A silicon-chromium alloy synergistically modified carbon / ceramic brake disc and a preparation method thereof

Abstract

The application relates to a carbon / ceramic brake disc with wear resistance improved by silicon-chromium alloy synergistic modification and a preparation method thereof. The carbon / ceramic brake disc is prepared through key steps of preparing a carbon fiber preform, a carbon / carbon composite material, ceramic powder and a carbon / ceramic composite material, and the process is through gradient melting impregnation and segmented heat treatment process, thereby avoiding the composition segregation problem caused by the traditional silicon powder embedding melting impregnation method; the structured laying of the ceramic powder positively superimposes the capillary force in the brake disc and the furnace pressure; the ceramic production efficiency is increased by 30%, and the waste rate is reduced to below 1%. In the structure aspect, the porosity of the brake disc prepared by the application is reduced to 2%-3%; in the material composition aspect, the ceramic phase in the matrix is formed by Si-Cr-C three elements to form crystals, so that the wear resistance of the composite material is increased by three times; the brake disc prepared by the application has excellent wear resistance and friction performance, and is suitable for the aerospace field.

Description

Technical Field

[0001] This invention belongs to the field of high-performance composite material preparation technology, specifically relating to a carbon / ceramic brake disc with improved wear resistance through synergistic modification with silicon-chromium alloy and its preparation method. Background Technology

[0002] As a critical braking component during aircraft landing, the performance of brake discs directly impacts flight safety. Carbon / ceramic composite materials, with their advantages of low density, high specific strength, and good frictional properties, have become ideal materials for brake discs. However, as the aviation industry moves towards higher loads and higher frequency of flights, higher demands are being placed on the wear resistance and thermal stability of traditional carbon / ceramic brake discs. High wear rates lead to shorter brake disc lifespans, increasing aircraft maintenance costs and safety hazards; therefore, there is still room for improvement in their wear resistance and frictional properties.

[0003] Currently, the mainstream preparation process for carbon / ceramic composites involves melt-infiltrating pure silicon into carbon / carbon preforms. While this process can react with pyrolytic carbon to generate a SiC reinforcing phase, the reaction between the molten silicon and the carbon matrix is ​​incomplete, leaving free silicon residue in the carbon / ceramic composite. This results in a whistling sound during aircraft braking, and the coefficient of friction decreases by more than 30% at high temperatures. Existing techniques exist to improve the wear resistance of carbon / ceramic brake discs, such as nanoparticle doping, multilayer composite structure design, and single alloy modification. Shubham et al. reported a method that introduces nano-alumina particles into carbon-based composites, improving the hardness of the composite, but uneven nanoparticle dispersion leads to fluctuations in the coefficient of friction. US Patent 4148962 discloses a modification method that enhances the wear resistance of the material by alternately laying fiber layers of different compositions, but the process is complex and the interlayer bonding strength between fibers is insufficient. Huang et al., in *Ceramic International*, proposed molten infiltration of FeSi75 alloy powder into a carbon / ceramic matrix, which reduced wear in the composite material. This method improves wear resistance because the alloy melts and cools to form a hard intermetallic compound (Fe3Si), filling the gaps in the ceramic matrix and enhancing grain boundary bonding, thus improving wear resistance. However, its frictional stability under high-speed braking conditions is relatively weak. AVIC reported introducing chromium powder into carbon / ceramic composites via mechanical mixing, but due to the poor wettability of the chromium phase with the carbon matrix, multiple density increases via chemical vapor deposition (CVD) are required, extending the production cycle and increasing costs. The wear resistance of the brake disc only improved by 50%. International giant SGL Carbon focused on surface coating modification technology for carbon fibers, but still failed to solve the inherent brittleness problem of carbon fiber materials. The composite material cracked after 50 thermal shock cycles, resulting in material failure. Summary of the Invention

[0004] To address the problems of large fluctuations in friction coefficient and high wear rate caused by free silicon in existing carbon-ceramic brake disc technology, as well as the deterioration of the mechanical properties of composite materials due to interfacial reactions between residual silicon and carbon fibers, this invention provides a carbon / ceramic brake disc with silicon-chromium alloy synergistic modification and its preparation method.

[0005] First, this invention provides a method for preparing a carbon / ceramic brake disc with synergistic modification of silicon and chromium alloys, comprising the following steps:

[0006] Step 1, Preparation of carbon fiber preform

[0007] Carbon cloth formed by arranging 12K carbon fiber bundles and a mesh made of short fibers are alternately laminated and then longitudinally needle-punched together, and then cut to form a prefabricated unit layer of a specific size.

[0008] Step 2, Preparation of carbon / carbon composite materials

[0009] The carbon fiber preform prepared above was transferred into a chemical vapor deposition furnace, and pyrolytic carbon was deposited in the porous carbon fiber preform using chemical vapor infiltration (CVI) with natural gas as the main carbon source to produce carbon / carbon composite material.

[0010] Step 3, Preparation of ceramic powder

[0011] The ceramic powders include silicon powder, silicon carbide powder and silicon-chromium alloy powder. All powders are sieved, and a specific proportion of ceramic powders are weighed and placed into a ceramic ball mill jar for wet ball milling.

[0012] Step 4, Preparation of carbon / ceramic composite materials

[0013] The carbon / ceramic composite material is prepared by melt infiltration process. The uniformly mixed ceramic powder is densely spread in a crucible, the brake disc is submerged in the powder, the upper surface is exposed, an opening is reserved in the middle, the top of the crucible is sealed with a plate, and then it is transferred to a high-temperature furnace for heat treatment, followed by cooling, to obtain the silicon-chromium alloy synergistic modified carbon / ceramic brake disc.

[0014] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy provided by the present invention, the bulk density of the preform obtained in step 1 reaches 0.5~0.8 g / cm³. 3 .

[0015] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy provided by the present invention, the carbon / carbon composite material obtained in step 2 has a density of 1.3~1.6 g / cm³. 3 The open porosity is over 15%.

[0016] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy provided by the present invention, the ceramic powder in step 3 is sieved through a 270-mesh sieve, the amount of silicon powder is 10~70 wt.%, the amount of silicon carbide powder is 30~60 wt.%, and the amount of silicon-chromium alloy powder is 5~30 wt.%, wherein the components of the silicon powder, silicon carbide powder and silicon-chromium alloy powder are Si, SiC and CrSi2, respectively.

[0017] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy provided by the present invention, the mass ratio of material to beads in the wet ball milling in step 3 is 1:2, the amount of anhydrous ethanol used is 90 mL, the speed of the ball mill is 200~400 r / min, and the time is 1~4 h.

[0018] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy provided by the present invention, the temperature of the high-temperature furnace in step 4 is 1400℃~1700℃, the pressure inside the furnace is -5000Pa, and the holding time is 2~5h.

[0019] Furthermore, in the preparation method of the silicon-chromium alloy synergistic modification carbon / ceramic brake disc provided by the present invention, the diameter of the pre-reserved opening in the middle of the brake disc in step 4 is 1 cm.

[0020] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon and chromium alloys provided by the present invention, the density of the cooled brake disc in step 4 is 2.1 g / cm³. 3 ~2.5g / cm 3 .

[0021] Furthermore, in the method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy provided by the present invention, in the composite material of step 4, the carbon fiber preform is the reinforcing phase, the pyrolytic carbon is part of the matrix phase, protecting the mechanical properties of the carbon fiber from being damaged; the remaining matrix phase is composed of a ceramic phase with frictional effect sintered from various ceramic powders.

[0022] Furthermore, the present invention provides a carbon / ceramic brake disc prepared by the above-mentioned method for preparing carbon / ceramic brake discs with synergistic modification of silicon-chromium alloy.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] Performance advantages: The carbon / ceramic brake disc obtained by this invention increases the density of the modified carbon / ceramic material, resulting in improved mechanical and frictional properties. The friction pair prepared from the silicon-chromium alloy-modified carbon / ceramic composite material exhibits a rectangular braking curve under low-speed, low-pressure conditions; under high-speed and high-pressure braking, the friction coefficient first decreases and then gradually increases, exhibiting an "inverted trapezoidal" shape. This braking state facilitates smooth braking, with no decrease in the friction coefficient and a stability coefficient of approximately 0.7. After modification with silicon-chromium alloy, both the dynamic and static friction coefficients increase, which is beneficial for aircraft takeoff and landing. The carbon / ceramic brake disc of this invention has a low wear rate; the addition of silicon-chromium alloy improves wear resistance by three times. The friction pair of the carbon / ceramic brake disc prepared by this invention experiences only 0.06 mm of wear per brake cycle, and the braking process is smooth. By controlling the proportions of different ceramic powder components, carbon / ceramic brake discs with varying densities can be prepared. In terms of structure, the porosity of the brake disc prepared by this invention is reduced to 2%–3%; in terms of material composition, the ceramic phase in the matrix is ​​formed by crystals of three elements: Si, Cr, and C, with a Cr atomic content of approximately 6%; thus, the wear resistance of the composite material is improved by three times. At a specific pressure of 1.9 MPa, the static friction coefficient can reach 0.6.

[0025] Technological innovation advantages: The gradient melt infiltration and segmented heat treatment process avoids the component segregation problem caused by the traditional silicon powder embedding melt infiltration method. The structured laying of ceramic powder makes the capillary force inside the brake disc and the furnace pressure positively superimposed, which improves the ceramic production efficiency by 30% and reduces the scrap rate to below 1%.

[0026] Cost advantage: By optimizing the raw material ratio and process parameters, high-performance products can be prepared without increasing investment in expensive equipment, and the production cost is reduced by 20% compared with similar technologies. Attached Figure Description

[0027] Figure 1 The friction curves were obtained from testing the C / C-SiC-CrSi2 composite material prepared in Example 1.

[0028] Figure 2 This is a surface morphology diagram of the brake disc after an emergency stop test according to the present invention;

[0029] Figure 3 The image shows the XRD pattern of the C / C-SiC-CrSi2 composite material prepared in Example 1. Detailed Implementation

[0030] The present invention is described in detail through the following embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection of the present invention, and all compositions based on the core substances of the present invention as the main components are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment describes a silicon-chromium alloy synergistic modification of a carbon / ceramic brake disc and its preparation method. The specific preparation process includes the following steps:

[0033] Step 1, Preparation of carbon fiber preforms. Carbon cloth formed by arranging 12K carbon fiber bundles and a mesh composed of short fibers are alternately laminated and longitudinally needle-punched together. The resulting preforms are then cut into unit layers of specific dimensions. Multiple unit layers are needle-punched together to achieve a bulk density of 0.5 g / cm³. 3 .

[0034] Step 2, Preparation of carbon / carbon composite material. The carbon fiber preform prepared above was transferred into a chemical vapor deposition furnace. Using natural gas as the main carbon source, pyrolytic carbon was deposited into the porous carbon fiber preform using chemical vapor infiltration (CVI). The density of the carbon / carbon composite material was 1.6 g / cm³. 3 The open porosity is 22%.

[0035] Step 3: Preparation of ceramic powder. The ceramic powder includes Si, SiC, and CrSi2, all of which are sieved through a 270-mesh sieve. The amount of silicon powder is 30 wt.%, the amount of silicon carbide powder is 40 wt.%, and the amount of silicon-chromium alloy powder is 30 wt.%. The specific proportions of ceramic powder are weighed and placed into a ceramic ball mill jar for wet ball milling. The mass ratio of powder to beads is 1:2. The amount of anhydrous ethanol used is 90 mL. The speed of the ball mill is 300 r / min, and the time is 2 h.

[0036] Step 4, Preparation of carbon / ceramic composite material. In the composite material, the carbon fiber preform is the reinforcing phase, and pyrolytic carbon is part of the matrix phase, protecting the mechanical properties of the carbon fiber from damage. The remaining matrix phase consists of a frictional ceramic phase sintered from various ceramic powders. The carbon-ceramic composite material is prepared using a melt infiltration process. The modification treatment of the carbon / carbon composite material by ceramic powder is carried out as follows: uniformly mixed ceramic powder is densely and evenly spread in a crucible, the carbon / carbon composite brake disc is submerged in the powder, the upper surface is exposed, a 1cm diameter opening is reserved in the middle, the top of the crucible is sealed with a flat plate, and it is transferred to a high-temperature furnace. The temperature of the high-temperature furnace is 1550℃, the pressure inside the furnace is -5000Pa, and the holding time is 3h. After cooling, the density of the brake disc is 2.3g / cm³. 3A carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy was prepared.

[0037] Example 2

[0038] Step 1, Preparation of carbon fiber preforms. Carbon cloth formed by arranging 12K carbon fiber bundles and a mesh composed of short fibers are alternately laminated and longitudinally needle-punched together. The resulting preforms are then cut into unit layers of specific dimensions. Multiple unit layers are needle-punched together to achieve a bulk density of 0.7 g / cm³. 3 .

[0039] Step 2, Preparation of carbon / carbon composite material. The carbon fiber preform prepared above is transferred into a chemical vapor deposition furnace. Using natural gas as the main carbon source, pyrolytic carbon is deposited into the porous carbon fiber preform using chemical vapor infiltration (CVI). The density of the carbon / carbon composite material is 1.55 g / cm³. 3 The open porosity is 16%.

[0040] Step 3: Preparation of ceramic powder. The ceramic powder includes Si, SiC, and CrSi2, all of which are sieved through a 270-mesh sieve. The amount of silicon powder used is 50 wt.%, silicon carbide powder is 40 wt.%, and silicon-chromium alloy powder is 10 wt.%. The specific proportions of ceramic powder are weighed and placed into a ceramic ball mill jar for wet ball milling. The material / bead mass ratio is 1:2. The amount of anhydrous ethanol used is 90 mL. The ball mill speed is 400 r / min, and the time is 3 h.

[0041] Step 4, Preparation of carbon / ceramic composite material. In the composite material, the carbon fiber preform is the reinforcing phase, and pyrolytic carbon is part of the matrix phase, protecting the mechanical properties of the carbon fiber from damage. The remaining matrix phase consists of a frictional ceramic phase sintered from various ceramic powders. The carbon-ceramic composite material is prepared using a melt infiltration process. The modification treatment of the carbon / carbon composite material by ceramic powder is carried out as follows: uniformly mixed ceramic powder is densely and evenly spread in a crucible, the carbon / carbon composite brake disc is submerged in the powder, the upper surface is exposed, a 1cm diameter opening is reserved in the middle, the top of the crucible is sealed with a flat plate, and it is transferred to a high-temperature furnace. The temperature of the high-temperature furnace is 1600℃, the pressure inside the furnace is -5000Pa, and the holding time is 2h. After cooling, the density of the brake disc is 2.1g / cm³. 3 A carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy was prepared.

[0042] Example 3

[0043] Step 1, Preparation of carbon fiber preforms. Carbon cloth formed by arranging 12K carbon fiber bundles and a mesh composed of short fibers are alternately laminated and longitudinally needle-punched together. The resulting preforms are then cut into unit layers of specific dimensions. Multiple unit layers are needle-punched together to achieve a bulk density of 0.8 g / cm³.3 .

[0044] Step 2, Preparation of carbon / carbon composite material. The carbon fiber preform prepared above was transferred into a chemical vapor deposition furnace. Using natural gas as the main carbon source, pyrolytic carbon was deposited into the porous carbon fiber preform using chemical vapor infiltration (CVI). The density of the carbon / carbon composite material was 1.6 g / cm³. 3 The open porosity is 15%.

[0045] Step 3: Preparation of ceramic powder. The ceramic powder includes Si, SiC, and CrSi2, all of which are sieved through a 270-mesh sieve. The amount of silicon powder is 65 wt.%, the amount of silicon carbide powder is 30 wt.%, and the amount of silicon-chromium alloy powder is 5 wt.%. The specific proportions of ceramic powder are weighed and placed into a ceramic ball mill jar for wet ball milling. The material / bead mass ratio is 1:2. The amount of anhydrous ethanol used is 90 mL. The ball mill speed is 200 r / min, and the time is 4 h.

[0046] Step 4, Preparation of carbon / ceramic composite material. In the composite material, the carbon fiber preform is the reinforcing phase, and pyrolytic carbon is part of the matrix phase, protecting the mechanical properties of the carbon fiber from damage. The remaining matrix phase consists of a frictional ceramic phase sintered from various ceramic powders. The carbon-ceramic composite material is prepared using a melt infiltration process. The modification treatment of the carbon / carbon composite material by ceramic powder is carried out as follows: The uniformly mixed ceramic powder is densely and evenly spread in a crucible, the carbon / carbon composite brake disc is submerged in the powder, the upper surface is exposed, and a 1cm diameter opening is reserved in the middle. The top of the crucible is sealed with a flat plate and transferred to a high-temperature furnace. The temperature of the high-temperature furnace is 1700℃, the pressure inside the furnace is -5000Pa, and the holding time is 4h. After cooling, the density of the brake disc is 2.4g / cm³. 3 A carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy was prepared.

[0047] Example 4

[0048] The following is a performance test of the carbon / ceramic brake disc prepared in Example 1 of the present invention.

[0049] The homogeneous friction pair of the carbon / ceramic brake disc prepared in Example 1 was subjected to braking tests on a friction and wear testing machine. The test results are as follows: Figure 1 As shown, from Figure 1As can be seen, the porosity of the C / C-SiC-CrSi2 composite material in this invention is 2.2%, which is 41.49% lower than that of the C / C-SiC composite material. This increases the density of the modified carbon / ceramic material, resulting in improved mechanical and frictional properties. The friction pair prepared from the silicon-chromium alloy-modified carbon / ceramic composite material exhibits a rectangular braking curve under low-speed, low-pressure conditions. Under high-speed and high-pressure braking, the friction coefficient initially decreases and then gradually increases, exhibiting an "inverted trapezoidal" shape. This braking state is beneficial for achieving smooth braking, with no decrease in the friction coefficient and a stability coefficient of 0.7. After modification with silicon-chromium alloy, both the dynamic and static friction coefficients increase, which is beneficial for aircraft takeoff and landing.

[0050] The wear resistance of the carbon / ceramic brake disc prepared in Example 1 (C / C-SiC-CrSi2) was tested, and the results are shown in Table 1 below:

[0051] Table 1

[0052]

[0053] As can be seen from Table 1, the carbon / ceramic brake disc in this invention has a low wear rate. After adding silicon-chromium alloy, after 173 sets of friction tests at speeds ranging from 860 r / min to 8031 ​​r / min and specific pressures of 0.17-1.46, the composite material showed a single-sided single-cycle mating mass wear of 0.0047 g and a single-sided single-cycle linear wear of 0.0008 mm, which improved the wear resistance by three times.

[0054] Example 5

[0055] The surface morphology of the carbon / ceramic brake discs prepared in Example 1 was observed after an emergency stop test. See [reference needed]. Figure 2 At the highest speed, during emergency braking, a friction film with a thickness of micrometers was observed on the surface of the composite material under an ultra-depth-of-field microscope, which helps to reduce brake wear.

[0056] Example 6

[0057] The carbon / ceramic brake disc composite material prepared in Example 1 was subjected to XRD pattern testing, as shown in the figure. Figure 3 As shown, the sharp diffraction peaks indicate that the composite material has high crystallinity, few defects, large SiC grain size, and low strain, which is beneficial for use under extreme conditions.

Claims

1. A method for preparing a carbon / ceramic brake disc with synergistic modification of silicon and chromium alloys, characterized in that, The preparation method includes the following steps: Step 1, Preparation of carbon fiber preform Carbon cloth formed by arranging 12K carbon fiber bundles and a mesh composed of short fibers are alternately laminated and longitudinally needle-punched together, then cut to form unit layers of preforms of specific sizes; the bulk density of the preforms reaches 0.5~0.8 g / cm³. 3 ; Step 2, Preparation of carbon / carbon composite materials The carbon fiber preform prepared above was transferred into a chemical vapor deposition furnace, and pyrolytic carbon was deposited in the porous carbon fiber preform using chemical vapor infiltration (CVI) with natural gas as the main carbon source to produce carbon / carbon composite material. Step 3, Preparation of ceramic powder The ceramic powder includes silicon powder, silicon carbide powder, and silicon-chromium alloy powder. All powders are sieved, and a specific proportion of the ceramic powder is weighed and placed into a ceramic ball mill jar for wet ball milling. The ceramic powder is sieved through a 270-mesh sieve. The amount of silicon powder is 10-70 wt.%, the amount of silicon carbide powder is 30-60 wt.%, and the amount of silicon-chromium alloy powder is 5-30 wt.%. The components of the silicon powder, silicon carbide powder, and silicon-chromium alloy powder are Si, SiC, and CrSi2, respectively. Step 4, Preparation of carbon / ceramic composite materials The carbon / ceramic composite material is prepared by melt infiltration process. The uniformly mixed ceramic powder is densely spread in a crucible, the brake disc is submerged in the powder, the upper surface is exposed, an opening is reserved in the middle, the top of the crucible is sealed with a plate, and then it is transferred to a high-temperature furnace for heat treatment, followed by cooling, to obtain the silicon-chromium alloy synergistic modified carbon / ceramic brake disc.

2. The method for preparing a carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy according to claim 1, characterized in that, The carbon / carbon composite material obtained in step 2 has a density of 1.3~1.6 g / cm³. 3 The open porosity is over 15%.

3. The method for preparing a carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy according to claim 1, characterized in that, In step 3, the mass ratio of material to beads in the wet ball mill is 1:2, the amount of anhydrous ethanol used is 90 mL, the speed of the ball mill is 200~400 r / min, and the time is 1~4 h.

4. The method for preparing a carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy according to claim 1, characterized in that, The temperature of the high-temperature furnace in step 4 is 1400℃~1700℃, the pressure inside the furnace is -5000Pa, and the holding time is 2~5h.

5. The method for preparing a silicon-chromium alloy synergistic modified carbon / ceramic brake disc according to claim 1, characterized in that, In step 4, the diameter of the pre-drilled hole in the center of the brake disc is 1 cm.

6. The method for preparing a carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy according to claim 1, characterized in that, The density of the cooled brake disc mentioned in step 4 is 2.1 g / cm³. 3 ~2.5g / cm 3 .

7. The method for preparing a carbon / ceramic brake disc with synergistic modification of silicon-chromium alloy according to claim 1, characterized in that, In the composite material of step 4, the carbon fiber preform is the reinforcing phase, the pyrolytic carbon is part of the matrix phase to protect the mechanical properties of the carbon fiber from being damaged, and the remaining matrix phase is composed of a ceramic phase with frictional effect sintered from various ceramic powders.

8. A carbon / ceramic brake disc prepared by the method for preparing a carbon / ceramic brake disc with silicon-chromium alloy synergistic modification as described in any one of claims 1-7.

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