CN114538964B

CN114538964B - MoSi 2-rich high-temperature oxidation resistant coating on surface of SiC-Si coated carbon/carbon composite material and preparation method thereof

Info

Publication number: CN114538964B
Application number: CN202210192112.6A
Authority: CN
Inventors: 张雨雷; 李涛; 吕君帅; 朱肖飞; 孙佳; 李贺军
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2022-03-01
Filing date: 2022-03-01
Publication date: 2023-01-24
Anticipated expiration: 2042-03-01
Also published as: CN114538964A

Abstract

The invention relates to a SiC-Si coated carbon/carbon composite material with rich MoSi on the surface ₂ The preparation method comprises the steps of firstly preparing an Mo original coating on the surface of a sample by adopting a slurry brushing method and taking absolute ethyl alcohol, polyvinyl alcohol (PVA) binder and Mo powder as raw materials, and secondly obtaining Mo through heat treatment ₅ Si ₃ Porous layer, finally filling the pores with liquid silicon at high temperature and with Mo ₅ Si ₃ Reaction to prepare the product rich in MoSi ₂ The multiphase damascene coating of (1). The method has simple process and low cost, can adjust the thickness of the coating by brushing times, indirectly regulate and control the phase composition of the final coating by changing the proportion of Mo powder added into slurry, or promote the Mo layer to be converted into Mo by properly increasing the heat treatment temperature and prolonging the time ₅ Si ₃ The efficiency of the porous layer is adjusted, and the pore size of the porous layer is adjusted, so that the MoSi in the coating is optimized ₂ And Si phase distribution. Finally, the design MoSi is adopted ₂ The base anti-oxidation coating system and the method for improving the anti-oxidation performance of the base anti-oxidation coating system provide a simple and effective method.

Description

SiC-Si coated carbon/carbon composite material with rich MoSi on surface 2 High-temperature oxidation-resistant coating and preparation method thereof

Technical Field

The invention belongs to the surface of a carbon/carbon (C/C) composite material, relates to a high-temperature antioxidant coating and a preparation method thereof, and particularly relates to a SiC-Si coated carbon/carbon composite material surface rich in MoSi ₂ A high-temperature oxidation-resistant coating and a preparation method thereof.

Background

The carbon fiber reinforced carbon matrix (C/C) composite material is an advanced composite material which can still maintain the mechanical property at room temperature under the non-oxidizing atmosphere of ultra-high temperature (above 2000 ℃) because of a series of excellent properties such as low density, high specific strength, high specific modulus, low thermal expansion coefficient, thermal shock resistance, abrasion resistance and the like. The C/C composite material is used as a hot end component (such as a turbine disc, a combustion chamber, a guide blade and the like) of an aircraft engine used at high temperature for a long time, and has a very wide application prospect. However, C/C composites are highly susceptible to oxidation in high temperature oxidizing atmospheres and the rate of oxidation increases rapidly with increasing temperature, without protective measures, with catastrophic consequences for long term use of C/C composites in high temperature oxidizing environments.

Therefore, oxidation resistance becomes a key to practical application of the C/C composite material. At present, the high-temperature long-time oxidation resistance of the C/C composite material mainly adopts a coating technology, namely, a high-temperature oxidation resistant coating is prepared on the surface of the C/C composite material and used for isolating oxygen from being in direct contact with the C/C composite material, and the method is a very effective method for improving the oxidation resistance of the C/C composite material. Wherein, moSi ₂ Since ceramics are materials with excellent high-temperature oxidation resistance, moSi is currently used ₂ The base coating is one of the most deeply researched and developed anti-oxidation coating systems. On the one hand, siO generated by oxidation reaction in an aerobic environment ₂ The composite material has extremely low oxygen diffusion coefficient at high temperature, and can provide effective oxidation protection for the C/C composite material; in addition, siO increases with increasing oxidation temperature ₂ The viscosity of the coating is reduced, and the coating can fill in defects such as cracks in the coating at high temperature and serve as a sealing substance to prevent oxygen from invading. So far, moSi is prepared ₂ The common methods for ceramic coating mainly include embedding solid infiltration method, electrophoretic deposition method, plasma spraying method, etc. Among these production methods, pack cementation method is liable to cause silicification damage to C/C matrix due to high production temperature (1900-2100 ℃), and suffers from MoSi ₂ The effect of ceramic settling in molten silicon eventually makes MoSi difficult to form ₂ The ceramic content is large, and the distribution is uniform; moSi prepared by the latter two methods ₂ The coating is usually formed by only particle accumulation, so that the binding force and compactness of the matrix are poor. Finally, the prepared coating C/C composite material can not meet the requirement of long-term service at high temperature.

Document 1"Oxidation-protective and mechanical properties of SiC nanowire-proof Si-Mo-Cr composition coating for C/C compositions, chu Yan Hui, li He-Jun, fu Qian-Gang, shi Xiao-Hong, qi Le-Hua, wei Bing-bo.corosion Science 58 (2012) 315-320 "reports that a Si-Mo-Cr multiphase composite coating is prepared on the surface of a C/C composite material by using an embedding cementation technology, and simultaneously, the coating is toughened by using SiC nanowires. Firstly, preparing a reticular SiC nanowire layer on the surface of a C/C composite material by adopting a CVD (chemical vapor deposition) method; secondly, moSi is processed by adopting an embedding method ₂ The particles are introduced into the coating by a molten silicon infiltration reaction. Although the technology is simple and convenient to operate, the period is short; however, during pack cementation, moSi is preferred because of the comparison between SiC and Si ₂ The relative molecular mass is large, so that the coating is easy to biologically settle in molten silicon and finally MoSi is arranged above and below the coating ₂ The phase distribution is very different and uneven, and further MoSi in the coating is caused ₂ The excellent high-temperature oxidation resistance cannot be exhibited sufficiently and uniformly.

Document 2 of the Influence of the iodine con-centration on microstructure and oxidation resistance of SiB ₆ –MoSi ₂ coating deposited by pulse arc discharge deposition, huang Jian-Feng, zhang Yong-Liang, zhu Kong-Jun, cao Li-Yun, li Cui-Yan, zhou Lei, ouyang Hai-Bo, zhang Bo-Ye, hao Wei. Journal of Alloys and Compounds 633 (2015) 317-322' discloses a novel pulsed arc discharge method for depositing SiB on the surface of a SiC-coated C/C composite ₆ –MoSi ₂ Coating, firstly preparing a MoSi ₂ Suspending the charged solution, placing the sample on a cathode in the solution, placing the sample in a hydrothermal reaction kettle, and finally completing the coating deposition process through arc discharge. The results show that the SiB prepared by the method ₆ – MoSi ₂ The coating structure is loose, the weight loss of a sample reaches 1.98% after the isothermal oxidation protection is carried out for 168 hours in an air environment at 1500 ℃, and the SiC inner layer resists most of oxygen corrosion in the oxidation protection.

Document 3"Oxidation and Oxidation resistance Property of SiC/Si-Mo-Cr/MoSi ₂ Multi-layer coated C/C compositions, fu Qian-Gang, shann Yu-Cai, cao Cui-Wei, li He-Jun, li Ke-Zhi. Ceramics International 41 (2015) 4101-4107 "reported coating with SiC/Si-Mo using a supersonic plasma spray techniqueMoSi prepared on surface of C/C composite material with-Cr double-layer coating ₂ An outer coating layer, the method firstly applies MoSi ₂ Granulating the powder, and carrying molten MoSi by ultrahigh-temperature plasma flow ₂ Splashing to the surface of the sample, and preparing MoSi after cooling ₂ And (4) coating. Although the technology is simple and convenient to operate and high in efficiency, the coating is easy to crack due to stress concentration because the spraying temperature is high and the cooling time is short; in addition, the coating is formed by stacking particles, a large number of pores are reserved, and the particles are only bonded by mechanical extrusion, so the bonding force is poor. Resulting in poor high temperature oxidation protection of the coating.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a SiC-Si coated carbon/carbon composite material with the surface rich in MoSi ₂ The high-temperature oxidation-resistant coating and the preparation method thereof can better realize that the coating can protect the long-term service of the C/C composite material in a high-temperature aerobic environment, and simultaneously solve the problem of the existing MoSi preparation ₂ Problems with the coating process.

Technical scheme

SiC-Si coated carbon/carbon composite material with rich MoSi on surface ₂ The high-temperature oxidation-resistant coating is characterized in that: the inner layer is SiC-Si, and the outer layer is MoSi ₂ And the coating is filled with molten silicon; the surface of the inner SiC-Si layer connected with the outer layer is of a rough structure, so that the inner SiC-Si layer and the MoSi layer are connected ₂ The outer layer forms a mechanically interlocking interface and the inner and outer layers form a tightly bonded integral structure.

Preparing the SiC-Si coated carbon/carbon composite material with rich MoSi on the surface ₂ The method for preparing the high-temperature oxidation-resistant coating is characterized by comprising the following steps:

step 1: ultrasonically cleaning and drying the C/C composite material coated with the SiC-Si coating;

and 2, step: brushing the slurry solution on the SiC-Si coating and drying;

the slurry solution is a mixed solution of 54-59.5% of absolute ethyl alcohol, 0.5% of polyvinyl alcohol PVA and 40-45% of Mo powder in percentage by mass;

and 3, step 3: then placing the corundum crucible into a high-temperature tubular furnace for heat treatment under protective atmosphere, wherein the temperature of the furnace is increased to 1500-1600 ℃ at the temperature rising speed of 5 ℃/min during heat treatment, and the temperature is kept for 3-4 h; after the heat preservation is finished, cooling the tube furnace to the room temperature at the cooling speed of 10 ℃/min;

and 4, step 4: paving the mixed powder at the bottom of the graphite crucible, putting the material subjected to the heat treatment in the step 3 into the graphite crucible, and burying and filling the mixed powder;

the mixed powder comprises the following components: weighing silicon-carbon powder according to a mass ratio of 15-20;

and 5: placing the graphite crucible in a tube furnace, and repeating the heat treatment step in the step 4, wherein the heat preservation temperature is 1450-1500 ℃, the heat preservation time is 1-1.5 h, the temperature rise and fall rates are consistent, and finally the MoSi-rich material is obtained ₂ The multiphase damascene coating of (1).

And 3, after the corundum crucible is placed into the high-temperature tube furnace, locking and sealing the tube furnace, vacuumizing, maintaining vacuum for a period of time, checking and determining that the equipment is good in air tightness, and then slowly introducing argon to normal pressure.

And 3, cooling the tube furnace to room temperature at a cooling speed of 10 ℃/min, finally closing argon, disassembling the locking valve, taking out the crucible, and obtaining the material from the crucible.

Advantageous effects

The surface of the SiC-Si coated carbon/carbon composite material provided by the invention is rich in MoSi ₂ The method comprises the steps of firstly preparing an Mo original coating on the surface of a sample by adopting a slurry brushing method and taking absolute ethyl alcohol, polyvinyl alcohol (PVA) binder and Mo powder as raw materials, and secondly obtaining Mo through heat treatment ₅ Si ₃ Porous layer, finally filling the pores with liquid silicon at high temperature and with Mo ₅ Si ₃ Reaction to prepare the product rich in MoSi ₂ The multiphase damascene coating of (1). The method has simple process and low cost, can adjust the thickness of the coating by brushing times, indirectly regulate and control the phase composition of the final coating by changing the proportion of Mo powder added into slurry, orPromoting the conversion of Mo layer into Mo by properly raising the heat treatment temperature and prolonging the time ₅ Si ₃ The efficiency of the porous layer is adjusted, and the pore size of the porous layer is adjusted, so that the MoSi in the coating is optimized ₂ And Si phase distribution. Finally is designed MoSi ₂ The base anti-oxidation coating system and the method for improving the anti-oxidation performance of the base anti-oxidation coating system provide a simple and effective method.

The invention has the beneficial effects that: the method of coating slurry and heat treatment is adopted to effectively lead Mo powder to be fully sintered, and then free silicon in the SiC-Si inner layer enters the Mo layer and reacts with the Mo layer in the high-temperature heat treatment process to finally generate Mo ₅ Si ₃ (ii) a In addition, the rough structure of the SiC-Si inner layer surface can be combined with Mo ₅ Si ₃ The porous layer forms a mechanical interlocking interface to ensure that the porous layer and the porous layer have stable interface combination; finally, after the molten silicon is filled, the inner layer and the outer layer form a compact integral structure. Furthermore, compared with the preparation of MoSi by embedding solid infiltration, electrophoretic deposition, plasma spraying and the like ₂ The preparation method adopted by the invention has simple and convenient working procedures and low cost, and the obtained coating has compact structure and MoSi ₂ The content and the thickness of the coating are controllable.

Drawings

FIG. 1 shows Mo prepared according to an embodiment of the present invention ₅ Si ₃ XRD spectrum of porous layer and scanning electron microscope photo.

FIG. 2 shows the preparation of an embodiment of the present invention rich in MoSi ₂ XRD pattern and scanning electron micrograph of the multiphase damascene coating.

FIG. 3 is a graph showing the isothermal oxidation of 1700 ℃ air for samples of coatings prepared according to embodiments of the present invention.

FIG. 4 is a scanning electron micrograph of a coating layer prepared in the reverse example 1 of the present invention.

FIG. 5 is a scanning electron micrograph of a coating prepared in example 2 of the present invention.

FIG. 6 is a scanning electron micrograph of a coating layer prepared in the reverse example 3 of the present invention.

Detailed Description

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

example 1:

1. the coated SiC-Si coating C/C composite material with the size of 10mm multiplied by 10mm is cleaned by absolute ethyl alcohol ultrasonic for 2h (the power is set as 100W), and then is put into an oven to be dried for standby.

2. Anhydrous ethanol, PVA and Mo powders were weighed to prepare slurry solutions in mass percentages of 54.5%, 0.5% and 45%, respectively. The slurry solution was then stirred with a stirrer for 12 h.

3. And (3) uniformly coating the prepared C/C composite material sample coated with the SiC-Si coating in the step (1) on the surface of the sample by using the prepared slurry solution in the step (2), and then drying the sample in an oven for later use.

4. And (3) putting the sample dried by brushing in the step (3) into a high-temperature tube furnace for heat treatment under a protective atmosphere, wherein the specific flow is as follows:

(1) Putting the dried Mo layer-coated sample in a corundum crucible, and then putting the corundum crucible in a tubular furnace;

(2) Locking and sealing the tube furnace, vacuumizing, maintaining vacuum for a period of time, checking and determining that the equipment has good air tightness, and slowly introducing argon to normal pressure;

(3) Heating the furnace to 1500 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 4h;

(4) And (4) after the heat preservation is finished, cooling the tube furnace to room temperature at the cooling speed of 10 ℃/min, finally closing argon, disassembling the locking valve, taking out the crucible, and obtaining a sample for later use.

5. Preparing infiltration powder, weighing a certain mass of silicon-carbon powder according to a mass ratio of 20.

6. And (3) paving the bottom of the graphite crucible with the mixed powder in the step (5), putting the sample obtained after the heat treatment in the step (4) into the graphite crucible, and burying the sample with the mixed powder in the step (5).

7. Placing the graphite crucible in the step 6 in a tube furnace, repeating the heat treatment step in the step 4, wherein the heat preservation temperature is changed to 1450 ℃, the heat preservation time is changed to 1.5h, the temperature rise and fall rates are kept consistent, and finally obtaining the product rich in MoSi ₂ The multiphase damascene coating sample of (1).

The XRD pattern shown in figure 1a can determine Mo which is the main component phase of the prepared coating ₅ Si ₃ . FIG. 1b shows that Mo prepared on the surface of the C/C composite material sample coated with the SiC-Si coating in the embodiment ₅ Si ₃ A porous layer having a pore size of 1-10 μm and a thickness of 155 μm. It forms a mechanical interlocking interface with the inner layer, which is beneficial to improving the interface combination of the inner and outer coatings.

Example 2:

1. the SiC-Si coated C/C composite material with the size of 10mm multiplied by 10mm is ultrasonically cleaned for 2h (the power is set as 100W) by absolute ethyl alcohol, and the cleaned composite material is placed into an oven to be dried for standby.

2. Anhydrous ethanol, PVA and Mo powders were weighed to 59.5%, 0.5% and 40% by mass, respectively, to prepare slurry solutions. The slurry solution was then stirred with a stirrer for 12 h.

3. And (3) uniformly coating the prepared C/C composite material sample coated with the SiC-Si coating in the step (1) on the surface of the sample by using the slurry solution prepared in the step (2), and then drying the sample in an oven for later use.

(3) Heating the furnace to 1600 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 3h;

5. Preparing infiltration powder, weighing a certain mass of silicon-carbon powder according to a mass ratio of 15 to 1, performing ball milling to fully mix the silicon-carbon powder, and screening out mixed powder and drying the mixed powder for later use.

6. And (3) paving the bottom of the graphite crucible with the mixed powder in the step 5, putting the sample obtained after the heat treatment in the step 4 into the graphite crucible, and burying the sample with the mixed powder in the step 5.

7. Placing the graphite crucible in the step 6 in a tube furnace, repeating the heat treatment step in the step 4, wherein the heat preservation temperature is changed to 1500 ℃, the heat preservation time is changed to 1h, the temperature rise and fall rates are kept consistent, and finally obtaining the product rich in MoSi ₂ The multiphase damascene coated sample of (1).

From the XRD pattern shown in FIG. 2a, the main composition phase of the prepared coating can be determined to be MoSi ₂ And Si. FIG. 2b shows that the MoSi-rich sample prepared by the embodiment on the surface of the C/C composite material sample coated with the SiC-Si coating ₂ Multiphase mosaic coating, and the coating thickness is 160 mu m. After the liquid silicon is infiltrated, the inner layer and the outer layer are fused into a whole, and no obvious interface is observed. In addition, FIG. 3 is a graph of the change of the isothermal oxidation mass of a coating sample in air at 1700 ℃, and the result shows that the coating can protect the C/C composite material in air at 1700 ℃ for more than 200h.

Example reverse example 1:

1. the SiC-Si coating C/C composite material with the size of 10mm multiplied by 10mm is ultrasonically cleaned for 2h (the power is set as 100W) by absolute ethyl alcohol, and is put into an oven to be dried for standby.

4. And (4) putting the sample which is coated and dried in the step (3) into a high-temperature tube furnace for heat treatment under a protective atmosphere, wherein the specific flow is as follows:

(2) Locking and sealing the tube furnace, vacuumizing, maintaining the vacuum for a period of time, checking and determining that the equipment has good air tightness, and slowly introducing argon to normal pressure;

5. Preparing infiltration powder, weighing a certain mass of silicon-carbon powder according to a mass ratio of 10.

7. And (4) placing the graphite crucible in the step (6) in a tube furnace, repeating the heat treatment step in the step (4), wherein the heat preservation temperature is changed to 1500 ℃, the heat preservation time is changed to 1h, the temperature rise and fall rates are kept consistent, and finally obtaining a coating sample for characterization observation.

From the scanning electron micrograph of the opposite example of FIG. 4, in which the coating was prepared on the surface of the SiC-Si coated C/C composite sample, it was found that the coating had some pores, since the decrease of the content of silicon powder in the infiltration powder affected the Mo in the molten silicon ₅ Si ₃ The filling effect of the holes in the porous layer. In addition, if the pure silicon powder is subjected to pack infiltration and sealing, the sample can be completely bonded in the solidified block of the liquid silicon, and the sampling cannot be smoothly completed. It is important to maintain a proper proportion of silicon powder in the infiltration mixture.

Example reverse example 2:

5. Preparing the infiltration powder, and weighing NH with a certain mass ratio of 15 ₃ F、Al ₂ O ₃ And the Si powder is ball-milled in a dry environment to be fully mixed for standby.

7. And (4) placing the graphite crucible in the 6 into a tubular furnace, and repeating the heat treatment step in the 4, wherein the heat preservation temperature is changed to 1250 ℃, the heat preservation time is changed to 5 hours, and the temperature rising and falling speed is kept consistent. The step refers to the reported halide-assisted siliconizing method to try to prepare MoSi ₂ And (4) coating.

From the observation of a scanning electron micrograph of the opposite example in FIG. 5, in which the coating is prepared on the surface of the C/C composite material sample coated with the SiC-Si coating, it is found that the coating still has a porous structure, and Mo cannot be treated by the halide-assisted siliconizing method ₅ Si ₃ The porous layer is effectively sealed.

Example reverse 3:

(3) Heating the furnace to 1600 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 3 hours;

(4) And after the heat preservation is finished, cooling the tube furnace to room temperature at the cooling speed of 10 ℃/min, finally closing argon, disassembling the locking valve, taking out the crucible, and obtaining a sample for later use.

5. Preparing infiltration powder, and weighing Si, C and Al according to a mass ratio of 5 ₂ O ₃ Ball milling the powder to mix completely, sieving out mixed powder and stoving.

7. And (4) placing the graphite crucible in the step (6) in a tube furnace, and repeating the heat treatment step in the step (4), wherein the heat preservation temperature is changed to 2100 ℃, the heat preservation time is changed to 2 hours, and the temperature rising and reducing speed is kept consistent. The step refers to Mo in the reported embedding method ₅ Si ₃ And carrying out hole sealing treatment on the porous layer.

From FIG. 6 the example is reversed and coated with SiC-SiScanning electron micrograph of coating prepared on the surface of C/C composite material sample of the layer can find that MoSi is compact in coating structure ₂ The proportion of phase (white area) content is obviously reduced, so that the high-temperature embedding method for hole sealing can not prepare the material rich in MoSi ₂ A multiphase damascene coating.

In all examples, the absolute ethyl alcohol is analytically pure (mass percentage content is more than or equal to 99.8%), the Si powder has the purity of 99.5% and the granularity of 500 meshes, the C powder has the purity of 99.5% and the granularity of 500 meshes, and Al is added ₂ O ₃ The purity of the powder is 99.5%, the granularity is 500 meshes, the purity of the Mo powder is 99.5%, and the grain diameter is 1-5 μm.

Claims

1. Preparation of SiC-Si coated carbon/carbon composite material with rich MoSi on surface ₂ The method for high-temperature oxidation-resistant coating is characterized by comprising the following steps: the inner layer is SiC-Si, and the outer layer is MoSi ₂ And the coating is filled with molten silicon; the surface of the inner SiC-Si layer connected with the outer layer is a rough structure, so that the inner SiC-Si layer and the MoSi layer are connected ₂ The outer layer forms a mechanical interlocking interface, and the inner layer and the outer layer form a tightly combined integral structure; the coating was prepared by the following steps:

step 2: coating the SiC-Si coating with slurry solution and drying;

and step 3: then placing the mixture into a corundum crucible, placing the corundum crucible into a high-temperature tube furnace for heat treatment under protective atmosphere, and heating the furnace to 1500-1600 ℃ at the heating speed of 5 ℃/min and preserving heat for 3-4 h during the heat treatment; after the heat preservation is finished, cooling the tube furnace to the room temperature at the cooling speed of 10 ℃/min;

the mixed powder comprises the following components: weighing silicon-carbon powder according to the mass ratio of 15 to 20, ball-milling, sieving out mixed powder and drying;

and 5: putting the graphite crucible into a tube furnace, and repeating the heat treatment step in the step 4, wherein the heat preservation temperature is 1450-1500 ℃, the heat preservation time is 1-1.5h, the temperature increase and decrease rate is kept consistent, and finally the product rich in MoSi is obtained ₂ The multiphase damascene coating of (1).

2. The method of claim 1, wherein: and 3, after the corundum crucible is placed into the high-temperature tube furnace, locking and sealing the tube furnace, vacuumizing, maintaining vacuum for a period of time, checking and determining that the equipment is good in air tightness, and then slowly introducing argon to normal pressure.

3. The method of claim 1, wherein: and 3, cooling the tubular furnace to room temperature at the cooling speed of 10 ℃/min, finally closing argon, disassembling a locking valve, taking out the crucible, and obtaining the material from the crucible.