Method for preparing carbon / carbon blank for high-performance carbon / ceramic friction disc

Abstract

The invention discloses a method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disc, and relates to the technical field of friction disc preparation. According to the method, accurate control over the rough layer pyrolytic carbon matrix is achieved through tool design, temperature field design and gas proportion collaborative design; the CVI process is reasonable in design, high in densification efficiency and uniform in rough layer pyrolytic carbon distribution; a deposited rough layer pyrolytic carbon structure is large in adjustable porosity range, the density and porosity of a C / C blank are accurately controlled, and a ceramized C / C-SIC disc is good in consistency, low in residual silicon content and excellent in braking stability. The preparation method is suitable for industrial mass production, the densification cost is low, and the yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of friction disk preparation, and particularly to a method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disk. Background Art

[0002] C / C-SiC composite materials are recognized as a new generation of friction materials and have broad application prospects in braking / transmission systems with high speed, high energy load, and harsh environments such as airplanes, high-speed trains, armored vehicles, automobiles, and construction machinery.

[0003] The preparation process of C / C-SiC friction materials mainly includes two steps: The first step is to prepare a C / C blank, and its preparation methods include chemical vapor infiltration (CVI), precursor infiltration and pyrolysis (PIP), or a method combining the first two. However, PIP resin carbon has certain disadvantages such as closed pores and specific heat capacity, which have a certain impact on subsequent ceramization and performance. The second step usually uses the silicon infiltration method (MI) to prepare a SiC matrix on the C / C blank.

[0004] Using CVI to prepare a C / C composite blank is a key link in the process of preparing high-performance C / C-SiC composite materials. The structure, density, etc. of pyrolytic carbon directly affect the subsequent RMI process and performance. Pyrolytic carbon is divided into three types: smooth layer (SL), rough layer (RL), and isotropic layer (ISO). Among them, the range of adjustable properties of rough layer pyrolytic carbon is wider than that of smooth layer pyrolytic carbon. It has a higher density, better thermal conductivity, and excellent friction and wear properties, and is suitable for making friction disk materials. The preparation process of C / C composite materials is very complex, and factors such as the preform structure, chemical vapor deposition temperature, and deposition pressure all affect the product structure and performance. In addition, different product shapes and sizes correspond to different process parameters and tooling.

[0005] Therefore, when producing a C / C composite blank for a friction disk, how to efficiently and accurately prepare a single pyrolytic carbon structure is crucial, which is also a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disk, which precisely controls the preparation parameters to accurately prepare a C / C blank with a uniform rough layer pyrolytic carbon structure, which is beneficial to the preparation of high-performance carbon / ceramic friction materials while shortening the overall preparation cycle and cost.

[0007] To achieve this technical purpose, the present invention adopts the following scheme:

[0008] A method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disk, comprising the following steps:

[0009] S1. Preform heat treatment

[0010] Place the carbon fiber preform into a heat treatment furnace, raise the temperature to 1800°C - 2000°C, and hold for 1 - 2 h for heat treatment;

[0011] S2. Chemical vapor deposition

[0012] S2-1. First chemical vapor deposition: After heat treatment, the density of the preform is 0.45 - 0.6 g / cm 3 , stack multiple heat-treated preforms at the center of the graphite pallet I of the material column I, separate them with a graphite outer diameter spacer ring with a thickness of 10 - 15 mm, add a graphite cover plate I on the top of the preform, then place it into the deposition chamber, cover the graphite cover plate of the deposition chamber, and introduce gaseous precursor reaction gas for chemical vapor infiltration;

[0013] Preheat the gas (including natural gas, propylene, and nitrogen) to 1025°C - 1045°C and feed it into the deposition chamber, further raise the temperature to the deposition temperature of 1040 - 1060°C; introduce natural gas and propylene for deposition, the flow rate of natural gas is 80 SLM - 100 SLM, the flow rate of propylene is 8 SLM - 10 SLM, introduce nitrogen as the carrier gas, and the deposition time is 70 h - 150 h;

[0014] S2-2. After the first chemical vapor deposition, a carbon / carbon composite material semi-finished product with a density of 1.2 g / cm 3 -1.3 g / cm 3 is obtained;

[0015] S2-3. Conduct the first rough machining on the carbon / carbon composite material semi-finished product, and the density remains almost constant;

[0016] S2-4. Second chemical vapor deposition: Arrange the rough-machined carbon / carbon composite material semi-finished products from bottom to top in ascending order of density, stack them at the center of the graphite pallet II of the material column II, separate them with a graphite inner diameter spacer ring with a thickness of 10 - 20 mm, add a graphite cover plate II on the top of the preform, then place it into the deposition chamber, cover the graphite cover plate of the deposition chamber, and introduce gaseous precursor for chemical vapor infiltration;

[0017] Preheat the gas to 1005°C - 1025°C, introduce it into the deposition chamber and raise the temperature to 1020 - 1040°C, introduce natural gas and propylene for deposition, the flow rate of natural gas is 72 SLM - 90 SLM, the flow rate of propylene is 7.2 SLM - 9 SLM, introduce nitrogen as the carrier gas, and the deposition time is 50 h - 150 h;

[0018] S2-5. After the second chemical vapor deposition, a carbon / carbon composite material semi-finished product with a density of 1.40 / cm 3 -1.50 / cm 3 is obtained;

[0019] S3. High-temperature heat treatment

[0020] Heat up the semi-finished carbon / carbon composite material with a density of 1.40 / cm 3 ~1.50 / cm 3 to 2100°C - 2600°C, keep it at a constant temperature for 4 hours for heat treatment to obtain a semi-finished carbon friction disc.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The present invention realizes the precise control of the pyrolytic carbon matrix of the rough layer through the collaborative design of tooling design, temperature field design, and gas ratio; the CVI process design is reasonable, the densification efficiency is high, and the pyrolytic carbon of the rough layer is evenly distributed;

[0023] (2) The deposited rough layer pyrolytic carbon structure can regulate a large range of porosity, precisely control the density and porosity of the C / C blank, the C / C-SiC disc has good consistency after ceramization, low residual silicon content, and excellent braking stability.

[0024] (3) The preparation method of the present invention is suitable for industrial mass production, with low densification cost and high yield.

[0025] The preferred solution of the present invention is:

[0026] In both S2-1 and S2-4, the volume ratio of the carbon source gas to the carrier gas is 1 - 2:1.

[0027] In both S2-1 and S2-4, the furnace pressure is 1 KPa - 4 KPa.

[0028] In S2-1, the gaseous precursor reaction gas enters the center of the stacked preforms through the centralized intake holes on the graphite pallet I, overflows to the periphery of the preforms through the graphite outer diameter gasket ring, and then overflows through the gap between the outer circumference of the graphite cover plate I and the inner wall of the deposition chamber. At the same time, the excess gaseous precursor reaction gas flows out through the through holes of the air vents on the graphite cover plate I, converges, and the reaction residual gas is discharged from the air vent through holes of the graphite cover plate of the deposition chamber.

[0029] In S2-4, the gaseous precursor reaction gas enters the periphery of the stacked preforms through the dispersed intake holes on the graphite pallet II, overflows to the center of the preforms through the graphite inner diameter gasket ring, and then is discharged through the centralized air vent through holes in the center of the graphite cover plate II. At the same time, the excess gaseous precursor reaction gas overflows through the pressure regulating air vent through holes on the graphite cover plate II to adjust the internal pressure, converges to the air vent through holes of the graphite cover plate of the deposition chamber, and the reaction residual gas is discharged from the air vent through holes of the graphite cover plate of the deposition chamber. Description of the Drawings

[0030] Figure 1Polarized micrograph of the semi-finished carbon friction disk provided in Embodiment 1 of the present invention;

[0031] Figure 2 Polarized micrograph of the semi-finished carbon friction disk provided in Embodiment 2 of the present invention;

[0032] Figure 3 Polarized micrograph of the semi-finished carbon friction disk provided in Comparative Example 1 of the present invention;

[0033] Figure 4 Polarized micrograph of the semi-finished carbon friction disk provided in Comparative Example 2 of the present invention;

[0034] Figure 5 Polarized micrograph of the semi-finished carbon friction disk provided in Comparative Example 3 of the present invention. Detailed Description of the Invention

[0035] To fully understand the purpose, features, and effects of the present invention, the present invention will be described in detail through the following specific embodiments, but the present invention is not limited thereto.

[0036] The chemical vapor deposition equipment used in this application is the equipment used in a method for gas-phase infiltration of annular carbon / carbon composites disclosed in Publication No. CN111348931B. Therefore, the structural details of components such as charge column I, charge column II, graphite support plate I, graphite support plate II, graphite outer diameter spacer ring, and graphite inner diameter spacer ring in the deposition chamber will not be elaborated here. Please refer to the above-mentioned published document.

[0037] Embodiment 1

[0038] S1. Heat treatment of the preform

[0039] High-temperature heat treatment of the carbon fiber preform: The carbon fiber preform is placed in a heat treatment furnace, heated to 2000 °C, and heat-treated for 2 h.

[0040] S2. CVI deposition

[0041] S2-1. First gas-phase deposition: Multiple groups of heat-treated preforms are stacked at the central position on the graphite support plate I of charge column I, with an initial density of 0.6 g / cm 3 , and separated by a graphite outer diameter spacer ring with a thickness of 10 mm. A graphite cover plate I is added on the top of the preforms; then it is placed in the deposition chamber; finally, the deposition chamber graphite cover plate is placed, and a gaseous precursor reaction gas is introduced for gas-phase infiltration. The gaseous precursor reaction gas enters the center of the stacked preforms through the centralized intake holes on the graphite support plate I. The gaseous precursor reaction gas overflows to the periphery of the preforms through the outer diameter spacer ring and then overflows through the gap between the outer circumference of the graphite cover plate I and the inner wall of the deposition chamber. At the same time, the excess gaseous precursor reaction gas flows out through the air holes on the graphite cover plate I, converges, and the reaction residual gas is discharged from the air outlet through holes of the deposition chamber graphite cover plate.

[0042] The deposition process is as follows:

[0043] The gas preheating temperature is 1045℃. The temperature is raised to the deposition temperature of 1060℃, and natural gas and propylene are introduced for deposition. The natural gas flow rate is 90SLM, the propylene flow rate is 9SLM, and nitrogen is introduced as the carrier gas. The volume ratio of the carbon source gas to the carrier gas is 2:1. The furnace pressure is 3KPa, and the deposition time is 150h.

[0044] S2-2, the first vapor deposition obtained a density of 1.2 g / cm 3 ~1.3g / cm 3 Carbon / carbon composite semi-finished products.

[0045] S2-3, after the first stage of CVI, the density is 1.2g / cm 3 ~1.3g / cm 3 The carbon / carbon composite semi-finished product undergoes the first rough machining with almost no change in density.

[0046] S2-4, Second vapor deposition: Arrange the roughly processed carbon / carbon composite semi-finished products from bottom to top and from low to high density, and place them at the center of the graphite support plate II of the material column II. Stacking The taken out preform is placed and separated by a graphite inner diameter gasket ring with a thickness of 10 mm, and a graphite cover plate II is added to the uppermost end of the preform; then it is placed in the deposition chamber; and finally the graphite cover plate of the deposition chamber is placed. The gaseous precursor reaction gas enters the periphery of the stacked preform through the dispersed air inlet holes on the graphite support plate II, and the gaseous precursor reaction gas overflows to the center of the preform through the inner diameter gasket ring, and then is discharged through the concentrated air outlet hole in the center of the graphite cover plate II. At the same time, the excess gaseous precursor reaction gas overflows through the pressure regulating air outlet hole on the graphite cover plate II, adjusts the internal pressure, and converges to the air outlet hole of the graphite cover plate of the deposition chamber. After convergence, the residual reaction gas is discharged from the air outlet hole of the graphite cover plate of the deposition chamber.

[0047] The deposition process is as follows:

[0048] The gas preheating temperature is 1005℃. The temperature is raised to the deposition temperature of 1020℃, and natural gas and propylene are introduced for deposition. The natural gas flow rate is 81SLM, the propylene flow rate is 8.1SLM, and nitrogen is introduced as the carrier gas. The volume ratio of the carbon source gas to the carrier gas is 1 to 2:1. The furnace pressure is 3KPa, and the deposition time is 150h.

[0049] S2-5, the second vapor deposition obtained a density range of 1.43 to 1.47 g / cm 3 , average density is 1.45g / cm 3 Carbon / carbon composite semi-finished products.

[0050] S3. High-temperature heat treatment

[0051] Heat up the semi-finished carbon / carbon composite material obtained by the second vapor deposition to 2300 °C, keep it at this temperature for 4 h for heat treatment to obtain a semi-finished carbon friction disc.

[0052] After silicification treatment, a carbon / carbon ceramic friction disc blank with a bulk density of 2.0 - 2.1 g / cm 3 is obtained.

[0053] Samples are taken from the semi-finished carbon friction disc after heat treatment at the inner and outer radii to test its density and polarized light structure. It can be seen that both samples are rough layer pyrolytic carbon. The inner diameter sample is selected for analysis. The data is shown in Table 1, specifically as Figure 1 shown.

[0054] Example 2

[0055] The difference from Example 1 is that: S2-1. The thickness of the graphite outer diameter spacer ring used is 15 mm;

[0056] The deposition process is as follows:

[0057] The gas preheating temperature is 1025 °C. Heat up to the deposition temperature of 1040 °C, and introduce natural gas and propylene for deposition. The flow rate of natural gas is 80 SLM, the flow rate of propylene is 10 SLM, and nitrogen is introduced as the carrier gas. The volume ratio of the carbon source gas to the carrier gas is 2:1.

[0058] S2-2. A semi-finished carbon / carbon composite material with a density of 1.2 g / cm 3 - 1.3 g / cm 3 is obtained.

[0059] In S2-4, the thickness of the graphite inner diameter spacer ring used is still 10 mm;

[0060] The second vapor deposition process is as follows:

[0061] The gas preheating temperature is 1005 °C. Heat up to the deposition temperature of 1020 °C, and introduce natural gas and propylene for deposition. The flow rate of natural gas is 72 SLM, the flow rate of propylene is 9 SLM, and nitrogen is introduced as the carrier gas. The volume ratio of the carbon source gas to the carrier gas is 1 - 2:1. The furnace pressure is 2.5 KPa.

[0062] Other parameters are the same as those in Example 1. The average density of the carbon / carbon composite material obtained by the second vapor deposition is 1.45 g / cm 3 , and the density range is 1.43 - 1.47 g / cm 3 . Samples are taken from products at different positions and the microstructure of the deposited carbon is observed. The structure of the deposited carbon is rough layer, and it can be seen that the density distribution is narrow and the consistency is good.

[0063] After silicification treatment, a carbon / ceramic friction disk blank with a bulk density of 1.97 - 2.1 g / cm 3 is obtained.

[0064] Samples are taken from the heat-treated carbon friction disk semi-finished product both radially inside and outside, and its density and polarized light structure are tested. It can be seen that both experiments are rough layer pyrolytic carbon. The inner diameter sample is selected for analysis, and the data are shown in Table 1, specifically as Figure 2 shown.

[0065] Comparative Example 1

[0066] All other conditions are the same as those in Example 1, except that: in the first vapor deposition, the dosages of natural gas and propylene are different. The natural gas flow rate is 60 SLM, and the propylene flow rate is 12 SLM.

[0067] The average density of the carbon / carbon composite material prepared by the above method is 1.45 g / cm 3 , and the density range is 1.38 - 1.50 g / cm 3 . Samples are taken from products at different positions and the microscopic structure of the deposited carbon is observed. The structure of the deposited carbon is a mixed carbon structure, the structure is uneven, and the density distribution range is wide. After silicification treatment, a carbon / ceramic friction disk blank with a bulk density of 1.8 - 2.1 g / cm 3 is obtained.

[0068] Samples are taken from the heat-treated carbon friction disk semi-finished product both radially inside and outside, and its density and polarized light structure are tested. It can be seen that both samples are mixed pyrolytic carbon. The inner diameter sample is selected for analysis, and the data are shown in Table 1, specifically as Figure 3 shown.

[0069] Comparative Example 2

[0070] All other conditions are the same as those in Example 1, except that: the preheating temperature of the S2-1 gas is 900 °C. The average density of the carbon / carbon composite material prepared by the above method is 1.45 g / cm 3 , and the density range is 1.38 - 1.50 g / cm 3 . Samples are taken from products at different positions and the microscopic structure of the deposited carbon is observed. The structure of the deposited carbon is a mixed carbon structure, the structure is uneven, and the density distribution range is wide. After silicification treatment, a carbon / ceramic friction disk blank with a bulk density of 1.75 - 2.1 g / cm 3 is obtained.

[0071] Samples are taken from the heat-treated carbon friction disk semi-finished product both radially inside and outside, and its density and polarized light structure are tested. It can be seen that both samples are mixed pyrolytic carbon. The inner diameter sample is selected for analysis, and the data are shown in Table 1, specifically as Figure 4 shown.

[0072] Comparative Example 3

[0073] All other conditions were the same as in Example 1, except that the thickness of the spacer ring was 20 mm. The average density of the carbon / carbon composite material prepared by the above method was 1.4 g / cm 3 , and the density range was 1.33 - 1.46 g / cm 3 , and a crusting phenomenon appeared on the surface of the disk body. Samples were taken from products at different positions and the microstructure of the deposited carbon was observed. The structure of the deposited carbon was a mixed carbon structure, with uneven structure and a wide density distribution range. After silicification treatment, a carbon / ceramic friction disk blank with a bulk density of 1.75 N 2.1 g / cm 3 was obtained.

[0074] Samples were taken from the inner and outer radii of the heat-treated carbon friction disk semi-finished products and their density and polarized light structure were tested. It can be seen that both samples were mixed pyrolytic carbon. The inner diameter sample was selected for analysis, and the data are shown in Table 1, specifically as Figure 5 shown.

[0075] Refer to the standard of QB / T 1642-2012 "Test Method for Apparent Porosity and Bulk Density of Ceramic Green Bodies" to detect the apparent porosity of the inner diameter samples of the carbon friction disk semi-finished products obtained in Examples 1-2 and Comparative Examples 1-3. The results are shown in Table 1.

[0076] Table 1 Test Data

[0077]

[0078] In Comparative Example 1 and Comparative Example 2, mainly due to unreasonable chemical vapor infiltration parameters, a single rough layer pyrolytic carbon structure was not formed, which was not conducive to high-temperature pore opening and uneven silicon infiltration, resulting in the density of the final blank material not meeting the standard. In Comparative Example 3, it was mainly caused by the too thick spacer ring. The too thick spacer ring caused too high a carbon atmosphere concentration around the carbon fiber preform, resulting in a crusting phenomenon on the surface of the disk body. On the basis of designing the tooling, it is necessary to strictly control the deposition temperature, deposition pressure, flow rate, and gas ratio to deposit a single rough layer pyrolytic carbon, thereby realizing the uniformity of the density and porosity of the entire disk body, and finally meeting the performance requirements of carbon-ceramic friction materials with different densities, such as carbon-ceramic friction disks and high-performance carbon-ceramic friction plates in the fields of aircraft, high-speed trains, armored vehicles, heavy trucks, etc.

[0079] Finally, it should be noted that: the above are only the preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered as the protection scope of the present invention.

Claims

1. A method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disc, characterized in that: The steps include: S1. Preform heat treatment The carbon fiber preform is placed in a heat treatment furnace, heated to 1800°C to 2000°C, and kept at this temperature for 1 to 2 hours for heat treatment; S2. Vapor Deposition S2-1, First vapor deposition: The density of the preform after heat treatment is 0.45~0.6g / cm 3 , stack multiple groups of heat-treated preforms at the center of the graphite support plate I of the material column I, and separate them with a graphite outer diameter gasket ring with a thickness of 10 to 15 mm, add a graphite cover plate I to the top of the preform, then put it into the deposition chamber, cover it with the deposition chamber graphite cover plate, and pass the gaseous precursor reaction gas for gas phase infiltration; The gas is preheated to 1025°C to 1045°C and fed into the deposition chamber, and then further heated to a deposition temperature of 1040 to 1060°C; natural gas and propylene are introduced for deposition, with a natural gas flow rate of 80 SLM to 100 SLM and a propylene flow rate of 8 SLM to 10 SLM, and nitrogen is introduced as a carrier gas, and the deposition time is 70 h to 150 h; S2-2, after the first vapor deposition, the density was 1.2 g / cm 3 ~1.3g / cm 3 Carbon / carbon composite semi-finished products; S2-3, performing the first rough processing on the carbon / carbon composite semi-finished product, the density remains almost constant; S2-4, second vapor deposition: the roughly processed carbon / carbon composite semi-finished products are arranged from bottom to top and in order from low to high density, stacked on the center of the graphite support plate II of the material column II, and separated by a graphite inner diameter gasket ring with a thickness of 10 to 15 mm, and a graphite cover plate II is added to the uppermost end of the preform, and then placed in a deposition chamber, covered with a deposition chamber graphite cover plate, and a gaseous precursor is introduced for vapor phase infiltration; The gas is preheated to 1005°C to 1025°C, introduced into the deposition chamber and heated to 1020 to 1040°C, and natural gas and propylene are introduced for deposition, with a natural gas flow rate of 72SLM to 90SLM and a propylene flow rate of 7.2SLM to 9SLM. Nitrogen is introduced as a carrier gas, and the deposition time is 50h to 150h. S2-5, after the second vapor deposition, the density is 1.40 / cm 3 ~1.50 / cm 3 Carbon / carbon composite semi-finished products; S3. High temperature heat treatment The density is 1.40 / cm 3 ~1.50 / cm 3 The carbon / carbon composite semi-finished product is heated to 2100° C. to 2600° C. and kept at this temperature for 4 hours for heat treatment to obtain a carbon friction disc semi-finished product.

2. The method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disc according to claim 1, characterized in that: The volume ratio of the carbon source gas to the carrier gas in S2-1 and S2-4 is 1 to 2:

1.

3. The method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disc according to claim 1, characterized in that: The furnace pressure in S2-1 and S2-4 is 1KPa~4KPa.

4. The method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disc according to claim 1, characterized in that: S2-1 The gaseous precursor reaction gas enters the center of the stacked preforms through the concentrated air inlet holes on the graphite support plate I, and the gaseous precursor reaction gas overflows to the periphery of the preform through the graphite outer diameter gasket ring, and then overflows through the gap between the outer circumference of the graphite cover plate I and the inner wall of the deposition chamber. At the same time, excess gaseous precursor reaction gas flows out through the air outlet holes on the graphite cover plate I, and the residual reaction gas after convergence is discharged from the air outlet holes of the graphite cover plate of the deposition chamber.

5. The method for preparing a carbon / carbon blank for a high-performance carbon / ceramic friction disc according to claim 1, characterized in that: S2-4 The gaseous precursor reaction gas enters the periphery of the stacked preform through the dispersed air inlet holes on the graphite support plate II, and the gaseous precursor reaction gas overflows through the graphite inner diameter gasket ring to the center of the preform, and then is discharged through the concentrated air outlet holes in the center of the graphite cover plate II. At the same time, excess gaseous precursor reaction gas overflows through the pressure-regulating air outlet holes on the graphite cover plate II, adjusts the internal pressure, and converges to the air outlet holes of the graphite cover plate of the deposition chamber. After convergence, the reaction residual gas is discharged from the air outlet holes of the graphite cover plate of the deposition chamber.

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