CN102503581A - Long-term high-temperature oxidation-resistant multi-element composite ceramic coating for carbon/carbon composite material and preparation and application methods thereof - Google Patents

Abstract

The invention provides a carbon/carbon composite material long-term high-temperature anti-oxidation multi-component composite ceramic coating and a preparation and application method. It is a composite coating on the surface of carbon/carbon composite materials, from the inside to the outside: SiC prepared by embedding method is used as the connection layer combined with the substrate, SiC prepared by chemical vapor deposition is used as the sealing layer, brush coating method and the SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ SiO ₅ ceramic layer prepared by the in-situ oxidation reaction method as an oxygen barrier layer, in which the SiC connection layer plays the role of connecting the substrate, and the sealing layer SiC layer plays the role of The function of sealing the defects of the inner layer, and the outermost ceramic coating plays the role of self-healing and oxygen barrier. It is firmly combined with the matrix, has no penetrating cracks, and can resist high temperature oxidation for a long time. It can be completely applied to the preparation of heat-resistant structural parts around the head and wings of hypersonic aircraft, as well as the preparation of aero-engine afterburner materials. .

Description

A carbon/carbon composite material long-term high-temperature anti-oxidation multi-component composite ceramic coating and its preparation and application method

technical field

The invention relates to the surface treatment of a carbon/carbon composite material, in particular to a carbon/carbon composite material used for indirect ablation heat-resistant structural parts around the head and wings of a hypersonic aircraft and a new type of aero-engine afterburner A long-time high-temperature oxidation-resistant multi-layer multi-component composite ceramic coating on the surface of a carbon/carbon composite material for a traditional superalloy material and its preparation and application method.

Background technique

Carbon/carbon composite material is a new type of high-temperature material with carbon fiber reinforced carbon matrix, which was accidentally discovered in 1958 by Chance-Vought Aviation in the United States. Carbon/carbon composite materials are entirely composed of a single carbon material, with high modulus, low density, small thermal expansion coefficient, ablation resistance, fatigue resistance, chemical inertness, high dimensional stability, especially at high temperatures, the strength increases with temperature With a series of advantages such as high fracture toughness and low creep, it is an ideal high-temperature structure and ablation-resistant material, and is widely used in the aerospace field. Especially applied to the heat-resistant structural parts of hypersonic aircraft, it has a series of advantages such as light weight and heat resistance. However, carbon/carbon composites are easily oxidized when used in a high-temperature aerobic environment, resulting in a significant reduction in their strength or even complete failure. Under aerobic conditions, the initial oxidation temperature of carbon/carbon composites is 370°C; when it is higher than 500°C, the carbon/carbon composites will be rapidly oxidized and destructively damaged. When a hypersonic vehicle flies at high speed, its fuselage often has to withstand a temperature of 1000°C-2200°C. For example, the leading edge or head of the wing must withstand the high-speed airflow of up to 2200°C, and the other indirect ablation parts of the wing and fuselage must also withstand temperatures as high as 1000°C-1500°C. In addition, hyper-vehicles must also meet the requirements of being able to be reused for a long time. Secondly, traditional aero-engine combustion chambers mostly use high-temperature alloy materials, and the outlet temperature of the combustion chamber reaches 1000°C-1500°C. If carbon/carbon composite materials are used instead of alloy materials, the weight of the engine will be greatly reduced, thereby improving the performance of the aircraft. Thrust-to-weight ratio. Therefore, it is of great significance to develop a new type of long-term high-temperature oxidation-resistant coated carbon/carbon composite material, so that it can be applied to the non-direct ablation parts of hypersonic aircraft wings and fuselage, as well as the combustion chamber of aircraft engines. .

Coating anti-oxidation composite ceramic coating on the surface of carbon/carbon composite material is an effective measure. The thermal expansion coefficient of SiC is close to that of carbon matrix, and it has good chemical compatibility. However, a single SiC coating has many defects (cracks and holes), and it is difficult to achieve long-term high-temperature oxidation resistance. Oxide ceramics can better prevent oxygen atoms from diffusing into the carbon matrix, but they will react with the carbon matrix at high temperatures. In addition, oxide ceramics often have a high thermal expansion coefficient, and the ceramic coating is prone to form penetrating cracks, and in severe cases, it will fall off. Therefore, it is of great significance to develop a new generation of ceramic composite coatings with good physical and chemical compatibility and good self-healing function.

Contents of the invention

The purpose of the present invention is to design and prepare a brand-new long-term high-temperature-resistant coating that is firmly bonded to the substrate and has no penetrating cracks for the situation that the ceramic coating on the surface of carbon/carbon composite materials is prone to defects such as cracks due to physical and chemical mismatches. Oxidized functional ceramic composite coatings, and methods for their preparation and application.

The purpose of the present invention is achieved in the following manner:

A method for preparing a carbon/carbon composite material long-term high-temperature oxidation-resistant multi-component composite ceramic coating,

It is prepared sequentially on the surface of carbon/carbon composite material from inside to outside: connection layer, sealing layer and ceramic coating, the connection layer is SiC layer prepared by embedding method, and the sealing layer is chemical vapor deposition method The prepared SiC layer, the ceramic coating is a SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ SiO ₅ ceramic layer prepared by a brush coating method and an in-situ oxidation reaction method.

The connection layer prepared by the embedding method uses Si powder, Al ₂ O ₃ powder, C powder, and SiC powder as raw materials. After ball milling and mixing, the carbon/carbon composite material is embedded and calcined at a high temperature. The obtained connection layer The thickness is about 30-50 μm.

Specific steps are as follows:

According to the mass ratio: Si 40-75%, Al ₂ O ₃ 2-13%, C 8-20%, SiC 10-38%, weigh Si powder, Al ₂ O ₃ powder, C powder, SiC powder, add Dispersant, ball milled and mixed thoroughly, taken out and dried before use; finally, put the carbon/carbon composite material in a graphite crucible, and completely bury it with the mixed powder, and then put the crucible into a high-temperature furnace, at 1700 Keep warm at ℃-2000℃ for 1.5-3h. The Si powder, SiC powder, C powder, and Al ₂ O ₃ powder are all preferably over 325 mesh.

The sealing layer prepared by the chemical vapor deposition method uses trichloromethylsilane as the SiC source, _H as the carrier gas, and Ar as the dilution gas, and deposits SiC on the surface of the carbon/carbon composite material embedded with the connecting layer at high temperature, The thickness of the resulting sealing layer is about 20-30 μm.

Specific steps are as follows:

The trichloromethylsilane is taken out from the raw material tank by bubbling method, _H2 and Ar are mixed in the gas mixing tank, and then passed into the chemical vapor deposition furnace body for reaction, after thermal decomposition, the residual gas is filtered, and the Vacuum pumping; H ₂ /trichloromethylsilane molar ratio = 6-12, Ar flow rate 150-280ml·min ^-1 , deposition pressure <1kPa; temperature 800°C-1280°C, holding time 3-12h.

The preparation of the SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ SiO ₅ ceramic layer by the brush coating method and in-situ oxidation reaction method is to mix SiC powder, YAG powder and YSZ powder according to the proportion, and add PVA The solution is prepared as a brushing slurry, and then the slurry is evenly brushed on the surface of the carbon/carbon composite material with a connecting layer and a sealing layer; the sample after brushing is sintered at a high temperature to obtain a coating; finally, it is applied at a high temperature It is pre-oxidized in the air, and the ceramic coating is prepared by in-situ oxidation reaction, and the thickness of the obtained ceramic coating is about 50-70 μm.

Specific steps are as follows:

Mix SiC powder, YAG powder and YSZ powder according to the mass ratio of 50-82:15-30:3-20, add PVA solution to prepare brush coating slurry, the volume ratio of powder and PVA solution is 0.5-0.8; PVA solution The concentration is 2wt%-8wt%; then the slurry is evenly painted on the surface of the carbon/carbon composite material with the connecting layer and the sealing layer; the sample after painting is dried and sintered at a high temperature to obtain a coating; finally, the It is pre-oxidized in the air at 1300°C-1500°C for 0.5-4h, and the ceramic coating is prepared by in-situ oxidation reaction.

The preparation of the YAG powder: prepare high-purity α-Al ₂ O ₃ powder and Y ₂ O ₃ powder with a molar ratio of 5:3, use a planetary high-energy ball mill, and use absolute ethanol as a medium to process the mixed powder For wet grinding, the ball-to-material ratio is 4-8, and the ball-milling time is 20-36h. After ball milling and calcining at 1400°C-1600°C for 2-3h, yttrium aluminum garnet (YAG) powder is obtained.

The YSZ powder is partially stabilized ZrO ₂ powder with yttrium oxide, which is a commercially available powder, with a particle size of 10-40 μm.

After the above slurry was evenly painted on the surface of the carbon/carbon composite material with the connection layer and the sealing layer, the sample was dried in a constant temperature oven at 100 °C for 4 h. The dried sample is placed in a vacuum carbon tube furnace, protected by argon, and sintered at a temperature of 1300°C-1500°C for 1-1.5h to obtain a coating.

The multi-component composite ceramic coating of the invention is applied to the preparation of indirect ablation heat-resistant structural parts around the head and wings of hypersonic aircraft, and the preparation of afterburner materials for aero-engines.

The method of the invention can prepare the anti-oxidation functional composite coating of the C/C composite material prepared by the chemical vapor phase infiltration and/or liquid phase impregnation process.

Advantages and positive effects of the invention

Compared with prior art, advantage and positive effect of the present invention are embodied in:

(1) The role of the embedding method in preparing the connecting layer. Oxide ceramic coatings have high thermal expansion coefficients and poor chemical compatibility with carbon substrates, which easily lead to rapid failure of protective coatings. The thermal expansion coefficient of SiC and carbon matrix is relatively close and the chemical compatibility is better. Using SiC as the inner layer can effectively alleviate the thermal expansion mismatch between the outer coating and the substrate. In addition, using the embedding method to prepare the connecting layer has the advantages of simple process and cost saving. The most important thing is that this method can prepare a C-SiC coating with a certain concentration gradient, which can greatly alleviate the CTE mismatch between the coating and the C/C composite material, so that the coating sample has excellent thermal shock resistance. performance.

(2) The role of the SiC intermediate sealing layer prepared by chemical vapor deposition. The basic principle of chemical vapor deposition is to form a coating on the surface of the substrate after a series of physical and chemical changes occur between the reactants at a certain temperature. The coating prepared by the method is compact and has high purity, and the structure, shape and composition of the coating can be controlled. The SiC layer prepared by this method can well fill the defects in the SiC connection layer, and then close the channel for rapid diffusion of oxygen to the substrate.

(3) Effects of brush coating method and in-situ oxidation reaction method on preparing SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ SiO ₅ ceramic coatings. The advantages of the brush coating method are that the method is simple, convenient, fast, and low in cost, and it is easy to prepare a pre-designed coating system. The chemical and physical compatibility of the coating can be improved and a series of silicate substances can be generated by the in-situ oxidation reaction method. Amorphous silica and aluminum silicate endow the coating with sealing function, self-healing function and better oxygen barrier function; while yttrium silicate and zirconium silicate with high melting point and similar thermal expansion coefficient to SiC have relatively Good high temperature resistance and thermal shock resistance, so that the entire coating forms a functional composite coating with good chemical and physical compatibility and high temperature resistance.

(4) Utilizing the main advantages of the above four methods to prepare a solid bond with the matrix, no penetrating cracks and interlayer cracks, and excellent thermal shock resistance, it can meet the long-term durability of carbon/carbon composites in an oxidizing environment. use.

Description of drawings

Fig. 1 is the macroscopic morphology (size is 20mm * 20mm * 5mm) of the coating after the composite coating sample is processed by different processes, respectively from left to right: carbon/carbon material matrix, only has the connecting layer sample of the present invention, Samples with connection layer and sealing layer of the present invention, samples with connection layer, sealing layer and ceramic coating of the present invention.

Fig. 2 is the scanning electron micrograph of the composite coating of the present invention before the in-situ oxidation reaction of the carbon/carbon composite material (a) the surface morphology of the outermost ceramic coating without the in-situ oxidation reaction (b) the cross-sectional appearance, and the A area represents For the connection layer, area B represents the middle sealing layer, and area C represents the outermost layer of YAG-SiC-YSZ ceramic coating without in-situ oxidation reaction layer.

Fig. 3 is the dense surface morphology of the composite coating carbon/carbon composite material sample of the present invention after in-situ oxidation reaction;

Fig. 4 is the scanning electron microscope photo (a) coating sample surface topography after oxidation 15h of composite coating carbon/carbon composite material sample of the present invention after isothermal oxidation experiment; (b) coating sample surface topography after oxidation 150h ; (c) Cross-sectional morphology of coating sample after oxidation for 150h

Fig. 5 is the oxidation weight loss curve of the composite coating sample of the present invention in static air at 1500°C. A is the oxidation curve of the carbon/carbon composite sample with SiC/SiC/SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ SiO ₅ composite ceramic coating; B is the carbon with SiC/SiC coating /Oxidation curves of carbon composite samples.

Detailed ways

The following examples are intended to further illustrate the present invention, rather than limit the present invention.

Example 1

First, cut the C/C composite material into a block sample of 20×20×5mm, grind the chamfer with 400# sandpaper, then finely grind it with 800# sandpaper, clean it with alcohol, and bake it at 120°C for 1-2 hours before use. ;

Next is the embedding process to prepare the SiC connection layer:

The mixed powder for embedding was prepared from Si powder, SiC powder, C powder and Al ₂ O ₃ powder. The mass ratio of the powder is: 50% Si-12% Al ₂ O ₃ -18% C-20% SiC. Weigh Si powder (pass 325 mesh), Al ₂ O ₃ powder (pass 325 mesh), C powder (pass 325 mesh), SiC powder (pass 325 mesh) and use ethanol as dispersant in the above ratio, and place them on planetary Mix well in a ball mill, take out and dry before use. Finally, put the C/C composite material in a graphite crucible and bury it completely with the mixed powder, then put the crucible into a high-temperature furnace, from room temperature to 1100°C, it takes 50min; 1.5h; heat preservation at 1800°C for 1.5h, protected by argon. This is followed by cooling, which takes 1 hour from 1800°C to 1200°C. Finally cool down with the furnace.

After the SiC connection layer is prepared, the powder adhering to the sample is cleaned with alcohol in an ultrasonic cleaner, and the sample is fully dried in an oven at 100°C. This is followed by the preparation of the SiC interlayer by chemical vapor deposition (CVD).

Using MTS (trichloromethylsilane) as the SiC source, _H2 as the carrier gas, and Ar as the diluent gas, trichloromethylsilane is taken out from the raw material tank by bubbling method, and _H2 is used as the diluent gas to adjust the _H2 /MTS ratio, various gases are mixed in the gas mixing tank, and then passed into the reaction zone of the furnace body from the bottom of the furnace body. After thermal decomposition, the residual gas is filtered and sucked away by a vacuum pump. The parameters are: H ₂ /MTS=8 (molar ratio), the Ar flow rate is 250ml·min ^-1 , and the deposition pressure is <1kPa. During the reaction process, it takes 30 minutes to heat from room temperature to 300°C, and it takes 1 hour to keep warm at 300°C; it takes 1.5 hours to heat from 300°C to 1200°C; 1.2h. Finally cool down with the furnace.

After the SiC intermediate layer is prepared, the outer coating of the ceramic system is prepared by the brush coating method and the in-situ oxidation reaction method.

Prepare high-purity α-Al ₂ O ₃ powder and Y ₂ O ₃ powder at a molar ratio of 5:3, and use a planetary high-energy ball mill to wet-grind the mixed powder with absolute ethanol as a medium, with a ball-to-material ratio of 4 : 1, ball milling time 32h. After ball milling, calcining, from room temperature to 300°C, it takes 30min, 300°C for 2h; from 300-1450°C, it takes 110min, 1450°C for 2h, and cools in the furnace to produce yttrium aluminum garnet (YAG) powder. SiC powder, YAG powder and yttrium oxide partially stabilized ZrO ₂ powder (YSZ) were weighed according to the ratio of 75:25:5. Add polyvinyl alcohol (PVA) (3wt%) solution to prepare brush coating slurry, and the volume ratio of powder and PVA is 1:2. The slurry was then evenly painted on the surface of the SiC sample with inner and middle layers. The painted samples were dried in a constant temperature oven at 100°C for 4 hours. The dried sample is placed in a vacuum carbon tube furnace, protected by argon, from room temperature to 300°C, it takes 60min, and 300°C for 1h; from 300-1450°C, it takes 110min, 1450°C for 1h; from 1450°C to 1450°C 600°C, it takes 80 minutes. Then cool down with the furnace. Finally, the above coating samples were pre-oxidized in air at 1500°C for 1-2 hours, and a very dense ceramic coating with good chemical and physical compatibility was prepared through in-situ oxidation reaction.

After 1500°C pre-oxidation, the composite coating sample has been subjected to 150h, 1500°C air oxidation resistance test and 10 thermal shock resistance tests. The coating remains intact without falling off or falling off, and its quality change is still in the weight gain. state, the weight gain rate is 1.77%, and the coating sample strength retention rate is 98.7%.

Example 2

The SiC connection layer was prepared by using 70% Si-4% Al ₂ O ₃ -12% C-14% SiC embedding material, and the parameters used were: H ₂ /MTS=10 (molar ratio), and the Ar flow rate was 200ml·min ^-1 , the deposition pressure is <1kPa, and the SiC sealing layer is prepared at 1100°C for 8h. SiC powder, YAG powder and yttrium oxide partially stabilized ZrO ₂ powder (YSZ) were used to prepare the ceramic outer coating according to the ratio of 60:30:10, and the rest of the steps were the same as above. After 150h, 1500°C air oxidation resistance test of the prepared coating sample, the coating remains intact without falling off, the oxidation weight gain rate is 0.35%, and the coating sample strength retention rate is 96.8%.

Example 3

The SiC connection layer was prepared by using 45% Si-10% Al ₂ O ₃ -10% C-35% SiC embedding material. The parameters used were: H ₂ /MTS=12 (molar ratio), and the Ar flow rate was 180ml·min ^-1 , deposition pressure < 1kPa, and heat preservation at 1000°C for 8h to prepare the SiC sealing layer. SiC powder, YAG powder and yttrium oxide partially stabilized ZrO ₂ powder (YSZ) were used to prepare the ceramic outer coating according to the ratio of 75:25:5, and the rest of the steps were the same as above. The prepared coating sample was subjected to the oxidation resistance test in air at 1500°C for 150 hours. The coating remained intact and did not fall off. The oxidation weight gain rate was 0.11%, and the strength retention rate of the coating sample was 95.7%.

Claims (10)

1. A method for preparing a carbon/carbon composite material for a long time high-temperature anti-oxidation multi-element composite ceramic coating, characterized in that, Preparation on the surface of the carbon/carbon composite material from inside to outside: connection layer, sealing layer and ceramic coating, the connection layer is SiC layer prepared by embedding method, and the sealing layer is prepared by chemical vapor deposition method SiC layer, the ceramic coating is a SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ SiO ₅ ceramic layer prepared by a brush coating method and an in-situ oxidation reaction method. 2. the preparation method of multi-element composite ceramic coating according to claim 1 is characterized in that, described embedding method prepares connection layer to be with Si powder, Al ₂ O ₃ powder, C powder, SiC powder is raw material, After ball milling and mixing, the carbon/carbon composite material is embedded and calcined at high temperature. 3. the preparation method of multi-element composite ceramic coating according to claim 2 is characterized in that, the concrete steps of described embedding method preparing connecting layer are as follows: According to the mass ratio: Si 40-75%, Al ₂ O ₃ 2-13%, C 8-20%, SiC 10-38%, weigh Si powder, Al ₂ O ₃ powder, C powder, SiC powder, add Dispersant, ball milled and mixed thoroughly, taken out and dried before use; finally, put the carbon/carbon composite material in a graphite crucible, and completely bury it with the mixed powder, and then put the crucible into a high-temperature furnace, at 1700 Keep warm at ℃-2000℃ for 1.5-3h. 4. The preparation method of multi-element composite ceramic coating according to claim 3, characterized in that, the Si powder, SiC powder, C powder and _Al2O3 powder all pass through ₃₂₅ mesh. 5. the preparation method of multielement composite ceramic coating according to claim 1 is characterized in that, described chemical vapor deposition method prepares sealing layer and is SiC source with trichloromethylsilane, H ₂ is carrier gas, and Ar is SiC is deposited on the surface of the carbon/carbon composite embedded with the bonding layer at high temperature with dilute gas. 6. multi-element composite ceramic coating according to claim 5, is characterized in that, the specific steps of described chemical vapor deposition method for sealing layer are as follows: Take trichloromethylsilane out of the raw material tank by bubbling method, mix _H2 and Ar in the gas mixing tank, and then pass it into the chemical vapor deposition furnace body for reaction, _H2 /trichloromethylsilane molar ratio=6 -12, the Ar flow rate is 150-280ml·min ^-1 , the deposition pressure is <1kPa; the temperature is 800°C-1280°C, and the holding time is 3-12h. 7. The preparation method of multi-element composite ceramic coating according to claim 1, characterized in that, SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ is prepared by the brushing method and in-situ oxidation reaction method The SiO ₅ ceramic layer is made by mixing SiC powder, YAG powder and YSZ powder according to the ratio, adding PVA solution to make a brushing slurry, and then evenly brushing the slurry on the carbon/carbon composite with a connecting layer and a sealing layer. The surface of the material; the painted sample is sintered at high temperature to obtain a coating; finally, it is pre-oxidized in high-temperature air to obtain a ceramic coating through an in-situ oxidation reaction. 8. The preparation method of multi-element composite ceramic coating according to claim 7, characterized in that, SiO ₂ -Y ₂ Si ₂ O ₇ -ZrSiO ₄ -Al ₂ is prepared by the brushing method and in-situ oxidation reaction method The specific steps of the SiO ₅ ceramic layer are as follows: Mix SiC powder, YAG powder and YSZ powder according to the mass ratio of 50-82:15-30:3-20, add PVA solution to prepare brush coating slurry, the volume ratio of powder and PVA solution is 0.5-0.8; PVA solution The concentration is 2wt%-8wt%; then the slurry is evenly painted on the surface of the carbon/carbon composite material with the connecting layer and the sealing layer; the sample after painting is dried and sintered at a high temperature to obtain a coating; finally, the It is pre-oxidized in the air at 1300°C-1500°C for 0.5-4h, and the ceramic coating is prepared by in-situ oxidation reaction. 9. A multi-component composite ceramic coating for long-term high-temperature oxidation resistance of carbon/carbon composite materials, characterized in that it is a multi-component composite ceramic coating prepared by the method described in any one of claims 1-8. 10. The application method of the multi-element composite ceramic coating as claimed in claim 9 is characterized in that, it is applied to the head around the preparation of hypersonic vehicles and the non-direct ablation heat-resistant structural parts of the wings, and the preparation of aero-engine afterburner room material.

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