CN101318835A - Oxidation protection processing method of carbon/carbon composite aviation brake parts - Google Patents

Abstract

The invention discloses an oxidation protection processing method for a carbon/carbon composite aviation brake part, which relates to a surface processing technology for metal products, and in particular to the oxidation protection processing technology field for aviation brake parts. First, the innermost layer of the brake part is passivated by using the surface oxidation activity of the carbon/carbon composite material, and then an air blocking treatment is performed outside the passivation layer, and a matching treatment of the thermal expansion coefficient between the coating and the substrate is performed on the outermost layer. The present invention uses a multi-layer coating method to comprehensively utilize various excellent properties of the material to achieve a comprehensive and optimal anti-oxidation effect.

Description

Oxidation protection processing method of carbon/carbon composite aviation brake parts

technical field

The invention relates to a surface processing technology of metal products, in particular to the technical field of oxidation protection processing of aviation brake parts.

Background technique

Carbon/carbon composite material is a kind of material that begins to oxidize slowly above 350°C. The use of this type of material under high temperature conditions must take oxidation protection measures. As an application of aviation brake materials, during the landing process of the aircraft, all aircraft 60% to 80% of the kinetic energy is converted into thermal energy in a very short time (20 seconds to 50 seconds), causing the temperature of the carbon/carbon composite brake parts to rise sharply. Depending on the energy and the design of the heat store, the temperature range can reach 500°C-120°C. If the carbon/carbon composite material is oxidized, its mechanical properties will decline rapidly, and all keyway transmission torque parts may fail, resulting in a landing accident. In addition, oxidation will also greatly change the friction and wear properties of carbon/carbon composite materials, which will greatly reduce the controllability of the aircraft during braking. For this reason, the quality of oxidation protection technology directly determines whether carbon/carbon composite materials can be used to manufacture aviation brake parts.

Because the method of matrix modification is easy to change the friction and wear properties of carbon/carbon composite materials that are not easy to control, which will have a negative impact on the braking performance of the aircraft, so the current common practice is to use non-friction surface coating Anti-oxidation of carbon/carbon composite aerospace brake parts is carried out by applying an oxidation protective coating. Anti-oxidation coatings are divided into two categories: surface covering coatings and surface modification coatings. The service temperature of surface-modified coatings is generally low, usually below 800°C. Such coatings generally have a long service life and are not easily damaged. Commonly known as low temperature long life coating. Another type of surface covering coating, this type of coating mainly covers the surface of the carbon/carbon composite material with a dense film, and the coating plays the role of isolating the air. This type of coating generally has a shorter service life, but a higher service temperature. The maximum applicable temperature can reach above 2000°C, but the time is short, and generally the long-term use does not exceed 1000°C. The main reason is that the thermal expansion coefficient of this kind of coating is generally different from that of carbon/carbon composite materials, and the bonding performance of carbon/carbon composite materials with other general materials is poor, and it will be damaged under repeated thermal shock conditions. A large number of microcracks appear to render the coating ineffective. This results in high temperature oxidation of carbon/carbon composites.

Contents of the invention

The purpose of the present invention is to invent a carbon/carbon composite aviation brake component oxidation protection processing method that can overcome the above-mentioned technical defects.

The technical scheme of the present invention is: first passivate the innermost layer of the brake parts by using carbon/carbon composite material surface oxidation activity, then perform air blocking treatment outside the passivation layer, and conduct the coating and substrate in the outermost layer. The matching treatment of the coefficient of thermal expansion.

The present invention comprehensively considers (1) the combination of the carbon/carbon composite material and different materials and (2) the influence of different materials on the oxidation activity of the surface of the carbon/carbon composite material. By adopting the method of multi-layer coating, various excellent properties of materials are comprehensively utilized to achieve the comprehensive and optimal anti-oxidation effect.

The three-layer coating method of aerospace brake parts with different functional gradients is carried out three times, and finally three different functional gradients are formed on the surface of the workpiece. The characteristics of the three layers of the coating are different. The first layer is mainly the surface modification of carbon/carbon composite materials, and the combination of silicon carbon and boron and boron carbide and carbon materials is used to form a surface modification layer + bonding transition layer. Therefore, the main components of the first layer are boron, silicon and their carbides and a small amount of oxides. The second layer is mainly the blocking layer, and the group plays the role of isolating the air. Therefore, the main component of this layer is mainly ceramic components. Blocking can be divided into physical blocking and chemical blocking. The main function of the third layer is a self-healing layer, mainly to overcome a large number of microcracks generated under thermal shock conditions. Due to the obvious difference in thermal expansion coefficient between the coating and the carbon/carbon composite material matrix, especially the thermal expansion coefficient of the carbon/carbon composite material is not the same in different directions, it is inevitable to produce a large thermal shock during the thermal shock process. The stress caused by the deformation difference of the coating will cause a large number of invisible micro-cracks in the coating, and the generation of such micro-cracks will easily lead to the failure of the coating's oxidation resistance. The self-healing ability of the third layer of coating is extremely important.

Wherein, the surface oxidation activity of the carbon/carbon composite material for passivation is to use the coating slurry prepared by mixing the powder A, solvent A and binder to brush on the non-friction surface of the carbon/carbon composite material brake. The surface is dried and cured at 220°C, then taken out, and then reacted and sintered at 1600°C under vacuum.

The powder A is composed of SiC, BC, B ₂ O ₃ , Si and B; the solvent A is composed of toluene and n-butanol; the binder includes silicone resin. The weight ratio of the powder A, solvent A and binder is 5:12:3.

The percentages of SiC, BC, B ₂ O ₃ , Si and B in the powder A to the total weight of the powder A are 10-20%, 10-30%, 8-20%, 4-9% and 10-20%, respectively. 20%; The volume ratio of toluene and n-butanol in the solvent A is 7:3.

The adhesive may also include a curing agent, and the weight ratio of the silicone resin to the curing agent is 20:1.

In the present invention, the air blocking treatment is applied to the passivation layer of carbon/carbon composite aviation brake parts after heating and stirring the coating material prepared by mixing powder B, solvent B and phosphoric acid ester for 40 minutes. In addition, it is dried and cured at 240°C, and finally heat-treated at 900°C;

The powder B is composed of SiC, BC, B ₂ O ₃ , ZrO ₂ , Al, Al ₂ O ₃ , Si, B and CeO ₂ ; the solvent B is composed of silica sol and aluminum dihydrogen phosphate. The weight ratio of powder B, solvent B and phosphoric acid ester is: 7:12:1.

Wherein, the percentages of SiC, BC, B ₂ O ₃ , ZrO ₂ , Al, Al ₂ O ₃ , Si, B and CeO ₂ in the powder B to the total weight of the powder B are 20-40%, 2- 5%, 10-30%, 3-12%, 2-26%, 3-17%, 12-17%, 20-40% and 0.5-10%; silica sol and aluminum dihydrogen phosphate in the solvent B The mass ratio is 9:1.

According to the matching treatment in the present invention, the outermost layer of the coating material prepared by mixing powder C, solvent C and binder is brushed, dried and cured at 240°C, and then heat-treated at 900°C;

The powder C is composed of SiC, BC, _B2O3 , _ZrO2 , Al, _Al2O3 , Si, B and _{CeO2 ;} the solvent C is _composed of xylene, acetone and n-butanol; the viscous The binder includes silicone resin. The weight ratio of powder C, solvent C and binder is: 5:14:1.

Wherein, the percentages of SiC, BC, B ₂ O ₃ , ZrO ₂ , Al, Al ₂ O ₃ , Si, B and CeO ₂ in the powder C to the total weight of the powder C are 20-40%, 3- 5%, 20-40%, 2-5%, 2-26%, 6-30%, 20-40%, 20-40% and 0.5-10%; xylene, acetone and n-butanol in the solvent C The volume ratio is 4:5:1.

The adhesive may also include a curing agent, and the weight ratio of the silicone resin to the curing agent is 20:1.

In addition, the average particle size of each powder described in the present invention is not greater than 38 microns. The purpose is to control the uniform distribution of various components in the coating, so that the formed coating is uniform during high temperature treatment.

Detailed ways

1. Coating preparation:

1. Preparation of each coating powder:

The strength of each coating powder should be less than 3838 μm, and it should be stored under absolute dry conditions after being dried at 120°C. See the table below for the ratio:

Element SiC BC B ₂ O _{3 ZrO2} Al Al ₂ O ₃ Si B _CeO2 Powder A 10-20 10-30 8-20 - - - 4-9 10-20 - Powder B 20-40 2-5 10-30 3-12 2-26 3-17 12-17 20-40 0.5-10 Powder C 20-40 3-5 20-40 2-5 2-26 6-30 20-40 20-40 0.5-10

Note: The average particle size of each powder raw material is not greater than 38 microns.

2. Solvent preparation

Solvent A volume ratio: toluene: n-butanol = 7:3

Solvent B mass ratio: silica sol: aluminum dihydrogen phosphate = 9:1

Solvent C volume ratio: xylene: acetone: n-butanol = 4:5:1

3. Binder mass ratio: silicone resin: curing agent = 20:1.

4. The surfactant is phosphoric acid ester.

5. Slurry preparation

(1) Dissolve powder A with solvent A, add binder, and mix uniformly to prepare coating slurry A.

Wherein, the weight ratio of powder A, solvent A and binder is: 5:12:3.

(2) Dissolve powder B in solvent B, add phosphoric acid ester, and mix uniformly to prepare coating slurry B.

Wherein, the weight ratio of powder B, solvent B and phosphoric acid ester is: 7:12:1.

(3) Dissolving powder C with solvent C, adding binder, and mixing uniformly to prepare coating slurry C.

Wherein, the weight ratio of powder C, solvent C and binder is: 5:14:1.

2. Processing technology:

1. Passivation:

(1) Clean the surface of the carbon/carbon composite aviation brake parts by ultrasonic cleaning and dry them for later use.

(2) Brush the coating slurry A on the non-friction surface of the carbon/carbon composite brake part, dry and solidify at 220°C for 2 hours, and then take it out.

(3) Reaction sintering is carried out under vacuum conditions at 1600° C., and the heat preservation is carried out for 1 hour to form a passivation layer.

In the process of preparing the coating slurry, adjust the ratio of silicone and solvent according to the required coating thickness. The commonly used thickness value is 1.4 liters of solvent per 100 grams of powder when the thickness is 8 microns. During the coating process, when the volatilization of the solvent occurs, an appropriate amount of solvent can be added at any time according to the situation on site, and the initial viscosity can be adjusted.

2. Air blocking treatment:

(1) Heat the coating slurry B on a heating agitator and stir it for 40 minutes at the same time, and then set it aside for later use. The holding temperature is 80°C. And control the viscosity control value of the coating slurry B to be 6 seconds to 10 seconds at normal temperature.

(2) Before coating, carbon/carbon composite aerospace brake parts need to be preheated to 120°C.

(3) Outside the passivation layer, after coating with coating slurry B, dry and cure at 240°C for 2 hours, then take it out.

(4) Heat treatment at 900° C. for 1 hour under vacuum conditions to form an air blocking layer.

3. Matching treatment of thermal expansion coefficient between coating and substrate:

(1) Heat the coating slurry C on a heating agitator and stir it for 40 minutes at the same time, and then set it aside for later use. The holding temperature is 80°C.

(2) Before coating, carbon/carbon composite aerospace brake parts need to be preheated to 120°C.

(3) On the outside of the air-blocking layer, after coating with coating slurry C, dry and cure at 240°C for 2 hours, then take it out.

(4) Heat treatment at 900° C. for 1 hour under vacuum conditions to form the outermost layer, that is, the thermal expansion coefficient matching treatment layer between the coating and the substrate.

4. Note:

All the drying and curing are carried out under normal pressure, and the oven is used for drying, and the oven is in a semi-open state.

Claims (10)

1. The oxidation protection processing method of carbon/carbon composite aviation brake parts is characterized in that the innermost layer of the brake parts is first passivated by the surface oxidation activity of carbon/carbon composite materials, and then the air is blocked outside the passivation layer Treatment, the matching treatment of the coefficient of thermal expansion between the coating and the substrate is performed on the outermost layer. 2. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 1, characterized in that the surface oxidation activity of the carbon/carbon composite material for passivation is the use of powder A, solvent A and bonding The coating slurry prepared after mixing the additives is brushed on the non-friction surface of the carbon/carbon composite brake parts, dried and cured at 220°C, taken out, and then reacted and sintered at 1600°C under vacuum. The powder A is composed of SiC, BC, B ₂ O ₃ , Si and B; Described solvent A is made up of toluene and n-butanol; The binder includes silicone resin; The weight ratio of the powder A, solvent A and binder is 5:12:3. 3. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 2, characterized in that: The percentages of SiC, BC, B ₂ O ₃ , Si and B in the powder A to the total weight of the powder A are 10-20%, 10-30%, 8-20%, 4-9% and 10-20%, respectively. 20%; The volume ratio of toluene and n-butanol in the solvent A is 7:3. 4. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 2 or 3, characterized in that the binder also includes a curing agent, and the weight ratio of the silicone resin to the curing agent is 20:1 . 5. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 1, characterized in that the air blocking treatment is a coating material prepared by mixing powder B, solvent B and phosphoric acid ester After heating and stirring for 40 minutes, apply it on the passivation layer of the carbon/carbon composite aviation brake, dry and solidify at 240°C, and finally heat-treat at 900°C; The _powder B is composed of SiC, BC, _B2O3 , _ZrO2 , Al, _Al2O3 , Si, B and _{CeO2 ;} The solvent B is composed of silica sol and aluminum dihydrogen phosphate; The weight ratio of the powder B, solvent B and phosphoric acid ester is: 7:12:1. 6. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 5, characterized in that: The percentages of SiC, BC, B ₂ O ₃ , ZrO ₂ , Al, Al ₂ O ₃ , Si, B and CeO ₂ in the powder B to the total weight of the powder B are 20-40%, 2-5% respectively , 10-30%, 3-12%, 2-26%, 3-17%, 12-17%, 20-40% and 0.5-10%; The mass ratio of silica sol and aluminum dihydrogen phosphate in the solvent B is 9:1. 7. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 1, characterized in that the matching treatment is brushed with a coating material prepared by mixing powder C, solvent C and binder The outermost layer is heat-treated at 900°C after drying and curing at 240°C; The powder C is composed of SiC, BC, _B2O3 , _ZrO2 , Al, _Al2O3 , Si, B _{and CeO2 ;} Described solvent C is made up of xylene, acetone and n-butanol; The binder includes silicone resin; The weight ratio of the powder C, the solvent C and the binder is: 5:14:1. 8. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 7, characterized in that: The percentages of SiC, BC, B ₂ O ₃ , ZrO ₂ , Al, Al ₂ O ₃ , Si, B and CeO ₂ in the powder C to the total weight of the powder C are 20-40%, 3-5% respectively , 20-40%, 2-5%, 2-26%, 6-30%, 20-40%, 20-40% and 0.5-10%; The volume ratio of xylene, acetone and n-butanol in the solvent C is 4:5:1. 9. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 7 or 8, characterized in that the binder also includes a curing agent, and the weight ratio of the silicone resin to the curing agent is 20:1 . 10. The oxidation protection processing method of carbon/carbon composite aviation brake parts according to claim 2, 5 or 7, characterized in that the average particle size of each powder is not greater than 38 microns.