Preparation method of metal surface carbide

Abstract

The invention provides a metal surface carbide preparation method, and belongs to the technical field of metal surface treatment. According to the preparation method, a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of a metal matrix through a high-energy micro-arc deposition technology, and then a second metal ceramic coating containing TiC is deposited on the surface of the first metal ceramic coating. In this way, the problems that when the metal ceramic coating containing TiC is directly deposited on the surface of the metal matrix, due to thermal expansion mismatching between the metal ceramic coating and the metal matrix, thermal cracks are generated on the metal ceramic coating, and stress is generated in the deposition process can be effectively solved; meanwhile, through the compactness of the first metal ceramic coating and the combination condition of the first metal ceramic coating and the metal matrix, the finally formed composite ceramic coating can effectively block diffusion of a corrosive medium, meanwhile, it is guaranteed that the composite ceramic coating has good conductivity, the corrosion resistance of the matrix material is greatly improved, and the service life of the matrix material is prolonged. And the application of the material in a fuel cell is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a method for preparing metal surface carbides. Background Art

[0002] In the prior art, in order to achieve good corrosion resistance and excellent electrical conductivity for bipolar plates in fuel cells, a ceramic coating is usually prepared on the surface of the stainless steel material used for the bipolar plates. However, at the level of fusion between the ceramic coating and the stainless steel material, there are density problems between the different materials, such as the most typical situation of poor bonding or inadequate bonding, which ultimately leads to poor chemical stability of the ceramic coating. The ceramic coating is affected by factors such as stress, resulting in cracks on the surface, which reduces the corrosion resistance and electrical conductivity of the overall structure. Therefore, how to prepare a ceramic coating on the surface of stainless steel so that it has good material density while meeting the requirements of corrosion resistance and electrical conductivity is particularly important in this field.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The present invention aims to provide a method for preparing metal surface carbides, so as to at least improve one of the above-mentioned problems existing in the prior art.

[0005] In order to achieve the above purpose, the following technical solutions are adopted:

[0006] The first object of the present invention is to provide a method for preparing metal surface carbides, comprising the following steps:

[0007] Depositing a first metal ceramic coating containing lanthanum oxide and TiC on the surface of a metal substrate by a high energy micro-arc deposition technique;

[0008] A second metal ceramic coating containing TiC is deposited on the surface of the first metal ceramic coating away from the metal substrate by high-energy micro-arc deposition technology, so that a composite ceramic coating including the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

[0009] Further, based on the above technical solution of the present invention, the metal substrate includes a stainless steel substrate;

[0010] And / or, before depositing the first metal ceramic coating on the surface of the metal substrate, the method further includes the steps of cutting and grinding the metal substrate.

[0011] Furthermore, based on the above technical solution of the present invention, a lanthanum-modified TiC electrode rod is used to perform high-energy micro-arc deposition on the surface of the metal substrate, so that a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate.

[0012] Furthermore, based on the above technical solution of the present invention, a TiC electrode rod is used to perform high-energy micro-arc deposition on the first metal ceramic coating to form a second metal ceramic coating.

[0013] Furthermore, based on the above technical solution of the present invention, the method for preparing metal surface carbide comprises the following steps:

[0014] S1. Cutting and grinding of metal substrate for pretreatment;

[0015] S2. Using TiC powder, La 2 O 3 Preparation of lanthanum-modified TiC electrode rods using lanthanum powder and pure nickel powder;

[0016] S3. Using a lanthanum-modified TiC electrode rod to perform high-energy micro-arc deposition on the pretreated surface of the metal substrate, so that a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate;

[0017] S4. Use a TiC electrode rod to perform high-energy micro-arc deposition on the first metal ceramic coating to deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating away from the metal substrate, so that a composite ceramic coating containing the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

[0018] Further, based on the above technical solution of the present invention, in step S2, the method for preparing the lanthanum-modified TiC electrode rod comprises the following steps:

[0019] (a) TiC powder, La 2 O 3 The carbide powder formed by ball milling the powder and the pure nickel powder is mixed with a binder, pressed into a carbide blank, and then subjected to a debonding treatment;

[0020] (b) The debonded carbide blank is subjected to sintering and densification treatment to obtain a lanthanum-modified TiC electrode rod.

[0021] Further, based on the above technical solution of the present invention, in step (a), the La in the carbide powder 2 O 3 The mass percentage of the powder is 0.3-0.5wt.%, the mass percentage of the pure nickel powder is 3-5wt.%, and the rest is TiC;

[0022] And / or, in step (a), the degumming treatment temperature is 180-220° C., and the degumming treatment time is 40-60 min;

[0023] And / or, in step (b), the carbide blank after degumming treatment is placed in a reducing atmosphere environment and kept at 400°C for 1 hour, then the temperature is increased from 400°C to 850°C, after the temperature reaches 850°C, the temperature is slowly increased from 850°C to 1450°C for 1 hour and kept for 30 minutes, then the temperature is increased from 1450°C to 1800°C and kept for 5 hours, and finally cooled to obtain a lanthanum-modified TiC electrode rod.

[0024] Further, on the basis of the above technical solution of the present invention, in step S3 and step S4, when high-energy micro-arc deposition is performed using the lanthanum-modified TiC electrode rod and the TiC electrode rod, at least one of the following process parameters is used:

[0025] The deposition power supply is a DC pulse power supply; and / or the voltage is 60-100V; and / or the frequency is 800-1000Hz; and / or the pulse width is 200μs; and / or the output power is 500-1800W; and / or the rotation speed of the lanthanum modified TiC electrode rod or the TiC electrode rod is 800-2500r / min; and / or the protective gas used during deposition is argon, the purity of argon is 99.99%, and the argon flow rate is 20-30L / min.

[0026] Further, based on the above technical solution of the present invention, the thickness of the deposited first metal ceramic coating containing lanthanum oxide and TiC is 1-2 μm;

[0027] And / or, the thickness of the deposited second metal ceramic coating containing TiC is 70-85 μm.

[0028] The second object of the present invention is to provide a metal surface carbide, which is prepared by the metal surface carbide preparation method provided by the first object of the present invention;

[0029] The composite ceramic coating comprises the first metal ceramic coating containing lanthanum oxide and TiC and the second metal ceramic coating containing TiC formed on the surface of the first metal ceramic coating;

[0030] Preferably, the composite ceramic coating has a composition gradient structure.

[0031] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0032] (1) The present invention provides a method for preparing carbides on a metal surface, which uses a high-energy micro-arc alloying technique to prepare a first metal ceramic coating containing lanthanum oxide and TiC on the surface of a metal substrate. By utilizing the compactness of the first metal ceramic coating and the bonding condition between the first metal ceramic coating and the metal substrate, the composite ceramic coating finally formed can effectively block the diffusion of corrosive media while ensuring that it has good electrical conductivity, thereby greatly improving the anti-corrosion performance of the substrate material and promoting the application of metal substrates in fuel cells.

[0033] (2) The method for preparing carbides on a metal surface of the present invention first deposits a first metal ceramic coating containing lanthanum oxide and TiC on the surface of a metal substrate, and then deposits a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating. This can effectively improve the problems of directly depositing the second metal ceramic coating containing TiC on the surface of a metal substrate, such as thermal cracks in the metal ceramic coating due to thermal expansion mismatch between the second metal ceramic coating and the metal substrate, and stress generation during the deposition process.

[0034] (3) The composite ceramic coating structure design of the present invention, which comprises a first metal ceramic coating containing lanthanum oxide and TiC as an inner layer and a second metal ceramic coating containing pure TiC as an outer layer, can significantly improve the compatibility of the interface between the second metal ceramic coating of pure TiC and the metal substrate, and also improve the interface structure between the inner and outer TiC layers. It is also easier to form a carbide layer on the metal surface using high-energy micro-arc deposition technology (high-energy micro-arc alloying technology). The use of high-energy micro-arc deposition technology ensures that the formed coating is denser, has good bonding performance, and has excellent conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1a The surface morphology of the first metal ceramic coating of lanthanum oxide and TiC deposited on the surface of the metal substrate of the present invention;

[0036] Figure 1b It is the surface morphology of the common carbide (TiC) metal ceramic coating deposited on the surface of the metal substrate in the prior art;

[0037] Figure 2 is the polarization curve of stainless steel matrix in acidic solution;

[0038] Figure 3 The polarization curve of the first metal ceramic coating containing lanthanum oxide and TiC deposited on the surface of the metal substrate of the present invention in an acidic solution. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0040] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0041] In order to better solve the density problem of the fusion of metal materials and ceramic coatings in the prior art, which leads to the decrease of the corrosion resistance and conductivity of the overall structure, the present invention is specially proposed.

[0042] According to a first aspect of the present invention, there is provided a method for preparing metal surface carbides, comprising the following steps:

[0043] Depositing a first metal ceramic coating containing lanthanum oxide and TiC on the surface of a metal substrate by a high energy micro-arc deposition technique;

[0044] A second metal ceramic coating containing TiC is deposited on the surface of the first metal ceramic coating away from the metal substrate by high-energy micro-arc deposition technology, so that a composite ceramic coating including the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

[0045] In the present invention, by first depositing a first metal ceramic coating containing lanthanum oxide and TiC on the surface of a metal substrate, and then depositing a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating, the composite ceramic coating structure design of the first metal ceramic coating containing lanthanum oxide and TiC in the inner layer and the second metal ceramic coating containing pure TiC in the outer layer can significantly improve the compatibility of the interface between the second metal ceramic coating containing pure TiC and the metal substrate, and effectively improve the problems of the second metal ceramic coating containing TiC directly deposited on the surface of the metal substrate, such as the thermal expansion mismatch between the second metal ceramic coating and the metal substrate, which leads to thermal cracks in the metal ceramic coating and stress generated during the deposition process. At the same time, the above-mentioned composite ceramic coating structure design also improves the interface structure between the inner and outer TiC layers, and is also easier to form a carbide layer on the metal surface using high-energy micro-arc deposition technology (high-energy micro-arc alloying technology). The use of high-energy micro-arc deposition technology ensures that the formed coating is more dense, has good bonding performance, and has excellent conductivity.

[0046] Therefore, the method for preparing carbides on metal surfaces of the present invention works together from two aspects: the structure of the composite ceramic coating and the preparation method. The composite ceramic coating finally formed has good bonding ability with the metal substrate, which improves the problems in the prior art such as thermal expansion mismatch leading to thermal cracks in the metal ceramic coating and stress generated during the deposition process. The composite ceramic coating can effectively block the diffusion of corrosive media while ensuring that it has good electrical conductivity, greatly improving the corrosion resistance of the substrate material and promoting the application of metal substrates in fuel cells.

[0047] Considering the specific application scenario, the type of metal substrate is further optimized. As an optional implementation of the technical solution of the present invention, the metal substrate includes a stainless steel substrate.

[0048] As an optional implementation of the technical solution of the present invention, before depositing the first metal ceramic coating on the surface of the metal substrate, the metal substrate is also cut and polished for pretreatment. The above pretreatment can ensure a smooth surface, thereby ensuring surface uniformity for subsequent deposition.

[0049] As an optional implementation of the technical solution of the present invention, a lanthanum-modified TiC electrode rod is used to perform high-energy micro-arc deposition on the surface of the metal substrate, so that a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate.

[0050] Specifically, in a high-energy micro-arc device, a lanthanum-modified TiC electrode rod is used as a deposition electrode to connect the anode of the device, and a surface-treated metal substrate with a smooth finish is connected to the cathode of the device. Deposition is performed under the protection of argon gas (purity, for example, 99.99%) to deposit a first metal ceramic coating containing lanthanum oxide and TiC on the surface of the metal substrate.

[0051] As an optional implementation of the technical solution of the present invention, the lanthanum-modified TiC electrode rod adopts TiC powder, La 2 O 3 Made of powder and nickel powder.

[0052] As an optional implementation of the technical solution of the present invention, a method for preparing a lanthanum-modified TiC electrode rod comprises the following steps:

[0053] (a) TiC powder, lanthanum oxide La 2 O 3 The powder and the nickel powder are mixed in proportion and then ball-milled to obtain carbide powder;

[0054] (b) mixing carbide powder with a binder and then pressing it into a cylindrical carbide blank through a die;

[0055] (c) Debinding the carbide blank, and after debinding, placing it in a high-temperature vacuum or reducing atmosphere for sintering and densification to prepare a lanthanum-modified TiC electrode rod.

[0056] As an optional implementation of the technical solution of the present invention, in step (a), the lanthanum oxide La in the carbide powder 2 O 3 The mass percentage of the powder is 0.3-0.5wt.%, preferably 0.4wt.%, the mass percentage of the nickel powder is 3-5wt.%, preferably 4.5wt.%, and the rest is TiC.

[0057] As an optional implementation of the technical solution of the present invention, in step (a), the particle size of the carbide powder is 10 μm or less. By controlling the particle size of the carbide, the particle size of the carbide is smaller, which is more conducive to improving the quality of the coating.

[0058] As an optional implementation of the technical solution of the present invention, in step (c), the degumming temperature is 180-220°C, for example, 180°C, 190°C, 200°C, 210°C or 220°C, etc., preferably 200°C, and the degumming time is 40-60min, for example, 40min, 50min or 60min, etc., preferably 50min. By further optimizing the degumming temperature and time, the degumming effect is better and more thorough, and the time is shorter.

[0059] As an optional implementation of the technical solution of the present invention, in step (c), the sintering densification process is specifically as follows: first, the prepared carbide blank that has been debonded is placed in a sintering oven at a temperature of 380-420°C (for example, 380°C, 390°C, 400°C, 410°C or 420°C, etc., preferably 400°C) with Ar+1%H 2The mixture is heated in a reducing atmosphere of (argon and hydrogen) for 1 hour, and then the temperature is increased from 380-420°C (preferably 400°C) to 830-870°C (for example, 830°C, 840°C, 850°C, 860°C or 870°C, etc., preferably 850°C). After the temperature reaches 830-870°C (preferably 850°C), the temperature is slowly increased from 830-870°C (preferably 850°C) to 1430-1470°C (for example, The temperature is then raised from 1430-1470°C (preferably 1450°C) to 1780-1820°C (for example, 1780°C, 1790°C, 1800°C, 1810°C or 1820°C, etc., preferably 1800°C) and then maintained for 5 hours, and finally cooled to prepare the lanthanum modified TiC electrode rod.

[0060] It should be noted that the time required for the temperature to be increased from 380-420°C (preferably 400°C) to 830-870°C (for example, 830°C, 840°C, 850°C, 860°C or 870°C, etc., preferably 850°C) is not particularly limited, and can be selected according to actual needs, for example, it can be 20-90 minutes. Similarly, the time required for the temperature to be increased from 1430-1470°C (preferably 1450°C) to 1780-1820°C (preferably 1800°C) is not particularly limited, for example, it can be 20-90 minutes.

[0061] As a preferred embodiment of the technical solution of the present invention, in step (c), the sintering densification process is specifically as follows: first, the prepared debonded carbide blank is placed in a 400°C oven with Ar+1%H 2 The sample was kept warm in a reducing atmosphere (argon and hydrogen) for 1 hour, then the temperature was increased from 400°C to 850°C. After the temperature reached 850°C, the temperature was slowly increased from 850°C to 1450°C for 1 hour and then kept warm for 30 minutes. Then the temperature was increased from 1450°C to 1800°C and kept warm for 5 hours. Finally, the sample was cooled to obtain a lanthanum-modified TiC electrode rod.

[0062] As an optional implementation of the technical solution of the present invention, a TiC electrode rod is used to perform high-energy micro-arc deposition on the first metal ceramic coating, so as to deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating away from the metal substrate, so that a composite ceramic coating comprising the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

[0063] As an optional implementation of the technical solution of the present invention, when high-energy micro-arc deposition is performed on the surface of the metal substrate using a lanthanum-modified TiC electrode rod and when high-energy micro-arc deposition is performed on the surface of the first metal ceramic coating using a TiC electrode rod, at least one of the following process parameters is used:

[0064] The deposition power supply is a DC pulse power supply;

[0065] and / or, the voltage is 60 to 100 V (for example, 60 V, 70 V, 80 V, 90 V or 100 V, etc.);

[0066] and / or, the frequency is 800-1000 Hz (e.g., 800 Hz, 900 Hz, or 1000 Hz, etc.);

[0067] and / or, the pulse width is 200 μs;

[0068] And / or, the output power is 500-1800 W (for example, 500 W, 800 W, 1000 W, 1200 W, 1500 W or 1800 W, etc.);

[0069] And / or, the rotation speed of the lanthanum-modified TiC electrode rod or the TiC electrode rod is 800-2500 r / min (for example, 800 r / min, 1000 r / min, 1200 r / min, 1500 r / min, 1800 r / min, 2000 r / min, 2200 r / min or 2500 r / min, etc.);

[0070] And / or, the protective gas used during deposition is argon, the purity of argon is 99.99%, and the flow rate of argon is 20 to 30 L / min (for example, 20 L / min, 22 L / min, 25 L / min, 28 L / min or 30 L / min, etc.).

[0071] By further limiting the above process parameters, better deposition effect can be achieved, better coating quality can be guaranteed, and it is also more economical.

[0072] As an optional implementation of the technical solution of the present invention, a method for preparing metal surface carbide comprises the following steps:

[0073] S1. Cutting and grinding of metal substrate for pretreatment;

[0074] S2. Using TiC powder, La 2 O 3 Preparation of lanthanum-modified TiC electrode rods using lanthanum powder and pure nickel powder;

[0075] S3. Using a lanthanum-modified TiC electrode rod to perform high-energy micro-arc deposition on the pretreated surface of the metal substrate, so that a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate;

[0076] S4. Use a TiC electrode rod to perform high-energy micro-arc deposition on the first metal ceramic coating to deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating away from the metal substrate, so that a composite ceramic coating containing the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

[0077] As an optional implementation of the technical solution of the present invention, the thickness of the deposited first metal ceramic coating containing lanthanum oxide and TiC is 1 to 2 μm. The thickness of the first metal ceramic coating should not be too thin or too thick, otherwise it will not achieve a better effect. Therefore, the typical but non-limiting thickness of the coating is 1 μm, 1.2 μm, 1.5 μm, 1.8 μm or 2 μm, etc.

[0078] As an optional embodiment of the technical solution of the present invention, the thickness of the deposited second metal ceramic coating containing TiC is 70-85 μm. Typical but non-limiting coating thicknesses are 70 μm, 72 μm, 75 μm, 78 μm, 80 μm, 82 μm or 85 μm, etc.

[0079] As a preferred embodiment of the technical solution of the present invention, the method for preparing metal surface carbide comprises the following steps:

[0080] S1. The metal substrate is prepared into a sheet for use in a fuel cell, and the surface of the metal substrate is polished and polished step by step using 400 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper on the working surface of the grinding machine, and then wiped with acetone to remove oxides and contaminants on the metal surface to make the metal surface smooth;

[0081] Alternatively, a metal substrate with a smooth surface is prepared into a sheet used in a fuel cell, the surface of the metal substrate is sandblasted to remove its surface oxide layer, and then the oxide and pollutants on the metal surface are wiped with acetone to make the metal surface rough.

[0082] S2. TiC powder with a purity of 99.9wt.%, lanthanum oxide La 2 O 3 After the powder and nickel powder are mixed, they are put into a ball mill for ball milling to make them uniformly mixed, wherein lanthanum oxide La 2 O 3The mass percentage of the powder is 0.4wt.%, the mass percentage of the nickel powder is 4.5wt.%, and the rest is TiC. The particle size of the carbide powder after ball milling and mixing is 10 microns or less. The carbide powder after ball milling and mixing is taken out from the ball mill, and a binder is added to fully mix the carbide powder with the binder. The carbide powder mixed with the binder is placed in a cylindrical mold, and the diameter of the cylindrical mold is 5-6mm. The carbide powder mixed with the binder is pressed into a cylindrical carbide blank by applying a pressure of 6MPa to the cylindrical mold. The pressure is maintained for 100s during the pressing process. Then the formed carbide blank is degummed, the degumming temperature is set to 200℃, the degumming time is 50min, and the carbide blank is taken out after the degumming is completed, and it is placed in a high-temperature vacuum or reducing atmosphere for sintering and densification treatment to make an electrode rod.

[0083] In this process, the sintering densification process is as follows: first, the prepared carbide blank that has been debonded is placed in an Ar+1%H 2 The sample was kept warm in a reducing atmosphere (argon and hydrogen) for 1 hour, then the temperature was increased from 400°C to 850°C. After the temperature reached 850°C, the temperature was slowly increased from 850°C to 1450°C for 1 hour and then kept warm for 30 minutes. Then the temperature was increased from 1450°C to 1800°C and kept warm for 5 hours. Finally, the sample was cooled to obtain a lanthanum-modified TiC electrode rod.

[0084] S3. In a high-energy micro-arc device, the lanthanum-modified TiC electrode rod prepared in step S2 is used as a deposition electrode and connected to the anode of the device, and the metal substrate with a smooth surface treated in step S1 is connected to the cathode of the device, and deposition is performed under the protection of argon gas with a purity of 99.99%, and a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate until the thickness of the first metal ceramic coating is 1 to 2 μm;

[0085] S4. Then use a TiC electrode rod as a deposition electrode, connect it to the anode of the equipment, and deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating. When the thickness of the second metal ceramic coating reaches 80 μm, stop the high-energy micro-arc deposition. At this time, a composite ceramic coating is formed on the surface of the metal substrate.

[0086] At the same time, during the deposition of the first metal ceramic coating and the second metal ceramic coating, the rotation speed of the electrode rod is adjusted so that the electrode rod cannot adhere to the metal substrate.

[0087] In this process, the deposition power source selects a DC pulse power source, the voltage is set to 60-100V, the frequency is 800-1000Hz, the pulse width is 200μs, and the output power is 500-1800W. The rotation speed of the lanthanum modified TiC electrode rod and the TiC electrode rod is 800-2500r / min. During deposition, the flow rate of argon gas with a purity of 99.99% is 20-30L / min. At the same time, by controlling the changes in the above process parameters during high-energy micro-arc deposition, the coating can have a composition gradient structure, for example, a gradient coating with dense top and sparse bottom can be formed.

[0088] The present invention avoids the problems of cracks easily generated when carbide ceramics are in direct contact with metal substrates and weak interface bonding through such coating design and corresponding preparation process, improves the density of the coating, thereby effectively improving the corrosion resistance of the substrate material and promoting the application of metal substrates (such as stainless steel materials) in fuel cells.

[0089] According to a second aspect of the present invention, there is also provided a metal surface carbide, which is prepared by the metal surface carbide preparation method provided by the first aspect of the present invention;

[0090] The composite ceramic coating includes the first metal ceramic coating containing lanthanum oxide and TiC and the second metal ceramic coating containing TiC formed on the surface of the first metal ceramic coating.

[0091] As an optional embodiment of the present invention, the composite ceramic coating has a composition gradient structure.

[0092] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0093] Example 1

[0094] This embodiment provides a method for preparing metal surface carbide, comprising the following steps:

[0095] S1. The metal substrate is prepared into a sheet for use in a fuel cell, and the metal surface is ground and polished step by step using 400 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper on the working surface on a pre-grinding machine, and then wiped with acetone to remove oxides and contaminants on the metal surface, so that the metal surface has a certain degree of smoothness;

[0096] S2. TiC powder with a purity of 99.9wt.%, lanthanum oxide La 2 O 3 After the powder and nickel powder are mixed, they are put into a ball mill for ball milling to make them uniformly mixed, wherein lanthanum oxide La 2 O 3The mass percentage of powder is 0.4wt.%, the mass percentage of nickel powder is 4.5wt.%, and the rest is TiC. The particle size of the carbide powder after ball milling and mixing is 10μm or less. The carbide powder after ball milling and mixing is taken out from the ball mill, and a binder is added to make the carbide powder fully mixed with the binder. The carbide powder mixed with the binder is placed in a cylindrical mold, and the diameter of the cylindrical mold is 5mm. The carbide powder mixed with the binder is pressed into a cylindrical carbide blank by applying a pressure of 6MPa to the cylindrical mold. The pressure is maintained for 100s during the pressing process. Then the formed carbide blank is degummed, the degumming temperature is set to 200℃, the degumming time is 50min, and the carbide blank is taken out after the degumming is completed, and it is placed in a high-temperature vacuum or reducing atmosphere for sintering and densification treatment to make a lanthanum-modified TiC electrode rod.

[0097] In this process, the sintering densification process is specifically as follows:

[0098] First, the prepared debonded carbide blank was placed in an atmosphere with Ar + 1% H at a temperature of 400 °C. 2 The sample was kept warm in a reducing atmosphere (argon and hydrogen) for 1 hour, then the temperature was increased from 400°C to 850°C. After the temperature reached 850°C, the temperature was slowly increased from 850°C to 1450°C for 1 hour and then kept warm for 30 minutes. Then the temperature was increased from 1450°C to 1800°C and kept warm for 5 hours. Finally, the sample was cooled to obtain a lanthanum-modified TiC electrode rod.

[0099] S3. In a high-energy micro-arc deposition device, the lanthanum-modified TiC electrode rod prepared in step S2 is used as a deposition electrode and connected to the anode of the device. The metal substrate with a smooth surface treated in step S1 is connected to the cathode of the device. Deposition is performed under the protection of argon gas with a purity of 99.99%. A first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate until the thickness of the first metal ceramic coating is 1 to 2 μm.

[0100] S4. Then use a TiC electrode rod as a deposition electrode, connect it to the anode of the equipment, and deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating. When the thickness of the second metal ceramic coating of pure TiC reaches 80μm, stop the high-energy micro-arc deposition. At this time, the thickness of the composite ceramic coating formed on the surface of the metal substrate is 81-82μm.

[0101] In the process of depositing the first metal ceramic coating in step S3 and the second metal ceramic coating in step S4, the deposition power source is set to a DC pulse power source, the voltage is set to 60V, the frequency is 800Hz, the pulse width is 200μs, and the output power is 500W. The rotation speed of the lanthanum modified TiC electrode rod and the TiC electrode rod is 800r / min. The flow rate of argon gas with a purity of 99.99% is 20L / min during deposition.

[0102] Example 2

[0103] This embodiment provides a method for preparing metal surface carbide, comprising the following steps:

[0104] S1. The metal substrate is prepared into a sheet for use in a fuel cell, and the metal surface is ground and polished step by step using 400 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper on the working surface on a pre-grinding machine, and then wiped with acetone to remove oxides and contaminants on the metal surface, so that the metal surface has a certain degree of smoothness;

[0105] S2. TiC powder with a purity of 99.9wt.%, lanthanum oxide La 2 O 3 After the powder and nickel powder are mixed, they are put into a ball mill for ball milling to make them uniformly mixed, wherein lanthanum oxide La 2 O 3 The mass percentage of powder is 0.4wt.%, the mass percentage of nickel powder is 4.5wt.%, and the rest is TiC. The particle size of the carbide powder after ball milling and mixing is 10μm or less. The carbide powder after ball milling and mixing is taken out from the ball mill, and a binder is added to make the carbide powder fully mixed with the binder. The carbide powder mixed with the binder is placed in a cylindrical mold, and the diameter of the cylindrical mold is 6mm. The carbide powder mixed with the binder is pressed into a cylindrical carbide blank by applying a pressure of 6MPa to the cylindrical mold. The pressure is maintained for 100s during the pressing process. Then the formed carbide blank is degummed, the degumming temperature is set to 200℃, the degumming time is 50min, and the carbide blank is taken out after the degumming is completed, and it is placed in a high-temperature vacuum or reducing atmosphere for sintering and densification treatment to make a lanthanum-modified TiC electrode rod.

[0106] In this process, the sintering densification process is specifically as follows:

[0107] First, the prepared debonded carbide blank was placed in an atmosphere with Ar + 1% H at a temperature of 400 °C. 2The sample was kept warm in a reducing atmosphere (argon and hydrogen) for 1 hour, then the temperature was increased from 400°C to 850°C. After the temperature reached 850°C, the temperature was slowly increased from 850°C to 1450°C for 1 hour and then kept warm for 30 minutes. Then the temperature was increased from 1450°C to 1800°C and kept warm for 5 hours. Finally, the sample was cooled to obtain a lanthanum-modified TiC electrode rod.

[0108] S3. In the high-energy micro-arc equipment, the lanthanum-modified TiC electrode rod prepared in step S2 is used as an electrode for high-energy micro-arc deposition (high-energy micro-arc electrospark deposition) and connected to the anode of the high-energy micro-arc deposition (high-energy micro-arc electrospark deposition) equipment. The metal substrate with a certain degree of smoothness that has been surface-treated in step S1 is connected to the cathode of the high-energy micro-arc deposition equipment. The equipment is powered on and electrodeposition is performed under the protection of 99.99% argon. At the same time, the electrode rotation speed is adjusted during the deposition process so that the electrode cannot be on the bonding substrate. A first metal ceramic coating containing lanthanum oxide and TiC is first deposited on the surface of the metal substrate until the thickness of the first metal ceramic coating is 1 to 2 μm.

[0109] S4. Then use a TiC electrode rod as a deposition electrode, connect it to the anode of the equipment, and deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating. When the thickness of the second metal ceramic coating of pure TiC reaches 75μm, stop the high-energy micro-arc deposition. At this time, the thickness of the composite ceramic coating formed on the surface of the metal substrate is 76-77μm.

[0110] In the process of depositing the first metal ceramic coating in step S3 and the second metal ceramic coating in step S4, the deposition power source is set to a DC pulse power source, the voltage is set to 100V, the frequency is 1000Hz, the pulse width is 200μs, and the output power is 100W. The rotation speed of the lanthanum modified TiC electrode rod and the TiC electrode rod is 1000r / min. The flow rate of argon gas with a purity of 99.99% is 30L / min during deposition.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing metal surface carbides, comprising the following steps:

[0113] S1. The metal substrate is prepared into a sheet for use in a fuel cell, and the metal surface is ground and polished step by step using 400 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper on the working surface on a pre-grinding machine, and then wiped with acetone to remove oxides and contaminants on the metal surface, so that the metal surface has a certain degree of smoothness;

[0114] S2. In the high-energy micro-arc equipment, a TiC electrode rod is used as a deposition electrode and connected to the anode of the equipment. The metal substrate with a smooth surface treated in step S1 is connected to the cathode of the equipment. Deposition is performed under the protection of argon gas with a purity of 99.99%. A metal ceramic coating containing only TiC is deposited on the surface of the metal substrate. When the thickness of the metal ceramic coating reaches 81 to 82 μm, the high-energy micro-arc deposition is stopped. At this time, a metal ceramic coating containing TiC is formed on the surface of the metal substrate.

[0115] The deposition power source set in this process is a DC pulse power source, with a voltage of 60V, a frequency of 800Hz, a pulse width of 200μs, and an output power of 500W. The speed of the TiC electrode rod is 800r / min. The flow rate of argon gas with a purity of 99.99% is 20L / min during deposition.

[0116] In order to compare the technical effects of the above embodiments and comparative examples, the following experimental examples are specially designed.

[0117] (1) Morphology test

[0118] The microscopic morphology of the stainless steel substrate with the first metal ceramic coating with lanthanum oxide and TiC deposited on the surface prepared in step S3 of Example 1 and the metal ceramic coating with TiC deposited on the surface prepared in Comparative Example 1 were detected, and the obtained SEM images were as follows: Figure 1a and Figure 1b As shown. Figure 1a and Figure 1b It can be seen that the first metal ceramic coating containing lanthanum oxide and TiC formed on the surface of the stainless steel substrate has a dense flaky feature on the surface morphology and a high degree of densification, so the corrosion resistance is better. However, the surface of the metal ceramic coating of ordinary carbide TiC in Comparative Example 1 has typical molten solidification characteristics, a low degree of densification, and a relatively poor corrosion resistance.

[0119] (2) Polarization curve comparison

[0120] The stainless steel substrate in Example 1 and the stainless steel substrate with the first metal ceramic coating containing lanthanum oxide and TiC formed on the surface prepared in Example 1 were placed in a fuel cell simulation environment (0.3 MH 2 SO 4 +3ppm HF) test, the polarization curves of the two are as follows Figure 2 and Figure 3 As shown. Figure 2 and Figure 3By comparing the polarization curves in the embodiment 2, it is found that the self-corrosion potential of the stainless steel substrate with the first metal ceramic coating containing lanthanum oxide and TiC formed on the surface is significantly increased by about 500mV compared with the stainless steel substrate without the coating. At the same time, the stainless steel substrate with the first metal ceramic coating containing lanthanum oxide and TiC formed on the surface of Example 2 was placed in a fuel cell simulation environment (0.3MH 2 SO 4 +3ppm HF) test, the corrosion potential of the coating increased by 510mV relative to the substrate material.

[0121] The above tests show that the first metal ceramic coating containing lanthanum oxide and TiC can effectively improve the corrosion resistance of the stainless steel substrate. This improvement in corrosion resistance is related to the compactness of the first metal ceramic coating containing lanthanum oxide and TiC deposited on the surface of the stainless steel substrate and the fact that the formed composite ceramic coating can maintain a high degree of chemical stability in an acidic solution.

[0122] The preparation method of metal carbide of the present invention can deposit a carbide coating with superior chemical stability and excellent physical shielding performance on the surface of a metal substrate, giving full play to the advantages of carbide materials in corrosion resistance and electrical conductivity, while providing long-term and effective protection for the metal substrate and ensuring that the metal substrate has good electrical conductivity.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A method for preparing metal surface carbide, characterized in that: The following steps are involved: Depositing a first metal ceramic coating containing lanthanum oxide and TiC on the surface of a metal substrate by a high energy micro-arc deposition technique; A second metal ceramic coating containing TiC is deposited on the surface of the first metal ceramic coating away from the metal substrate by high-energy micro-arc deposition technology, so that a composite ceramic coating including the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

2. The method for preparing metal surface carbides according to claim 1, characterized in that: The metal substrate comprises a stainless steel substrate; And / or, before depositing the first metal ceramic coating on the surface of the metal substrate, the method further includes the steps of cutting and grinding the metal substrate.

3. The method for preparing metal surface carbides according to claim 1, characterized in that: A lanthanum-modified TiC electrode rod is used to perform high-energy micro-arc deposition on the surface of the metal substrate, so that a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate.

4. The method for preparing metal surface carbides according to claim 1, characterized in that: A TiC electrode rod is used to perform high-energy micro-arc deposition on the first metal ceramic coating to form a second metal ceramic coating.

5. The method for preparing metal surface carbide according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Cutting and grinding of metal substrate for pretreatment; S2. Lanthanum-modified TiC electrode rods were prepared using TiC powder, La2O3 powder and pure nickel powder; S3. Using a lanthanum-modified TiC electrode rod to perform high-energy micro-arc deposition on the pretreated surface of the metal substrate, so that a first metal ceramic coating containing lanthanum oxide and TiC is deposited on the surface of the metal substrate; S4. Use a TiC electrode rod to perform high-energy micro-arc deposition on the first metal ceramic coating to deposit a second metal ceramic coating containing TiC on the surface of the first metal ceramic coating away from the metal substrate, so that a composite ceramic coating containing the first metal ceramic coating and the second metal ceramic coating is formed on the surface of the metal substrate.

6. The method for preparing metal surface carbides according to claim 5, characterized in that: In step S2, the method for preparing the lanthanum-modified TiC electrode rod comprises the following steps: (a) mixing carbide powder formed by ball milling TiC powder, La2O3 powder and pure nickel powder with a binder, pressing the mixture into a carbide blank, and then performing a debonding treatment; (b) The debonded carbide blank is subjected to sintering and densification treatment to obtain a lanthanum-modified TiC electrode rod.

7. The method for preparing metal surface carbides according to claim 6, characterized in that: In step (a), the mass percentage of La2O3 powder in the carbide powder is 0.3-0.5wt.%, the mass percentage of pure nickel powder is 3-5wt.%, and the rest is TiC; And / or, in step (a), the degumming treatment temperature is 180-220° C., and the degumming treatment time is 40-60 min; And / or, in step (b), the carbide blank after degumming treatment is placed in a reducing atmosphere environment and kept at 400°C for 1 hour, then the temperature is increased from 400°C to 850°C, after the temperature reaches 850°C, the temperature is slowly increased from 850°C to 1450°C for 1 hour and kept for 30 minutes, then the temperature is increased from 1450°C to 1800°C and kept for 5 hours, and finally cooled to obtain a lanthanum-modified TiC electrode rod.

8. The method for preparing metal surface carbides according to claim 5, characterized in that: In step S3 and step S4, when high-energy micro-arc deposition is performed using the lanthanum-modified TiC electrode rod and the TiC electrode rod, at least one of the following process parameters is used: The deposition power supply is a DC pulse power supply; and / or the voltage is 60-100V; and / or the frequency is 800-1000Hz; and / or the pulse width is 200μs; and / or the output power is 500-1800W; and / or the rotation speed of the lanthanum modified TiC electrode rod or the TiC electrode rod is 800-2500r / min; and / or the protective gas used during deposition is argon, the purity of argon is 99.99%, and the argon flow rate is 20-30L / min.

9. The method for preparing metal surface carbide according to any one of claims 1 to 4, characterized in that: The thickness of the deposited first metal ceramic coating containing lanthanum oxide and TiC is 1-2 μm; And / or, the thickness of the deposited second metal ceramic coating containing TiC is 70-85 μm.

10. A metal surface carbide, characterized in that: Prepared by the method for preparing metal surface carbide according to any one of claims 1 to 9; The composite ceramic coating comprises the first metal ceramic coating containing lanthanum oxide and TiC and the second metal ceramic coating containing TiC formed on the surface of the first metal ceramic coating; Preferably, the composite ceramic coating has a composition gradient structure.

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