Refractory metal modified C / C composite material with controllable infiltration depth and preparation method thereof

Abstract

The application discloses a refractory metal modified C / C composite material with controllable infiltration depth and a preparation method, and belongs to the technical field of preparation of modified C / C composite materials. The method is as follows: pretreating low-density C / C composite material; mixing WO3 powder, Cu powder, NaCl powder and KCl powder, then performing ball milling treatment, and then performing sieving and drying treatment to obtain infiltration powder; sequentially laying the first layer of infiltration powder, the low-density C / C composite material and the second layer of infiltration powder from bottom to top to obtain multilayer powder; and performing heat treatment on the multilayer powder, and then cooling to obtain the refractory metal modified C / C composite material with controllable infiltration depth. The high-toughness refractory metal is used as a modified component, and the preparation is performed at a lower temperature, so that the infiltration depth can be controlled by adjusting the content of NaCl-KCl in the infiltration powder.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of modified C / C composite materials, and particularly relates to a refractory metal modified C / C composite material with controllable infiltration depth and a preparation method. BACKGROUND

[0002] When a hypersonic vehicle flies at a high Mach number, the thermal end components are easily subjected to material performance degradation and structural strength damage due to the coupling of comprehensive loads. Therefore, the development of ultra-high temperature materials capable of resisting harsh working environments has become a key to the stable service of hypersonic vehicles. C / C composite materials are carbon-based composite materials with carbon fibers as reinforcing materials, and have the characteristics of low density, high specific strength / modulus, thermal shock resistance, corrosion resistance, and mechanical properties that do not decrease but increase with temperature rise. C / C composite materials are one of the few ultra-high temperature composite materials that can be used at temperatures above 3000℃. However, C / C composite materials have poor resistance to erosion, and are easily damaged by excessive ablation in a high-speed particle erosion environment.

[0003] Currently, the methods for improving the ablation resistance of C / C composite materials mainly include coating protection technology and matrix modification technology. These two technologies can be further divided into active protection mainly using metal materials and passive protection mainly using ceramic materials according to the protection methods. In terms of coating protection technology, the prior art uses supersonic plasma spraying technology to prepare a W-Cu metal coating on the surface of C / C composite materials. This technology improves the ablation resistance of the material. However, the difference in the thermal expansion coefficients of the coating and the matrix is large, so the thickness of the coating should not be too thick, otherwise the coating will fail due to thermal mismatch, which limits its application in harsh environments with large ablation amounts. In terms of matrix modification technology, ZrC-SiC ceramic modified C / C composite materials prepared by reaction infiltration exhibit good ablation resistance under an oxyacetylene flame. However, the modified sample surface is prone to cracking, showing insufficient toughness, especially in extreme environments where it is difficult to resist high-speed particle erosion. Moreover, more importantly, the content of the modification components introduced by the existing reaction infiltration technology is difficult to control, and the designability of the modification range is poor, which leads to the overall high density of the modified sample and the difficulty in accurately modifying specific regions. SUMMARY

[0004] In order to overcome the above-mentioned prior art defects, the purpose of the present application is to provide a refractory metal modified C / C composite material with controllable infiltration depth and a preparation method. Firstly, the problems of uncontrollable modification range, too high modification component introduction amount and too large overall density of the modified sample after modification are solved. Secondly, the technical problems of too high infiltration temperature and brittle ceramic modification component introduced by the reaction of refractory metal and carbon at high temperature to form brittle carbide ceramic, and poor impact resistance are solved. Then, the technical problem of low coating technology damage tolerance caused by serious thermal mismatch between the coating and the substrate and the thin coating thickness is avoided.

[0005] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0006] The present application provides a preparation method of a refractory metal modified C / C composite material with controllable infiltration depth, comprising the following steps:

[0007] S1: pretreating a low-density C / C composite material;

[0008] S2: mixing WO3 powder, Cu powder, NaCl powder and KCl powder, then performing ball milling treatment, and then performing sieving and drying treatment to obtain infiltration powder;

[0009] S3: sequentially laying the first layer of infiltration powder, the low-density C / C composite material and the second layer of infiltration powder from bottom to top to obtain multi-layer powder;

[0010] S4: performing heat treatment on the multi-layer powder, and then cooling to obtain a refractory metal modified C / C composite material with controllable infiltration depth.

[0011] In the specific implementation process, the low-density C / C composite material is a 2.5D C / C composite material with a density of 1.1-1.6 g / cm 3 .

[0012] In the specific implementation process, in S1, the pretreatment includes polishing treatment of the low-density C / C composite material using a sand disc, ultrasonic cleaning with deionized water and drying treatment.

[0013] In the specific implementation process, the polishing treatment includes:

[0014] sequentially polishing the low-density C / C composite material using 400-mesh, 1000-mesh and 2000-mesh diamond sand discs;

[0015] The drying temperature of the drying treatment is 60-120 DEG C, and the drying time is 12 h.

[0016] In the specific implementation process, the molar ratio of NaCl powder and KCl powder in the infiltration powder is 1:1.

[0017] In a specific implementation, the mass ratio of the WO3 powder and the Cu powder in the infiltrating powder is (1-2):(1-2).

[0018] In a specific implementation, the mass ratio of the first group of mixed powders formed by the WO3 powder and the Cu powder to the second group of mixed powders formed by the NaCl powder and the KCl powder is (1-200):1.

[0019] In a specific implementation, the screen mesh is a 200-mesh screen; the drying temperature of the drying treatment is 70-120 DEG C, and the drying time of the drying treatment is 24-48 h.

[0020] In a specific implementation, the heat treatment is performed as follows:

[0021] The temperature is raised to 1200-1500 DEG C at a temperature raising rate of 5 DEG C / min under a vacuum environment, and then the temperature is kept for 2 h and naturally cooled to room temperature.

[0022] The application also provides a refractory metal modified C / C composite material with controllable infiltration depth, which is prepared by the method.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] The method for preparing the refractory metal modified C / C composite material with controllable infiltration depth provided by the application first uses the refractory metal W with high melting point and low saturated vapor pressure and the sweating metal Cu with low melting point and high phase change enthalpy as the modified components, which not only improves the anti-erosion performance of the C / C composite material in a high-speed particle impact environment, but also lowers the surface temperature of the material by absorbing heat with the sweating material in a high-temperature environment; secondly, the WO3-Cu-NaCl-KCl mixed powder is used as the infiltrating powder to perform the infiltration treatment on the low-density C / C composite material, so that the refractory metal modified C / C composite material with controllable infiltration depth is obtained, and more importantly, the NaCl-KCl molten salt is doped in the infiltrating powder, which not only acts as the carrier of the infiltrating agent to accelerate the reaction between the WO3 and the carbon and promote the infiltration of the melt into the material, but also lowers the heat treatment temperature to avoid the reaction between the refractory metal and the carbon to form brittle carbide ceramic at high temperature. The application can control the infiltration depth by adjusting the content of the NaCl-KCl in the infiltrating powder, and does not need additional tooling, has high accuracy and low cost, and can design the modification range according to the actual application requirement, so that the lightweight is realized while the service reliability is ensured, and more possibilities are provided for the subsequent structural design of the modified C / C composite material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1SEM images of cross-sections of W-Cu modified C / C composites with different infiltration depths prepared according to the present application; wherein (a) is the composite prepared in Example 1 with an infiltration depth of about 100 μm, (b) is the composite prepared in Example 2 with an infiltration depth of about 500 μm, (c) is the composite prepared in Example 3 with an infiltration depth of about 1.5 mm, and (d) is the composite prepared in Example 4 with an infiltration depth of more than 5 mm.

[0026] Figure 2 XRD images of surfaces of W-Cu modified C / C composites with different infiltration depths prepared according to the present application; wherein (a) is the composite prepared in Example 1 with an infiltration depth of about 100 μm, (b) is the composite prepared in Example 2 with an infiltration depth of about 500 μm, (c) is the composite prepared in Example 3 with an infiltration depth of about 1.5 mm, and (d) is the composite prepared in Example 4 with an infiltration depth of more than 5 mm. DETAILED DESCRIPTION

[0027] To enable persons skilled in the art to better understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used in the specification have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the specification shall prevail.

[0028] Theories or mechanisms described and disclosed herein, whether or not correct, should not be considered limiting the scope of the present application, i.e., the present application can be practiced without relying on any particular theory or mechanism.

[0029] In the present application, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, amounts, contents and concentrations, are for the sake of brevity and convenience. Therefore, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0030] In the present application, unless otherwise specified, "comprise", "include", "contain", "have" or similar words encompass the meaning of "consist of" and "consist essentially of", e.g., "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".

[0031] In the present application, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not contradict each other, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present specification.

[0032] The application provides a preparation method of a refractory metal modified C / C composite material with controllable infiltration depth, and specific steps are as follows:

[0033] Step 1: pretreating the low-density C / C composite material; wherein the pretreatment comprises polishing the low-density C / C composite material by using a sand disc, ultrasonic cleaning with deionized water and drying treatment.

[0034] More specifically, the low-density C / C composite material is polished by using a diamond sand disc, and then dried by using deionized water ultrasonic cleaning and placing in an oven.

[0035] Step 2: mixing WO3 powder, Cu powder, NaCl powder and KCl powder, then performing ball milling treatment, and then performing sieving and drying treatment to obtain infiltration powder; wherein the molar ratio of NaCl powder and KCl powder in the infiltration powder is 1:1, the mass ratio of WO3 powder and Cu powder in the infiltration powder is (1-2):(1-2), and the mass ratio of a first group of mixed powders formed by the WO3 powder and the Cu powder to a second group of mixed powders formed by the NaCl powder and the KCl powder is (1-200):1.

[0036] Step 3: sequentially laying the first layer of infiltration powder, the low-density C / C composite material and the second layer of infiltration powder from bottom to top to obtain a multilayer powder;

[0037] Step 4: performing heat treatment on the multilayer powder, and then cooling to obtain the refractory metal modified C / C composite material with controllable infiltration depth.

[0038] The application adopts the reaction infiltration process in the matrix modification technology, avoids the problem of serious thermal mismatch between the coating and the matrix in the coating technology and low damage tolerance, controls the infiltration depth by adjusting the NaCl-KCl content in the infiltration powder, solves the problem of large density of refractory metal, realizes the lightweight of the sample, and provides more ideas for the subsequent structural design of the modified C / C composite material.

[0039] Specifically, step 3 is as follows: sequentially laying the first layer of infiltration powder, the low-density C / C composite material and the second layer of infiltration powder from bottom to top at the bottom of a graphite crucible to obtain a multilayer powder; placing a graphite paper above the second layer of infiltration powder in the multilayer powder, placing a carbon felt above the graphite paper for sealing treatment, then covering a graphite cover, and then wrapping the graphite crucible with a graphite paper to obtain a treated graphite crucible;

[0040] Specific step 4 is as follows: the treated graphite crucible is placed in a heat treatment furnace and heated to 1200-1500 DEG C at a heating rate of 5 DEG C / min in a vacuum environment, heat treated for 2h, and naturally cooled to room temperature to obtain a refractory metal modified C / C composite material with controllable infiltration depth.

[0041] The refractory metal modified C / C composite material with controllable infiltration depth provided by the application solves the problem of brittle carbide ceramic formed by the reaction of the refractory metal with carbon at high temperature, and avoids the problem of large brittleness and poor impact resistance of the ceramic material.

[0042] The application also provides a refractory metal modified C / C composite material with controllable infiltration depth based on the preparation method.

[0043] In the specific implementation process, the preparation method of the refractory metal modified C / C composite material with controllable infiltration depth is as follows:

[0044] Step 1: sequentially polish the low-density C / C composite material by using 400-mesh, 1000-mesh and 2000-mesh diamond sand discs, the low-density C / C composite material is a 2.5D C / C composite material with a density of 1.1-1.6 g / cm 3 , and after ultrasonic cleaning with deionized water, the low-density C / C composite material is placed in an oven for drying treatment at a drying temperature of 60-120 DEG C, and the drying time is 12h;

[0045] Step 2: weigh a certain amount of WO3, Cu, NaCl and KCl powders, pour them into a ball mill jar for ball milling treatment, sieve the mixed powders through a 200-mesh sieve, and place them in an oven for drying treatment at a drying temperature of 70-120 DEG C for 24-48h to obtain infiltration powders;

[0046] The molar ratio of the NaCl powder to the KCl powder in the NaCl-KCl mixed powder is 1:1; the mass ratio of the WO3 powder to the Cu powder is 2:1-1:2; and the mass ratio of the WO3-Cu mixed powder, i.e. the first group of mixed powders formed by the WO3 powder and the Cu powder, to the NaCl-KCl mixed powder, i.e. the second group of mixed powders formed by the NaCl powder and the KCl powder, is 1:1-200:1.

[0047] Step 3: lay a layer of the infiltration powders on the bottom of a graphite crucible, place the low-density C / C composite material on the powders, and then pour the powders into the graphite crucible until the infiltration powders completely cover the low-density C / C composite material and exceed a certain thickness.

[0048] Step 4: after the addition of the infiltration powders is completed, first place a graphite paper above the infiltration powders, then place a carbon felt above the graphite paper for sealing treatment, and finally cover a graphite cover and wrap the graphite crucible with a graphite paper to obtain a treated graphite crucible.

[0049] Step 5: The treated crucible is placed in a heat treatment furnace for heat treatment, and is heated to 1200-1500°C at a heating rate of 5°C / min in a vacuum environment, and is kept for 2h, the power is turned off, and the treated crucible is taken out after natural cooling to room temperature, to obtain a W-Cu modified C / C composite material with controllable infiltration depth.

[0050] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content taught by the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0051] The following examples use the conventional instrument equipment in the art. The experimental methods not specified in the following examples are generally carried out according to the conventional conditions, or according to the conditions recommended by the manufacturer. Various raw materials are used in the following examples, and unless otherwise specified, the conventional commercially available products are used, and the specifications are conventional specifications in the art. In the specification of the application and the following examples, unless otherwise specified, “%” means weight percent, “parts” means weight parts, and the ratio means weight ratio.

[0052] Example 1

[0053] Step 1: 2.5D C / C composite material with a density of 1.1 g / cm 3 is used, and the deionized water is ultrasonically cleaned for 0.5h, and then is placed in a 60°C oven for drying for 12h for standby.

[0054] Step 2: A certain amount of WO3 and Cu powder is weighed according to the mass ratio of WO3 to Cu of 1:1, and a certain amount of NaCl and KCl powder is weighed according to the molar ratio of NaCl to KCl of 1:1, the WO3-Cu mixed powder and the NaCl-KCl mixed powder are poured into a ball mill jar according to the mass ratio of 200:1, the rotation speed is set to 300r / min, and the planetary ball mill is used for ball milling for 8h, then the mixed powder is poured into a 200 mesh sieve for sieving, and is placed in a 70°C oven for drying for 24h to obtain infiltration powder;

[0055] Step 3: The obtained infiltration powder is evenly spread inside the graphite crucible, and the thickness of the spread powder is 5mm, and the low-density C / C composite material is placed above the powder, and the infiltration powder is poured to completely cover the low-density C / C composite material, and then the infiltration powder with a thickness of 5mm is evenly spread.

[0056] Step 4: After the powder is added, two layers of graphite paper are placed above the powder, and then a layer of carbon felt is placed above the graphite paper for sealing treatment, and finally a graphite cover is covered, and the graphite crucible is wrapped with graphite paper;

[0057] Step 5: Put the processed crucible into a heat treatment furnace, heat to 1300℃ at a heating rate of 5℃ / min in a vacuum environment, keep for 2h, turn off the power, take out after natural cooling to room temperature, polish the sample surface residual melt with sandpaper to remove, get W-Cu modified C / C composite material with a infiltration depth of about 100μm.

[0058] Example 2

[0059] Step 1: Use 2.5D C / C composite material with a density of 1.1g / cm 3 , use 400 mesh, 1000 mesh, 2000 mesh diamond sand disc to polish in turn, use deionized water ultrasonic cleaning for 0.5h, then put in 60℃ oven and dry for 12h for standby.

[0060] Step 2: According to the mass ratio of WO3 and Cu 1:1, a certain amount of WO3, Cu powder is weighed, according to the molar ratio of NaCl and KCl 1:1, a certain amount of NaCl, KCl powder is weighed, WO3-Cu mixed powder and NaCl-KCl mixed powder are poured into the ball mill pot according to the mass ratio of 100:1, the ball to material ratio is 2:1, the rotation speed is set to 300r / min, the planetary ball mill is used for 8h, then the mixed powder is poured into a 200 mesh sieve and dried in a 70℃ oven for 24h to get the infiltration powder;

[0061] Step 3: The obtained infiltration powder is evenly spread inside the graphite crucible, the powder thickness is 5mm, the low density C / C composite material is placed above the powder, the infiltration powder is poured to completely cover the low density C / C composite material, and then the infiltration powder with a thickness of 5mm is evenly spread.

[0062] Step 4: After the powder is added, two layers of graphite paper are placed above the powder, and a layer of carbon felt is placed above the graphite paper for sealing treatment, and finally a graphite cover is covered, and the graphite crucible is wrapped with graphite paper;

[0063] Step 5: Put the processed crucible into a heat treatment furnace, heat to 1300℃ at a heating rate of 5℃ / min in a vacuum environment, keep for 2h, turn off the power, take out after natural cooling to room temperature, polish the sample surface residual melt with sandpaper to remove, get W-Cu modified C / C composite material with a infiltration depth of about 500μm.

[0064] Example 3

[0065] Step 1: Use 2.5D C / C composite material with a density of 1.1g / cm 3 , use 400 mesh, 1000 mesh, 2000 mesh diamond sand disc to polish in turn, use deionized water ultrasonic cleaning for 0.5h, then put in 60℃ oven and dry for 12h for standby.

[0066] Step 2: A certain amount of WO3, Cu powder was weighed according to the mass ratio of WO3 and Cu 1:1, and a certain amount of NaCl, KCl powder was weighed according to the molar ratio of NaCl and KCl 1:1, the WO3-Cu mixed powder and the NaCl-KCl mixed powder were poured into a ball mill tank according to the mass ratio 50:1, the ball-to-material ratio was 2:1, the rotation speed was set to 300r / min, the planetary ball mill was used for 8h, then the mixed powder was poured into a 200 mesh sieve, and was placed in a 70℃ oven for 24h to obtain a sintered powder;

[0067] Step 3: The obtained sintered powder was evenly spread inside the graphite crucible, the powder thickness was 5mm, the low-density C / C composite material was placed above the powder, and the sintered powder was poured to completely cover the low-density C / C composite material, and then the sintered powder with a thickness of 5mm was evenly spread.

[0068] Step 4: After the powder was added, two layers of graphite paper were placed above the powder, and a layer of carbon felt was placed above the graphite paper for sealing treatment, and finally a graphite cover was covered, and the graphite crucible was wrapped with graphite paper;

[0069] Step 5: The treated crucible was placed in a heat treatment furnace, and the temperature was raised to 1300℃ at a rate of 5℃ / min in a vacuum environment, and the temperature was kept for 2h, the power was turned off, and the sample was taken out after natural cooling to room temperature, the surface residual melt of the sample was polished and removed with sandpaper, and a W-Cu modified C / C composite material with a sintering depth of about 1.5mm was obtained.

[0070] Example 4

[0071] Step 1: A 2.5D C / C composite material with a density of 1.4g / cm 3 was used, and the diamond sand disc with a mesh size of 400, 1000 and 2000 was used for polishing in sequence, and then the sample was placed in a 60℃ oven for 12h after ultrasonic cleaning with deionized water for 0.5h.

[0072] Step 2: A certain amount of WO3, Cu powder was weighed according to the mass ratio of WO3 and Cu 1:1, and a certain amount of NaCl, KCl powder was weighed according to the molar ratio of NaCl and KCl 1:1, the WO3-Cu mixed powder and the NaCl-KCl mixed powder were poured into a ball mill tank according to the mass ratio 50:1, the ball-to-material ratio was 2:1, the rotation speed was set to 300r / min, the planetary ball mill was used for 8h, then the mixed powder was poured into a 200 mesh sieve, and was placed in a 70℃ oven for 24h to obtain a sintered powder;

[0073] Step 3: The obtained infiltration powder is evenly laid inside the graphite crucible with a powder thickness of 5 mm. The low-density C / C composite material is placed above the powder, and the infiltration powder is poured to completely cover the low-density C / C composite material. Then, the infiltration powder with a thickness of 5 mm is evenly laid again.

[0074] Step 4: After the powder addition is completed, two layers of graphite paper are placed above the powder, followed by a layer of carbon felt for sealing treatment. Finally, a graphite cover is placed, and the graphite crucible is wrapped with graphite paper.

[0075] Step 5: The treated crucible is placed in a heat treatment furnace. In a vacuum environment, the temperature is raised to 1300℃ at a rate of 5℃ / min, and the temperature is maintained for 2h. The power is turned off, and the sample is naturally cooled to room temperature. The surface residual melt of the sample is polished and removed with sandpaper. A W-Cu modified C / C composite material with an infiltration depth of more than 5 mm is obtained.

[0076] Example 5

[0077] Step 1: A 2.5D C / C composite material with a density of 1.6g / cm 3 is used. The diamond sand disc with a mesh size of 400, 1000, and 2000 is used for polishing in sequence. After ultrasonic cleaning with deionized water for 0.5h, the sample is placed in a 60℃ oven for drying for 12h for standby.

[0078] Step 2: A certain amount of WO3 and Cu powder is weighed according to the mass ratio of WO3 to Cu of 2:1. A certain amount of NaCl and KCl powder is weighed according to the molar ratio of NaCl to KCl of 1:1. The WO3-Cu mixed powder and the NaCl-KCl mixed powder are poured into a ball mill jar according to the mass ratio of 1:1. The ball-to-material ratio is 2:1. The rotation speed is set to 300r / min. The planetary ball mill is used for 8h. Then, the mixed powder is sieved through a 200 mesh sieve and dried in a 70℃ oven for 24h to obtain the infiltration powder.

[0079] Step 3: The obtained infiltration powder is evenly laid inside the graphite crucible with a powder thickness of 5 mm. The low-density C / C composite material is placed above the powder, and the infiltration powder is poured to completely cover the low-density C / C composite material. Then, the infiltration powder with a thickness of 5 mm is evenly laid again.

[0080] Step 4: After the powder addition is completed, two layers of graphite paper are placed above the powder, followed by a layer of carbon felt for sealing treatment. Finally, a graphite cover is placed, and the graphite crucible is wrapped with graphite paper.

[0081] Step 5: Put the processed crucible into the heat treatment furnace, and heat to 1200℃ at a heating rate of 5℃ / min in a vacuum environment, keep for 2h, turn off the power, take out after natural cooling to room temperature, polish the sample surface with sandpaper to remove the residual melt, and get W-Cu modified C / C composite material with a infiltration depth of >5mm.

[0082] Example 6

[0083] Step 1: Use 2.5D C / C composite material with a density of 1.4g / cm 3 , and polish with 400 mesh, 1000 mesh, and 2000 mesh diamond sand discs in turn, and then ultrasonic clean with deionized water for 0.5h, and then dry in an oven at 120℃ for 12h for standby.

[0084] Step 2: Weigh a certain amount of WO3 and Cu powder according to the mass ratio of WO3 to Cu of 1:2, weigh a certain amount of NaCl and KCl powder according to the molar ratio of NaCl to KCl of 1:1, pour the WO3-Cu mixed powder and the NaCl-KCl mixed powder into the ball mill jar according to the mass ratio of 10:1, add grinding balls according to the ball-to-material ratio of 2:1, set the rotation speed to 300r / min, and use the planetary ball mill to mill for 8h, then sieve the mixed powder through a 200 mesh sieve, and dry in an oven at 120℃ for 48h to obtain the infiltration powder;

[0085] Step 3: Uniformly spread the obtained infiltration powder inside the graphite crucible, with a powder thickness of 5mm, place the low-density C / C composite material above the powder, pour the infiltration powder to completely cover the low-density C / C composite material, and then uniformly spread another 5mm thick infiltration powder.

[0086] Step 4: After the powder is added, first place two layers of graphite paper above the powder, then place a layer of carbon felt above the graphite paper for sealing treatment, and finally cover the graphite cover and wrap the graphite crucible with graphite paper;

[0087] Step 5: Put the processed crucible into the heat treatment furnace, and heat to 1200℃ at a heating rate of 5℃ / min in a vacuum environment, keep for 2h, turn off the power, take out after natural cooling to room temperature, polish the sample surface with sandpaper to remove the residual melt, and get W-Cu modified C / C composite material with a infiltration depth of >5mm.

[0088] Figure 1 Figs. (a) to (d) are SEM photos of the cross sections of the modified samples with different infiltration depths prepared by using different salt contents in the initial infiltration powder. As can be seen from the figures, as the salt content in the initial infiltration powder increases, the infiltration depth also increases, indicating that the infiltration depth can be controlled by the salt content in the initial infiltration powder.

[0089] Figure 2The middle line a-d is the XRD pattern of the surface of the modified sample with different infiltration depths prepared by using different salt contents in the initial infiltration powder. As can be seen from the figure, the composition of the prepared sample is metal W and Cu within a certain salt content and temperature range, and the metal W does not further react with the carbon matrix to form brittle carbide ceramic, indicating that the refractory metal W-Cu modified C / C composite material can be successfully prepared within the process parameters described in the patent without the introduction of other ceramic components.

[0090] Comparative Example 1

[0091] Different from Example 1, the mass ratio of WO3-Cu powder to NaCl-KCl powder is 1:2.5.

[0092] Step 1: 2.5D C / C composite material with a density of 1.1 g / cm 3 is used for polishing, and after ultrasonic cleaning with deionized water for 0.5 h, it is placed in a 60℃ oven for drying for 12 h for standby.

[0093] Step 2: A certain amount of WO3 and Cu powder is weighed according to the mass ratio of WO3 to Cu 1:1, and a certain amount of NaCl and KCl powder is weighed according to the molar ratio of NaCl to KCl 1:1. The WO3-Cu mixed powder and the NaCl-KCl mixed powder are poured into the ball mill jar according to the mass ratio 1:2, the ball-to-material ratio is 2:1, the rotation speed is set to 300 r / min, and the planetary ball mill is used for 8 h. Then, the mixed powder is sieved through a 200 mesh sieve and dried in a 70℃ oven for 24 h to obtain the infiltration powder;

[0094] Step 3: The obtained infiltration powder is evenly spread inside the graphite crucible, the powder thickness is 5 mm, the low-density C / C composite material is placed above the powder, the infiltration powder is poured to completely cover the low-density C / C composite material, and then the infiltration powder with a thickness of 5 mm is evenly spread.

[0095] Step 4: After the powder is added, two layers of graphite paper are placed above the powder, and then a layer of carbon felt is placed above the graphite paper for sealing treatment. Finally, a graphite cover is covered, and the graphite crucible is wrapped with graphite paper.

[0096] Step 5: The treated crucible is placed in a heat treatment furnace, and the temperature is raised to 1300℃ at a rate of 5℃ / min in a vacuum environment, and the temperature is kept for 2 h. The power is turned off, and the crucible is naturally cooled to room temperature. It is found that the melt volatilizes seriously at high temperature, there is no infiltration powder left in the crucible after cooling, and only a small amount of melt penetrates into the sample. The densification degree of the modified area of the sample is low, and there are still a large number of pores.

[0097] From the results of the pair of examples, it can be seen that the salt content in the infiltration powder has a significant effect on the infiltration process. When the salt content is too high, the molten salt volatilizes at high temperature, which cannot play the role of auxiliary infiltration, but inhibits the infiltration of the remaining melt into the sample, ultimately resulting in poor modification effect of the sample.

[0098] Pair of example 2

[0099] Different from example 3, the mass ratio of WO3 to Cu powder is 1:5.

[0100] Step 1: using 2.5D C / C composite material with a density of 1.1 g / cm 3 , polishing with 400 mesh, 1000 mesh and 2000 mesh diamond sand discs in turn, and then drying in a 60℃ oven for 12h after ultrasonic cleaning with deionized water for 0.5h.

[0101] Step 2: according to the mass ratio of WO3 to Cu powder 1:5, a certain amount of WO3 and Cu powder is weighed, and a certain amount of NaCl and KCl powder is weighed according to the molar ratio of 1:1, then the WO3-Cu mixed powder and the NaCl-KCl mixed powder are poured into the ball mill pot according to the mass ratio of 50:1, the ball-to-material ratio is 2:1, the rotation speed is set to 300r / min, and the planetary ball mill is used for 8h, then the mixed powder is sieved through a 200 mesh sieve and dried in a 70℃ oven for 24h to obtain the infiltration powder;

[0102] Step 3: the obtained infiltration powder is evenly spread in the graphite crucible, the powder thickness is 5mm, the low-density C / C composite material is placed above the powder, and the infiltration powder is poured to completely cover the low-density C / C composite material, then the infiltration powder with a thickness of 5mm is evenly spread.

[0103] Step 4: after the powder is added, two layers of graphite paper are placed above the powder, and then a layer of carbon felt is placed above the graphite paper for sealing treatment, and finally a graphite cover is covered, and the graphite crucible is wrapped with graphite paper;

[0104] Step 5: the treated crucible is placed in a heat treatment furnace, and the temperature is raised to 1300℃ at a rate of 5℃ / min in a vacuum environment, and the temperature is kept for 2h, then the power is turned off, and the sample is taken out after natural cooling to room temperature. It is found that due to the high content of Cu, Cu blocks are formed after cooling and are adhered to the crucible, the sample is wrapped in the Cu blocks, and the sample is difficult to take out and is easy to be damaged.

[0105] From the results of the comparative example, it can be seen that the Cu content in the infiltration powder has a significant effect on the infiltration process, and the ratio of WO3 and Cu should be controlled within a certain range. When the Cu content is too high, the mixed melt has poor wettability with the carbon matrix, the melt is difficult to penetrate into the inside of the sample, and a large amount of Cu-rich melt is left to form irregular metal blocks outside the sample during the cooling process and is adhered to the crucible. The sample is difficult to be directly taken out, and forcibly taking out will damage the crucible. Moreover, the wrapped sample is easy to be damaged by mechanical processing.

[0106] Comparative Example 3

[0107] Different from Example 3, the infiltration temperature is 1800℃

[0108] Step 1: A 2.5D C / C composite material with a density of 1.1 g / cm 3 is used, and is polished with diamond sand discs of 400 mesh, 1000 mesh and 2000 mesh in turn. After ultrasonic cleaning with deionized water for 0.5 h, it is placed in an oven at 60℃ for drying for 12 h for standby.

[0109] Step 2: A certain amount of WO3 and Cu powder is weighed according to the mass ratio of 1:1, and a certain amount of NaCl and KCl powder is weighed according to the molar ratio of 1:1. The WO3-Cu mixed powder and the NaCl-KCl mixed powder are poured into a ball mill pot according to the mass ratio of 50:1, and the grinding balls are added according to the ball-to-material ratio of 2:1. The rotation speed is set to 300 r / min, and the planetary ball mill is used for 8 h. Then the mixed powder is sieved through a 200 mesh sieve and dried in a 70℃ oven for 24 h to obtain the infiltration powder;

[0110] Step 3: The obtained infiltration powder is evenly spread inside the graphite crucible, and the polishing thickness is 5 mm. The low-density C / C composite material is placed above the powder, and the infiltration powder is poured to completely cover the low-density C / C composite material. Then, the infiltration powder with a thickness of 5 mm is evenly spread.

[0111] Step 4: After the powder is added, two layers of graphite paper are placed above the powder, and a layer of carbon felt is placed above the graphite paper for sealing treatment. Finally, the graphite cover is covered, and the graphite crucible is wrapped with graphite paper.

[0112] Step 5: The treated crucible is placed in a heat treatment furnace, and the temperature is raised to 1800℃ at a rate of 5℃ / min in a vacuum environment. After 2 h of holding, the power is turned off, and the sample is taken out after natural cooling to room temperature. XRD detection is performed, and it is found that the composition in the sample is WC ceramic and Cu, and there is no metal W.

[0113] From the results of the pair of examples, it can be seen that the infiltration temperature has a significant effect on the composition of the modified sample. At a lower temperature, after the reaction of WO3 with the carbon matrix to form metallic W, the reactivity of W with the carbon matrix is weak due to the low ambient temperature, and almost no WC ceramic is generated in the sample. However, when the infiltration temperature is too high, the reduced metal W continues to react with the carbon matrix to form WC ceramic, and the generated metal W is completely consumed.

[0114] The present application provides a method for preparing a refractory metal modified C / C composite material with controllable infiltration depth. The method uses a reaction infiltration method to introduce refractory metal W with high melting point and sweating metal Cu with high phase change enthalpy into the C / C composite material to improve its ablation resistance in a high-speed particle erosion environment. The infiltration powder used in the present application is a mixture of WO3-Cu-NaCl-KCl, and the low-density C / C composite material is subjected to a melting infiltration treatment to obtain a refractory metal modified C / C composite material with controllable infiltration depth. The melting salt NaCl-KCl is doped in the infiltration powder, which can not only act as a carrier for the infiltration powder to accelerate the reaction of WO3 with carbon and promote the infiltration of the melt into the material, but also reduce the heat treatment temperature to avoid the reaction of refractory metal with carbon at high temperature to form brittle carbide ceramic. The present application can control the infiltration depth by adjusting the content of NaCl-KCl in the infiltration powder.

[0115] The above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the claims of the present application.

Claims

1. A method for preparing a refractory metal-modified C / C composite material with controllable infiltration depth, characterized in that, Includes the following steps: S1: Pretreatment of low-density C / C composite materials; S2: WO3 powder, Cu powder, NaCl powder and KCl powder are mixed and ball-milled, then sieved and dried to obtain melt-infiltrated powder. S3: Lay out the first layer of melt-infiltrating powder, the low-density C / C composite material and the second layer of melt-infiltrating powder from bottom to top to obtain multi-layer powder; S4: Heat-treat multilayer powder and then cool to obtain a refractory metal modified C / C composite material with controllable melting penetration depth; The molar ratio of NaCl powder to KCl powder in the melt-infiltrating powder is 1:1; The mass ratio of WO3 powder to Cu powder in the melt-infiltrating powder is (1~2):(1~2). The mass ratio of the first mixed powder formed by WO3 powder and Cu powder to the second mixed powder formed by NaCl powder and KCl powder is (1~200):

1.

2. The method for preparing the refractory metal-modified C / C composite material with controllable infiltration depth according to claim 1, characterized in that, The low-density C / C composite material has a density of 1.1~1.6 g / cm³. 3 2.5DC / C composite material.

3. The method for preparing the refractory metal-modified C / C composite material with controllable infiltration depth according to claim 1, characterized in that, In step S1, the pretreatment includes grinding the low-density C / C composite material with a sanding disc, ultrasonic cleaning with deionized water, and drying.

4. The method for preparing the refractory metal-modified C / C composite material with controllable infiltration depth according to claim 3, characterized in that, The polishing process includes: The low-density C / C composite material was polished sequentially using diamond grinding discs of 400 mesh, 1000 mesh, and 2000 mesh. The drying temperature for the drying process is 60~120 ℃, and the drying time is 12 h.

5. The method for preparing the refractory metal-modified C / C composite material with controllable infiltration depth according to claim 1, characterized in that, The sieve used for sieving is a 200-mesh sieve; the drying temperature for the drying process is 70~120 ℃, and the drying time for the drying process is 24~48 h.

6. The method for preparing the refractory metal-modified C / C composite material with controllable infiltration depth according to claim 1, characterized in that, The heat treatment process is as follows: The temperature was increased to 1200~1500 ℃ in a vacuum environment at a heating rate of 5 ℃ / min, held at that temperature for 2 hours, and then naturally cooled to room temperature.

7. A method for preparing a refractory metal modified C / C composite material with controllable infiltration depth according to any one of claims 1 to 6, wherein the refractory metal modified C / C composite material with controllable infiltration depth is obtained.

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