CN101602616A - Surface Metallization of Ceramic Matrix Composite Components Based on Molten Salt Method - Google Patents

Abstract

The invention discloses a surface metallization process of a ceramic matrix composite material component based on a molten salt method, which comprises the following steps: firstly placing molten salt mixed raw materials in a fixed container, and then embedding the surface cleaned ceramic matrix composite material component Put it in the molten salt mixed raw material, raise the temperature to 800 ℃ ~ 1200 ℃ in an inert atmosphere, keep it warm for 1 ~ 5 hours and then lower it to room temperature with the furnace; take out the ceramic matrix composite material component and repeatedly clean the surface and then dry it to obtain surface metallization ceramic matrix composite components. The process of the invention has the advantages of fast preparation speed, high efficiency, simple and easy operation, high bonding strength between the obtained metallized layer and the ceramic matrix composite material, and can meet the metallization requirements of the ceramic matrix composite material component.

Description

Surface Metallization of Ceramic Matrix Composite Components Based on Molten Salt Method

technical field

The invention relates to a method for processing the surface of a ceramic matrix composite material component, in particular to a method for metallizing the surface of a ceramic matrix composite material component.

Background technique

Realizing the surface metallization of ceramic matrix composites changes the physical and chemical properties of the surface and improves the wettability between ceramic matrix composites and metals, which plays a very important role in the application fields of ceramic matrix composites and metal sealing or connection.

Ceramic matrix composites can be divided into particle-reinforced, whisker-reinforced, and fiber-reinforced according to the properties of the reinforcing phase. They have high specific strength, high specific stiffness, high temperature resistance, oxidation resistance, and erosion resistance. They are mainly used in aerospace , aviation, nuclear energy, transportation and other important fields. Due to the late start of research on ceramic matrix composites, the research on its surface metallization is even less involved. At present, the surface metallization of ceramic matrix composites mostly follows the method of ceramic surface metallization. The surface metallization methods of ceramic materials mainly include: Mo-Mn method, sputtering method, ion plating, chemical vapor deposition, thermal spraying, etc. Among these methods, the Mo-Mn method uses the generated glass to connect metal and ceramics to achieve surface metallization, but this cannot meet the high-temperature performance requirements of the metallization layer; the sputtering method has a slow deposition rate and is not suitable for complex shapes. Surface metallization of ceramic matrix composite components; the ion plating process is complex and requires a high degree of vacuum, and for more complex components, the deposition thickness on different surfaces is different; sputtering and ion plating processes lead to metallization due to their physical deposition properties The layer and the substrate do not form a strong chemical bond, so the connection strength between the metallized layer and the substrate is also low; the prominent process problem of chemical vapor deposition is that the deposition temperature is high, the mechanical properties of the composite material after deposition may decrease, and at the same time, diffusion heat treatment is required after deposition In order to improve the connection strength between the deposited metal layer and the substrate.

The surface metallization of ceramic matrix composites faces three problems: 1. It is difficult for ceramic matrix composites to form bonds with metals directly. Since the chemical bonds between atoms in ceramic materials are mainly ionic bonds and covalent bonds, which are very stable electronic coordination, it is difficult to break and form bonds with metals. 2. The thermal expansion coefficients of ceramic materials and metal materials do not match. The thermal expansion coefficient of ceramic matrix composites is generally small, which is quite different from that of metals, which is prone to thermal stress and reduces the bonding strength between the metallized layer and ceramic matrix composites. 3. The complex surface properties of ceramic matrix composites make it difficult to completely cover the metallized layer. For example, there are a certain number of pores of different sizes on the surface of C _f /SiC ceramic matrix composites produced by the precursor impregnation pyrolysis (PIP) process. If metallization cannot be realized on the inner surface of the pores, it is easy to leave oxidation channels, thereby reducing the high temperature performance of the material.

Based on the above requirements, it is necessary to develop a surface metallization that can achieve strong bonding between the ceramic matrix composite material and the surface metallization layer, and whose surface expansion coefficient is gradient to relieve thermal stress, and can realize the complete coating of the ceramic matrix composite material surface. craft.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and to provide a method with fast preparation speed, high efficiency, simple and easy operation, high bonding strength between the metallized layer and the ceramic matrix composite material, and can meet the metallization requirements of complex components. Surface metallization process of ceramic matrix composite components based on molten salt method.

In order to solve the above technical problems, the technical solution proposed by the present invention is a surface metallization process of ceramic matrix composite components based on the molten salt method, which includes the following steps: firstly, the molten salt mixed raw material is placed in a fixed container (such as a crucible furnace) , and then embed the surface-cleaned ceramic matrix composite member in the molten salt mixed raw material, and raise the temperature to 800°C-1200°C under an inert atmosphere (preferably Ar) (the heating rate is preferably 5°C/min-15°C/min. min), keep warm for 1 to 5 hours, and then drop to room temperature with the furnace; take out the ceramic matrix composite member and repeatedly clean its surface (the cleaning method can be to place it in water for repeated cleaning, and then use ethanol for ultrasonic cleaning for 15 ~30min) drying to obtain surface metallized ceramic matrix composite components;

The mixed raw material of molten salt is composed of base salt, high-valent salt containing surface metallization elements and metal powder of surface metallization elements, and the mass ratio of the base salt to high-valent salt containing surface metallization elements is (1.5～ 5): 1, the molar ratio of the metal powder of the surface metallization element to the hypervalent salt containing the surface metallization element is (2-5):1.

The metallization process of the present invention is carried out in molten salt, and the mixed raw material of molten salt is mainly composed of base salt and high-valence salt containing surface metallization elements. In the above technical scheme, the base salt can be a single salt, preferably NaCl or KCl, etc.; the base salt can also be a commonly used molten salt system, preferably a mixed salt composed of NaCl and KCl, and NaCl and KCl in the mixed salt The mass ratio is (9～49):21.

In the above technical solution, the high-valent salt containing surface metallization elements is preferably a high-valent fluorine salt containing surface metallization elements, especially a high-valent fluorine salt with a chemical formula of _{K2XF6 ,} wherein X refers to surface metallization elements, When the surface metallization element is preferably titanium, zirconium or niobium, the high-valent fluorine salt is K ₂ TiF ₆ , K ₂ ZrF ₆ or K ₂ NbF ₆ .

The selection and optimization of the above-mentioned molten salt mixed raw materials mainly consider factors such as process cost and temperature zone.

The material of the metallization layer should generally choose a metal that is easy to combine with the components of the ceramic matrix composite material, so that during the surface metallization process, the material of the metallization layer can form a certain strong bonding compound with the ceramic matrix composite material. At the same time, it is also necessary to meet the requirement that the thermal expansion coefficient difference between the metallization layer material and the ceramic matrix composite material is small. In the above technical solution, when the ceramic matrix composite member is a C _f /SiC composite material or a C _f /C composite material member, the surface metallization elements combined with its components are preferably titanium, zirconium or niobium, and the corresponding metals The powder is preferably titanium powder, titanium sponge, zirconium powder, zirconium particles, niobium powder or niobium particles. Because metals such as Ti, Zr, and Nb have close thermal expansion coefficients to the ceramic matrix composite material, and are easy to form bonds with the ceramic matrix composite material.

The basic principle of the above technical solution is: put the base salt, the high-valent salt containing the surface metallization element, the metal powder of the surface metallization element and the ceramic matrix composite material in a fixed container, and heat it to a predetermined temperature to make the molten salt When the mixed raw materials are melted, the metal powder reacts with the high-valent salt containing surface metallization elements to generate low-valent metal ions, which are enriched and deposited on the surface of the ceramic matrix composite material, and disproportionate on the surface to form metallization surface layer. Taking Ti metallization on the surface of C _f /SiC composite material as an example, at the reaction temperature, titanium powder (that is, the metal powder of surface metallization elements) reacts with K ₂ TiF ₆ Ti ⁴⁺ +Ti=2Ti ²⁺ , forming Ti ²⁺ ions, Ti ²⁺ ions are enriched and deposited on the surface of the C _f /SiC composite material, and a disproportionation reaction 2Ti ²⁺ =Ti ⁴⁺ +Ti occurs to generate Ti. Ti atoms are attached to the surface of the _Cf /SiC composite to form a Ti metallization layer. The metallization layer material Ti reacts with C, SiC and other substances in the matrix to form strong bonding compounds such as ionic bonds and covalent bonds, which significantly improves the bonding strength between the metallization layer and the C _f /SiC composite material.

Compared with the prior art, the present invention has the advantages of:

1. A method for surface metallization of ceramic matrix composites is proposed. Utilizing the principle of disproportionation reaction of metals, metal ions are attached to the surface of the ceramic matrix composite material and undergo disproportionation reaction to generate metal element and deposit on the surface of the ceramic matrix composite material. The deposition of refractory metals on the surface of ceramic matrix composites is realized through the control of process factors such as molten salt system, raw material ratio selection, reaction temperature, and reaction time.

2. The method can meet the surface metallization requirements of various ceramic matrix composite components with complex structures and complex surface states. Ceramic matrix composites often need to be prepared into complex special-shaped structures, and the surface state of ceramic matrix composites is also relatively complicated. Some materials also have more pores, and it is difficult to cover the inside of the pores by ordinary methods. The invention utilizes the high fluidity and low viscosity characteristics of the molten salt to realize metallization on the matrix material and the reinforcement material, and realize coating on the inner surface of the pores.

3. The bonding strength between the metallized layer and the ceramic matrix composite material is high. The bond energy of the ceramic material is high, and it is difficult to combine with the metallized layer to form a strong bond, so that the bonding strength between the metallized layer and the substrate is low. The invention reacts with molten salt at high temperature, generates metal at the reaction temperature and deposits it on the surface of the ceramic matrix composite material. The metal in this state has high activity and reacts with the ceramic matrix composite to form a compound with a strong bond, so that the metallization layer and the ceramic matrix composite have high bonding strength.

4. The preparation speed of the metallized layer is fast, the efficiency is high, and the operation is simple and easy. In the present invention, rapid and efficient metallization of the ceramic matrix composite material can be realized by controlling the influencing factors such as reaction temperature and raw material ratio. The metallization equipment is simple and low in cost.

Description of drawings

Fig. 1 is the surface XRD spectrum of the Ti metallization layer of the embodiment of the present invention 1;

Fig. 2 is the surface XRD pattern of the Zr metallization layer of Example 2 of the present invention.

Detailed ways

Example 1: Ti metallization on the surface of C _f /SiC composites

The metallization process of the composite material in this embodiment is as follows:

1. Prepare molten salt raw materials of the following quality: 340g NaCl, 430g KCl, 330g K ₂ TiF ₆ and 200g Ti powder;

2. Mix the molten salt raw materials prepared above evenly, put them in the crucible boiler, then clean the surface of the C _f /SiC composite material components, dry them and bury them in the molten salt mixed raw materials. Under the protection of Ar gas atmosphere, Raise the temperature to 1000°C at a rate of 10°C/min, keep it warm for 5 hours, and cool to room temperature with the furnace;

3. Take out the above C _f /SiC composite material component, put it in water and wash it repeatedly, then perform ultrasonic cleaning with ethanol for 15 minutes, take it out and dry it, and obtain a C _f /SiC composite material component with Ti metallization on the surface.

The surface of the C _f /SiC composite member after surface Ti metallization was analyzed. The thickness of the surface metallization layer is 25-30 μm. The phase composition of the metallization layer is shown in Figure 1, including TiC _x , Ti ₅ Si _3. Phases such as Ti _x O _y , although from the XRD pattern, the content of Ti metal on the surface is relatively small, but from the properties and performance of the product, it has reached the effect of metallization on the surface of composite components.

Example 2: Zr metallization on the surface of C _f /SiC composite material

The metallization process of the composite material in this embodiment is as follows:

1. Prepare molten salt raw materials of the following quality: 400g NaCl, 500g KCl, 385g K ₂ ZrF ₆ and 370g Zr powder;

2. Mix the molten salt raw materials prepared above evenly, put them in the crucible boiler, then clean the surface of the C _f /SiC composite material components, dry them and bury them in the molten salt mixed raw materials. Under the protection of Ar gas atmosphere, Heat up to 1100°C at a rate of 10°C/min, keep warm for 3 hours and then cool to room temperature with the furnace;

3. Take out the above C _f /SiC composite material component, put it in water and wash it repeatedly, then perform ultrasonic cleaning with ethanol for 15 minutes, take it out and dry it, and obtain a C _f /SiC composite material component with Zr metallization on the surface.

The surface of the C _f /SiC composite member after surface Zr metallization was analyzed, and the thickness of the surface metallization layer was 5-15 μm. The phase composition of the metallization layer was shown in Figure 2, including Zr, ZrC, Zr ₂ Si, Zr ₃ O and other phases.

Claims (8)

1. A surface metallization process of ceramic matrix composite components based on the molten salt method, comprising the following steps: firstly placing molten salt mixed raw materials in a fixed container, and then embedding the surface cleaned ceramic matrix composite components in In the mixed raw material of molten salt, the temperature is raised to 800°C-1200°C under an inert atmosphere, kept for 1-5 hours, and then lowered to room temperature with the furnace; the ceramic matrix composite component is taken out and its surface is repeatedly cleaned and then dried to obtain a surface metal Ceramic matrix composite components; The mixed raw material of molten salt is composed of base salt, high-valent salt containing surface metallization elements and metal powder of surface metallization elements, and the mass ratio of the base salt to high-valent salt containing surface metallization elements is (1.5～ 5): 1, the molar ratio of the metal powder of the surface metallization element to the hypervalent salt containing the surface metallization element is (2-5):1. 2. The surface metallization process of ceramic matrix composite components based on the molten salt method according to claim 1, characterized in that: the base salt is NaCl, or KCl, or a mixed salt composed of NaCl and KCl; The mass ratio of NaCl and KCl in the salt is (9-49):21. 3. The surface metallization process of ceramic matrix composite components based on the molten salt method according to claim 1, characterized in that: the high-valent salt containing surface metallization elements is a high-valent fluorine salt containing surface metallization elements. 4. The surface metallization process of ceramic matrix composite components based on molten salt method according to claim 3, characterized in that: the chemical formula of the high-valent fluorine salt containing surface metallization elements is K ₂ XF ₆ , where X refers to Represents surface metallization elements. 5. The surface metallization process of ceramic matrix composite material components based on the molten salt method according to any one of claims 1 to 4, characterized in that: the ceramic matrix composite material components are C _f /SiC composite material components or C _f /C composite material component; said surface metallization element refers to titanium, zirconium or niobium, and the metal powder of said surface metallization element is titanium powder, sponge titanium, zirconium powder, zirconium particle, niobium powder or niobium grain. 6. The surface metallization process of ceramic matrix composite components based on the molten salt method according to any one of claims 1 to 4, characterized in that: the inert atmosphere is protected by an Ar atmosphere; The rate is 5°C/min～15°C/min. 7. The surface metallization process of ceramic matrix composite components based on molten salt method according to claim 5, characterized in that: the inert atmosphere is protected by Ar atmosphere; the heating rate in the heating process is 5°C/min ~15°C/min. 8. The surface metallization process of ceramic matrix composite material components based on the molten salt method according to any one of claims 1 to 4, characterized in that: the ceramic matrix composite material components are taken out and the surface is repeatedly cleaned The method refers to firstly placing the ceramic matrix composite component in water for repeated cleaning, and then ultrasonic cleaning with ethanol for 15-30 minutes.

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