Carbon / carbon composite brake disc and method of making same

Abstract

The application discloses a carbon / carbon composite brake disc and a preparation method thereof. The carbon / carbon composite brake disc comprises a circular ring-shaped brake disc body and a plurality of tooth portions which are circumferentially distributed on the inner or outer ring of the brake disc body. A circular ring-shaped graphite paper is arranged at the center position of the brake disc body. The carbon / carbon composite brake disc has the graphite paper arranged at the center position of the thickness of the brake disc body, which is beneficial to the stability of the performance of the carbon / carbon composite brake disc. In addition, the densified carbon of the brake disc is a full rough layer structure, so that the material performance of the brake disc meets the requirements, and the brake disc has excellent heat conduction performance and friction and wear performance, and has a long service life and low use cost.

Description

Technical Field

[0001] This invention belongs to the field of brake disc manufacturing technology, specifically relating to a carbon / carbon composite brake disc and its preparation method. Background Technology

[0002] Carbon / carbon composite materials possess characteristics such as low density, high specific strength, high temperature resistance, excellent thermal shock resistance, excellent friction and wear performance, and high braking energy absorption, making them an excellent friction material. Especially when applied to aircraft brake discs, they significantly improve the reliability, safety, and economy of aircraft, and are therefore widely used in modern aircraft.

[0003] Carbon / carbon composite materials are all-carbon composite materials with carbon fiber fabric as reinforcement and carbon as the matrix, mainly prepared through gas-phase densification and / or liquid-phase densification processes to achieve the required density. Currently, there are two main routes for densification in the industry for preparing carbon / carbon composite brake discs: one is to use propylene as the carbon source gas to densify the carbon fiber preform to a certain density in the gas phase, and then use resin or asphalt to continue liquid-phase densification to the required density; the other is to use natural gas as the main carbon source gas to densify the carbon fiber preform in the gas phase until the required density is achieved. Both densification routes require a final high-temperature heat treatment (usually 2000–2400℃) to adjust the thermal and mechanical properties of the material to ensure that the carbon / carbon composite aircraft brake discs meet the performance requirements.

[0004] Both of the above-mentioned densification routes for preparing carbon / carbon composite brake discs have shortcomings. Route one's product contains carbon fibers, vapor-deposited pyrolytic carbon, and liquid-phase impregnated carbon; Route two's product contains carbon fibers and vapor-deposited pyrolytic carbon. These three types of carbon exhibit significant differences in thermal properties, making it difficult to control their thermal conductivity uniformly through high-temperature heat treatment. Furthermore, different carbons possess different tribological characteristics, leading to poor product performance stability and insufficient lifespan to meet usage requirements.

[0005] Currently, products typically undergo a final high-temperature heat treatment to balance the required thermal and mechanical properties of the materials and achieve good tribological performance. Therefore, the selection and matching of the carbon fiber preform, the carbon densification process route, and the final high-temperature heat treatment are crucial. Excessively high heat treatment temperatures can increase the thermal conductivity of the material, but may lead to a decrease in the product's tribological performance; conversely, excessively low heat treatment temperatures may result in insufficient thermal conductivity, leading to heat dissipation difficulties, or even excessive temperature rise during braking, causing large fluctuations in tribological performance that fail to meet requirements.

[0006] Therefore, how to simultaneously take into account the excellent thermal conductivity and friction and wear resistance of carbon / carbon composite brake discs is the key and difficult point in developing high-performance, long-life brake discs.

[0007] Industry professionals have conducted research, development, and application of high thermal conductivity carbon / carbon composite materials, with patent CN...

[0008] 109437949A uses pitch-based carbon fiber as reinforcement, is molded with mesophase pitch powder, and then prepared into a high thermal conductivity carbon / carbon composite material using a composite process combining chemical vapor infiltration and resin impregnation. This carbon / carbon composite material contains carbon fiber, pitch carbon, resin carbon, and vapor-deposited pyrolytic carbon. If used as an aircraft brake disc, it may not be able to simultaneously meet all the product's performance requirements. Therefore, it is necessary to develop a new type of carbon / carbon composite material specifically for the requirements of aircraft brake discs (excellent thermal conductivity and tribological properties). Summary of the Invention

[0009] Currently, carbon / carbon composite brake discs have multiple components, and the performance differences between these components are difficult to adjust to be consistent through process parameters. This results in carbon / carbon composite brake discs being unable to simultaneously meet various performance requirements, leading to poor brake disc performance and short lifespan. The first objective of this invention is to provide a carbon / carbon composite brake disc containing graphite paper in the middle. The dense carbon of the brake disc has a fully roughened layer structure, and the material properties meet the requirements. It has excellent thermal conductivity and friction and wear resistance, and the brake disc has a long lifespan and low operating cost.

[0010] The second objective of this invention is to provide a method for preparing carbon / carbon composite brake pairs.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] The present invention discloses a carbon / carbon composite brake disc, which includes an annular brake disc body and a plurality of teeth circumferentially distributed on the inner or outer ring of the brake disc body, wherein an annular graphite paper is disposed at the center of the brake disc body.

[0013] The carbon / carbon composite brake disc provided by this invention has graphite paper placed at the center of the disc body thickness. This fully utilizes the excellent thermal conductivity of graphite paper to rapidly conduct heat from the center of the carbon / carbon composite material to the surface during braking, thereby reducing the surface temperature rise of the carbon / carbon composite material and contributing to the stability of the brake disc's performance. Furthermore, the tooth region does not contain graphite paper, while other locations do. This design differentiates the thermal conductivity of the material in the tooth region from that in locations containing graphite paper, and makes the thermal conductivity of the tooth region lower than other parts (such as the tooth groove). This prevents overheating in the tooth region, which could lead to deterioration of the tooth and tooth clamp performance, thus avoiding brake disc failure under extreme conditions (such as aborted takeoff / RTO).

[0014] In a preferred embodiment, the thickness of the graphite paper is 0.6-1 mm. Controlling the graphite paper thickness within this range optimizes the performance of the carbon / carbon composite brake disc. If the graphite paper is too thin, it is prone to breakage during the carbon fiber preform preparation process, preventing the effective utilization of its excellent thermal conductivity. If the graphite paper is too thick, the Z-axis fibers are easily jammed during the needle-punched Z-axis fiber pull-back process in the carbon fiber preform preparation, resulting in the Z-axis fiber content and distribution failing to meet design requirements, thus affecting the mechanical properties of the carbon / carbon composite brake disc.

[0015] In a preferred embodiment, the thermal conductivity of the graphite paper on the hot side is ≥400W / mK, preferably 400~600W / mK, and the thermal conductivity on the thickness side is <22W / mK, preferably 8~22W / mK.

[0016] The graphite paper in this invention has the characteristic that its thermal conductivity in the oriented direction is much greater than its thermal conductivity in the thickness direction. High thermal conductivity in both the oriented and thickness directions is required, which is conducive to the rapid transfer of heat from the brake disc core to the surface (especially in the XY direction) to dissipate heat and reduce the temperature rise of the brake disc.

[0017] In a preferred embodiment, the carbon content of the graphite paper is ≥99.0%.

[0018] In a preferred embodiment, the number of teeth is ≤16.

[0019] The stationary brake disc has teeth located on the inner ring of the brake disc body, while the moving brake disc has teeth located on the outer ring of the brake disc body. The stationary and moving brake discs together form a brake pair.

[0020] In a preferred embodiment, the carbon matrix in the carbon / carbon composite brake disc has a fully roughened layer structure.

[0021] In a preferred embodiment, the density of the carbon / carbon composite brake disc is ≥1.78 g / cm³. 3 .

[0022] This invention discloses a method for preparing a carbon / carbon composite brake disc, which involves alternately laying carbon fiber nonwoven fabric and carbon fiber mesh, and laying a layer of graphite paper at the center position. Then, the carbon fiber preform is obtained by needle punching layer by layer. The carbon fiber preform is then heat-treated and then chemically vapor-deposited to obtain a carbon / carbon composite preform. Finally, the preform is heat-treated and machined to obtain a carbon / carbon composite brake disc.

[0023] In a preferred embodiment, carbon fiber nonwoven fabric and carbon fiber mesh are alternately laid, with the interlayer density controlled at 10-20 layers / cm, the weight ratio of carbon fiber nonwoven fabric to carbon fiber mesh at 60-80:40-20, and the layup angle of adjacent carbon fiber nonwoven fabrics at 0° / 90°.

[0024] In actual operation, when laying graphite paper, the operability of prefabrication and the amount of removal of inner and outer diameters during machining are comprehensively considered. When the outer ring of the brake disc body contains teeth, the inner diameter of the graphite paper is designed to be consistent with the inner diameter of other components in the prefabrication, and the outer diameter is equal to the outer diameter of the finished moving disc brake disc minus twice the tooth height. When the inner ring of the brake disc body contains teeth, the outer diameter of the graphite paper is designed to be consistent with the outer diameter of other parts of the prefabrication, and the inner diameter is equal to the inner diameter of the finished stationary disc brake disc plus twice the tooth height. This ensures that after final processing, the brake disc body contains graphite paper, while the toothed area does not contain graphite paper.

[0025] In a preferred embodiment, during needle acupuncture, with the graphite paper surface as a reference, the needle acupuncture row spacing in the thickness direction region 2-4 mm away from the upper and lower surfaces of the graphite paper is 1-3 mm, and the row spacing in other regions is 2-4 mm. Furthermore, the needle acupuncture row spacing in the thickness direction region 2-4 mm away from the upper and lower surfaces of the graphite paper is at least 0.5 mm smaller than the needle acupuncture row spacing in other regions.

[0026] In this invention, the needle-punching density is controlled by the above method during needle-punching. The needle-punching density is higher in the area near the graphite paper, which helps to compensate for the loss of mechanical properties caused by the addition of graphite paper. At the same time, the high needle-punching density results in a relatively high Z-axis fiber content, which is beneficial to improving the thermal conductivity of the brake disc material. However, an excessively high Z-axis needle-punching density will lead to excessive breakage of carbon fibers in the preform, increasing the number of pinholes, which will damage the mechanical properties of the carbon brake disc.

[0027] In a preferred embodiment, the bulk density of the preform is 0.4–0.6 g / cm³. 3 .

[0028] In a preferred embodiment, the heat treatment temperature of the carbon fiber preform is 1500–2000℃, the heat treatment time is 2–4 hours, the heating rate is ≤200℃ / h, and the furnace pressure is <3000Pa.

[0029] In this invention, the graphite paper has a carbon content ≥99.0%. Heat treatment in conjunction with the carbon fiber preform ensures low ash content in the subsequently prepared carbon / carbon composite brake disc, which is beneficial for improving product performance. High-temperature pretreatment not only removes sizing agents and broken needles (metal needles) from the carbon fiber preform, but also further reduces the ash content of the graphite paper (e.g., SiO2 / Al2O3 / Fe2O3 / CaO). Besides purifying the preform and altering the surface state of the carbon fiber, heat treatment also helps to control the carbon fiber's performance by adjusting the heat treatment temperature, thus reducing the difference between the carbon fiber and the subsequently obtained densified pyrolytic carbon, and laying the foundation for controlling the performance of the carbon / carbon composite material obtained after densification (the final heat treatment temperature is mainly for controlling the performance of the densified pyrolytic carbon). Furthermore, because graphite paper is placed at the center of the carbon fiber preform, the heat treatment temperature in this invention is lower.

[0030] In a preferred embodiment, during chemical vapor deposition, carbon fiber preforms or carbon / carbon porous bodies are stacked, with a gasket of 1 to 7 mm thickness placed between any adjacent carbon fiber preforms or carbon / carbon porous bodies. During chemical vapor deposition, gas is introduced from the inner diameter of the carbon fiber preforms or carbon / carbon porous bodies, flows through the surface of the carbon fiber preforms or carbon / carbon porous bodies, and then flows out from the outer diameter to the exhaust gas pipe.

[0031] In a preferred embodiment, natural gas is used as the carbon source gas in the chemical vapor deposition furnace, the flow rate of natural gas introduced per kilogram of carbon fiber preform is 0.2 to 0.7 SL / min, the temperature of chemical vapor deposition is 1000 to 1300℃, and the pressure is 2 to 15 kPa.

[0032] The natural gas used in this invention contains CH4 content > 90 wt% and H2O content < 100 PPM.

[0033] In this invention, during the chemical vapor deposition process, the furnace loading and gas inlet methods of this invention are adopted, allowing the carbon source gas to mainly permeate into the core through the surface of the carbon fiber preform (carbon / carbon porous body), and decompose into pyrolytic carbon under high temperature conditions, thus densifying the carbon / carbon porous body. At the same time, because graphite paper is placed at the center of the carbon fiber preform, the distance from the upper and lower surfaces of the preform to the center is equal, avoiding significant differences in the carbon source gas path length that would lead to differences in the internal structure and density consistency of the product. The pyrolytic carbon obtained by adopting the furnace loading and gas inlet methods of this invention, in conjunction with the chemical vapor deposition process, is a fully rough layer without other structures (such as smooth layers).

[0034] Further preferred, the chemical vapor deposition is divided into three stages. In the first stage, the gasket thickness is 5.0–7.0 mm, the natural gas flow rate per kilogram of carbon fiber preform is 0.50–0.70 SL / min, the chemical vapor deposition temperature is 1000–1100℃, the pressure is 10–15 kPa, and the time is 200–300 h. In the second stage, the gasket thickness is 3.0–4.9 mm, and the natural gas flow rate per kilogram of carbon fiber preform is... The flow rate is 0.30–0.49 SL / Min, the temperature of chemical vapor deposition is 1100–1200℃, the pressure is 6.0–10 kPa, and the time is 200–300 h. In the third stage of chemical vapor deposition, the thickness of the gasket used is 1.0–2.9 mm, the flow rate of natural gas introduced per kilogram of carbon fiber preform is 0.20–0.29 SL / Min, the temperature of chemical vapor deposition is 1200–1300℃, the pressure is 2.0–6.0 kPa, and the time is 100–200 h.

[0035] In actual operation, the three stages of chemical vapor deposition include surface machining of carbon / carbon composite materials between stages. The purpose of this machining is to increase the porosity of the material surface, which is conducive to gas permeation and thus enhances the densification effect of chemical vapor deposition on carbon / carbon composite materials.

[0036] In this preferred scheme, the first stage has a low temperature and a high flow rate, with the aim of making gas diffusion dominant and allowing the gas to diffuse to the core. That is, the initial densification design is: densification is relatively slow but mainly focuses on core densification. The later stage densification has a relatively low flow rate and a high temperature, with the aim of taking into account the overall densification efficiency to achieve the requirements of density and pyrolytic carbon structure. The primary objective of the first stage is to ensure a relatively long residence time of the carbon source gas (natural gas) in the deposition chamber. The low temperature ensures a low gas reaction rate. These two factors work together to allow sufficient penetration and diffusion into the core of the preform, enabling deposition and densification of the core. In particular, the central location of the carbon fiber preform contains graphite paper, and the needle-punch density of adjacent thicknesses of the graphite paper is greater than that of other areas. Therefore, the areas adjacent to the graphite paper with a central thickness have relatively more pores due to needle punching. The chemical vapor deposition parameters of the first stage can prevent premature surface sealing, which would prevent subsequent stages from achieving the required density, resulting in a more uniform and dense composite material. The second and third stages aim to densify the porous carbon fiber. Since its porosity decreases with increasing density, the thickness of the gasket can be appropriately reduced.

[0037] Increasing the deposition temperature, decreasing the gas flow rate, and lowering the deposition pressure, along with reducing the gasket thickness, increasing the deposition temperature, and decreasing the deposition pressure, can shorten the residence time of the carbon source gas. This, combined with the reduction in gas flow rate, balances the deposition rate and diffusion depth of the porous carbon fiber, allowing the prepared carbon / carbon composite material to reach the required density and performance more quickly.

[0038] In a preferred embodiment, the heat treatment temperature of the carbon / carbon composite preform is 1300-1500℃, which is ≥100℃ higher than the highest temperature during chemical vapor deposition. The heat treatment time is 1-3h, the heating rate is ≤200℃ / h, and the furnace pressure is <2000Pa.

[0039] The inventors discovered that when the final heat treatment temperature is controlled within the above-mentioned range, the resulting carbon / carbon composite brake disc exhibits optimal performance. Temperatures that are too high or too low cannot effectively adjust the thermal and mechanical properties of the two types of carbon (carbon fiber and pyrolytic carbon) in the carbon / carbon composite brake disc to the optimal match, thus reducing the friction and wear performance of the final product.

[0040] In actual operation, the heat-treated carbon / carbon composite material is machined to meet the dimensional requirements of the brake disc drawing, thus obtaining the carbon / carbon composite brake disc.

[0041] Beneficial effects

[0042] The carbon / carbon composite brake disc provided by this invention has graphite paper placed at the center of the disc body thickness. This fully utilizes the excellent thermal conductivity of graphite paper to rapidly conduct heat from the center of the carbon / carbon composite material to the surface during braking, thereby reducing the surface temperature rise of the carbon / carbon composite material and contributing to the stability of the brake disc's performance. Furthermore, the tooth region does not contain graphite paper, while other locations do. This design differentiates the thermal conductivity of the material in the tooth region from that in locations containing graphite paper, and makes the thermal conductivity of the tooth region lower than other parts (such as the tooth groove). This prevents overheating in the tooth region, which could lead to deterioration of the tooth and tooth clamp performance, thus avoiding brake disc failure under extreme conditions (such as aborted takeoff / RTO).

[0043] Furthermore, during the preparation process, the graphite paper placed at the center of the carbon fiber preform ensures that the distance from the carbon source gas to the center from the upper and lower surfaces of the preform is equal, thus avoiding significant differences in the path length of the carbon source gas, which would lead to differences in the internal structure and density consistency of the product. By adopting the furnace loading and gas inlet method of the present invention, and in conjunction with the chemical vapor deposition process, the pyrolytic carbon obtained is a fully rough layer without other structures (such as smooth layers), thereby giving the brake disc of the present invention excellent friction and wear performance.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] 1. The carbon / carbon composite brake disc friction layer prepared by this invention contains only two types of carbon: carbon fibers and a roughening layer.

[0046] Deposited carbon, without other types of carbon (such as resin / asphalt carbon, smooth layer deposited carbon, etc.).

[0047] 2. The present invention incorporates graphite paper in the preform and, in conjunction with process design, produces carbon / carbon composite brake discs with density and mechanical properties that meet the requirements.

[0048] 3. The carbon / carbon composite material prepared by this invention controls the properties of carbon fibers and carbon deposited in the rough layer through high-temperature heat treatment, resulting in a brake disc with excellent thermal and tribological properties.

[0049] The carbon / carbon composite brake disc prepared by this invention meets all material performance requirements and, when used as an aircraft brake disc, exhibits excellent friction and wear resistance and a long service life. Attached Figure Description

[0050] Figure 1 This is an isometric view of the carbon / carbon composite brake disc (stationary disc, with teeth located in the inner ring of the brake disc body) of the present invention.

[0051] Figure 2 This is a cross-sectional view of the carbon / carbon composite brake disc (stationary disc, with teeth set in the inner ring of the brake disc body) of the present invention.

[0052] Figure 3 This is a partially enlarged view of the carbon / carbon composite brake disc (stationary disc, with teeth located in the inner ring of the brake disc body) of the present invention.

[0053] Figure 4 This is an isometric view of the carbon / carbon composite brake disc (moving disc, with teeth located on the outer ring of the brake disc body) of the present invention.

[0054] Figure 5 This is a cross-sectional view of the carbon / carbon composite brake disc (moving disc, with teeth located on the outer ring of the brake disc body) of the present invention.

[0055] Figure 6 A partially enlarged view of the carbon / carbon composite brake disc (moving disc, with teeth located on the outer ring of the brake disc body) of the present invention.

[0056] Figure 7 Microscopic structure diagram of carbon / carbon composite brake disc in Example 1 of the present invention (metallographic microscope). Detailed Implementation

[0057] The present invention will be further illustrated below with reference to examples.

[0058] Example 1

[0059] Step 1: Preparation of carbon fiber preforms

[0060] The prefabricated structure is constructed by alternating layers of a non-woven carbon fiber fabric and a carbon fiber mesh layer. Then, it is continuously needle-punched with a needle-punching density of 3 mm between rows and 0° / 90° layup of adjacent non-woven fabric layers. The interlayer density of the carbon fiber prefabricated structure is 15 layers / cm, and the weight ratio of non-woven fabric to mesh layer in the prefabricated structure is 70:30.

[0061] A layer of graphite paper ring (inner diameter: 260mm, outer diameter: 415mm) with a carbon content of 99.5%, a thermal conductivity of 500W / mK in the axial direction, a thermal conductivity of 15W / mK in the thickness direction, and a thickness of 0.8mm is laid flat between the carbon fiber nonwoven fabric and the carbon fiber mesh layer. The needle punching density in the thickness direction region 3mm away from the upper and lower surfaces of the graphite paper is set to a row spacing of 2mm.

[0062] The preform is designed as the moving disc of the brake assembly. By considering the machining process of the moving disc and the final removal of the outer diameter during machining, it is ensured that the finished moving disc brake disc, except for the toothed areas, contains graphite paper (see the schematic diagram in the attached drawing). Therefore, the final preform has an inner diameter of 260 mm, an outer diameter of 450 mm, a thickness of 30 mm, and a density of 0.50 g / cm³. 3 .

[0063] Step 2: Preparation of carbon / carbon composite brake discs

[0064] The 50 preforms containing graphite paper obtained in step one were first subjected to high-temperature heat treatment. The heat treatment heating rate was 100℃ / h, the heat treatment temperature was 1750℃, the heat treatment time was 3h, and the furnace pressure was controlled to be less than 2500Pa during the heat treatment heating and holding process.

[0065] The preform obtained after high-temperature heat treatment is placed in a chemical vapor deposition furnace for chemical vapor deposition. The carbon source gas used in chemical vapor deposition is natural gas, with a CH4 content of 93.8 wt% and an H2O content of 25 PPM.

[0066] The first stage of chemical vapor deposition used a 6mm thick gasket, a deposition temperature of 1060℃, a gas flow rate of 0.6SL / Min per kilogram of preform, a pressure of about 12.5Kpa, and a deposition time of 250h.

[0067] The second stage of chemical vapor deposition used a 4mm thick gasket, a deposition temperature of 1150℃, a gas flow rate of 0.4SL / Min per kilogram of preform, a pressure of about 8 kPa, and a deposition time of 250h.

[0068] The third stage of chemical vapor deposition used a 2mm thick gasket, a deposition temperature of 1250℃, a gas flow rate of 0.25SL / Min per kilogram of preform, a pressure of about 4Kpa, and a deposition time of 150h.

[0069] Between stages, the process also includes machining the surface of the carbon fiber porous body to improve the porosity of the product surface, which is beneficial to the densification efficiency of the subsequent chemical deposition stage.

[0070] The carbon / carbon composite material after chemical vapor deposition densification was placed in a high-temperature furnace for final high-temperature heat treatment: the heating rate was 150℃ / h, the heat treatment temperature was 1400℃, the heat treatment holding time was 2h, and the pressure inside the furnace was controlled to be less than 1500Pa throughout the heat treatment process.

[0071] Finally, the carbon / carbon composite material is machined according to the design drawings to obtain the carbon / carbon composite moving disc brake disc. The carbon / carbon composite stationary disc brake disc and end disc brake disc prepared in this invention are matched to obtain the carbon / carbon composite brake pair. Performance tests are carried out, and the results of the friction and wear test are shown in Table 1.

[0072] Figure 7 The image shows the microstructure of the carbon / carbon composite brake disc obtained in Example 1. As can be seen from the image, the carbon matrix is ​​entirely composed of rough layers.

[0073] Example 2

[0074] Step 1: Preparation of carbon fiber preforms

[0075] The prefabricated structure is constructed by alternating layers of non-woven carbon fiber fabric and carbon fiber mesh; then continuous needle punching is performed with a row spacing of 4 mm and adjacent non-woven fabric layers laid at 0° / 90°. The interlayer density of the carbon fiber prefabricated structure is 18 layers / cm, and the weight ratio of non-woven fabric to mesh layer in the prefabricated structure is 62:38.

[0076] A layer of graphite paper ring (inner diameter: 230mm, outer diameter: 415mm) with a carbon content of 99.6%, a thermal conductivity of 550W / mK in the axial direction, a thermal conductivity of 20W / mK in the thickness direction, and a thickness of 1.0mm is laid flat between the carbon fiber nonwoven fabric and the carbon fiber mesh layer. The needle punching density in the thickness direction region 4mm away from the upper and lower surfaces of the graphite paper is set to a row spacing of 3mm.

[0077] The preform is designed as the stationary disc or end disc of the brake assembly. Considering the machining process during stationary disc or end disc fabrication and the final inner diameter removal during machining, it is ensured that the finished stationary disc or end disc brake disc contains graphite paper in all areas except the teeth (see schematic diagram in the attached diagram). Therefore, the final prepared stationary disc preform has an inner diameter of 230 mm, an outer diameter of 415 mm, and a thickness of 31 mm; the end disc preform has a density of 0.45 g / cm³.3 .

[0078] Step 2: Preparation of carbon / carbon composite brake discs

[0079] The 55 prefabricated static and end plates containing graphite paper obtained in step one were first subjected to high-temperature heat treatment. The heat treatment heating rate was 200℃ / h, the heat treatment temperature was 2000℃, the heat treatment time was 2h, and the furnace pressure was controlled to be less than 3000Pa during the heat treatment heating and holding process.

[0080] The preform obtained after high-temperature heat treatment is placed in a chemical vapor deposition furnace for chemical vapor deposition. The carbon source gas used in chemical vapor deposition is natural gas, with a CH4 content of 94.0 wt% and an H2O content of 25 PPM.

[0081] The first stage of chemical vapor deposition used a 7mm thick gasket, a deposition temperature of 1100℃, a gas flow rate of 0.7SL / Min per kilogram of preform, a pressure close to 15Kpa but not exceeding that pressure value, and a deposition time of 200h.

[0082] The second stage of chemical vapor deposition used a 4.9 mm thick gasket, a deposition temperature of 1200 °C, a gas flow rate of 0.49 SL / Min per kilogram of preform, a pressure close to 10 kPa but not exceeding that pressure value, and a deposition time of 200 h.

[0083] The third stage of chemical vapor deposition used a 2.9 mm thick gasket, a deposition temperature of 1300 °C, a gas flow rate of 0.29 SL / Min per kilogram of preform, a pressure close to 6 kPa but not exceeding that pressure value, and a deposition time of 180 h.

[0084] Between stages, the process also includes machining the surface of the carbon fiber porous body to improve the porosity of the product surface, which is beneficial to the densification efficiency of the subsequent chemical deposition stage.

[0085] The carbon / carbon composite material after chemical vapor deposition densification was placed in a high-temperature furnace for final high-temperature heat treatment: the heating rate was 200℃ / h, the heat treatment temperature was 1500℃, the heat treatment holding time was 1h, and the pressure inside the furnace was controlled to be less than 2000Pa throughout the heat treatment process.

[0086] Finally, the carbon / carbon composite material is machined according to the design drawings to obtain the carbon / carbon composite static disc and end disc brake disc. The carbon / carbon composite dynamic disc brake disc prepared in this invention is matched to obtain the carbon / carbon composite brake pair. Performance tests are carried out, and the results of the friction and wear test are shown in Table 1.

[0087] Example 3

[0088] Step 1: Preparation of carbon fiber preforms

[0089] A layer of carbon fiber nonwoven fabric and a layer of carbon fiber mesh are interleaved and stacked; then continuous needle punching is performed with a needle punching density of 2 mm between rows and 0° / 90° layup of adjacent nonwoven fabrics; the interlayer density of the carbon fiber preform is 10 layers / cm and the weight ratio of nonwoven fabric to mesh layer in the preform is 80:20.

[0090] A layer of graphite paper ring (inner diameter: 260mm, outer diameter: 415mm) with a carbon content of 99.2%, a thermal conductivity of 410W / mK in the axial direction, a thermal conductivity of 11W / mK in the thickness direction, and a thickness of 0.6mm is laid flat between the carbon fiber nonwoven fabric and the carbon fiber mesh layer. The needle punching density in the thickness direction region 2mm away from the upper and lower surfaces of the graphite paper is set to a row spacing of 1mm.

[0091] The preform is designed as the moving disc of the brake assembly. By considering the machining process of the moving disc and the final removal of the outer diameter during machining, it is ensured that the finished moving disc brake disc, except for the toothed areas, contains graphite paper (see the schematic diagram in the attached drawing). Therefore, the final preform has an inner diameter of 260 mm, an outer diameter of 450 mm, a thickness of 30 mm, and a density of 0.55 g / cm³. 3 .

[0092] Step 2: Preparation of carbon / carbon composite brake discs

[0093] The 50 preforms containing graphite paper obtained in step one were first subjected to high-temperature heat treatment. The heat treatment heating rate was 150℃ / h, the heat treatment temperature was 1500℃, the heat treatment time was 4h, and the pressure inside the furnace during the heat treatment heating and holding process was controlled to be less than 2000Pa.

[0094] The preform obtained after high-temperature heat treatment is placed in a chemical vapor deposition furnace for chemical vapor deposition. The carbon source gas used in chemical vapor deposition is natural gas, with a CH4 content of 94.0 wt% and an H2O content of 60 PPM.

[0095] The first stage of chemical vapor deposition used a 5mm thick gasket, a deposition temperature of 1000℃, a gas flow rate of 0.5SL / Min per kilogram of preform, a pressure of about 10Kpa, and a deposition time of 280h.

[0096] The second stage of chemical vapor deposition used a 3mm thick gasket, a deposition temperature of 1100℃, a gas flow rate of 0.3SL / Min per kilogram of preform, a pressure of about 6 kPa, and a deposition time of 250h.

[0097] The third stage of chemical vapor deposition used a 1mm thick gasket, a deposition temperature of 1200℃, a gas flow rate of 0.2SL / Min per kilogram of preform, a pressure of about 2Kpa, and a deposition time of 100h.

[0098] Between stages, the process also includes machining the surface of the carbon fiber porous body to improve the porosity of the product surface, which is beneficial to the densification efficiency of the subsequent chemical deposition stage.

[0099] The carbon / carbon composite material after chemical vapor deposition densification was placed in a high-temperature furnace for final high-temperature heat treatment: the heating rate was 100℃ / h, the heat treatment temperature was 1300℃, the heat treatment holding time was 3h, and the pressure inside the furnace was controlled to be less than 1800Pa throughout the heat treatment process.

[0100] Finally, the carbon / carbon composite material is machined according to the design drawings to obtain the carbon / carbon composite moving disc brake disc. The carbon / carbon composite stationary disc brake disc and end disc brake disc prepared in this invention are matched to obtain the carbon / carbon composite brake pair. Performance tests are carried out, and the results of the friction and wear test are shown in Table 1.

[0101] Example 4

[0102] Step 1: Preparation of carbon fiber preforms

[0103] A layer of carbon fiber nonwoven fabric and a layer of carbon fiber mesh are interleaved and stacked; then continuous needle punching is performed with a needle punching density of 3 mm between rows and 0° / 90° layup of adjacent nonwoven fabrics; the interlayer density of the carbon fiber preform is 16 layers / cm, and the weight ratio of nonwoven fabric to mesh in the preform is 75:25.

[0104] A layer of graphite paper ring (inner diameter: 230mm, outer diameter: 415mm) with a carbon content of 99.6%, a thermal conductivity of 460W / mK in the axial direction, a thermal conductivity of 16W / mK in the thickness direction, and a thickness of 0.9mm is laid flat between the carbon fiber nonwoven fabric and the carbon fiber mesh layer. The needle punching density in the thickness direction region 3mm away from the upper and lower surfaces of the graphite paper is set to a row spacing of 2mm.

[0105] The preform is designed as the stationary disc or end disc of the brake assembly. Considering the machining process during stationary disc or end disc fabrication and the final inner diameter removal during machining, it is ensured that the finished stationary disc or end disc brake disc contains graphite paper in all areas except the teeth (see schematic diagram in the attached diagram). Therefore, the final prepared stationary disc preform has an inner diameter of 230 mm, an outer diameter of 415 mm, and a thickness of 31 mm; the end disc preform has a density of 0.52 g / cm³. 3 .

[0106] Step 2: Preparation of carbon / carbon composite brake discs

[0107] The 55 prefabricated static and end plates containing graphite paper obtained in step one were first subjected to high-temperature heat treatment. The heat treatment heating rate was 180℃ / h, the heat treatment temperature was 1800℃, the heat treatment time was 3h, and the furnace pressure was controlled to be less than 2600Pa during the heat treatment heating and holding process.

[0108] The preform obtained after high-temperature heat treatment is placed in a chemical vapor deposition furnace for chemical vapor deposition. The carbon source gas used in chemical vapor deposition is natural gas, with a CH4 content of 93.5 wt% and an H2O content of 80 PPM.

[0109] The first stage of chemical vapor deposition used a 7mm thick gasket, a deposition temperature of 1080℃, a gas flow rate of 0.65SL / Min per kilogram of preform, a pressure close to 12Kpa but not exceeding that pressure value, and a deposition time of 260h.

[0110] The second stage of chemical vapor deposition used a 3mm thick gasket, a deposition temperature of 1130℃, a gas flow rate of 0.35SL / Min per kilogram of preform, a pressure close to 7Kpa but not exceeding that pressure value, and a deposition time of 260h.

[0111] The third stage of chemical vapor deposition used a 1 mm thick gasket, a deposition temperature of 1260℃, a gas flow rate of 0.25 SL / Min per kilogram of preform, a pressure close to 3 kPa but not exceeding that pressure value, and a deposition time of 120 h.

[0112] Between stages, the process also includes machining the surface of the carbon fiber porous body to improve the porosity of the product surface, which is beneficial to the densification efficiency of the subsequent chemical deposition stage.

[0113] The carbon / carbon composite material after chemical vapor deposition densification was placed in a high-temperature furnace for final high-temperature heat treatment: the heating rate was 160℃ / h, the heat treatment temperature was 1450℃, the heat treatment holding time was 2.5h, and the pressure inside the furnace was controlled to be less than 1600Pa throughout the heat treatment process.

[0114] Finally, the carbon / carbon composite material is machined according to the design drawings to obtain the carbon / carbon composite static disc and end disc brake disc. The carbon / carbon composite dynamic disc brake disc prepared in this invention is matched to obtain the carbon / carbon composite brake pair. Performance tests are carried out, and the results of the friction and wear test are shown in Table 1.

[0115] Example 5

[0116] All other conditions were the same as in Example 1, except that the temperature of the three chemical vapor deposition stages was 1150℃ for performance testing. The results of the friction and wear test are shown in Table 1.

[0117] Example 6

[0118] All other conditions were the same as in Example 1, except that the thickness of the gasket used in the three stages of chemical vapor deposition was 4 mm. Performance tests were conducted, and the results of the tribological test are shown in Table 1.

[0119] Comparative Example 1

[0120] All other conditions were the same as in Example 1, except that: no graphite paper was placed in the carbon / carbon composite brake disc preform, and the needle density in the thickness direction of the entire preform, i.e. the spacing between rows, was 3 mm. Performance tests were conducted, and the results of the friction and wear test are shown in Table 1.

[0121] Comparative Example 2

[0122] All other conditions were the same as in Example 1, except that the thermal conductivity of the graphite paper was 350 W / mK. Performance tests were conducted, and the results of the friction and wear test are shown in Table 1.

[0123] Comparative Example 3

[0124] All other conditions were the same as in Example 1, except that the needle-punching density of the graphite paper area was the same as that of other areas, which was 3 mm. Performance tests were conducted, and the results of the friction and wear test are shown in Table 1.

[0125] As can be seen from Comparative Examples 1 to 3, due to unreasonable settings related to graphite paper, the thermal conductivity and friction and wear performance of the resulting composite material deteriorated.

[0126] Comparative Example 4

[0127] All other conditions were the same as in Example 1, except that the final heat treatment temperature was 1700℃. Performance tests were conducted, and the results of the friction and wear test are shown in Table 1.

[0128] Comparative Example 5

[0129] All other conditions were the same as in Example 1, except that the final heat treatment temperature was 1320℃, which was 70℃ (<100℃) different from the highest temperature of chemical vapor deposition (1250℃). Performance tests were conducted, and the results of the friction and wear test are shown in Table 1.

[0130] As can be seen from Comparative Examples 4 and 5, heat treatment can adjust the matching degree between carbon fiber and matrix carbon. However, due to unreasonable heat treatment temperature, the properties of the two carbons are not properly matched. Although the thermal conductivity is good, the wear is particularly large.

[0131] The performance data of the carbon / carbon composite brake discs prepared in the above embodiments and comparative examples, and the carbon / carbon composite brake pairs obtained by combining them, under the same conditions are shown in Table 1 below:

[0132] Table 1 Performance Data of Carbon / Carbon Composite Brake Discs & Brake Pairs

[0133]

[0134]

[0135] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the invention. Any modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a carbon / carbon composite brake disc, characterized in that: Carbon fiber nonwoven fabric and carbon fiber mesh are alternately laid, and a layer of graphite paper is laid in the center. Then, carbon fiber preforms are obtained by needle punching layer by layer. The carbon fiber preforms are heat-treated and then chemical vapor deposition is performed to obtain carbon / carbon composite preforms. After heat treatment and machining, carbon / carbon composite brake discs are obtained. During needle acupuncture, with the graphite paper surface as a reference, the needle acupuncture row spacing in the thickness direction area 2-4 mm away from the upper and lower surfaces of the graphite paper is 1-3 mm, and the row spacing in other areas is 2-4 mm. Furthermore, the needle acupuncture row spacing in the thickness direction area 2-4 mm away from the upper and lower surfaces of the graphite paper is more than 0.5 mm smaller than the needle acupuncture row spacing in other areas. The thickness of the graphite paper is 0.6-1 mm; The thermal conductivity of the graphite paper on the hot side is ≥400W / mK; the thermal conductivity on the thickness side is <22W / mK. The carbon / carbon composite brake disc includes an annular brake disc body and multiple teeth circumferentially distributed on the inner or outer ring of the brake disc body. An annular graphite paper is disposed at the center of the brake disc body.

2. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: Carbon fiber nonwoven fabric and carbon fiber mesh are alternately laid, with the interlayer density controlled at 10~20 layers / cm, the weight ratio of carbon fiber nonwoven fabric to carbon fiber mesh at 60~80:40~20, and the layup angle of adjacent carbon fiber nonwoven fabrics at 0° / 90°.

3. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: The bulk density of the carbon fiber preform is 0.4~0.6 g / cm³. 3 .

4. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: The heat treatment temperature of the carbon fiber preform is 1500~2000℃, the heat treatment time is 2~4h, the heating rate is ≤200℃ / h, and the furnace pressure is <3000Pa.

5. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: During chemical vapor deposition, carbon fiber preforms or carbon / carbon porous bodies are stacked together, with a gasket of 1-7 mm thickness placed between any adjacent carbon fiber preforms or carbon / carbon porous bodies. During chemical vapor deposition, gas is introduced from the inner diameter of the carbon fiber preforms or carbon / carbon porous bodies, flows through the surface of the carbon fiber preforms or carbon / carbon porous bodies, and then flows out from the outer diameter to the exhaust gas pipe. The chemical vapor deposition furnace uses natural gas as the carbon source gas, with a natural gas flow rate of 0.2~0.7 SL / Min per kilogram of carbon fiber preform, a chemical vapor deposition temperature of 1000~1300℃, and a pressure of 2~15 kPa.

6. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: The chemical vapor deposition (CVD) process consists of three stages. In the first stage, the gasket thickness is 5.0–7.0 mm, the natural gas flow rate per kilogram of carbon fiber preform is 0.50–0.70 SL / min, the CVD temperature is 1000–1100℃, the pressure is 10–15 kPa, and the time is 200–300 h. In the second stage, the gasket thickness is 3.0–4.9 mm, and the natural gas flow rate per kilogram of carbon fiber preform is… The flow rate of natural gas introduced per kilogram of carbon fiber preform is 0.30~0.49 SL / Min, the temperature of chemical vapor deposition is 1100~1200℃, the pressure is 6.0~10Kpa, and the time is 200~300h. In the third stage of chemical vapor deposition, the thickness of the gasket used is 1.0~2.9mm, the flow rate of natural gas introduced per kilogram of carbon fiber preform is 0.20~0.29 SL / Min, the temperature of chemical vapor deposition is 1200~1300℃, the pressure is 2.0~6.0Kpa, and the time is 100~200h.

7. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: The heat treatment temperature of the carbon / carbon composite preform is 1300~1500℃, which is ≥100℃ higher than the highest temperature during chemical vapor deposition. The heat treatment time is 1~3h, the heating rate is ≤200℃ / h, and the furnace pressure is <2000Pa.

8. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: The graphite paper has a carbon content of ≥99.0%.

9. The method for preparing a carbon / carbon composite brake disc according to claim 1, characterized in that: The carbon matrix in the carbon / carbon composite brake disc has a fully roughened layer structure. The density of the carbon / carbon composite brake disc is ≥1.78 g / cm³. 3 .

Images