1. CVD-Ta based on gradient evaporation mold_xHf_1-xThe preparation method of the C solid solution coating is characterized by comprising the following steps:

step 1: polishing the C/C matrix, ultrasonically cleaning the C/C matrix by deionized water for 30min, drying the C/C matrix in an oven at the temperature of 80 ℃ for 6h, and then hanging the C/C matrix in a chemical vapor deposition furnace;

step 2: the precursor HfCl is added₄And TaCl₅The powder is placed in an evaporation container according to the molar ratio of 1: 3-3: 1 and is placed in a low-temperature volatilization zone of a chemical vapor deposition furnace;

and step 3: vacuumizing the chemical vapor deposition furnace to 5Kpa, closing a valve and a vacuum pump, and maintaining the pressure for 1h to ensure that the pressure of the chemical vapor deposition furnace is not obviously changed and then introducing argon with the flow rate of 100-140 ml/min;

and 4, step 4: the heating is divided into two steps, wherein the first step is heating to 900 ℃ at the speed of 7 ℃/min, the second step is heating to 1100-1250 ℃ at the speed of 6 ℃/min, and the furnace chamber is heated to the preset temperature under the protection of argon;

and 5: when the deposition furnace reaches the deposition temperature, introducing hydrogen with the flow rate of 450-600ml/min and methane with the flow rate of 40-80ml/min into the deposition furnace after mixing the hydrogen and the argon in a gas mixing tank, and preserving the heat for 2-3h at the deposition temperature;

step 6: after the deposition is finished, straightly introducing hydrogen and methane, continuously introducing argon to clean and cool the furnace chamber, naturally cooling the furnace body to obtain the alloy with Ta_xHf_1-xC/C composite material of C solid solution coating.

2. The gradient evaporation mold based CVD-Ta of claim 1_xHf_1-xThe preparation method of the C solid solution coating is characterized by comprising the following steps: after the deposition is finished, increasing the flow of argon gas to 240mL/min, and charging the furnaceThe cavity is cleaned, and volatile and reflective impurities are pumped away in time.

3. The gradient evaporation mold based CVD-Ta of claim 1_xHf_1-xThe preparation method of the C solid solution coating is characterized by comprising the following steps: and when the C/C matrix is ground, the SiC sand paper of 600#, 800#, and 1000# is respectively adopted for grinding.

Background

CN106699233B reports two chemical vapor codeposited ZrBs₂-TaB₂The composite coating and the preparation method thereof adopt a Chemical Vapor Deposition (CVD) method to prepare the composite coating containing ZrB₂-TaB₂Co-deposited composite coating of solid solution (Zr (Ta) B₄) The other containing HfB₂-TaB₂Co-deposited composite coating of solid solution (Hf (Ta) B)₄) The two codeposited composite coatings are compared with single CVD-ZrB₂Coating or CVD-HfB₂Has higher oxidation resistance and ablation resistance.

Document 1 "Ghaffari S A, Faghhi-Sani M A, Golestani-Fard F, et al.Diffusion and solution formation between the binding partners of TaC, HfC and ZrC [ J]International Journal of Refractory Metals and Hard Materials,2013,41: 180-. The research finds the process of forming solid solution of TaC and HfC and the diffusion behavior of TaC in HfC. Thus, it is explained that HfC and TaC form Ta_xHf_1-xMode of ceramer solid solution.

Document 2 "Gabala O, Cook B A, Russell A M.reduced-temperature processing and consolidation of ultra-recovery Ta₄HfC₅[J]International Journal of Refractory Metals and Hard Materials,2013,41:293 Materials 299 "mixing TaC, HfC and WC powders by a hot press sintering process, subjecting to high energy milling and hot pressing, preparing Ta at relatively low 1500 ℃₄HfC₅And (3) sampling.

HfC and TaC are group IVB and VB transition metal carbides having the same sodium chloride face-centered cubic structure. The atomic radii of Hf (144 μm) and Ta (138 μm) are similar, maintaining a continuous solid solution throughout the composition interval above 927 ℃ and the formation of a solid solution not only reduces the diffusion activation energy at the grain boundaries to facilitate densification, but also has higher mechanical properties than the carbides that make up it, while having higher hardness and wear resistance. Apart from very high melting temperatures, also have excellent physical/mechanical properties, and therefore, Ta_xHf_1-xSolid solution of C ceramicsIs an excellent anti-ablation coating material. In the traditional ultrahigh-temperature ablation-resistant coating, an HfC coating of the ultrahigh-temperature carbide has better oxidation/ablation resistance compared with TaC and ZrC, but when the HfC coating is applied to the surface ablation-resistant coating of the C/C composite material, two problems exist: low resistance to scour and oxidation penetration and HfO₂The phase change causes the coating to expand in volume resulting in cracking of the layer. Therefore, the single coating layer for the ablation protection of the C/C composite material has its limitations, which are difficult to satisfy such as: the throat insert of the solid rocket engine, the thermal protection system of the supersonic aircraft and the like are in complicated and extreme ablation environments. Compared with the traditional binary ceramic modified system, the multi-element single-phase Ta_xHf_1-xThe C ceramic solid solution forms a single stable face-centered cubic structure, not only has the original excellent performances of TaC and HfC of each ceramic component, but also can form a continuous solid solution by an oxide generated at high temperature, has a more stable crystal structure, and the C/C composite material is isolated from high-temperature oxygen-containing atmosphere by the ceramic coating taking the C ceramic solid solution as a component, so that the C/C composite material can be stably used in an environment with the temperature of more than 2200 ℃.

Preparation of Ta at home and abroad_xHf_1-xThe C ceramic is mainly concentrated on the nano powder and the ceramic block, and is difficult to form a uniform coating on the surface of the C/C composite material, which greatly limits Ta_xHf_1-xThe application range of the C ceramic solid solution. Further, Ta is used by CVD_xHf_1-xThe precursors of the C solid solution have different evaporation temperatures and are difficult to reach the surface of the substrate at the same time to react to form Ta_xHf_1-xAnd C, coating with solid solution.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides CVD-Ta based on a gradient evaporation mold_xHf_1-xA preparation method of the C solid solution coating.

Technical scheme

CVD-Ta based on gradient evaporation mold_xHf_1-xThe preparation method of the C solid solution coating is characterized by comprising the following steps:

step 1: polishing the C/C matrix, ultrasonically cleaning the C/C matrix by deionized water for 30min, drying the C/C matrix in an oven at the temperature of 80 ℃ for 6h, and then hanging the C/C matrix in a chemical vapor deposition furnace;

step 2: the precursor HfCl is added₄And TaCl₅The powder is placed in an evaporation container according to the molar ratio of 1: 3-3: 1 and is placed in a low-temperature volatilization zone of a chemical vapor deposition furnace;

and step 3: vacuumizing the chemical vapor deposition furnace to 5Kpa, closing a valve and a vacuum pump, and maintaining the pressure for 1h to ensure that the pressure of the chemical vapor deposition furnace is not obviously changed and then introducing argon with the flow rate of 100-140 ml/min;

and 4, step 4: the heating is divided into two steps, wherein the first step is heating to 900 ℃ at the speed of 7 ℃/min, the second step is heating to 1100-1250 ℃ at the speed of 6 ℃/min, and the furnace chamber is heated to the preset temperature under the protection of argon;

and 5: when the deposition furnace reaches the deposition temperature, introducing hydrogen with the flow rate of 450-600ml/min and methane with the flow rate of 40-80ml/min into the deposition furnace after mixing the hydrogen and the argon in a gas mixing tank, and preserving the heat for 2-3h at the deposition temperature;

step 6: after the deposition is finished, straightly introducing hydrogen and methane, continuously introducing argon to clean and cool the furnace chamber, naturally cooling the furnace body to obtain the alloy with Ta_xHf_1-xC/C composite material of C solid solution coating.

And after the deposition is finished, increasing the flow of argon gas to 240mL/min, cleaning the furnace chamber, and pumping out the volatile and reflected impurities in time.

And when the C/C matrix is ground, the SiC sand paper of 600#, 800#, and 1000# is respectively adopted for grinding.

Advantageous effects

The invention provides CVD-Ta based on a gradient evaporation mold_xHf_1-xThe preparation method of the C solid solution coating comprises the following steps of suspending a C/C matrix in a chemical vapor deposition furnace; the precursor HfCl is added₄And TaCl₅Placing the powder in an evaporation container and in a low-temperature volatilization area of a chemical vapor deposition furnace; vacuumizing the chemical vapor deposition furnace to 5Kpa, closing a valve and a vacuum pump, and keeping pressure and introducing argon; two heating steps, the first heating step is carried out at the temperature of 7 ℃/minHeating to 900 ℃, heating to 1100-1250 ℃ at the speed of 6 ℃/min in the second step, and heating the furnace chamber to a preset temperature under the protection of argon; after the deposition is finished, straightly introducing hydrogen and methane, continuously introducing argon to clean and cool the furnace chamber, naturally cooling the furnace body to obtain the alloy with Ta_xHf_1-xC/C composite material of C solid solution coating.

1 the invention adopts a newly designed precursor evaporation mold to successfully prepare Ta_xHf_1-xAnd C, coating with solid solution. Due to the design of a new mold, the precursor with different volatilization points can be volatilized simultaneously in the graph 2, so that Ta is deposited on the C/C surface_xHf_1-xA solid solution of C becomes possible. In addition, a large number of experiments are required on the basis of the new mold. And the process parameters for depositing the solid solution with good crystallinity are obtained by adjusting the position of the precursor and the proportion of the precursor.

2 the preparation process is simple and easy to operate, has short preparation period, can be suitable for composite material members with complex shapes, and deepens Ta_xHf_1-xC solid solution ceramic and application thereof in the field of ultra-high temperature materials.

Drawings

FIG. 1: CVD-Ta_xHf_1-xC, preparing a process diagram of the solid solution coating; 1-gas supply system, 2-gas mixing tank, 3,4, 7, 8-gas valve, 5-program control table, 6-deposition furnace, 9-tail gas treatment tank, 10-electromagnetic valve, 11-vacuum pump

FIG. 2: a precursor volatilizing device in the furnace body; 17-TaCl₅Volatilization zone, 12-HfCl₄A volatilization zone, 13-a gas concentration zone, 14-a corundum crucible, 15-a bearing bracket and 16-a bearing rail of the bracket

FIG. 3: ta_xHf_1-xXRD pattern of C solid solution coating;

FIG. 4: ta_xHf_1-xElectron microscope photograph and element distribution map of the C solid solution coating;

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

example 1:

ta by CVD method_xHf_1-xA method for preparing a C solid solution coating, the method comprising the steps of: cutting a C/C matrix into square blocks with the size of 10mm multiplied by 10mm, polishing the surface of the matrix by sequentially adopting 600#, 800# and 1000# SiC abrasive paper, then placing the polished smooth sample in deionized water for ultrasonic cleaning for 30min, and finally placing the cleaned sample in an oven with the temperature of 80 ℃ for 6h to obtain the initial C/C sample. 38g and 12g of HfCl were weighed in accordance with the Hf: Ta molar ratio of 3:1, respectively₄、TaCl₅Placed in respective orbital graphite crucibles 14, and then the crucibles are combined with a support frame and an evaporation cover into a precursor evaporation system, as shown in fig. 2. And binding a sample by using a carbon rope, suspending the sample in a deposition furnace to enable the sample to be positioned in the center of the silicon-molybdenum rod heating body, then placing a precursor evaporation system in the furnace body 6, and covering a base. And starting the vacuum pump 11, then opening the air valve 7, vacuumizing the deposition furnace until the pressure in the furnace reaches about 5Kpa, sequentially closing the air valve and the vacuum pump, waiting for observing the pressure in the furnace, and if the pressure does not change obviously after 1 hour, proving that the air tightness is good. And setting a heating program 5 through a control system, simultaneously opening a vacuum pump 11 and a gas valve 7 to vacuumize the deposition furnace, simultaneously opening a gas control system, and introducing argon at 100ml/min to keep the pressure in the deposition furnace about 5Kpa all the time. When the deposition furnace reaches the deposition temperature, a gas control system is opened to respectively introduce hydrogen and methane at 450ml/min and 40ml/min so that the hydrogen and the methane are mixed with argon in a gas mixing tank 2 and are introduced into the furnace body through a gas inlet pipeline. And (4) after the deposition is finished, stopping conveying hydrogen and methane through the gas control system, continuously maintaining the conveying of argon, increasing the flow rate of the argon to 240ml/min, cleaning and cooling the furnace chamber, and cooling the furnace body according to the program. When the temperature is reduced to 350 ℃, the gas control system stops conveying argon gas, the gas valve 7 is closed, the gas valve 8 is opened, the vacuum pump 11 is closed, and the furnace body 6 is naturally cooled. After the furnace body is cooled to room temperature, the air valve 4 is opened to inflate, and then the furnace cover is opened to take out the furnace body with Ta_xHf_1-xC/C composite material of C ceramic solid solution coating.

Example 2:

ta by CVD method_xHf_1-xA process for the preparation of a C solid solution coating, the process comprisingThe following steps: cutting a C/C matrix into square blocks with the size of 10mm multiplied by 10mm, polishing the surface of the matrix by sequentially adopting 600#, 800# and 1000# SiC abrasive paper, then placing the polished smooth sample in deionized water for ultrasonic cleaning for 30min, and finally placing the cleaned sample in an oven with the temperature of 80 ℃ for 6h to obtain the initial C/C sample. 20g and 20g of HfCl were weighed in accordance with a 1:1 Hf: Ta molar ratio₄、TaCl₅Placed in respective orbital graphite crucibles 14, and then the crucibles are combined with a support frame and an evaporation cover into a precursor evaporation system, as shown in fig. 2. And binding a sample by using a carbon rope, suspending the sample in a deposition furnace to enable the sample to be positioned in the center of the silicon-molybdenum rod heating body, then placing a precursor evaporation system in the furnace body 6, and covering a base. And starting the vacuum pump 11, then opening the air valve 7, vacuumizing the deposition furnace until the pressure in the furnace reaches about 5Kpa, sequentially closing the air valve and the vacuum pump, waiting for observing the pressure in the furnace, and if the pressure does not change obviously after 1 hour, proving that the air tightness is good. And setting a heating program 5 through a control system, simultaneously opening a vacuum pump 11 and a gas valve 7 to vacuumize the deposition furnace, simultaneously opening a gas control system, and introducing argon at 100ml/min to keep the pressure in the deposition furnace about 5Kpa all the time. When the deposition furnace reaches the deposition temperature, a gas control system is opened to respectively introduce hydrogen and methane at 450ml/min and 40ml/min so that the hydrogen and the methane are mixed with argon in a gas mixing tank 2 and are introduced into the furnace body through a gas inlet pipeline. And (4) after the deposition is finished, stopping conveying hydrogen and methane through the gas control system, continuously maintaining the conveying of argon, increasing the flow rate of the argon to 240ml/min, cleaning and cooling the furnace chamber, and cooling the furnace body according to the program. When the temperature is reduced to 350 ℃, the gas control system stops conveying argon gas, the gas valve 7 is closed, the gas valve 8 is opened, the vacuum pump 11 is closed, and the furnace body 6 is naturally cooled. After the furnace body is cooled to room temperature, the air valve 4 is opened to inflate, and then the furnace cover is opened to take out the furnace body with Ta_xHf_1-xC/C composite material of C ceramic solid solution coating.

Example 3:

ta by CVD method_xHf_1-xA method for preparing a C solid solution coating, the method comprising the steps of: cutting C/C matrix into 10mm × 10mm × 10mm squareAnd block polishing the surface of the substrate by sequentially adopting 600#, 800# and 1000# SiC abrasive paper, placing the polished smooth sample in deionized water for ultrasonic cleaning for 30min, and finally placing the cleaned sample in an 80 ℃ oven for 6h to obtain the initial C/C sample. 12g and 38g of HfCl were weighed in accordance with a 1:1 Hf: Ta molar ratio, respectively₄、TaCl₅Placed in respective orbital graphite crucibles 14, and then the crucibles are combined with a support frame and an evaporation cover into a precursor evaporation system, as shown in fig. 2. And binding a sample by using a carbon rope, suspending the sample in a deposition furnace to enable the sample to be positioned in the center of the silicon-molybdenum rod heating body, then placing a precursor evaporation system in the furnace body 6, and covering a base. And starting the vacuum pump 11, then opening the air valve 7, vacuumizing the deposition furnace until the pressure in the furnace reaches about 5Kpa, sequentially closing the air valve and the vacuum pump, waiting for observing the pressure in the furnace, and if the pressure does not change obviously after 1 hour, proving that the air tightness is good. And setting a heating program 5 through a control system, simultaneously opening a vacuum pump 11 and a gas valve 7 to vacuumize the deposition furnace, simultaneously opening a gas control system, and introducing argon at 100ml/min to keep the pressure in the deposition furnace about 5Kpa all the time. When the deposition furnace reaches the deposition temperature, a gas control system is opened to respectively introduce hydrogen and methane at 450ml/min and 40ml/min so that the hydrogen and the methane are mixed with argon in a gas mixing tank 2 and are introduced into the furnace body through a gas inlet pipeline. And (4) after the deposition is finished, stopping conveying hydrogen and methane through the gas control system, continuously maintaining the conveying of argon, increasing the flow rate of the argon to 240ml/min, cleaning and cooling the furnace chamber, and cooling the furnace body according to the program. When the temperature is reduced to 350 ℃, the gas control system stops conveying argon gas, the gas valve 7 is closed, the gas valve 8 is opened, the vacuum pump 11 is closed, and the furnace body 6 is naturally cooled. After the furnace body is cooled to room temperature, the air valve 4 is opened to inflate, and then the furnace cover is opened to take out the furnace body with Ta_xHf_1-xC/C composite material of C ceramic solid solution coating.

And (4) after the deposition is finished, stopping conveying hydrogen and methane through the gas control system, continuously maintaining the conveying of argon, increasing the flow rate of the argon to 240ml/min, cleaning and cooling the furnace chamber, and cooling the furnace body according to the program. When the temperature is reduced to 350 ℃, the argon gas is stopped to be conveyed through the gas control system,and closing the air valves, opening the air valves and closing the vacuum pump in sequence to naturally cool the furnace body. After the furnace body is cooled to room temperature, the gas valve is opened to inflate the gas, and then the furnace cover is opened to take out the furnace body with Ta_xHf_1-xC/C composite material of C ceramic solid solution coating.