CN102757260B - A method for repairing a ceramic matrix composite coating with a service temperature greater than or equal to 1400°C - Google Patents

Abstract

The invention relates to a method for repairing a coating of a ceramic matrix composite material whose service temperature is greater than or equal to 1400°C. 400 ℃ ~ 1400 ℃ oxide) as raw materials, by adding organosilane and solvent, prepared into a uniform slurry coated on the surface of the damaged coating of ceramic matrix composites, after low temperature curing, it can be well combined with the matrix and dense coating. This method effectively solves the problem of online repair of ceramic matrix composite coating damage. At the same time, the invention has short preparation period, simple process and good repeatability. The prepared coating system has been verified to effectively improve the oxidation resistance of the composite material in the temperature range of 1400 ° C or higher.

Description

A method for repairing a ceramic matrix composite coating with a service temperature greater than or equal to 1400°C

technical field

The invention relates to a method for repairing high-temperature coatings of ceramic matrix composite materials (use temperature greater than or equal to 1400°C), an online repair method for high-temperature coatings of ceramic matrix composite materials (use temperature greater than or equal to 1400°C), and a ceramic Low-temperature preparation technology for high-temperature coating of matrix composite materials (use temperature greater than or equal to 1400°C).

Background technique

In recent years, with the development of aerospace technology, space power has become the main force for implementing national security and military strategies in the 21st century. During the re-entry process of the spacecraft, due to the strong aerodynamic heating, the temperature of the nose cone and the leading edge of the wing can reach as high as 1650°C. The thermal protection system is one of the four key technologies of the spacecraft. The ceramic matrix composite material C/SiC has become the most promising heat-resistant structural integrated material for the second generation of aerospace vehicles. The components of thermal structural materials include nose cones, guide wings, wings and covers of space shuttles and missiles. board etc.

One of the main problems in the application of C/SiC composites is poor oxidation resistance at high temperatures. On the one hand, it is due to the low density of the C/SiC composite material; on the other hand, there are many tiny cracks on the SiC matrix due to the mismatch of the coefficient of thermal expansion (CTE) between the SiC matrix and the fibers. These tiny cracks will become flow channels for oxygen to corrode carbon fibers during the use of C/SiC composites. Therefore, it is necessary to develop a protection system for C/SiC composites to prevent the diffusion of oxygen to carbon fibers through cracks and open pores.

The main solution at this stage is to treat the surface of C/SiC material with anti-oxidation coating. The main coating processes include CVD method, sol-gel method, etc. However, the existing problem is that the surface coating of C/SiC composite materials will be damaged to a certain extent during the process of processing and equipment. The damage of the coating may cause the carbon fiber to be exposed to the gas environment, and the oxidation of the carbon fiber will cause the failure of the component and seriously affect the material. normal use.

For example, in the crash caused by the failure of Columbia's thermal protection system, Neil Ott, the chief engineer of NASA's "Columbia" external fuel tank project, said that the problem is that the process of laying foam on the outside of the fuel tank with a spray gun will cause damage. Gaps are left between the individual pieces of foam through which liquid hydrogen can penetrate. After the space shuttle took off, the hydrogen was heated and expanded, which eventually caused large pieces of foam to fall off. A piece of foam that came off the surface of the outer fuel tank hit a material called "enhanced carbon carbon" (that is, enhanced carbon-carbon heat shield) on the leading edge of the shuttle's left wing. When the space shuttle returned, it passed through the atmosphere and produced severe friction, causing the air with a temperature of 1400 degrees Celsius to melt the internal structure after rushing into the left wing, causing the wing and the body to melt, leading to tragedy. Therefore, any issues that may have potential safety hazards are worthy of our consideration and research.

The damage to the surface coating of the above-mentioned materials during the processing and preparation process is a very worthwhile research problem, and the re-preparation of the coating is not only a long period, but also costs a lot of money. In order to solve this problem, research on coating repair technology become a hotspot. However, there are few reports on the online repair technology of coatings in areas where high-temperature coatings (used at temperatures greater than or equal to 1400 °C) are used.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for repairing the coating of the ceramic matrix composite material whose service temperature is greater than or equal to 1400° C., which can realize online repair.

A method for repairing a ceramic matrix composite coating with a service temperature greater than or equal to 1400°C, characterized in that the repair steps are as follows:

Step 1: Use the mixed slurry of Si powder, refractory metal carbide, boride, oxide and organic silane binder as the coating material of the inner coating, and then brush the coating material on the damaged coating place, solidify it at a low temperature of 40~120°C to obtain an inner coating; the mass ratio of organosilane:Si powder:carbide of refractory metal is 1~3:4~7:1~3;

Step 2: Use the mixed slurry of refractory metal carbides, borides, oxides and silicone binders as the coating material for the high-temperature resistant coating, and then apply the high-temperature resistant coating on the inner coating. Curing it at a low temperature of 80-120°C to obtain a high-temperature resistant coating; the mass ratio of the organosilane:carbide of the refractory metal is 1-3:4-7;

Step 3: Use a mixed slurry of glass powder with a softening point of 400°C~1400°C and an organosilane binder as the outer coating glass coating material, and then brush the glass coating material on the high temperature resistant coating, It is cured at a low temperature of 40-120°C to obtain a glass coating and complete the repair of the coating; the mass ratio of the organosilane:glass powder is 1-3:4-7.

The curing in the step 1, step 2 and step 3 adopts infrared lamp, ultraviolet lamp irradiation or oven to make it cure.

The carbides of the refractory metals are replaced by borides or oxides.

The carbides of the refractory metals are: carbides of zirconium, aluminum, tungsten, molybdenum, tantalum, niobium, hafnium, chromium, vanadium and titanium.

The oxides are oxides with a melting point of 1000°C to 1400°C, including barium strontium aluminum silicon BSAS and five series of oxides of carbonate, sulfate, barium, aluminum or gallium.

The glass powder is: bismuth glass powder, lead glass powder, vanadium glass powder, phosphate glass powder or borosilicate glass powder.

The organosilane binder is: polyazinosilane, polysiloxane, polycarbosilane or polyboronazide silane.

The method for repairing the coating of the ceramic matrix composite material with a service temperature greater than or equal to 1400°C provided by the present invention is based on a reasonable coating structure design, and the coatings of each layer cooperate with each other to meet the use requirements of the corresponding temperature. In the coating system, the purpose of adding silicon powder to the inner coating (a mixed layer of silicon powder and carbides, borides, and oxides of some refractory metals) is to improve the bonding force between the coating and the substrate, adding refractory metals The purpose of carbide, boride and oxide is to improve the high temperature resistance of the inner coating; the middle coating (high temperature resistant layer) is mainly to improve the high temperature resistance of the coating system; the outer coating (glass layer) is mainly The liquid phase can be formed at the corresponding temperature. On the one hand, it can seal the cracks and holes in the substrate, on the other hand, it can self-heal the coating, and also improve the reliability of the coating system.

The advantages are:

(1) The preparation process of this method is simple, and the preparation can be completed by simple painting, without complicated heat treatment process: (2) This method has low requirements for preparation equipment, and basically does not require sophisticated equipment; (3) The preparation cycle of this method Short: (4) This method is low in cost: (5) This method provides an online repair technology for high-temperature coatings of ceramic matrix composites (use temperature greater than or equal to 1400°C). (6) This method can be adjusted according to different service temperature (use temperature greater than or equal to 1400 ℃) to meet the repair needs.

Description of drawings

Figure 1: SEM image of the coating surface after the coating sample of Example 1 was oxidized in air at 1500°C for 60 minutes;

Figure 2: SEM image of the coating surface after the coating sample of Example 1 was oxidized in air at 1500°C for 60 minutes;

Figure 3: SEM image of the coating cross-section after the coating sample of Example 1 was oxidized in air at 1500°C for 60 minutes;

Figure 4: EDS diagram of the coating section after the coating sample of Example 1 was oxidized in air at 1500°C for 60 minutes;

Figure 5: EDS diagram of the coating section after the coating sample of Example 1 was oxidized in air at 1500°C for 60 minutes;

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

Example 1:

Step 1: Ultrasonic cleaning the C/SiC composite material to be repaired with clean water for 30 minutes, then placed in an oven at 100°C for 30 minutes and dried for use;

Step 2: add 100% ethanol to silicon powder as a solvent, add 20% polyazoxane as a binder, add 20% aluminum hydroxide as a solid filler, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 3: Brush the uniformly mixed slurry on the surface of the substrate, and cure it for about 5-6 hours at 120°C (infrared lamps can be used on site), so as to obtain an inner coating;

Step 4: Add 100% ethanol to aluminum hydroxide powder as a solvent, add 20% polyazoxane as a binder, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 5: Brush the uniformly mixed slurry on the inner coating prepared in steps 2 and 3, and cure it completely at 120°C (infrared lamps can be used on site) for about 5-6 hours to obtain a high temperature resistant coating ;

Step 6: Add 100% ethanol as a solvent to borosilicate glass powder, add 20% polyazide as a binder, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 7: Brush the uniformly mixed slurry on the high-temperature-resistant coating prepared in steps 4 and 5, and cure it completely at 120°C (infrared lamps can be used on site) for about 5-6 hours to obtain a glass coating. layer;

Oxidation experiments were carried out on the prepared coated and uncoated samples. The results showed that the weight loss of the coated sample was only about 4.31% at 1500°C for 60 minutes, while the weight loss of the uncoated sample was 53.7%. From Figure 1 above, it can be seen that the surface of the coating is not very smooth, and there are some micro-cracks and holes, but through the high-magnification SEM image (Figure 2), it can be seen that these holes are not through holes, and there is a dense coating inside the holes.

Combining the cross-sectional morphology diagram (Figure 3) and the EDS diagram (Figure 4 and Figure 5), we can draw the following conclusions: after the oxidation test, the coating has two layers, the outer coating is denser than the inner coating, and the inner coating The combination with the substrate is not very good, but the substrate does not appear to be oxidized, and the coating does not peel off; the outer coating and the inner coating are well combined. Combined with the EDS analysis, we deduce that the outer coating is a borosilicate glass coating, and the inner layer is a combined layer of aluminum hydroxide layer and inner silicon layer. The thickness of both inner and outer coatings is about 50 μm. Combining the weight loss values with the microscopic appearance of the coated samples, we can see the protective effect of the coating system.

Example 2:

Step 1: Ultrasonic cleaning the C/SiC composite material to be repaired with clean water for 30 minutes, then placed in an oven at 100°C for 30 minutes and dried for use;

Step 2: Add 100% ethanol to silicon powder as a solvent, add 20% polycarbosilane as a binder, add 20% zirconium diboride as a solid filler, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 3: Brush the uniformly mixed slurry on the surface of the substrate, and cure it for about 10-12 hours at 80°C (infrared lamps can be used on site), so as to obtain the inner coating;

Step 4: Add 100% ethanol to zirconium diboride as a solvent, add 20% polycarbosilane as a binder, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 5: Brush the uniformly mixed slurry on the inner coating prepared in steps 2 and 3, and cure it completely at 80°C (infrared light can be used on site) for about 10-12 hours to obtain a high temperature resistant coating ;

Step 6: Add 100% ethanol to borosilicate glass powder as a solvent, add 20% polycarbosilane as a binder, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 7: Brush the uniformly mixed slurry on the high-temperature-resistant coating prepared in steps 4 and 5, and cure it completely at 80°C (infrared lamps can be used on site) for about 10-12 hours to obtain a glass coating. layer;

Oxidation experiments were carried out on the prepared coated and uncoated samples. The results showed that the weight loss of the coated sample was about 5.12% after oxidation at 1500°C for 60 minutes, while the weight loss of the uncoated sample was 53.7%.

Example 3:

Step 1: Ultrasonic cleaning the C/SiC composite material to be repaired with clean water for 30 minutes, then placed in an oven at 100°C for 30 minutes and dried for use;

Step 2: Add 100% ethanol to silicon powder as a solvent, 20% polyazide as a binder, and 20% boron carbide as a solid filler, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 3: Brush the uniformly mixed slurry on the surface of the substrate, and cure it for about 5-6 hours at 120°C (infrared lamps can be used on site), so as to obtain an inner coating;

Step 4: Add 100% ethanol to aluminum hydroxide powder as a solvent, add 20% polyazoxane as a binder, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 5: Brush the uniformly mixed slurry on the inner coating prepared in steps 2 and 3, and cure it completely at 120°C (infrared lamps can be used on site) for about 5-6 hours to obtain a high temperature resistant coating ;

Step 6: Add 100% ethanol to barium strontium aluminum silicon powder (BSAS) as a solvent, add 20% polyazide silane as a binder, and ball mill for about 30 minutes to obtain a uniformly mixed slurry;

Step 7: Brush the uniformly mixed slurry on the high-temperature-resistant coating prepared in steps 4 and 5, and cure it completely at 120°C (infrared lamps can be used on site) for about 5-6 hours to obtain a glass coating. layer;

Oxidation experiments were carried out on the prepared coated and uncoated samples. The results showed that the weight loss of the coated sample was about 4.91% after oxidation at 1500°C for 60 minutes, while the weight loss of the uncoated sample was 53.7%.

Claims (6)

1. A method for repairing a ceramic matrix composite material with a service temperature greater than or equal to 1400° C., characterized in that the repair steps are as follows: Step 1: Use the mixed slurry of Si powder and refractory metal carbide or refractory metal boride or refractory metal oxide and organosilane binder as the coating material of the inner coating, and then coat the The material is brushed on the damaged coating, and cured at a low temperature of 40-120°C to obtain an inner coating; the organosilane: Si powder: carbide of refractory metal or boride of refractory metal or refractory The mass ratio of metal oxides is 1～3:4～7:1～3; Step 2: Use refractory metal carbide or refractory metal boride or refractory metal oxide mixed slurry with organic silicon binder as the coating material for the high temperature resistant coating, and then apply the high temperature resistant coating Apply it on the inner coating and cure it at a low temperature of 80-120°C to obtain a high-temperature resistant coating; the organosilane: carbide of refractory metal or boride of refractory metal or oxide of refractory metal The mass ratio is 1～3:4～7; Step 3: Use a mixed slurry of glass powder with a softening point of 400°C to 1400°C and an organic silane binder as the outer coating glass coating material, and then brush the glass coating material on the high temperature resistant coating. It is cured at a low temperature of 40-120°C to obtain a glass coating and complete the repair of the coating; the mass ratio of the organosilane:glass powder is 1-3:4-7. 2. According to claim 1, the method for repairing the coating of the ceramic matrix composite material with a service temperature greater than or equal to 1400°C is characterized in that: the curing in the steps 1, 2 and 3 is irradiated by infrared lamps, ultraviolet lamps or Oven to cure. 3. The method for repairing the coating of the ceramic matrix composite material with a service temperature greater than or equal to 1400°C according to claim 1 or 2, characterized in that: the carbide of the refractory metal is replaced by boride or oxide. 3. According to claim 1 or 2, a method for repairing a ceramic matrix composite coating with a service temperature greater than or equal to 1400°C, characterized in that: the carbides of the refractory metal are: zirconium, aluminum, tungsten, molybdenum , tantalum, niobium, hafnium, chromium, vanadium and titanium carbides. 4. According to claim 1 or 2, the method for repairing the coating of the ceramic matrix composite material with a service temperature greater than or equal to 1400°C, characterized in that: the oxide is an oxide with a melting point of 1000°C to 1400°C, including barium strontium Aluminum silicon BSAS and five series of oxides of carbonate, sulfate, barium, aluminum or gallium. 5. According to claim 1 or 2, the method for repairing the coating of the ceramic matrix composite material with a service temperature greater than or equal to 1400° C. is characterized in that: the glass powder is: bismuth glass powder, lead glass powder, vanadium glass powder, phosphoric acid Salt glass powder or borosilicate glass powder. 6. According to claim 1 or 2, the method for repairing the coating of the ceramic matrix composite material with a service temperature greater than or equal to 1400 ° C, characterized in that: the organosilane binder is: polyazide silane, polysiloxane, poly Carbosilane or polyboronazide silane.

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