake disc blank by in-situ reaction are as follows: brushing the prepared ceramic precursor glue on the surface of the carbon/ceramic brake disc blank or immersing the carbon/ceramic brake disc blank in the prepared ceramic precursor glue, then loading it into a high-temperature furnace after drying, heating it to 1600~2000℃, and keeping it warm for 1~3 hours to form a ceramic functional layer on the surface of the carbon/ceramic brake disc blank.
A high-strength carbon/ceramic brake disc with a ceramic functional layer according to claim 1, 8 or 9, characterized in that the thickness of the ceramic functional layer is 0.5 to 3 mm.