Carbon ceramic brake disc with wear-resistant coating and method for manufacturing the same

Abstract

The application relates to the field of carbon ceramic materials, and particularly discloses a carbon ceramic brake disc with a wear-resistant coating and a preparation method thereof. The preparation method comprises the following steps: spraying a binder on a carbon-carbon brake disc blank to form a bonding layer, and then paving wear-resistant agent to obtain a wear-resistant coating; wherein the binder is prepared from the following raw materials: phenolic resin, silicon dioxide powder and carbon powder; the wear-resistant agent is prepared from the following raw materials: phenolic resin, carbon powder and silicon carbide powder; the carbon-carbon brake disc blank treated in step S1 is pressed and solidified to form a carbon-carbon brake disc; carbonization treatment is carried out; densification treatment is carried out; silicon melt infiltration is carried out; and the carbon-carbon brake disc coating blank after the silicon infiltration and densification treatment is sequentially subjected to finishing and heat treatment to obtain the carbon ceramic brake disc. The application also discloses the carbon ceramic brake disc prepared by the above method, and has the characteristics of solving the cracking problem caused by the large difference between the thermal expansion coefficients of the coating and the blank during the ceramicization process of the existing carbon-carbon brake disc.

Description

Technical Field

[0001] This application relates to the field of carbon ceramic materials, and more specifically, it relates to a carbon ceramic brake disc with a wear-resistant coating and a method for preparing the same. Background Technology

[0002] Braking materials for modern transportation vehicles such as automobiles and high-speed trains have evolved from asbestos materials, semi-metallic materials, and powder metallurgy materials to carbon-carbon composite materials and carbon-ceramic composite materials. Among various braking materials, powder metallurgy and carbon-carbon composite materials are currently the most widely used in high-speed trains, automobiles, and aircraft. However, powder metallurgy braking materials have disadvantages such as easy adhesion at high temperatures, easy degradation of friction performance, significant decrease in high-temperature strength, poor thermal shock resistance, and short service life. Carbon-carbon automotive brake discs are mainly made of carbon fiber and pre-oxidized filaments. However, carbon-carbon materials are prone to react with oxygen at high temperatures, leading to surface oxidation. Especially under long-term and high-intensity use, the temperature of the brake disc increases significantly, further aggravating the oxidation process. This causes the surface material of the brake disc to peel off layer by layer, exposing the internal fiber structure and affecting the performance and safety of the brake disc.

[0003] To address the oxidation problem of carbon fibers, a silicon infiltration densification process is employed. For example, Chinese patent application CN113277869A discloses a carbon-ceramic brake disc with a wear-resistant and oxidation-resistant coating and its preparation method. The preparation method includes the following steps: Grooving is performed on both the upper and lower surfaces of the carbon / carbon composite disc; a coating slurry is first applied to the grooves on the upper surface until the slurry fills the grooves; then the carbon / carbon composite disc is flipped over, and the coating slurry is applied to the grooves on the lower surface until the slurry fills the grooves, resulting in a carbon / carbon composite disc containing the coating slurry. This disc is then subjected to curing, carbonization, and ceramicization treatments to obtain the carbon-ceramic brake disc. This technology, by coating a carbon-carbon composite disc with a coating slurry containing resin, silicon carbide powder, and silicon powder, followed by carbonization and silicon infiltration treatments, yields a wear-resistant and oxidation-resistant coating, thus solving the oxidation problem of carbon fibers.

[0004] However, during the silicon infiltration process, due to the large difference in the coefficients of thermal expansion between silicon carbide and carbon-carbon brake disc blanks, the brake disc coating obtained after silicon infiltration is prone to cracking and peeling, affecting safety in use. Summary of the Invention

[0005] To address the problem of cracking caused by the large difference in thermal expansion coefficients between the coating and the blank during the ceramicization process of existing carbon-carbon brake discs, this application provides a carbon-ceramic brake disc with a wear-resistant coating and its preparation method.

[0006] In a first aspect, this application provides a method for preparing a carbon-ceramic brake disc with a wear-resistant coating, employing the following technical solution:

[0007] A method for preparing a carbon ceramic brake disc with a wear-resistant coating includes the following steps:

[0008] S1. Loading: A binder is sprayed onto the carbon-carbon brake disc blank to form a bonding layer, thus obtaining a primary blank. Then, a wear-resistant agent is spread on the primary blank to obtain a wear-resistant coating.

[0009] The adhesive is made from the following raw materials in parts by weight: 55-65 parts of phenolic resin, 5-12 parts of silica powder, and 15-25 parts of carbon powder.

[0010] The wear-resistant agent is made from the following raw materials in parts by weight: 15-25 parts of phenolic resin, 60-70 parts of carbon powder and 15-25 parts of silicon carbide powder;

[0011] S2. Hot pressing curing: The carbon-carbon brake disc preform processed in step S1 is pressed and cured by step pressure and step temperature to obtain a carbon-carbon brake disc coating preform.

[0012] S3, carbonization treatment;

[0013] S4. Densification treatment: The carbon-carbon brake disc coating preform after carbonization treatment in step S3 is subjected to molten silicon infiltration.

[0014] S5. Finishing and heat treatment: The carbon-carbon brake disc coating preform after silicon infiltration densification treatment in step S4 is sequentially finished and heat treated to obtain a carbon-ceramic brake disc.

[0015] By adopting the above technical solution, in the preparation of carbon-ceramic brake discs in this application, an adhesive layer is first sprayed onto the carbon-carbon brake disc blank and a wear-resistant layer is laid flat. Then, hot pressing curing, carbonization treatment, and silicon infiltration treatment are performed. The adhesive layer raw materials are phenolic resin, silica powder, and carbon powder, and the wear-resistant agent raw materials are phenolic resin, carbon powder, and silicon carbide powder. During the high-temperature silicon infiltration treatment, the silica powder in the adhesive layer reacts chemically with the carbon powder in the adhesive layer to form silicon carbide. At the same time, the silica powder can also react chemically with the carbon on the carbon-carbon brake disc blank to form silicon carbide. During the carbonization process, the phenolic resin forms resin carbon, and the resin carbon can also react with the silica powder to form silicon carbide. Through the formation of chemical bonds between the silica in the adhesive and the carbon in the wear-resistant layer, the carbon in the adhesive layer, and the carbon in the carbon-carbon brake disc blank, the coating and the carbon-carbon brake disc blank are chemically bonded and fused together, and the coating is not easy to fall off.

[0016] Furthermore, in this application, the bonding layer and wear-resistant layer with specific raw material ratios undergo a chemical reaction with the carbon-carbon brake disc blank through silicon infiltration. In particular, the addition of phenolic resin and additional carbon powder in the bonding layer, as well as the resin carbon formed by the additional carbon powder and phenolic resin in the wear-resistant layer, can form silicon carbide with silicon infiltration. This allows silicon elements to react synchronously with carbon elements in the coating and the carbon-carbon brake disc blank during the silicon infiltration process. Moreover, the silicon dioxide in the bonding layer also reacts synchronously with carbon elements in the coating and the carbon-carbon brake disc blank. This results in the final coating and the carbon-carbon blank having similar coefficients of thermal expansion, significantly improving the problems of coating peeling and cracking, and greatly extending the service life of the brake disc.

[0017] Optionally, the phenolic resin in the binder may be liquid phenolic resin or powdered phenolic resin with a mass ratio of 1:(0.5-0.7); the phenolic resin in the wear-resistant agent may be powdered phenolic resin.

[0018] By adopting the above technical solution, the phenolic resin in the binder is a mixture of liquid and powder forms. On the one hand, the addition of liquid resin makes the binder fluid, which is helpful for spraying onto the carbon-carbon brake disc blank. More importantly, liquid phenolic resin has good fluidity and can penetrate into the fine pores of the brake disc blank, which helps to form a uniform coating and reduces stress concentration points in the coating, thereby reducing the risk of subsequent cracking or peeling. On the other hand, powdered phenolic resin particles can be evenly distributed on the surface of the brake disc to form a strong protective layer and improve the coating adhesion. Moreover, powdered phenolic resin enhances the hardness and wear resistance of the coating. The two work together. The fluidity of liquid phenolic resin helps the powdered phenolic resin to form a uniform distribution on the surface of the brake disc, while the hardness and strength of powdered phenolic resin enhance the overall performance of the coating. The combination of the two not only improves the uniformity and density of the coating, but also enhances the bonding force between the coating and the blank, reducing coating peeling or cracking.

[0019] Optionally, in the binder, the phenolic resin powder has a particle size of 50-60 μm, the silica powder has a particle size of 5-15 μm, and the carbon powder has a particle size of 50-60 μm.

[0020] By adopting the above technical solution, in the binder raw materials of this application, the phenolic resin powder and carbon powder have similar and relatively large particle sizes, while the silica powder has a smaller particle size. The large-particle-size phenolic resin powder forms a strong skeleton during the curing process, which helps to improve the overall strength and stability of the coating. The large-size carbon powder also forms a supporting structure in the coating, reducing the cracking phenomenon of the coating in the subsequent ceramization process. The small-particle-size silica is distributed in the coating, filling the micropores and defects in the coating, improving the density and uniformity of the coating. Moreover, the small-particle-size silica powder has a higher specific surface area and activity, and is more evenly distributed around the carbon element, making it easier to react with the carbon element. Furthermore, the good skeleton structure formed by the large-particle-size phenolic resin and carbon powder helps to maintain the stability of the coating, reduces stress concentration in the subsequent ceramization process, provides support and protection for the reaction between silica and carbon element, thereby improving the bonding strength between the coating and the substrate, reducing the difference in thermal expansion coefficients between the coating and the substrate, and reducing the phenomenon of coating peeling.

[0021] Optionally, in the wear-resistant agent, the particle size of phenolic resin powder is 50-60μm, the particle size of carbon powder is 50-60μm, and the particle size of silicon carbide powder is 1-5μm.

[0022] By adopting the above technical solution, the silicon carbide powder in the wear-resistant agent is selected as ultrafine powder. The ultrafine silicon carbide powder is more evenly distributed in the wear-resistant coating, thereby improving the hardness and wear resistance of the coating.

[0023] Optionally, the amount of adhesive sprayed onto the carbon-carbon brake disc blank is 0.05-0.10 g / cm³. 2 The amount of wear-resistant agent added should be such that the thickness of the wear-resistant coating is 1.5-2 mm.

[0024] By adopting the above technical solution and controlling the amount of binder and wear-resistant agent added, the probability of cracking of carbon-carbon brake disc blanks during subsequent processing is reduced. On the other hand, with sufficient silicon penetration during subsequent silicon infiltration, the coefficient of thermal expansion of the coating and the brake disc blank are close, preventing the coating from peeling off or cracking.

[0025] Optionally, the specific parameters for hot pressing curing in step S2 are as follows: first, apply an initial pressure of 0.5±0.2MPa, and at the same time heat to 100±10℃ and keep warm for 1-2 hours;

[0026] Then, the pressure is increased to 5±1MPa, and the temperature is increased to 130±10℃ at a heating rate of 1-2℃ / min, and held for 0.5-1h. Then, the temperature is increased to 160±10℃ at a heating rate of 0.5-1℃ / min, and held for 1-1.5h. The material is then naturally cooled to obtain a carbon-carbon brake disc coating blank.

[0027] By employing the above technical solution, after sequentially spraying adhesive and spreading wear-resistant agent onto the carbon-carbon brake disc blank, the coating is cured and formed using stepped pressurization and stepped heating. This ensures that the coating can react and cure evenly and fully during the curing process, avoiding uneven stress distribution and defects caused by excessively rapid temperature and pressure, thus reducing the risk of cracking. Furthermore, by controlling the heating rate, the internal structure of the coating is optimized, further improving the coating's crack resistance and mitigating the problem of coating peeling.

[0028] Optionally, the specific operation of carbonization in step S3 is as follows:

[0029] When the vacuum is ≤1KPa, the temperature is increased from room temperature to 200±20℃ at a heating rate of 100±5℃ / min, then increased to 600±50℃ at a heating rate of 20-30℃ / h, and held for 1.5-2.5h. Then the temperature is increased to 900±50℃ at a heating rate of 20-25℃ / h, and held for 2-4h. The furnace is then cooled to room temperature.

[0030] By adopting the above technical solution, the carbonization treatment transforms the organic matter of phenolic resin in the coating into carbon, increasing the carbon content in the material. This allows silicon carbide to be formed in the subsequent silicon infiltration treatment, along with the infiltrated silicon and carbon dioxide in the coating, thus achieving the ceramicization of the carbon-carbon brake disc. The carbonization treatment uses a stepped heating method to ensure uniform heating of the material during the carbonization process, reducing internal stress caused by rapid temperature changes, avoiding thermal stress concentration caused by sudden temperature changes, reducing the risk of cracking, and controlling the reaction process of organic matter transforming into carbon to avoid cracking problems caused by excessively rapid reactions.

[0031] Optionally, the densification process in step S4 is specifically performed as follows:

[0032] Spread silicon powder evenly on the graphite paper inside the graphite crucible. The amount of silicon powder added is 1-2 times the mass of the carbon-carbon brake disc coating preform after carbonization treatment in step S3. Place the carbon-carbon brake disc coating preform on the silicon powder inside the graphite crucible.

[0033] The graphite crucibles containing the carbon-carbon brake disc coating preforms are stacked in the silicon infiltration path for molten silicon infiltration. Specifically:

[0034] Evacuate to <1KPa, maintain vacuum for 10-12h, then heat to the deposition temperature of 1600-1800℃ and hold for 1-4h; then cool to room temperature with the furnace.

[0035] By adopting the above technical solution, during the silicon infiltration densification process, the amount of silicon powder added is 1-2 times the mass of the carbon-carbon brake disc coating blank after the carbonization treatment in step S3, ensuring sufficient silicon during the silicon infiltration process. The silicon element infiltrates into the coating and the carbon-carbon brake disc blank and reacts with the carbon element to generate silicon carbide, thereby realizing the ceramicization of the carbon-carbon brake disc and obtaining a carbon-ceramic brake disc.

[0036] Optionally, the specific operation of heat treatment in step S5 is as follows:

[0037] The carbon-ceramic brake disc is prepared by heating the furnace from room temperature to 1000±50℃ at a heating rate of 90-95℃ / h and holding it at that temperature for 1-1.5h, then heating it to 2300±50℃ at a heating rate of 90-95℃ / h and holding it at that temperature for 1.5-2.5h, and then cooling it to room temperature in the furnace.

[0038] By adopting the above technical solution, residual stress may be generated during the ceramicization process of carbon-carbon brake discs due to factors such as temperature changes and material shrinkage. These residual stresses may make the material more prone to cracking when subjected to external forces. In this application, the carbon-carbon brake disc coating preform with silicon-diffused densification treatment is subjected to heat treatment and graphitization treatment. Through high-temperature heating and heat preservation, stress release treatment can be performed to eliminate or reduce these residual stresses, thereby improving the crack resistance of the brake disc and helping to reduce the cracking or coating peeling of the brake disc under high pressure, high temperature and high friction conditions. Graphitization is performed when the temperature is raised to 2300±50℃, so that the carbon element undergoes graphitization transformation to form a graphite structure, which further enhances the thermal stability, mechanical properties and oxidation resistance of the material, improves the crack resistance and oxidation resistance of the brake disc, and reduces the cracking or coating peeling of the brake disc under high pressure, high temperature and high friction conditions.

[0039] Optionally, the silica powder is added after undergoing the following modification treatment:

[0040] Preparation of silica suspension: Silica powder, surfactant, silica anti-settling agent and water are mixed and ultrasonically dispersed to obtain silica suspension;

[0041] Emulsion polymerization: 3-methacryloyloxypropylmethyldiethoxysilane monomer and butyl acrylate monomer are mixed at a mass ratio of 1:(0.5-0.7) to obtain a mixed monomer. The mixture is heated to 65-75℃, and then a mixed solution of emulsifier and water is added. Then, a silica suspension and the initiator azobisisobutyronitrile are added. The mixture is subjected to high-speed shear reaction at 11000-12000 rpm for 2-3 hours. After cooling and standing, the modified silica is obtained by washing, filtration and drying.

[0042] By adopting the above technical solution, silica powder is added after being coated with silane monomer emulsion polymerization, which enhances the dispersion uniformity of silica and phenolic resin. This allows the silica powder to be coated more evenly on the carbon-carbon brake disc blank, and subsequently reacts better with the adhesive layer, wear-resistant layer, and carbon in the blank. This improves the chemical bonding between the coating and the blank, while further reducing the difference in thermal expansion coefficients between the coating and the blank. Moreover, the monomers selected in the coating layer are acrylate monomers and silane monomers, which form carbon and silicon elements in subsequent processing. Silicon carbide crystals can be further formed in the coating, which improves the antioxidant performance and further reduces the difference in expansion coefficients, thus reducing the phenomenon of coating cracking or peeling.

[0043] Optionally, in the step of preparing the silica suspension, the amount of surfactant added is 1-3 wt% of the silica powder, the amount of silica anti-settling agent added is 0.5-1 wt% of the silica powder, and the amount of water added is 8-10 times the mass of the silica powder; in the emulsion polymerization step, the amount of mixed monomers and silica powder added is 8-10 wt%, the amount of emulsifier added is 5-8 wt% of the mass of the mixed monomers, the amount of initiator added is 0.5-1.5 wt% of the mass of the mixed monomers, and the amount of water added is 3-4 times the mass of the mixed monomers.

[0044] Secondly, this application provides a carbon ceramic brake disc with a wear-resistant coating, employing the following technical solution:

[0045] A carbon-ceramic brake disc with a wear-resistant coating is prepared by the aforementioned method.

[0046] By adopting the above technical solution, compared to carbon-carbon brake discs which begin to oxidize and peel off layer by layer at 350°C after high-intensity operation, the wear-resistant coating formed on the carbon-carbon brake disc blank in this application, after silicon infiltration treatment, can remain stable above 1000°C without peeling off. Moreover, it has better hardness and stability under high pressure and high temperature conditions compared to carbon-carbon brake discs. In addition, by controlling the addition of raw materials in the binder and wear-resistant agent, the silica in the binder layer can react with the carbon powder in the binder layer, the carbon powder in the wear-resistant layer, and the carbon powder in the carbon-carbon brake disc blank to form new chemical bonds. This makes the coating and the blank fused together and not easy to peel off. Moreover, during the silicon infiltration process, while the silicon element reacts with the carbon powder in the coating, the silicon element reacts simultaneously with the carbon fibers in the carbon-carbon brake disc blank. This makes the thermal expansion coefficients of the coating and the carbon-carbon brake disc blank similar, which greatly solves the problem of cracking and peeling caused by the large difference in thermal expansion coefficients between the coating and the carbon-carbon brake disc blank, thus improving the service life of the brake disc.

[0047] In summary, this application has the following beneficial effects:

[0048] 1. In this application, by controlling the addition of raw materials in the adhesive and wear-resistant agent, the silica in the adhesive layer can react with the carbon powder in the adhesive layer, the carbon powder in the wear-resistant layer and the carbon powder in the carbon-carbon brake disc blank to generate new chemical bonds, so that the coating is fused with the blank and is not easy to fall off.

[0049] 2. In this application, the bonding layer and wear-resistant layer with specific raw material ratios undergo a chemical reaction with the carbon-carbon brake disc blank through silicon infiltration. In particular, the phenolic resin added to the bonding layer and the additional carbon powder, as well as the resin carbon formed by the additional carbon powder and phenolic resin in the wear-resistant layer, can form silicon carbide with silicon infiltration. This allows silicon elements to react synchronously with carbon elements in the coating and carbon-carbon brake disc blank during the silicon infiltration process. Moreover, the silicon dioxide in the bonding layer also reacts synchronously with carbon elements in the coating and carbon-carbon brake disc blank. This results in the final coating and carbon-carbon blank having similar coefficients of thermal expansion, significantly improving the problems of coating peeling and cracking, and greatly extending the service life of the brake disc.

[0050] 3. In this application, the carbon-carbon brake disc coating preform that has undergone silicon-diffused densification treatment is subjected to heat treatment and graphitization treatment. Through high-temperature heating and heat preservation, stress release treatment is carried out, which can eliminate or reduce these residual stresses, thereby improving the crack resistance of the brake disc and helping to reduce the cracking or coating peeling of the brake disc under high pressure, high temperature and high friction conditions. Graphitization is carried out when the temperature is raised to 2300±50℃, so that the carbon elements undergo graphitization transformation to form a graphite structure, which further enhances the thermal stability and mechanical properties of the material, improves the crack resistance of the brake disc, and reduces the cracking or coating peeling of the brake disc under high pressure, high temperature and high friction conditions. Detailed Implementation

[0051] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0052] In the following examples, the liquid phenolic resin can be selected from the liquid phenolic resin of Shandong Shouhua Chemical Co., Ltd. with CAS number 9003-35-4;

[0053] The powdered phenolic resin used is powdered phenolic resin from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0054] In the following embodiments, the carbon-carbon brake disc preform is preferably prepared by impregnating and carbonizing a carbon fiber preform in resin after densification by vapor deposition.

[0055] Preparation Example 1

[0056] A method for preparing a carbon-carbon brake disc blank includes the following steps:

[0057] A single layer of 0° non-woven fabric, a carbon fiber mesh, a 90° non-woven fabric, and another carbon fiber mesh are sequentially layered and stacked to a predetermined thickness. A carbon fiber preform is then prepared by relay needle punching, with a needle punching density of 25-30 needles / cm². 2 The density of the carbon fiber preform is 0.4 g / cm³. 3 Densification of carbon fiber preforms by vapor deposition: using natural gas as a precursor, pyrolytic carbon is deposited inside the carbon fiber preforms for densification. The natural gas flow rate is 35 L / h, the vacuum degree during the densification process is 1500 Pa, the deposition temperature is 1100℃, the deposition time is 250 h, and the natural gas purity is 99.9%. After the densification process, a densified preform is obtained.

[0058] The prepared densified preform was impregnated in a slurry obtained by mixing phenolic resin and acetone in a mass ratio of 1:2. The liquid level of the slurry was above the densified preform. The impregnation temperature was 50℃, the pressure was 2.5 MPa, and the impregnation time was 4 h to obtain the impregnated preform. The impregnated preform was then carbonized at a carbonization temperature of 1000℃ and a carbonization time of 8 h to obtain a carbon-carbon brake disc blank.

[0059] Preparation Example 2

[0060] A method for preparing a carbon-carbon brake disc blank includes the following steps:

[0061] A single layer of 0° non-woven fabric, a carbon fiber mesh, a 90° non-woven fabric, and another carbon fiber mesh are sequentially layered and stacked to a predetermined thickness. A carbon fiber preform is then prepared by relay needle punching, with a needle punching density of 25-30 needles / cm². 2 The density of the carbon fiber preform is 0.4 g / cm³. 3 Densification of carbon fiber preforms by vapor deposition: using natural gas as a precursor, pyrolytic carbon is deposited inside the carbon fiber preforms for densification. The natural gas flow rate is 35 L / h, the vacuum degree during the densification process is 1500 Pa, the deposition temperature is 1100℃, the deposition time is 250 h, and the natural gas purity is 99.9%. After densification, carbon-carbon brake disc preforms are obtained.

[0062] Example 1

[0063] A method for preparing a carbon ceramic brake disc with a wear-resistant coating includes the following steps:

[0064] S1. Loading: This includes the following steps:

[0065] S1-1. A binder is prepared by mixing 60 kg of phenolic resin, 8 kg of silica powder with a particle size of 5-15 μm, and 20 kg of carbon powder with a particle size of 50-60 μm. The phenolic resin includes liquid phenolic resin with a mass ratio of 1:0.6 and powdered phenolic resin with a particle size of 50-60 μm.

[0066] S1-2, A wear-resistant agent is prepared by mixing 20 kg of phenolic resin powder with a particle size of 50-60 μm, 65 kg of carbon powder with a particle size of 50-60 μm, and 20 kg of silicon carbide powder with a particle size of 1-5 μm.

[0067] S1-3. Place the carbon-carbon brake disc preform obtained in Preparation Example 1 into a mold, and then apply a 0.08 g / cm³ coating to the carbon-carbon brake disc preform. 2 The amount of spraying agent is sprayed with the adhesive obtained in step S1-2 to form an adhesive layer, and a primary preform is obtained. Then, the wear-resistant agent obtained in step S1-2 is spread on the primary preform to obtain a wear-resistant coating including the adhesive layer and the wear-resistant layer. The amount of wear-resistant agent added is up to the thickness of the wear-resistant coating being 2 mm.

[0068] S2. Hot pressing and curing: The carbon-carbon brake disc blank processed in step S1 is pressed and cured by step pressure and step temperature increase. Specifically, the mold is first pressed with an initial pressure of 0.5MPa by a hydraulic press, and the mold is heated to 100℃ and kept at that temperature for 1.5h.

[0069] Then, the hydraulic press is pressurized to 5MPa, and the temperature is raised to 130℃ at a heating rate of 1.5℃ / min, held for 0.5h, and then raised to 160℃ at a heating rate of 0.5℃ / min, held for 1h, and then naturally cooled to room temperature to demold, thus obtaining the carbon-carbon brake disc coating preform.

[0070] S3. Carbonization treatment: When the vacuum is ≤1KPa, the temperature is increased from room temperature to 200℃ at a heating rate of 100℃ / min, then increased to 600℃ at a heating rate of 25℃ / h, held for 2h, then increased to 900℃ at a heating rate of 20℃ / h, held for 3h, and then cooled to room temperature with the furnace to obtain the carbonized brake disc.

[0071] S4. Densification treatment: The carbon-carbon brake disc coating preform after carbonization in step S3 is subjected to molten silicon infiltration. The specific operation is as follows: Silicon powder is evenly spread on graphite paper inside a graphite crucible. The amount of silicon powder added is 1.5 times the mass of the carbonized brake disc in step S3. The carbonized brake disc is placed on the silicon powder inside the graphite crucible. Then, the graphite crucible containing the carbonized brake disc is stacked in the silicon infiltration path for molten silicon infiltration. Specifically, the vacuum is drawn to <1KPa and held for 11 hours. Then, the temperature is raised to the deposition temperature of 1700℃ and held for 2.5 hours. Then, the furnace is cooled to room temperature.

[0072] S5. Finishing and heat treatment: The carbonized brake disc after silicon infiltration densification treatment in step S4 is finished by grinding and then subjected to heat treatment. The heat treatment parameters are: heating from room temperature to 1000℃ at a heating rate of 90℃ / h, holding for 1h, then heating to 2300℃ at a heating rate of 90℃ / h, holding for 2h, and then cooling to room temperature in the furnace to obtain the carbon ceramic brake disc.

[0073] Example 2

[0074] A method for preparing a carbon ceramic brake disc with a wear-resistant coating includes the following steps:

[0075] S1. Loading: This includes the following steps:

[0076] S1-1. A binder is prepared by mixing 55 kg of phenolic resin, 5 kg of silica powder with a particle size of 5-15 μm, and 15 kg of carbon powder with a particle size of 50-60 μm. The phenolic resin includes liquid phenolic resin with a mass ratio of 1:0.5 and powdered phenolic resin with a particle size of 50-60 μm.

[0077] S1-2, A wear-resistant agent is prepared by mixing 15 kg of phenolic resin powder with a particle size of 50-60 μm, 60 kg of carbon powder with a particle size of 50-60 μm, and 15 kg of silicon carbide powder with a particle size of 1-5 μm.

[0078] S1-3. Place the carbon-carbon brake disc preform obtained in Preparation Example 1 into a mold, and then apply a 0.05 g / cm³ coating to the carbon-carbon brake disc preform. 2 The amount of spraying agent is sprayed with the adhesive obtained in step S1-2 to form an adhesive layer, and a primary preform is obtained. Then, the wear-resistant agent obtained in step S1-2 is spread on the primary preform to obtain a wear-resistant coating including the adhesive layer and the wear-resistant layer. The amount of wear-resistant agent added is up to the thickness of the wear-resistant coating being 1.5 mm.

[0079] S2. Hot pressing and curing: The carbon-carbon brake disc blank processed in step S1 is pressed and cured by step pressure and step temperature increase. Specifically, the mold is first pressed with an initial pressure of 0.3MPa by a hydraulic press, and the mold is heated to 90℃ and kept at that temperature for 2 hours.

[0080] Then, the hydraulic press is pressurized to 4MPa, and the temperature is raised to 120℃ at a heating rate of 1℃ / min, held for 1h, then raised to 150℃ at a heating rate of 0.5℃ / min, held for 1.5h, and naturally cooled to room temperature for demolding to obtain a carbon-carbon brake disc coating preform; S3, carbonization treatment; when the vacuum is ≤1KPa, the temperature is raised from room temperature to 220℃ at a heating rate of 95℃ / min, then raised to 550℃ at a heating rate of 20℃ / h, held for 2.5h, then raised to 850℃ at a heating rate of 20℃ / h, held for 4h, and cooled to room temperature with the furnace to obtain a carbonized brake disc;

[0081] S4. Densification treatment: The carbon-carbon brake disc coating preform after carbonization treatment in step S3 is subjected to molten silicon infiltration. The specific operation is as follows: Silicon powder is evenly spread on graphite paper in a graphite crucible. The amount of silicon powder added is 1 times the mass of the carbonized brake disc in step S3. The carbonized brake disc is placed on the silicon powder in the graphite crucible. Then, the graphite crucible with the carbonized brake disc is stacked in the silicon infiltration path for molten silicon infiltration. Specifically, the vacuum is drawn to <1KPa and held for 10h. Then, the temperature is raised to the deposition temperature of 1600℃ and held for 4h. Then, the furnace is cooled to room temperature.

[0082] S5. Finishing and heat treatment: The carbonized brake disc after silicon infiltration densification treatment in step S4 is finished by grinding and then subjected to heat treatment. The heat treatment parameters are: heating from room temperature to 1000℃ at a heating rate of 90℃ / h, holding at that temperature for 1.5h, then heating to 2300℃ at a heating rate of 90℃ / h, holding at that temperature for 2.5h, and then cooling to room temperature in the furnace to obtain the carbon ceramic brake disc.

[0083] Example 3

[0084] A method for preparing a carbon ceramic brake disc with a wear-resistant coating includes the following steps:

[0085] S1. Loading: This includes the following steps:

[0086] S1-1. A binder is prepared by mixing 65 kg of phenolic resin, 12 kg of silica powder with a particle size of 5-15 μm, and 25 kg of carbon powder with a particle size of 50-60 μm. The phenolic resin includes liquid phenolic resin with a mass ratio of 1:0.7 and powdered phenolic resin with a particle size of 50-60 μm.

[0087] S1-2, A wear-resistant agent is prepared by mixing 25 kg of phenolic resin powder with a particle size of 50-60 μm, 70 kg of carbon powder with a particle size of 50-60 μm, and 25 kg of silicon carbide powder with a particle size of 1-5 μm.

[0088] S1-3. Place the carbon-carbon brake disc preform obtained in Preparation Example 1 into a mold, and then apply a 0.10 g / cm³ coating to the carbon-carbon brake disc preform.2 The amount of spraying agent is sprayed with the adhesive obtained in step S1-2 to form an adhesive layer, and a primary preform is obtained. Then, the wear-resistant agent obtained in step S1-2 is spread on the primary preform to obtain a wear-resistant coating including the adhesive layer and the wear-resistant layer. The amount of wear-resistant agent added is up to the thickness of the wear-resistant coating being 2 mm.

[0089] S2. Hot pressing and curing: The carbon-carbon brake disc blank processed in step S1 is pressed and cured by step pressure and step temperature increase. Specifically, the mold is first pressed with an initial pressure of 0.7MPa by a hydraulic press, and the mold is heated to 110℃ and kept at that temperature for 1 hour.

[0090] Then, the hydraulic press is pressurized to 6MPa, and the temperature is raised to 140℃ at a heating rate of 2℃ / min, held for 0.5h, and then raised to 170℃ at a heating rate of 1℃ / min, held for 1h, and then naturally cooled to room temperature to demold, thus obtaining the carbon-carbon brake disc coating preform.

[0091] S3, carbonization treatment; when the vacuum is ≤1KPa, the temperature is increased from room temperature to 220℃ at a heating rate of 105℃ / min, then increased to 650℃ at a heating rate of 30℃ / h, held for 1.5h, then increased to 950℃ at a heating rate of 25℃ / h, held for 2h, and then cooled to room temperature with the furnace to obtain the carbonized brake disc;

[0092] S4. Densification treatment: The carbon-carbon brake disc coating preform after carbonization in step S3 is subjected to molten silicon infiltration. The specific operation is as follows: Silicon powder is evenly spread on graphite paper inside a graphite crucible. The amount of silicon powder added is twice the mass of the carbonized brake disc in step S3. The carbonized brake disc is placed on the silicon powder inside the graphite crucible. Then, the graphite crucible containing the carbonized brake disc is stacked in the silicon infiltration path for molten silicon infiltration. Specifically, the vacuum is drawn to <1 kPa and held for 12 hours. Then, the temperature is raised to the deposition temperature of 1800℃ and held for 1 hour. Then, the furnace is cooled to room temperature.

[0093] S5. Finishing and heat treatment: The carbonized brake disc after silicon infiltration densification treatment in step S4 is finished by grinding and then subjected to heat treatment. The heat treatment parameters are as follows: the temperature is increased from room temperature to 1000℃ at a heating rate of 95℃ / h and held for 1h, then increased to 2300℃ at a heating rate of 95℃ / h and held for 1.5h, and then cooled to room temperature in the furnace to obtain the carbon ceramic brake disc.

[0094] Example 4

[0095] A method for preparing a carbon-ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the carbon-carbon brake disc blank in step S1 is the carbon-carbon brake disc blank obtained in Preparation Example 2.

[0096] Example 5

[0097] A method for preparing a carbon ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the phenolic resin in the binder in step S1 is all liquid phenolic resin.

[0098] Example 6

[0099] A method for preparing a carbon ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the particle size of the silica powder in step S1 is 20-30 μm.

[0100] Example 7

[0101] A method for preparing a carbon-ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the heat treatment operation in step S5 is as follows: the temperature is raised from room temperature to 1000℃ at a heating rate of 90℃ / h, held for 3h, and then cooled to room temperature in the furnace to obtain the carbon-ceramic brake disc.

[0102] Example 8

[0103] A method for preparing a carbon-ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the silica powder is added in step S1 after undergoing the following modification treatment:

[0104] Preparation of silica suspension: Silica powder, surfactant, silica anti-settling agent and water are mixed and ultrasonically dispersed for 15 min to obtain silica suspension. The surfactant is sodium dodecyl sulfate, and the amount of surfactant added is 2 wt% of silica powder. The silica anti-settling agent is HD-668 silica anti-settling agent from Qingyuan Xinhui Chemical Co., Ltd., and the amount of silica anti-settling agent is 0.8 wt% of silica powder. The amount of water added is 9 times the mass of silica powder.

[0105] Emulsion polymerization: 3-methacryloyloxypropylmethyldiethoxysilane monomer and butyl acrylate monomer were mixed at a mass ratio of 1:0.6 to obtain a mixed monomer. The mixture was heated to 70°C, and then a mixed solution of emulsifier polyoxypropylene ether and water was added. Silica suspension and initiator azobisisobutyronitrile were then added. The mixture was subjected to high-speed shear reaction at 11000 rpm for 2.5 h, cooled and allowed to stand. After washing, filtration and drying, modified silica was obtained.

[0106] In the emulsion polymerization step, the amount of mixed monomers and silica powder added is 9 wt%, the amount of emulsifier added is 6 wt% of the mass of mixed monomers, the amount of initiator added is 1 wt% of the mass of mixed monomers, and the amount of water added is 3 times the mass of mixed monomers.

[0107] Example 9

[0108] A method for preparing a carbon-ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the silica powder is added in step S1 after undergoing the following modification treatment:

[0109] Preparation of silica suspension: Silica powder, surfactant, silica anti-settling agent and water are mixed and ultrasonically dispersed for 10 min to obtain silica suspension. The surfactant is sodium dodecyl sulfate, and the amount of surfactant added is 1 wt% of silica powder. The silica anti-settling agent is HD-668 silica anti-settling agent from Qingyuan Xinhui Chemical Co., Ltd., and the amount of silica anti-settling agent is 0.5 wt% of silica powder. The amount of water added is 8 times the mass of silica powder.

[0110] Emulsion polymerization: 3-methacryloyloxypropylmethyldiethoxysilane monomer and butyl acrylate monomer were mixed at a mass ratio of 1:0.5 to obtain a mixed monomer. The mixture was heated to 65°C, and then a mixed solution of emulsifier polyoxypropylene ether and water was added. Then, a silica suspension and initiator azobisisobutyronitrile were added. The mixture was subjected to high-speed shear reaction at 11000 rpm for 2 hours, cooled and allowed to stand. After washing, filtration and drying, modified silica was obtained.

[0111] In the emulsion polymerization step, the amount of mixed monomers and silica powder added is 8 wt%, the amount of emulsifier added is 5 wt% of the mass of mixed monomers, the amount of initiator added is 0.5 wt% of the mass of mixed monomers, and the amount of water added is 3 times the mass of mixed monomers.

[0112] Example 10

[0113] A method for preparing a carbon-ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that the silica powder is added in step S1 after undergoing the following modification treatment:

[0114] Preparation of silica suspension: Silica powder, surfactant, silica anti-settling agent and water are mixed and ultrasonically dispersed for 20 min to obtain silica suspension. The surfactant is sodium dodecyl sulfate, and the amount of surfactant added is 3 wt% of silica powder. The silica anti-settling agent is HD-668 silica anti-settling agent from Qingyuan Xinhui Chemical Co., Ltd., and the amount of silica anti-settling agent is 1 wt% of silica powder. The amount of water added is 10 times the mass of silica powder.

[0115] Emulsion polymerization: 3-methacryloyloxypropylmethyldiethoxysilane monomer and butyl acrylate monomer were mixed at a mass ratio of 1:0.7 to obtain a mixed monomer. The mixture was heated to 75°C, and then a mixed solution of emulsifier polyoxypropylene ether and water was added. Then, a silica suspension and initiator azobisisobutyronitrile were added. The mixture was subjected to high-speed shear reaction at 12000 rpm for 3 hours, cooled and allowed to stand. After washing, filtration and drying, modified silica was obtained.

[0116] In the emulsion polymerization step, the amount of mixed monomers and silica powder added is 10 wt%, the amount of emulsifier added is 8 wt% of the mass of mixed monomers, the amount of initiator added is 1.5 wt% of the mass of mixed monomers, and the amount of water added is 4 times the mass of mixed monomers.

[0117] Comparative Example 1

[0118] A method for preparing a carbon ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that silica powder is not added to the binder raw material in step S1.

[0119] Comparative Example 2

[0120] A method for preparing a carbon ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that in step S1, the silica powder in the binder raw material is replaced with an equal amount of silicon carbide powder.

[0121] Comparative Example 3

[0122] A method for preparing a carbon ceramic brake disc with a wear-resistant coating is carried out according to the method in Example 1, except that no heat treatment operation is performed in step S5.

[0123] Performance testing

[0124] Following the preparation methods described in the above embodiments and comparative examples, carbon-ceramic brake discs were prepared. The presence of cracks in the prepared carbon-ceramic brake discs was observed, and the number of cracks was counted. For each crack, three points were taken to test the crack width, and the average width of each crack was calculated. The average crack width was then calculated for all cracks. The results are shown in Table 1.

[0125] Table 1:

[0126]

[0127]

[0128] Referring to the test results in Table 1 above, it can be seen that when no silica powder was added to the adhesive layer in Comparative Example 1, obvious cracks appeared in the carbon-ceramic brake disc. When the carbon-ceramic brake disc was prepared using the method of this application without heat treatment in Comparative Example 3, cracks also appeared. In Example 4, when the carbon-carbon brake disc preform was densified with carbon fiber preform and not impregnated with resin, a small number of cracks appeared. In Example 6, when silica powder with a larger particle size was selected, some cracks also appeared.

[0129] To better detect the impact of the method provided in this application on the crack resistance of the final carbon-ceramic brake disc, this application also conducted a thermal shock test on the prepared carbon-ceramic brake disc. Specifically, the disc was subjected to a rapid cooling and heating cycle at 900℃ for 3 minutes and at room temperature for 2 minutes. After 100 cycles within 10 hours, the area of ​​coating peeling off the carbon-ceramic brake disc was observed. The test results are shown in Table 2 below.

[0130] Table 2:

[0131]

[0132] The test results in Table 2 above show that the carbon-ceramic brake discs prepared in this application still exhibit excellent bonding strength between the coating and the preform after thermal cycling treatment, and also possess excellent crack resistance. Referring to the test results of Example 1 and Comparative Example 1, when no silica is added to the adhesive layer, the difference in thermal expansion coefficients between the coating and the preform leads to severe cracking and peeling of the coating during repeated use in high and low temperature environments. Combining the test results of Example 1 and Comparative Example 2, when the silica in the adhesive is replaced with an equal amount of silicon carbide, the cracking situation is improved compared to Comparative Example 1, but still far weaker than the effect in Example 1. In Comparative Example 3, when the carbon-ceramic brake disc undergoes silicon infiltration treatment without heat treatment, the cracking situation is also quite severe. Combining the test results of Example 7, when only heat treatment is performed without subsequent graphitization treatment, the cracking situation is improved compared to Comparative Example 3, but still weaker than Example 1.

[0133] Combining the test results of Examples 1 and 4, it can be seen that when the carbon-carbon brake disc preform is densified from a carbon fiber preform without resin impregnation, the cracking of the final brake disc product is more severe than in Example 1. This is because in Example 1, the brake disc preform is densified from a carbon fiber preform, impregnated with resin, and then subjected to silicon infiltration heat treatment after curing and molding the adhesive layer and wear-resistant layer as described in this application. The control of resin, silica, and carbon powder raw materials in the coating makes the coating raw materials similar to the carbon-carbon brake disc preform raw materials, further mitigating the cracking caused by the difference in thermal expansion coefficients between the coating and the preform. Combining the test results of Examples 5 and 6, when all phenolic resin in the binder is liquid phenolic resin, or when the silica powder particle size is large, the final crack resistance is reduced. The morphology and particle size of the raw materials in the binder affect the structure of the final coating, thus affecting the crack resistance of the final product. Referring to the test results of Examples 1 and Examples 8-10, the brake disc prepared by adding modified silica powder has better crack resistance.

[0134] In addition, the prepared carbon-ceramic brake disc was first subjected to constant temperature treatment at 1000℃ for 8 hours, and the thermal oxidation weight loss rate was measured to test its antioxidant properties. The test results are shown in Table 3 below.

[0135] Table 3:

[0136]

[0137] Based on the test results in Table 3 above, the brake discs prepared in the embodiments of this application exhibit excellent oxidation resistance. Furthermore, the brake discs prepared in the embodiments of this application have a bending strength of 120-160 MPa, a dynamic friction coefficient of 0.3-0.5, and a density of 2.0-2.5 g / cm³. 3 Its service life is greater than 300,000 kilometers.

[0138] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a carbon-ceramic brake disc with a wear-resistant coating, characterized in that, Includes the following steps: S1. Loading: A binder is sprayed onto the carbon-carbon brake disc blank to form a bonding layer, thus obtaining a primary blank. Then, a wear-resistant agent is spread on the primary blank to obtain a wear-resistant coating. The adhesive is made from the following raw materials in parts by weight: 55-65 parts of phenolic resin, 5-12 parts of silica powder, and 15-25 parts of carbon powder. The wear-resistant agent is made from the following raw materials in parts by weight: 15-25 parts of phenolic resin, 60-70 parts of carbon powder and 15-25 parts of silicon carbide powder; S2. Hot pressing curing: The carbon-carbon brake disc blank processed in step S1 is pressed and cured by step pressure and step temperature to obtain a carbon-carbon brake disc coating blank. S3, carbonization treatment; S4. Densification treatment: The carbon-carbon brake disc coating blank after the carbonization treatment in step S3 is subjected to molten silicon infiltration. S5. Fine machining and heat treatment: The carbon-carbon brake disc coating blank after silicon densification treatment in step S4 is subjected to fine machining and heat treatment in sequence to obtain carbon ceramic brake disc. The specific operation of heat treatment in step S5 is as follows: the temperature is raised from room temperature to 1000℃ at a heating rate of 90-95℃ / h, held for 1-1.5h, then raised to 2300℃ at a heating rate of 90-95℃ / h, held for 1.5-2.5h, and then cooled to room temperature in the furnace to obtain a carbon ceramic brake disc. The phenolic resin used in the binder is either liquid phenolic resin or powdered phenolic resin with a mass ratio of 1:(0.5-0.7); the phenolic resin used in the wear-resistant agent is powdered phenolic resin. In the binder, the particle size of phenolic resin powder is 50-60μm, the particle size of silica powder is 5-15μm, and the particle size of carbon powder is 50-60μm. In wear-resistant agents, the particle size of phenolic resin powder is 50-60μm, the particle size of carbon powder is 50-60μm, and the particle size of silicon carbide powder is 1-5μm. The specific parameters for hot-press curing in step S2 are as follows: First, apply an initial pressure of 0.5±0.2 MPa while heating to 100±10℃ and holding for 1-2 hours; then pressurize to 5±1 MPa while heating to 130±10℃ at a rate of 1-2℃ / min and holding for 0.5-1 hours; then heat to 160±10℃ at a rate of 0.5-1℃ / min and holding for 1-1.5 hours, followed by natural cooling to obtain a carbon-carbon brake disc coating blank.

2. The method for preparing a carbon ceramic brake disc with a wear-resistant coating according to claim 1, characterized in that: The amount of adhesive applied to the carbon-carbon brake disc blank is 0.05-0.10 g / cm³. 2 The amount of wear-resistant agent added should be such that the thickness of the wear-resistant coating is 1.5-2 mm.

3. The method for preparing a carbon ceramic brake disc with a wear-resistant coating according to claim 1, characterized in that: The specific operation of carbonization in step S3 is as follows: When the vacuum is ≤1kPa, the temperature is increased from room temperature to 200±20℃ at a heating rate of 100±5℃ / min, then increased to 600±50℃ at a heating rate of 20-30℃ / h, and held for 1.5-2.5h. Then the temperature is increased to 900±50℃ at a heating rate of 20-25℃ / h, and held for 2-4h. The furnace is then cooled to room temperature.

4. The method for preparing a carbon ceramic brake disc with a wear-resistant coating according to claim 1, characterized in that: The densification process in step S4 is specifically performed as follows: Spread silicon powder evenly on the graphite paper inside the graphite crucible. The amount of silicon powder added is 1-2 times the mass of the carbon-carbon brake disc coating blank after carbonization treatment in step S3. Place the carbon-carbon brake disc coating blank on the silicon powder inside the graphite crucible. The graphite crucibles containing the carbon-carbon brake disc coating blanks are stacked in a silicon infiltration furnace for molten silicon infiltration. Specifically, the vacuum is evacuated to <1 kPa and maintained for 10-12 hours. Then, the temperature is raised to the deposition temperature of 1600-1800℃ and held for 1-4 hours. Finally, the furnace is cooled to room temperature.

5. A carbon ceramic brake disc with a wear-resistant coating prepared by the preparation method according to any one of claims 1-4.

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