Preparation method of manganese-cobalt spinel coating for SOFC (solid oxide fuel cell) connector and coating

Abstract

The invention relates to the technical field of solid oxide fuel cells, in particular to a preparation method of a manganese-cobalt spinel coating for a solid oxide fuel cell (SOFC) connector and the coating. The method comprises the following steps: treating a substrate, cleaning a target material, depositing a MnCo alloy coating by high-power pulse magnetron sputtering, and performing thermal conversion to form the (Mn, Co) 3O4 spinel coating. By optimizing process parameters, the uniformity, compactness and high-temperature oxidation resistance of the coating are remarkably improved, and the problems of shadow effect and coating defects existing in traditional direct-current magnetron sputtering are solved. The thickness of the obtained coating ranges from 4.8 micrometers to 5.3 micrometers, the surface roughness is lower than 1 micrometer, external diffusion of the Cr element can still be effectively restrained after the coating serves for 840 hours for a long time at the temperature of 800 DEG C, and the ASR value is lower than 30 m omega.cm. The preparation process is simple, is suitable for industrial production, and has high practical value and popularization prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid oxide fuel cells, and more particularly, relates to a method for preparing a manganese-cobalt spinel coating for a SOFC interconnect and the coating. Background Art

[0002] A solid oxide fuel cell (SOFC) is a power generation device that directly converts the chemical energy in fuel into electrical energy through an electrochemical reaction. It has the characteristics of high energy utilization efficiency and clean and pollution-free, and is an important part of the new generation of clean energy. The interconnect is an important part of the SOFC, which plays the role of connecting the cathode and the anode, and at the same time separating the cathode and anode atmospheres, and its performance affects the overall performance of the battery stack. Currently, the operating temperature of the SOFC is between 600 and 800 o °C, making it possible for metal materials to be used as interconnect materials. Ferritic stainless steel has a thermal expansion coefficient similar to that of other components of the battery stack, good high-temperature oxidation resistance, and low cost, and is widely used in SOFC interconnect materials.

[0003] Although ferritic stainless steel has the above advantages, due to the Cr element content in ferritic stainless steel being 16 - 20 wt.%, when it serves for a long time at high temperature, the following problems will be faced: Problem of Cr2O3 formation: A Cr2O3 oxide layer will be formed on the surface of the stainless steel. Although it has a certain protective effect, its growth will consume chromium in the matrix, affecting the long-term performance of the material; Problem of Cr(VI) volatilization: At high temperature, Cr2O3 will volatilize to form toxic Cr(VI) gas, causing environmental pollution and safety hazards; Problem of cathode poisoning: The volatilized Cr(VI) will migrate to the cathode and react with the cathode material, resulting in a decrease in cathode performance and even failure.

[0004] To solve the above problems, the existing technology mainly adopts the method of applying a high-conductivity high-temperature protective coating on the surface of ferritic stainless steel to reduce the outward diffusion of Cr element. Common coating types include active element oxide coatings, rare earth perovskite coatings, and spinel coatings, etc. Among them, the (Mn,Co)3O4 spinel coating has been widely studied and applied due to its excellent conductivity and suitable thermal expansion coefficient.

[0005] Currently, the main method for preparing the spinel coating is to prepare a metal alloy coating on the surface of ferritic stainless steel and then convert it into a spinel coating through heat treatment. DC magnetron sputtering is a commonly used method for depositing metal coatings. However, traditional DC magnetron sputtering has the following defects: Low ionization rate: The ionization rate of target atoms is relatively low, resulting in a low density of the deposited coating.

[0006] Shadow effect: Due to the low ionization rate, ions are easily blocked during deposition, resulting in uneven coating thickness, especially on the surface of substrates with complex shapes.

[0007] Non-uniform performance: The microstructure may have pores or columnar crystal defects, and the uneven coating thickness will lead to non-uniform performance, affecting the protective effect of the coating.

[0008] These problems limit the long-term stability and reliability of the coating in high-temperature environments. In addition, in the existing technology, the coating preparation process also faces problems such as oxide contamination on the target surface, incomplete substrate pretreatment, and impurities in the sputtering source. These factors further affect the quality and performance of the coating. Especially under high-temperature service conditions, the uniformity, density, and adhesion of the coating directly determine its barrier performance and long-term stability. Therefore, developing a preparation method that can effectively improve the uniformity, density, and high-temperature oxidation resistance of the coating is of great significance for improving the service performance of SOFC connectors. Summary of the Invention

[0009] Aiming at the problems of uneven coating thickness and non-uniform performance in the preparation of manganese cobalt spinel coatings for SOFC connectors by DC magnetron sputtering in the existing technology, the present invention aims to provide a new preparation method and coating of manganese cobalt spinel coatings for SOFC connectors. By using high-power pulsed magnetron sputtering technology, the high-power pulsed magnetron sputtering technology has an extremely high ionization rate of target atoms and substrate bias voltage, which can ensure the uniformity and consistency of the coating, and obtain a uniform, dense, and excellent-performance spinel coating, thereby improving the service performance of SOFC connectors.

[0010] The technical solution of the present invention is as follows: A preparation method of a manganese cobalt spinel coating for an SOFC connector, comprising the following steps: (1) Substrate treatment: The surface of ferritic stainless steel is polished and polished in sequence, and then ultrasonically cleaned in a mixed solution of acetone and ethanol and dried. (2) Target cleaning: In the state without a substrate, the target is cleaned by a composite process of DC and pulsed magnetron sputtering to remove surface oxides and impurities. The sputtering time is 45 - 60 min, the sputtering temperature is 180 - 220 °C, and the vacuum degree is 0.4 Pa. The DC target cleaning parameters include a voltage of 350 - 400 V, a current of 1.0 - 1.5 A, and a power of 400 - 600 W. The pulsed target cleaning parameters include a voltage of 610 - 680 V, a frequency of 120 - 150 Hz, a pulse width of 150 - 170 μs, and a power of 450 - 550 W. (3) Coating deposition: The MnCo alloy coating was deposited using high-power pulsed magnetron sputtering technology. The specific process parameters are as follows: The parameters for bias cleaning the sample include a temperature of 180 - 220 °C, a vacuum degree of 1.0 - 2.0 Pa, a bias voltage of 650 - 750 V, and a time of 30 - 60 min; The parameters for high-power pulsed sputtering include a temperature of 180 - 220 °C, a vacuum degree of 0.38 - 0.42 Pa, a voltage of 500 - 700 V, a pulse width of 140 - 150 μs, a frequency of 140 - 510 Hz, a duty cycle of 2.1 - 7.7%, a corresponding peak current of 50 - 150 A, an average power of 1960 - 2040 W, and a substrate bias voltage of -30 to -80 V; (4) Thermal conversion: The deposited substrate was oxidized at 800 °C to form a (Mn,Co)3O4 spinel coating.

[0011] Further, in the preparation method of the manganese cobalt spinel coating for the SOFC connector described above, the volume ratio of the acetone to ethanol mixture is 1:3, and the ultrasonic cleaning time is 15 - 30 min.

[0012] Further, in the preparation method of the manganese cobalt spinel coating for the SOFC connector described above, in step (3), the distance between the target and the substrate is 15 cm, the chamber vacuum degree is controlled to 0.4 Pa, and Ar gas is introduced during the sputtering process to maintain the vacuum degree at 1.0 - 2.0 Pa.

[0013] Further, in the preparation method of the manganese cobalt spinel coating for the SOFC connector described above, the thickness of the MnCo alloy coating is 4.8 - 5.3 μm, the coating has a columnar structure, and the surface roughness of the coating is less than 25 nm.

[0014] Further, in the preparation method of the manganese cobalt spinel coating for the SOFC connector described above, during the coating deposition process, the plasma density is controlled by adjusting the pulse frequency and duty cycle to ensure that the ionization rate of the target atoms reaches more than 80%.

[0015] The manganese cobalt spinel coating prepared by the above preparation method has a coating composition of (Mn,Co)3O4, has a dense structure and high-temperature oxidation resistance, and can still effectively inhibit the outward diffusion of Cr elements after serving at 800 °C for 840 hours. The surface roughness of the spinel coating formed after thermal conversion is less than 1 μm.

[0016] Further, for the manganese cobalt spinel coating prepared by the above preparation method, the oxidation kinetic curve of the coating is parabolic.

[0017] Further, for the manganese cobalt spinel coating prepared by the above preparation method, the ASR value of the coating after serving at 800 °C for 840 hours is less than 25 mΩ·cm 2 .

[0018] Advantages and beneficial effects of the present invention: The coating prepared by this method not only has a dense structure and few defects, but also has high-temperature stability and high-temperature oxidation resistance. It can effectively inhibit the outward diffusion of Cr elements, avoid the pollution of the environment caused by the volatilization of Cr(VI) and the poisoning effect on the cathode performance. In addition, the coating preparation process is simple, easy to operate, and all process parameters can be precisely controlled, which is suitable for industrial production, and has high practical value and popularization prospects. At the same time, compared with the existing technology, it also has the following advantages: (1) Compared with the existing DC magnetron sputtering technology, the (Mn,Co)3O4 coating of the present invention is prepared by high-power pulsed magnetron sputtering process, which greatly improves the bonding force between the coating and the substrate; (2) The high-power pulsed magnetron sputtering technology effectively reduces the generation of large particles during the deposition process, the coating surface is smoother and flatter, and has fewer defects, reducing the surface roughness of the coating; (3) The high-power pulsed magnetron sputtering technology significantly improves the ionization rate of target atoms. The high ionization rate of target atoms promotes the migration and diffusion ability of sputtered ions on the substrate surface under the action of substrate bias voltage, effectively solving the shadow effect problem existing in DC magnetron sputtering, and ensuring the uniformity and consistency of the coating thickness. Brief Description of the Drawings

[0019] Figure 1 are the surface and cross-sectional morphology diagrams of the coating before thermal conversion under different current conditions. Among them, (a) is the surface morphology of the 50A coating before thermal conversion, (b) is the surface morphology of the 100A coating before conversion, (c) is the surface morphology of the 150A coating before conversion, (d) is the cross-sectional morphology of the 50A coating before conversion, (e) is the cross-sectional morphology of the 100A coating before conversion, and (f) is the cross-sectional morphology of the 150A coating before conversion; Figure 2 are the XRD patterns of the coating before thermal conversion under different current conditions; the left figure is the overall pattern of the main phase composition of the coating, and the right figure is the enlarged local pattern to show the change of peak width; Figure 3 are the surface and cross-sectional morphology diagrams of the coating after 840h of thermal conversion under different current conditions. Among them, (a) is the surface morphology of the 50A coating after 840h of thermal conversion, (b) is the surface morphology of the 100A coating after 840h of conversion, (c) is the surface morphology of the 150A coating after 840h of conversion, (d) is the cross-sectional morphology of the 50A coating after 840h of conversion, (e) is the cross-sectional morphology of the 100A coating after 840h of conversion, and (f) is the cross-sectional morphology of the 150A coating after 840h of conversion; Figure 4XRD patterns after thermal conversion of the coating under different current conditions, showing the presence of the (Mn,Co)3O4 spinel phase; Figure 5 ASR values of the coating after thermal conversion under different current conditions. Among them, (a) shows the ASR values of the 50A coating after conversion for 168 h and 840 h, (b) shows the ASR values of the 100A coating after conversion for 168 h and 840 h, and (c) shows the ASR values of the 150A coating after conversion for 168 h and 840 h; Figure 6 3D images and surface roughness of the 50A coating before and after thermal conversion. Among them, (a) is the 3D image and surface roughness (Ra = 18.4 nm) before thermal conversion, and (b) is the 3D image and surface roughness (Ra = 0.422 μm) after thermal conversion. Detailed implementation manners

[0020] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the accompanying drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0021] In the prior art, solid oxide fuel cell connectors have long faced the problem of cathode poisoning caused by the outward diffusion of chromium elements in high-temperature environments. Although traditional magnetron sputtering technology can prepare protective coatings, it is limited by the insufficient ionization rate of the plasma, resulting in defects such as uneven coating thickness and poor compactness. Especially on the surface of substrates with complex shapes, it is difficult for traditional processes to eliminate the shadow effect, and the weak areas of the coating are prone to become diffusion channels for chromium elements, seriously affecting the long-term stability of the battery stack.

[0022] To solve the above problems, the high ionization rate characteristics of high-power pulse technology may improve the coating uniformity, but initial experiments found that the oxide contamination on the target surface would significantly reduce the deposition efficiency. By analyzing the formation mechanism of coating defects, it was found that incomplete substrate pretreatment and sputtering source impurities are the key factors affecting the coating quality. Further research found that the phase transformation process of metal alloys to the spinel structure at a specific oxidation temperature directly affects the barrier performance of the coating, which provides a direction for optimizing the heat treatment parameters.

[0023] Therefore, the present application proposes a preparation method including substrate treatment, target cleaning, coating deposition, and thermal conversion. Substrate treatment includes surface grinding and polishing and ultrasonic cleaning with a solvent of a specific ratio. Target cleaning adopts a composite magnetron sputtering mode. Coating deposition uses high-power pulse magnetron sputtering in combination with substrate bias control. The thermal conversion stage completes the alloy oxidation at a set temperature.

[0024] Example 1

[0025] A preparation method of a manganese-cobalt spinel coating for an SOFC interconnect in this embodiment specifically includes the following steps: (1) Substrate treatment: The surface of ferritic stainless steel is polished successively with 400#, 600#, 1000# and 2000# SiC waterproof abrasive papers, and chamfering and rounding treatments are carried out. It is polished with diamond grinding paste until the surface is bright and free of scratches, ensuring that the surface roughness is lower than 0.5 μm, so as to improve the bonding force between the coating and the substrate. The polished substrate is ultrasonically cleaned in a mixed solution of acetone and ethanol for 20 min, and then dried in an oven for standby. The volume ratio of the acetone and ethanol mixed solution is 1:3.

[0026] (2) Target cleaning: In the state without a substrate, the target is cleaned by a combined process of DC and pulsed magnetron sputtering to remove surface oxides and impurities. Sputtering is carried out for 60 min, the sputtering temperature is 180 °C, and the vacuum degree is 0.4 Pa; the DC sputtering parameters are: voltage 350 V, current 1.0 A, power 400 W; the pulsed target cleaning parameters are: voltage 610 V, frequency 150 Hz, pulse width 150 μs, power 450 W.

[0027] (3) Coating deposition: Use high-power pulsed magnetron sputtering technology to deposit a MnCo alloy coating. Open the chamber door of the magnetron sputtering instrument, place the substrate on the turntable, close the chamber door, and the distance between the target and the substrate is 15 cm. First, turn on the mechanical pump and the pre-pumping valve. When the vacuum is pumped to 5 Pa, then turn on the diffusion pump and the fore-vacuum valve. When the vacuum is pumped to 6×10 -3 Pa, then introduce Ar to make the chamber vacuum degree 1.0 Pa, set the bias voltage to 650 V, and clean the sample with the bias voltage for 60 min. The high-power pulsed sputtering parameters are: temperature 180 °C, vacuum degree 0.42 Pa, substrate bias voltage -80 V, voltage 500 V, pulse width 150 μs, frequency 510 Hz, duty cycle 7.7%, corresponding peak current 50 A, average power 2000 W. Figure 1 (a) shows that the coating surface is in a cauliflower shape of dense packing, Figure 1 (d) shows that the coating thickness is uniform and has good bonding with the substrate. Figure 2 It shows that the coating composition before thermal conversion is a single γ-Co.

[0028] (4) Thermal conversion: The deposited substrate is oxidized in a muffle furnace at 800 °C to form a (Mn,Co)3O4 spinel coating. Figure 4 It shows that the composition of the oxide film is a single MnCo2O4. Figure 5 The ASR result of... shows that it is only 28.728 mΩ·cm after 840 hours of oxidation 2 .

[0029] In this embodiment, the thickness of the MnCo alloy coating of the SOFC interconnect manganese cobalt spinel coating obtained is 5.2 μm, and the surface roughness of the spinel coating formed after thermal conversion is 0.422 μm. The coating composition is (Mn,Co)3O4, which has a dense structure, high-temperature oxidation resistance, and can effectively inhibit the outward diffusion of Cr elements after serving at 800 °C for 840 hours.

[0030] Example 2

[0031] A preparation method of a manganese cobalt spinel coating for an SOFC interconnect in this embodiment specifically includes the following steps: (1) Substrate treatment: The surface of ferritic stainless steel is polished successively with 400#, 600#, 1000#, and 2000# SiC water sandpapers, and chamfering and rounding are carried out. It is polished with diamond grinding paste until the surface is bright and free of scratches, ensuring that the surface roughness is lower than 0.5 μm. It is ultrasonically cleaned in a mixed solution of acetone and ethanol for 15 min, and then dried in an oven for standby. The volume ratio of the acetone-ethanol mixture is 1:3.

[0032] (2) Target cleaning: In the absence of a substrate, the target is cleaned by a combined process of DC and pulsed magnetron sputtering to remove surface oxides and impurities. Sputtering is carried out for 45 min, the sputtering temperature is 220 °C, and the vacuum degree is 0.4 Pa; the DC sputtering parameters are: voltage 380 V, current 1.5 A, power 570 W; the pulsed sputtering parameters are: voltage 650 V, frequency 120 Hz, pulse width 160 μs, power 520 W.

[0033] (3) Coating deposition: The MnCo alloy coating is deposited using high-power pulsed magnetron sputtering technology. Open the chamber door of the magnetron sputtering instrument, place the substrate on the turntable, close the chamber door, and the distance between the target and the substrate is 15 cm. First, turn on the mechanical pump and the pre-pumping valve. When the vacuum is pumped to 5 Pa, then turn on the diffusion pump and the fore-vacuum valve. When the vacuum is pumped to 6×10 -3 Pa, then introduce Ar to make the chamber vacuum degree 2.0 Pa, set the bias voltage to 750 V, and clean the sample with the bias voltage for 30 min. The high-power pulsed sputtering parameters are: temperature 220 °C, vacuum degree 0.38 Pa, substrate bias voltage -50 V, voltage 600 V, pulse width 145 μs, frequency 230 Hz, duty cycle 3.5%, corresponding peak current 100 A, and average power 2040 W. Figure 1 (b) indicates that the coating has no obvious defects, Figure 1 (e) indicates that the coating is tightly bonded to the substrate. The XRD pattern indicates that the coating composition is γ-Co.

[0034] (4) Thermal conversion: The deposited substrate was oxidized in a muffle furnace at 800 °C to form a (Mn,Co)3O4 spinel coating. The XRD pattern showed that the oxide was only MnCo2O4. The ASR results showed that it was 28.994 mΩ·cm after 5 weeks of oxidation. 2 。

[0035] The thickness of the MnCo alloy coating of the manganese-cobalt spinel coating for the SOFC connector obtained in this example was 5.3 μm, and the surface roughness of the spinel coating formed after thermal conversion was 0.589 μm. The coating composition was (Mn,Co)3O4, which had a dense structure, high-temperature oxidation resistance, and could effectively inhibit the outward diffusion of Cr elements after serving at 800 °C for 840 hours.

[0036] Example 3

[0037] A preparation method of a manganese-cobalt spinel coating for an SOFC connector in this example specifically includes the following steps: (1) Substrate treatment: The surface of the ferritic stainless steel was polished successively with 400#, 600#, 1000#, and 2000# SiC water sandpapers, and chamfering and rounding were carried out. It was polished with diamond grinding paste until the surface was bright and free of scratches, ensuring that the surface roughness was less than 0.5 μm. It was ultrasonically cleaned in a mixed solution of acetone and ethanol for 30 min, and then dried in an oven for standby. The volume ratio of the acetone-ethanol mixture was 1:3.

[0038] (2) Target cleaning: In the absence of a substrate, the target was cleaned by a combined process of DC and pulsed magnetron sputtering to remove surface oxides and impurities. Sputtering was carried out for 45 min, the sputtering temperature was 200 °C, and the vacuum degree was 0.4 Pa; the DC sputtering parameters were: voltage 400 V, current 1.5 A, power 600 W; the pulsed sputtering parameters were: voltage 680 V, frequency 160 Hz, pulse width 170 μs, power 550 W.

[0039] (3) Coating deposition: The MnCo alloy coating was deposited using high-power pulsed magnetron sputtering technology. The chamber door of the magnetron sputtering instrument was opened, the substrate was placed on the turntable, the chamber door was closed, the distance between the target and the substrate was 15 cm. First, the mechanical pump and the forepump valve were opened. When the vacuum was pumped to 5 Pa, then the diffusion pump and the foreline valve were opened. When the vacuum was pumped to 6×10 -3 Pa, then Ar was introduced to make the chamber vacuum degree 1.5 Pa. The bias voltage was set to 700 V, and the sample was bias-cleaned for 45 min. The high-power pulsed sputtering parameters were: temperature 200 °C, vacuum degree 0.4 Pa, substrate bias voltage -30 V, voltage 700 V, pulse width 140 μs, frequency 140 Hz, duty cycle 2.1%, corresponding peak current 150 A, average power 1960 W. Figure 2The XRD results show that the phase composition is the same as that of the 50A and 100A coatings. However, compared with the former two, the full width at half maximum (FWHM) increases significantly, and the coating grains are significantly refined at this time.

[0040] (4) Thermal conversion: The deposited substrate was oxidized in a muffle furnace at 800 °C to form a (Mn,Co)3O4 spinel coating. Figure 4 It shows that the oxidation is the same as the former two. Figure 5 It shows that the ASR value after 5 weeks of oxidation is 27.864 mΩ·cm 2 .

[0041] The thickness of the MnCo alloy coating of the manganese-cobalt spinel coating for the SOFC connector obtained in this example is 4.8 μm, and the surface roughness of the spinel coating formed after thermal conversion is 0.508 μm. The coating composition is (Mn,Co)3O4, which has a dense structure, high-temperature oxidation resistance, and can effectively inhibit the outward diffusion of Cr elements after serving at 800 °C for 840 hours.

[0042] From Figure 1 it can be seen that as the current increases, the coating surface gradually becomes dense and binds well with the substrate.

[0043] Figure 2 shows the XRD patterns of the coating before thermal conversion under different current conditions. The left figure is the overall pattern of the main phase composition of the coating, and the right figure is the enlarged local pattern to show the change in peak width.

[0044] Figure 3 shows the surface and cross-sectional morphologies of the coating after 840 hours of thermal conversion under different current conditions. Among them, (a), (b), and (c) are the surface morphologies of the coating under 50A, 100A, and 150A currents respectively, and (d), (e), and (f) are the corresponding cross-sectional morphologies. From Figure 3 it can be seen that after long-term high-temperature oxidation, the coating still maintains a dense structure and binds tightly with the substrate.

[0045] Figure 4 shows the XRD pattern of the coating after thermal conversion, indicating that the coating is completely converted into a single-phase MnCo2O4 spinel structure.

[0046] Figure 5 shows the ASR values of the coating after thermal conversion under different current conditions. Among them, (a), (b), and (c) are the ASR values of the coating under 50A, 100A, and 150A currents at 168 hours and 840 hours respectively. From Figure 5 it can be seen that the ASR values of the coating after serving at 800 °C for 840 hours are all lower than 25 mΩ·cm², indicating that the coating has excellent electrical conductivity.

[0047] Figure 6 Shows the 3D images and surface roughness of the 50A coating before and after thermal conversion, where (a) is the 3D image and surface roughness before thermal conversion (Ra = 18.4 nm), and (b) is the 3D image and surface roughness after thermal conversion (Ra = 0.422 μm). From Figure 6 It can be seen that the surface of the coating is smoother and flatter after thermal conversion, and the roughness is significantly reduced.

Claims

1. A preparation method of a manganese-cobalt spinel coating for a SOFC interconnect, characterized in that, It includes the following steps: (1) Substrate treatment: The surface of ferritic stainless steel is polished and buffed in sequence, and then ultrasonically cleaned in a mixed solution of acetone and ethanol and dried; (2) Target cleaning: In the state without substrate, the target is cleaned by a composite process of DC and pulsed magnetron sputtering to remove surface oxides and impurities. The sputtering time is 45 - 60 min, the sputtering temperature is 180 - 220 °C, and the vacuum degree is 0.4 Pa. The DC target cleaning parameters include voltage 350 - 400 V, current 1.0 - 1.5 A, and power 400 - 600 W. The pulsed target cleaning parameters include voltage 610 - 680 V, frequency 120 - 150 Hz, pulse width 150 - 170 μs, and power 450 - 550 W; (3) Coating deposition: The MnCo alloy coating is deposited using high - power pulsed magnetron sputtering technology. The specific process parameters are as follows: The parameters for bias - cleaning the sample include vacuum degree 1.0 - 2.0 Pa, bias voltage 650 - 750 V, and time 30 - 60 min. The high - power pulsed sputtering parameters include temperature 180 - 220 °C, vacuum degree 0.38 - 0.42 Pa, voltage 500 - 700 V, pulse width 140 - 150 μs, frequency 140 - 510 Hz, duty cycle 2.1 - 7.7%, corresponding peak current 50 - 150 A, average power 1960 - 2040 W, and substrate bias voltage of - 30 to - 80 V; (4) Thermal conversion: The deposited substrate is oxidized at 800 °C to form a (Mn, Co)3O4 spinel coating.

2. The preparation method of the manganese-cobalt spinel coating for the SOFC interconnect according to claim 1, characterized in that The volume ratio of the mixed solution of acetone and ethanol is 1:3, and the ultrasonic cleaning time is 15 - 30 min.

3. The preparation method of the manganese-cobalt spinel coating for the SOFC interconnect according to claim 1, wherein, In step (3), the distance between the target and the substrate is 15 cm, the chamber vacuum degree is controlled at 0.4 Pa, and Ar gas is introduced during sputtering to maintain the vacuum degree at 1.0 - 2.0 Pa.

4. The preparation method of the manganese-cobalt spinel coating for the SOFC interconnect according to claim 1, characterized in that, The thickness of the MnCo alloy coating deposited in step (3) is 4.8 - 5.3 μm. The coating has a columnar structure, and the surface roughness of the coating is less than 25 nm.

5. The preparation method of a manganese-cobalt spinel coating for an SOFC interconnect according to claim 1, characterized in that, During the coating deposition process, the plasma density is controlled by adjusting the pulse frequency and duty cycle to ensure that the ionization rate of target atoms reaches more than 80%.

6. A manganese-cobalt spinel coating prepared by the preparation method according to any one of claims 1-5, characterized in that, After thermal conversion, the coating composition is (Mn, Co)3O4, which has a dense structure and high - temperature oxidation resistance, and can still effectively inhibit the outward diffusion of Cr elements after serving at 800 °C for 840 hours. The surface roughness of the spinel coating formed after thermal conversion is less than 1 μm.

7. A manganese-cobalt spinel coating prepared by the preparation method according to any one of claims 1-5, characterized in that, The oxidation kinetic curve of the said coating is parabolic.

8. A manganese-cobalt spinel coating prepared by the preparation method according to any one of claims 1-5, characterized in that, The ASR value of the said coating after long-term service at 800 °C for 840 hours is less than 30 mΩ·cm 2 .

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