Highly conductive, high temperature oxidation resistant coating and method for producing same

Abstract

The present invention discloses a highly conductive, high-temperature oxidation-resistant coating and a method for manufacturing the same. The highly conductive, high-temperature oxidation-resistant coating contains 15% to 25% by weight of Al, 1% to 3% by weight of Ni, 1% to 5% by weight of Cr, 1% to 3% by weight of Au, and the balance being Fe. The method for manufacturing the highly conductive, high-temperature oxidation-resistant coating includes the steps of (1) pretreating the surface of a workpiece, (2) immersing the workpiece in an Au plating solution to deposit an Au coating on the workpiece, and (3) burying the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere to obtain a highly conductive, high-temperature oxidation-resistant coating. The coating has excellent high-temperature oxidation resistance, a uniform thickness, and adheres well to the substrate, and is relatively simple to manufacture.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of high temperature coatings and relates to a highly conductive, high temperature oxidation resistant coating and a method for producing the same. [Background technology]

[0002] In solid oxide fuel cells, the connecting plate must have good electrical conductivity and an acceptable surface resistivity of 0.1 mΩ / cm 2 The connecting plate must meet certain requirements, including a temperature of less than 100°C, stability of 40,000 hours at an operating temperature of 800°C, excellent barrier properties to prevent direct bonding between the oxidant and fuel, a thermal expansion coefficient that matches the electrode and electrolyte materials, no reaction or internal diffusion between the connecting plate and SOFC components, and excellent resistance to oxidation, sulfidation, and carbon deposition. Considering cost performance, the connecting plate is generally made of stainless steel with a chromium content of 18% to 25%, but oxidation of the connecting plate over long periods of use increases contact resistance and reduces cell efficiency.

[0003] In general, the formation of a protective oxide film through selective high-temperature oxidation of an alloy is an important basis for the design of high-temperature alloys and their coatings. Selective oxidation of an alloy can be promoted by increasing the content of selectively oxidizable elements in the alloy, increasing their diffusion rate in the alloy, decreasing the oxygen content and diffusion rate in the alloy, or increasing the oxide nucleation rate. The most oxidation-resistant selective oxide films include Al2O3, SiO2, and Cr2O3 films. However, for titanium alloys, stainless steels with low Cr, Al, and Si contents, and nickel-based alloys, it is impossible to form protective Al2O3, SiO2, and Cr2O3 films during the oxidation process, and the high-temperature oxidation resistance of metallic materials can only be improved by surface modification.

[0004] Aluminide coatings provide protection primarily by forming an Al2O3 film on the coating surface at high temperatures. This dense alumina film prevents further oxidation and corrosion. Aluminide coatings provide continuous protection by providing aluminum elements to form the alumina film. Aluminide coatings have excellent high-temperature oxidation resistance but inferior hot corrosion resistance to chromium coatings. Generally, the high-temperature oxidation and hot corrosion resistance of aluminide coatings are improved through two main approaches: first, by improving the bonding strength between the oxide film and the substrate, and second, by reducing the internal diffusion of aluminum within the coating. Specific approaches include (1) modifying the aluminide coating with Cr, Si, Pt, or rare earth elements to improve the bonding strength between the oxide film and the substrate, and (2) creating a diffusion barrier between the coating and the substrate to inhibit the internal diffusion of aluminum. Modified aluminide coatings (such as Si-Al, Cr-Al, and Pt-Al coatings) are widely used overseas. Since the commercial application of aluminide coatings, modified aluminide coatings have been systematically optimized and advanced in terms of manufacturing process and technology, microstructure, and composition control, forming a series of coatings.

[0005] In addition to the thermal diffusion manufacturing process, there are many methods for producing high-temperature resistant coatings, such as composite thermal spraying technology, composite electroplating technology, sintering technology, etc. However, the quality of the coatings produced by these technologies is low, and due to the line-of-sight effect, the coating on the surface of a workpiece with a complex shape will have uneven thickness and will not be dense, making it particularly difficult to manufacture devices with complex structures. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to overcome the above-mentioned drawbacks of the prior art and to provide a highly conductive, high-temperature oxidation-resistant coating that has excellent high-temperature oxidation resistance, a uniform thickness, adheres closely to the substrate, and is relatively easy to manufacture, as well as a method for manufacturing the same. [Means for solving the problem]

[0007] To achieve the above object, the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises 15% by mass to 25% by mass of Al, 1% by mass to 3% by mass of Ni, 1% by mass to 5% by mass of Cr, 1% by mass to 3% by mass of Au, and the balance being Fe element.

[0008] The method for producing the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises the steps of: (1) preparing the surface of a workpiece; (2) immersing the workpiece in an Au plating solution and plating it to deposit an Au coating on the surface of the workpiece; and (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere to obtain a highly conductive, high-temperature oxidation-resistant coating.

[0009] The specific operation of step (1) is to degrease and remove rust from the surface of the workpiece, and then grind and polish the surface of the workpiece.

[0010] In step (2), the specific plating process is to plate in a water bath environment at 90°C to 95°C for 5 to 10 hours.

[0011] In step (2), the Au plating solution consists of 5 g / L AuCl3, 70 g / L NH4Cl, 60 g / L C6H5Na3O7, 15 g / L NiCl2, and 20 g / L NaH2PO2.

[0012] The specific process of the diffusion in step (3) is to diffuse at 850°C to 1050°C for 2 to 6 hours.

[0013] The Al-containing powder is composed of 1% to 3% by mass of Al powder, 1% to 3% by mass of NH4Cl powder, 1% to 3% by mass of NH4NO3 powder, 30% to 40% by mass of Fe-Al alloy powder, and the balance Al2O3 powder.

[0014] In step (3), the particle size of the Al-containing powder is less than 200 mesh. [Effects of the Invention]

[0015] The present invention has the following beneficial effects:

[0016] The highly conductive, high-temperature oxidation-resistant coating and its manufacturing method of the present invention incorporate gold (Au) and gold phases into conventional aluminide coatings, taking full advantage of the excellent thermal stability of gold. The gold modification further improves the high-temperature oxidation resistance of the aluminide coating, slowing the coating's degradation rate and significantly reducing the contact resistance of metal connectors in solid oxide fuel cells during long-term use. The coating adheres closely to the metal substrate, has a uniform thickness, and possesses excellent high-temperature oxidation resistance, effectively resolving the problem of rapid electrode corrosion caused by the volatilization of CrO₂(OH)₂ in fuel cell environments. After long-term corrosion, the surface resistivity at a high temperature of 800°C is 40 mΩ / cm. 2 When used in a metal connector of a solid oxide fuel cell, the metal connector can have a longer service life. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing the morphology of the coating on the surface of 316L stainless steel in Example 1 of the present invention. [Figure 2] FIG. 1 shows the morphology and component characteristics of the coating after oxidation in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to help those skilled in the art better understand the solutions of the present invention, the following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the disclosure of the present invention. Furthermore, in the following description, descriptions of well-known structures and techniques will be omitted to avoid unnecessarily obscuring the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative ingenuity should be included within the protection scope of the present invention.

[0019] The drawings show structural schematic diagrams of the embodiments disclosed in the present invention. These drawings are not drawn to scale, and some details may be enlarged or omitted for clarity. The shapes of various regions and layers shown in the drawings, as well as their relative sizes and positions, are merely illustrative and may differ in reality due to manufacturing tolerances or technical limitations. Those skilled in the art can separately design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0020] The highly conductive, high-temperature oxidation-resistant coating of the present invention contains 15% by mass to 25% by mass of Al, 1% by mass to 3% by mass of Ni, 1% by mass to 5% by mass of Cr, 1% by mass to 3% by mass of Au, and the balance being Fe element.

[0021] The method for producing the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises the steps of: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece better than 0.8; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 90°C to 95°C for 5 to 10 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L C6H5Na3O, 15 g / L NiCl, and 20 g / L NaH2PO2; and (3) burying the workpiece on which the Au coating has been deposited in Al-containing powder and diffusing it in an argon atmosphere at 850-1050°C for 2-6 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is 1-3 wt% Al powder, 1-3 wt% NH4Cl powder, 1-3 wt% NH4NO3 powder, 30-40 wt% Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is less than 200 mesh.

[0022] The highly conductive, high-temperature oxidation-resistant coating of the present invention is applicable to stainless steel materials of the series having a Cr content of 18% to 25% by mass. [Example]

[0023] Example 1 The method for producing a highly conductive, high-temperature oxidation-resistant coating of the present invention for electrode plates made of 316L stainless steel includes the following steps: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.6; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 95°C for 10 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L CHNaO, 15 g / L NiCl, and 20 g / L NaHPO; and (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere at 860°C for 6 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is composed of 1.2 wt% Al powder, 1.1 wt% NH4Cl powder, 3 wt% NH4NO3 powder, 35 wt% Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 300 mesh.

[0024] Testing revealed that the coating was metallurgically bonded to the substrate, had a thickness of 38 microns, and consisted of, by mass, 16.5% Al, 2.5% Au, 2.8% Ni, 4.0% Cr, and the balance Fe, the substrate element. The cross-sectional morphology of the coating is shown in Figure 2. When the coating was tested in still air at 800°C, the oxidation rate was 0.012 mg / cm. 2 The surface resistivity at a high temperature of 800°C is 38.2mΩ / cm 2 is.

[0025] Example 2 The method for producing a highly conductive, high-temperature oxidation-resistant coating of the present invention for electrode plates made of 316L stainless steel includes the following steps: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.6; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 90°C for 5 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L C6H5Na3O7, 15 g / L NiCl, and 20 g / L NaH2PO2; and (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere at 1050°C for 2 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is composed of 3 wt% Al powder, 3 wt% NH4Cl powder, 2.5 wt% NH4NO3 powder, 300 wt% Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 300 mesh.

[0026] Testing showed that the coating was metallurgically bonded to the substrate, had a thickness of 86 microns, and consisted of, by mass, 24.5% Al, 1.1% Au, 1.5% Ni, 2.5% Cr, and the balance Fe, a substrate element. When the coating was tested in still air at 800°C, the oxidation rate was 0.009 mg / cm. 2The surface resistivity at a high temperature of 800°C is 37.8mΩ / cm 2 is.

[0027] Example 3 The method for producing a highly conductive, high-temperature oxidation-resistant coating of the present invention for electrode plates made of 316L stainless steel includes the following steps: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.6; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 95°C for 5 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L C6H5Na3O7, 15 g / L NiCl, and 20 g / L NaH2PO2; and (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere at 950°C for 4 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is composed of 1.8% by weight Al powder, 2% by weight NH4Cl powder, 1% by weight NH4NO3 powder, 40% by weight Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 300 mesh.

[0028] Testing showed that the coating was metallurgically bonded to the substrate, had a thickness of 66 microns, and consisted of, by mass, 22.5% Al, 1.8% Au, 2.1% Ni, 3.2% Cr, and the balance Fe, a substrate element. When the coating was tested in still air at 800°C, the oxidation rate was 0.010 mg / cm. 2 The surface resistivity at a high temperature of 800°C is 37.9mΩ / cm 2 is.

[0029] Example 4 The method for producing a highly conductive, high-temperature oxidation-resistant coating of the present invention for a 310 stainless steel electrode plate comprises: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.6; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 95°C for 8 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L CHNaO, 15 g / L NiCl, and 20 g / L NaHPO; and (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere at 950°C for 4 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is composed of 1.2 wt% Al powder, 1.1 wt% NH4Cl powder, 1 wt% NH4NO3 powder, 35 wt% Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 300 mesh.

[0030] Testing showed that the coating was metallurgically bonded to the substrate, had a thickness of 59 microns, and consisted of, by mass, 20.5% Al, 1.1% Au, 2.5% Ni, 4.8% Cr, and the balance Fe, the substrate element. When the coating was tested in still air at 800°C, the oxidation rate was 0.009 mg / cm. 2 The surface resistivity at a high temperature of 800°C is 37.8mΩ / cm 2 is.

[0031] Example 5 The method for producing the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises the steps of: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.3; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 90°C for 5 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L CHNaO, 15 g / L NiCl, and 20 g / L NaHPO; and (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere at 850°C for 2 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is 1% by weight Al powder, 1% by weight NH4Cl powder, 1% by weight NH4NO3 powder, 30% by weight Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 400 mesh.

[0032] Example 6 The method for producing the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises the steps of: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.7; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 95°C for 10 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L C6H5Na3O7, 15 g / L NiCl, and 20 g / L NaH2PO2; and (3) burying the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere at 1050°C for 6 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is composed of 3% by weight Al powder, 3% by weight NH4Cl powder, 3% by weight NH4NO3 powder, 40% by weight Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 500 mesh.

[0033] Example 7 The method for producing the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises the steps of: Step (1) of degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.5; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 92°C for 6 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L CHNaO, 15 g / L NiCl, and 20 g / L NaHPO; and (3) embedding the workpiece with the deposited Au coating in an Al-containing powder and diffusing it in an argon atmosphere at 1000°C for 4 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is 2% by weight Al powder, 2% by weight NH4Cl powder, 2% by weight NH4NO3 powder, 32% by weight Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is less than 200 mesh.

[0034] Example 8 The method for producing the highly conductive, high-temperature oxidation-resistant coating of the present invention comprises the steps of: (1) degreasing and removing rust from the surface of the workpiece, and then using a grinding and polishing device to make the surface roughness of the workpiece 0.6; Step (2) of immersing the workpiece in an Au plating solution and plating it in a water bath environment at 94°C for 8 hours, the Au plating solution consisting of 5 g / L AuCl, 70 g / L NHCl, 60 g / L CHNaO, 15 g / L NiCl, and 20 g / L NaHPO; and (3) embedding the workpiece with the deposited Au coating in an Al-containing powder and diffusing it in an argon atmosphere at 950°C for 5 hours to obtain a highly conductive, high-temperature oxidation-resistant coating, wherein the Al-containing powder is 2.5% by weight Al powder, 2.5% by weight NH4Cl powder, 2.5% by weight NH4NO3 powder, 38% by weight Fe-Al alloy powder, and the balance Al2O3 powder, and the particle size of the Al-containing powder is 300 mesh.

[0035] Finally, it should be explained that the above examples are only used to illustrate the technical solutions of the present invention, and are not intended to limit the same. Although the present invention has been described in detail with reference to the above examples, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A highly conductive, high-temperature oxidation-resistant coating comprising 15% to 25% by mass of Al, 1% to 3% by mass of Ni, 1% to 5% by mass of Cr, 1% to 3% by mass of Au, and the balance being Fe element.

2. (1) preparing the surface of a workpiece; (2) immersing the workpiece in an Au plating solution to deposit an Au coating on the surface of the workpiece; (3) embedding the workpiece with the deposited Au coating in Al-containing powder and diffusing it in an argon atmosphere to obtain a highly conductive, high-temperature oxidation-resistant coating; 2. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 1, comprising:

3. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 2, characterized in that the specific operations of step (1) are to degrease and remove rust on the surface of the workpiece, and then to grind and polish the surface of the workpiece.

4. 3. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 2, wherein in step (2), the specific plating process is plating in a water bath environment at 90°C to 95°C for 5 to 10 hours.

5. In step (2), the Au plating solution contains 5 g / L of AuCl ３ and 70 g / L NH ４ Cl and 60 g / L of C ６ H ５ Na ３ O ７ and 15 g / L NiCl ２ and 20 g / L NaH ２ P.O. ２ 3. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 2, comprising:

6. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 2, wherein the specific process of diffusion in step (3) is to diffuse at 850°C to 1050°C for 2 to 6 hours.

7. The Al-containing powder contains 1 mass % to 3 mass % of Al powder and NH ４ Cl powder in an amount of 1 mass % to 3 mass % and NH ４ NO ３ 1% by mass to 3% by mass of Fe—Al alloy powder, 30% by mass to 40% by mass of Fe—Al alloy powder, and the remaining amount of Al ２ O ３ 3. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 2, characterized in that the highly conductive, high-temperature oxidation-resistant coating comprises a powder.

8. 3. The method for producing a highly conductive, high-temperature oxidation-resistant coating according to claim 2, characterized in that in step (3), the particle size of the Al-containing powder is less than 200 mesh.

Images