High-corrosion-resistance conductive composite coating of titanium metal bipolar plate, preparation method and bipolar plate

Abstract

The embodiment of the invention provides a high-corrosion-resistance conductive composite coating of a titanium metal bipolar plate, a preparation method and the bipolar plate. The composite coating comprises a titanium mixed bottom layer, a gradient transition titanium carbonitride middle layer and an amorphous carbon surface layer from inside to outside. The thickness of the titanium mixed bottom layer is 0.2-0.5 mu m, and the titanium mixed bottom layer is formed through titanium ion implantation and deposition by combining high-power pulse magnetron sputtering with 15-25kV high-voltage pulse target table bias; the thickness of the titanium carbonitride middle layer is 0.3-0.5 mu m, the titanium carbonitride middle layer is deposited in a nitrogen and acetylene reaction atmosphere through high-power pulse magnetron sputtering, and the content of nitrogen atoms is gradually reduced from the position close to the titanium mixed bottom layer to the outside; the thickness of the amorphous carbon surface layer is 0.5 mu m-1 mu m, and the amorphous carbon surface layer is deposited on the surface of the titanium metal bipolar plate through high-power pulse magnetron sputtering assisted by an anode layer ion source. According to the technical scheme, preparation of the multilayer-structure high-corrosion-resistance conductive composite coating on the surface of the metal bipolar plate substrate can be achieved, the high-corrosion-resistance conductive requirements of the titanium metal bipolar plate of the hydrogen fuel cell are met, the performance of the hydrogen fuel cell is improved, the service life of the hydrogen fuel cell is prolonged, and the reliability of the hydrogen fuel cell is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface coatings, and in particular relates to a highly corrosion-resistant conductive composite coating for a titanium metal bipolar plate, a preparation method, and the bipolar plate. Background Art

[0002] Hydrogen fuel cells are power generation devices that use hydrogen as fuel and air or pure oxygen as an oxidant, converting chemical energy directly into electrical energy. They have attracted widespread attention from governments and research institutions worldwide due to their high efficiency, energy efficiency, safety, and environmental friendliness. Bipolar plates are the core component of hydrogen fuel cell stacks. Operating in a complex environment characterized by acid, heat, and electrochemical corrosion, they perform multiple functions, including current collection and conduction, heat dissipation, uniform dispersion of the reaction medium, and leakage prevention. Corrosion and damage to the bipolar plates will lead to hydrogen fuel cell failure, and therefore largely determine the performance, lifespan, and reliability of the fuel cell.

[0003] Common bipolar plate materials include graphite, metal, and composite materials. Metal bipolar plates are the main direction of future development due to their good mechanical strength, processing performance, and electrical conductivity, especially impact and vibration resistance. Metal bipolar plates are mainly divided into two categories: stainless steel and titanium alloys. Titanium alloys have the advantages of corrosion resistance, high temperature resistance, low density, high specific strength, and non-magnetic properties. In addition, they do not precipitate heavy metal elements that are toxic to precious metal catalysts. They can significantly improve the performance, reliability, and life of hydrogen fuel cells, and reduce the overall weight of hydrogen fuel cells. They are ideal materials for the substrate of hydrogen fuel cell metal bipolar plates. However, titanium alloys are very prone to passivation in the harsh corrosive environment of hydrogen fuel cells, such as high potential, oxygen-rich, high operating temperature, and acidic environment. Although this improves their corrosion resistance, it increases the surface contact resistance, seriously affecting the electrical performance and durability of the bipolar plate.

[0004] Therefore, how to provide a highly corrosion-resistant conductive composite coating for titanium metal bipolar plates, a preparation method and a bipolar plate, realize the preparation of a multi-layer highly corrosion-resistant conductive composite coating on the surface of the metal bipolar plate substrate, meet the high corrosion resistance and conductivity requirements of hydrogen fuel cell titanium metal bipolar plates, and improve the performance, life and reliability of hydrogen fuel cells has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The embodiments of the present invention provide a highly corrosion-resistant conductive composite coating for a titanium metal bipolar plate, a preparation method, and a bipolar plate, thereby enabling the preparation of a highly corrosion-resistant conductive composite coating with a multilayer structure on the surface of a metal bipolar plate substrate, meeting the high corrosion resistance and conductivity requirements of titanium metal bipolar plates for hydrogen fuel cells, and improving the performance, life, and reliability of hydrogen fuel cells.

[0006] In one embodiment of the present invention, a highly corrosion-resistant conductive composite coating for a titanium metal bipolar plate is provided. The composite coating comprises, from the inside to the outside, a titanium mixed bottom layer, a gradient transition titanium carbonitride (TiCN) middle layer, and an amorphous carbon surface layer.

[0007] The titanium mixed bottom layer has a thickness of 0.2 μm to 0.5 μm and is formed by high-power pulsed magnetron sputtering combined with 15 kV to 25 kV high-voltage pulsed target bias, and titanium ion implantation and deposition;

[0008] The titanium carbonitride (TiCN) intermediate layer has a thickness of 0.3 μm to 0.5 μm and is deposited by high-power pulsed magnetron sputtering in a nitrogen and acetylene reaction atmosphere, wherein the nitrogen atomic content decreases from the titanium mixed bottom layer toward the outside;

[0009] The amorphous carbon surface layer has a thickness of 0.5 μm to 1 μm and is deposited on the surface of the titanium metal bipolar plate by high-power pulsed magnetron sputtering assisted by an anode layer ion source.

[0010] Furthermore, the film-base bonding strength of the titanium mixed bottom layer is ≥51N, and the surface contact resistance of the amorphous carbon surface layer is ≤1.6mΩ·cm 2 , corrosion current density ≤ 2.0μA / cm 2 .

[0011] Furthermore, the C / N atomic ratio of the TiCN intermediate layer is regulated to be 0.6:1 to 1.9:1 by adjusting the flow rate ratio of acetylene to nitrogen, and the Vickers hardness is ≥2400 HV.

[0012] In another embodiment of the present invention, a method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate is provided, comprising:

[0013] S101, ultrasonically degreasing the titanium bipolar plates for 10 to 30 minutes using an industrial degreasing agent, and then ultrasonically rinsing them with distilled water for 10 to 30 minutes to remove oil stains;

[0014] S102, performing ultrasonic-assisted electrochemical polishing on the surface of the titanium metal bipolar plate to achieve a surface roughness Ra of less than 0.4 μm;

[0015] S103. In a vacuum chamber, using a titanium arc electron ion source to generate high-energy argon ions to etch and clean the cleaned and polished titanium bipolar plate at a working pressure of 0.3 Pa to 0.6 Pa, a negative bias voltage of 1 kV to 5 kV on the substrate of the titanium bipolar plate, and a time of 10 min to 120 min.

[0016] S104, using a high-power pulsed magnetron sputtering power supply to generate titanium plasma, applying a negative pulse high voltage of 15 kV to 25 kV to the substrate of the titanium metal bipolar plate, with a pulse width of 10 μs to 100 μs and a frequency of 30 Hz to 300 Hz, to deposit a 0.2 μm to 0.5 μm titanium mixed bottom layer in an argon atmosphere;

[0017] S105, using a high-power pulsed magnetron sputtering power supply to generate titanium plasma, applying a negative pulse high voltage of 15 kV to 25 kV to the substrate of the titanium metal bipolar plate, with a pulse width of 10 μs to 50 μs and a frequency of 30 Hz to 80 Hz, using nitrogen and acetylene as working gases, and depositing a titanium carbonitride intermediate layer of 0.3 μm to 0.5 μm in the nitrogen and acetylene mixed gas atmosphere;

[0018] S106. Carbon plasma is generated by synergistically using the anode layer ion source and high-power pulse magnetron sputtering, and a negative pulse high voltage of 15kV to 20kV is applied to the substrate of the titanium metal bipolar plate. The pulse width is 10μs to 50μs, and the frequency is 30Hz to 80Hz. An amorphous carbon surface layer with a thickness of 0.5μm to 0.5μm is deposited in an argon + acetylene + hydrogen atmosphere.

[0019] Furthermore, the argon gas working pressure for the etching and cleaning is 0.5 Pa, the substrate negative bias voltage is 3 kV, and the time is 30 minutes.

[0020] Furthermore, the flow rate ratio of nitrogen to acetylene is 1:1 to 1.5:1, and the working pressure is 0.03Pa to 0.3Pa; wherein, when the flow rate ratio of acetylene to nitrogen is 1:1, the contact resistance of the TiCN layer is the lowest.

[0021] Furthermore, the working pressure of the argon+acetylene+hydrogen mixed atmosphere is 0.01Pa to 0.1Pa.

[0022] Furthermore, the amount of hydrogen added is 3% to 8% by volume, which is used to suppress the internal stress of the amorphous carbon surface layer and improve the conductivity.

[0023] In another embodiment of the present invention, a titanium metal composite coating bipolar plate for a hydrogen fuel cell is provided. The composite bipolar plate includes the highly corrosion-resistant conductive composite coating of the titanium metal bipolar plate described in any one of the above items.

[0024] The beneficial effects brought about by the present invention are as follows:

[0025] As can be seen from the above scheme, the embodiment of the present invention provides a highly corrosion-resistant conductive composite coating for titanium bipolar plates, a preparation method, and a bipolar plate. The composite coating comprises, from the inside to the outside, a titanium mixed bottom layer, a gradient transition titanium carbonitride (TiCN) middle layer, and an amorphous carbon top layer. The titanium mixed bottom layer has a thickness of 0.2μm to 0.5μm and is formed by high-power pulsed magnetron sputtering combined with a 15kV to 25kV high-voltage pulse target bias, through titanium ion implantation and deposition; the titanium carbonitride (TiCN) middle layer has a thickness of 0.3μm to 0.5μm and is deposited by high-power pulsed magnetron sputtering in a nitrogen and acetylene reaction atmosphere, wherein the nitrogen atomic content decreases from the titanium mixed bottom layer to the outside; the amorphous carbon top layer has a thickness of 0.5μm to 1μm and is deposited on the surface of the titanium bipolar plate by high-power pulsed magnetron sputtering assisted by an anode layer ion source. The technical solution of the present invention can realize the preparation of a multi-layer structured highly corrosion-resistant conductive composite coating on the surface of a metal bipolar plate substrate, meet the high corrosion-resistant and conductive requirements of the titanium metal bipolar plate of hydrogen fuel cells, and improve the performance, life and reliability of hydrogen fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a highly corrosion-resistant conductive composite coating and a preparation method for a titanium metal bipolar plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] In an embodiment of the present invention, a highly corrosion-resistant and conductive composite coating with strong bonding on the surface of a titanium bipolar plate and a preparation process are provided. High-energy argon ion etching is performed by a titanium arc electron source to completely remove the natural passivation film on the surface of the titanium metal. Titanium plasma is generated by high-power pulsed magnetron sputtering. Titanium ion implantation and deposition are achieved under the action of pulsed high voltage on the substrate. Titanium carbonitride deposition is achieved under acetylene and nitrogen conditions. A carbon surface layer is prepared under the assistance of an anode layer ion source. Finally, a composite coating with strong bonding (far better than Toyota's second generation, with a membrane-base bonding force greater than 50N), high corrosion resistance (comparable to Toyota's second generation, with a corrosion current density less than 2.0μA / cm2), and high conductivity (better than Toyota's second generation, with a surface contact resistance less than 1.6mΩ·cm2) on the surface of the titanium bipolar plate is prepared, meeting the high corrosion resistance and conductivity requirements of the titanium bipolar plate surface of hydrogen fuel cells, and improving the performance, life, and reliability of hydrogen fuel cells.

[0029] In one embodiment of the present invention, a highly corrosion-resistant conductive composite coating for a titanium metal bipolar plate comprises, from the inside to the outside, a titanium mixed bottom layer, a gradient transition titanium carbonitride (TiCN) middle layer, and an amorphous carbon surface layer.

[0030] The titanium mixed bottom layer has a thickness of 0.2 μm to 0.5 μm and is formed by high-power pulsed magnetron sputtering combined with 15 kV to 25 kV high-voltage pulsed target bias, and titanium ion implantation and deposition;

[0031] The titanium carbonitride (TiCN) intermediate layer has a thickness of 0.3 μm to 0.5 μm and is deposited by high-power pulsed magnetron sputtering in a nitrogen and acetylene reaction atmosphere, wherein the nitrogen atomic content decreases from the titanium mixed bottom layer toward the outside;

[0032] The amorphous carbon surface layer has a thickness of 0.5 μm to 1 μm and is deposited on the surface of the titanium metal bipolar plate by high-power pulsed magnetron sputtering assisted by an anode layer ion source.

[0033] In an embodiment of the present invention, an optimized multi-layer structure high corrosion-resistant conductive coating is prepared on the surface of a titanium bipolar plate, that is, the surface of the titanium bipolar plate is first etched and cleaned for 10 minutes to 120 minutes using a titanium arc electron ion source, and then titanium ions are implanted and deposited on the surface of the titanium bipolar plate using high-power pulsed magnetron sputtering + high-voltage pulsed target bias to form a dense titanium mixed bottom layer with a thickness of 0.2μm to 0.5μm, and then a titanium carbonitride intermediate layer with a thickness of 0.3μm to 0.5μm is deposited on the surface of the titanium bipolar plate using high-energy reactive magnetron sputtering, and finally a carbon surface layer with a thickness of 0.5μm to 1μm is deposited on the surface of the titanium bipolar plate using an anode layer ion source + high-power pulsed magnetron sputtering.

[0034] Among them, etching and cleaning are used to remove the oxide film on the surface of the titanium bipolar plate substrate; the titanium mixed bottom layer is used to improve the corrosion resistance and adhesion of the titanium bipolar plate substrate surface; the titanium carbonitride intermediate layer is used to improve the carrying capacity of the titanium bipolar plate substrate, match the physical and chemical and mechanical property differences between the titanium bipolar plate substrate and the carbon coating, and realize the gradient transition of chemical composition and mechanical properties; the carbon surface layer has excellent corrosion resistance, conductivity and other properties, and ultimately realizes the preparation of high corrosion-resistant and conductive functional coatings on the surface of the titanium bipolar plate, meeting the high corrosion resistance and conductivity requirements of hydrogen fuel cell titanium bipolar plates, and improving the performance, life and reliability of hydrogen fuel cells.

[0035] In one embodiment of the present invention, the film-base bonding strength of the titanium mixed bottom layer is ≥51N, and the surface contact resistance of the amorphous carbon top layer is ≤1.6mΩ·cm 2 , corrosion current density ≤ 2.0μA / cm 2 .

[0036] In another embodiment of the present invention, the C / N atomic ratio of the TiCN intermediate layer is controlled to be 0.6:1 to 1.9:1 by adjusting the flow rate ratio of acetylene to nitrogen, and the Vickers hardness is ≥2400 HV.

[0037] like Figure 1 As shown, a flow chart of a high corrosion-resistant conductive composite coating and a preparation method for a titanium metal bipolar plate according to an embodiment of the present invention.

[0038] Figure 1 A method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate comprises:

[0039] S101, ultrasonically degreasing the titanium bipolar plates for 10 to 30 minutes using an industrial degreasing agent, and then ultrasonically rinsing them with distilled water for 10 to 30 minutes to remove oil stains;

[0040] S102, performing ultrasonic-assisted electrochemical polishing on the surface of the titanium metal bipolar plate to achieve a surface roughness Ra of less than 0.4 μm;

[0041] S103. In a vacuum chamber, using a titanium arc electron ion source to generate high-energy argon ions to etch and clean the cleaned and polished titanium bipolar plate at a working pressure of 0.3 Pa to 0.6 Pa, a negative bias voltage of 1 kV to 5 kV on the substrate of the titanium bipolar plate, and a time of 10 min to 120 min.

[0042] S104, using a high-power pulsed magnetron sputtering power supply to generate titanium plasma, applying a negative pulse high voltage of 15 kV to 25 kV to the substrate of the titanium metal bipolar plate, with a pulse width of 10 μs to 100 μs and a frequency of 30 Hz to 300 Hz, to deposit a 0.2 μm to 0.5 μm titanium mixed bottom layer in an argon atmosphere;

[0043] S105, using a high-power pulsed magnetron sputtering power supply to generate titanium plasma, applying a negative pulse high voltage of 15 kV to 25 kV to the substrate of the titanium metal bipolar plate, with a pulse width of 10 μs to 50 μs and a frequency of 30 Hz to 80 Hz, using nitrogen and acetylene as working gases, and depositing a titanium carbonitride intermediate layer of 0.3 μm to 0.5 μm in the nitrogen and acetylene mixed gas atmosphere;

[0044] S106. Carbon plasma is generated by synergistically using the anode layer ion source and high-power pulse magnetron sputtering, and a negative pulse high voltage of 15kV to 20kV is applied to the substrate of the titanium metal bipolar plate. The pulse width is 10μs to 50μs, and the frequency is 30Hz to 80Hz. An amorphous carbon surface layer with a thickness of 0.5μm to 0.5μm is deposited in an argon + acetylene + hydrogen atmosphere.

[0045] In the embodiments of the present invention, ultrasonic degreasing is performed using an industrial degreasing agent for 10 to 30 minutes, followed by ultrasonic rinsing with distilled water for 10 to 30 minutes to ensure that there is no oil contamination that could affect the next process. The titanium bipolar plate surface is polished using an ultrasonic + electrochemical composite polishing process to remove surface microscopic defects, achieving a surface roughness of less than 0.4 μm. The titanium bipolar plate surface is then ultrasonically rinsed with distilled water for 10 to 30 minutes to ensure a clean surface.

[0046] In one embodiment of the present invention, the argon gas working pressure for the etching and cleaning is 0.5 Pa, the substrate negative bias voltage is 3 kV, and the time is 30 minutes.

[0047] High-energy ion etching: After cleaning and polishing, the titanium bipolar plate is placed in a vacuum chamber for high-energy ion etching to remove the natural passivation film on the surface of the titanium bipolar plate substrate. The ion etching cleaning process uses argon gas at a pressure of 0.3 Pa to 0.6 Pa. A titanium arc electron ion source generates high-energy argon ions. Etching and cleaning are performed under a negative bias voltage of 1 kV to 5 kV on the titanium bipolar plate substrate for 10 to 120 minutes.

[0048] In one embodiment of the present invention, the flow ratio of nitrogen to acetylene is 1:1 to 1.5:1, and the working pressure is 0.03 Pa to 0.3 Pa; wherein, when the flow rate ratio of acetylene to nitrogen is 1:1, the contact resistance of the TiCN layer is the lowest.

[0049] In one embodiment of the present invention, the working pressure of the argon+acetylene+hydrogen mixed atmosphere is 0.01Pa-0.1Pa.

[0050] The titanium mixed bottom layer uses a high-power pulsed magnetron sputtering power supply to vaporize and ionize the titanium target through instantaneous MW-level energy to form titanium metal plasma, and then applies a 15kV to 25kV negative pulse high voltage to the titanium metal bipolar plate substrate, with a pulse width of 10μs to 100μs, a pulse frequency of 30Hz to 300Hz, argon as the working gas, and a working pressure of 0.03Pa to 0.3Pa, to achieve titanium ion implantation and deposition, forming a dense titanium mixed bottom layer with a thickness of 0.2μm to 0.5μm, thereby improving the adhesion and corrosion resistance of the titanium metal bipolar plate substrate.

[0051] The titanium carbonitride intermediate layer uses a high-power pulsed magnetron sputtering power supply to vaporize and ionize the titanium target through instantaneous MW-level energy to form titanium metal plasma, and then applies a 15kV~25kV negative pulse high voltage to the titanium metal bipolar plate substrate, with a pulse width of 10us~50us and a pulse frequency of 30Hz~80Hz. The working gases are nitrogen and acetylene, and the working pressure is 0.03Pa~0.3Pa. Under the action of the titanium metal plasma, nitrogen and acetylene undergo ionization and chemical reaction to form a titanium carbonitride layer with a thickness of 0.3μm~0.5μm on the surface of the titanium mixed layer prepared in the previous process. By changing the flow ratio of nitrogen and acetylene, the composition and mechanical properties of titanium carbonitride can be controlled, thereby improving the hardness, adhesion, corrosion resistance and conductivity of the metal bipolar plate substrate.

[0052] The amorphous carbon surface layer uses the anode layer ion source to generate a carbon ion beam source, and then uses high-power pulse magnetron sputtering to generate carbon plasma. Then, a 15kV~20kV negative pulse high voltage is applied to the titanium metal bipolar plate substrate, with a pulse width of 10us~50us, a pulse frequency of 30Hz~80Hz, and the working gas is argon + acetylene + hydrogen. The working pressure is 0.01Pa~0.1Pa. A 0.5μm~1μm thick carbon surface layer is deposited on the surface of the titanium carbonitride layer prepared in the previous process to achieve excellent corrosion resistance, conductivity and other functions.

[0053] In one embodiment of the present invention, the amount of hydrogen added is 3% to 8% by volume, which is used to suppress the internal stress of the amorphous carbon surface layer and improve the conductivity.

[0054] In an embodiment of the present invention, an ultrasonic + electrochemical composite polishing process is used to polish the surface of the rolled titanium bipolar plate, which can effectively remove surface microscopic defects or optimize the surface microstructure, thereby improving the comprehensive performance of the subsequent high-corrosion-resistant conductive coating. A titanium arc electron ion source is used to generate high-energy argon ions to etch the surface of the titanium bipolar plate, which can effectively remove the natural passivation film on the surface and improve the conductivity of the titanium bipolar plate. An anode layer ion source + high-power pulse magnetron sputtering is used to generate a large area of ​​uniform titanium + carbon plasma, which is combined under the action of negative pulse high voltage to form a titanium carbonitride intermediate layer + carbon surface layer, which can significantly improve the hardness, adhesion, corrosion resistance and conductivity of the titanium bipolar plate.

[0055] In another embodiment of the present invention, a titanium metal composite coating bipolar plate for a hydrogen fuel cell is provided. The composite bipolar plate includes the highly corrosion-resistant conductive composite coating of the titanium metal bipolar plate described in any one of the above items.

[0056] Example 1:

[0057] The titanium bipolar plates were ultrasonically degreased for 15 minutes using LT-T4030 industrial degreaser, followed by an ultrasonic rinse with distilled water for 10 minutes to ensure that there were no oil stains that could affect the next process. The plates were then polished using an ultrasonic + electrochemical composite polishing process to remove surface microscopic defects, achieving a surface roughness of less than 0.4μm. The plates were then ultrasonically rinsed with distilled water for 10 minutes to ensure a clean surface. The cleaned and polished plates were then placed in a vacuum chamber and etched for 30 minutes using high-energy argon ions generated by a titanium arc electron ion source. The etching pressure was 0.5Pa and the substrate was negatively biased at 3kV to remove the natural passivation film on the titanium bipolar plate substrate. A high-power pulsed magnetron sputtering power supply is then used to generate titanium metal plasma through instantaneous 2MW energy output. Under the action of negative pulse high voltage (high voltage amplitude 25kV, pulse width 20μs, pulse frequency 100Hz) on the titanium metal bipolar plate substrate, titanium ion implantation and deposition are achieved, forming a dense titanium mixed bottom layer with a thickness of 0.2-0.5μm. 25sccm acetylene and 25sccm nitrogen are introduced, and high-power pulsed magnetron sputtering is used to generate titanium metal plasma. Under the action of negative pulse high voltage (high voltage amplitude 20kV, pulse width 60μs, pulse frequency 50Hz) on the substrate, nitrogen and acetylene undergo ionization and chemical reaction under the action of titanium metal plasma, forming a titanium carbonitride layer with a thickness of 0.3μm to 0.5μm. Finally, the anode layer ion source is used to generate a carbon ion beam source, and then high-power pulsed magnetron sputtering is used to generate carbon plasma. Under the action of negative pulse high voltage on the substrate (high voltage amplitude 15kV, pulse width 20μs, pulse frequency 50Hz), a 0.5μm to 1μm thick carbon surface layer is deposited to achieve excellent strong bonding, high corrosion resistance, high conductivity and other composite coatings. The film-base bonding strength is 53N and the corrosion current density is 2.0μA / cm 2 ), surface contact resistance is less than 1.6mΩ·cm 2 Specific embodiment 2:

[0058] The titanium bipolar plates were ultrasonically degreased for 15 minutes using LT-T4030 industrial degreaser, followed by an ultrasonic rinse with distilled water for 15 minutes to ensure that there were no oil stains that could affect the next process. The plates were then polished using an ultrasonic + electrochemical composite polishing process to remove surface microscopic defects, achieving a surface roughness of less than 0.4μm. The plates were then ultrasonically rinsed with distilled water for 15 minutes to ensure a clean surface. The cleaned and polished plates were then placed in a vacuum chamber and etched for 60 minutes using high-energy argon ions generated by a titanium arc electron ion source. The etching pressure was 0.3Pa and the substrate was negatively biased at 5kV to remove the natural passivation film on the titanium bipolar plate substrate. A high-power pulsed magnetron sputtering power supply is then used to generate titanium metal plasma through instantaneous 2MW energy output. Under the action of negative pulse high voltage (high voltage amplitude 25kV, pulse width 25μs, pulse frequency 80Hz) on the titanium metal bipolar plate substrate, titanium ion implantation and deposition are achieved, forming a dense titanium mixed bottom layer with a thickness of 0.2-0.5μm. 30sccm acetylene and 20sccm nitrogen are introduced, and high-power pulsed magnetron sputtering is used to generate titanium metal plasma. Under the action of negative pulse high voltage (high voltage amplitude 20kV, pulse width 30μs, pulse frequency 50Hz) on the substrate, nitrogen and acetylene undergo ionization and chemical reaction under the action of titanium metal plasma, forming a titanium carbonitride layer with a thickness of 0.3μm to 0.5μm. Finally, the anode layer ion source is used to generate a carbon ion beam source, and then high-power pulsed magnetron sputtering is used to generate carbon plasma. Under the action of negative pulse high voltage on the substrate (high voltage amplitude 15kV, pulse width 20μs, pulse frequency 50Hz), a 0.5μm to 1μm thick carbon surface layer is deposited to achieve excellent strong bonding, high corrosion resistance, high conductivity and other composite coatings. The film-base bonding strength is 58N and the corrosion current density is 1.8μA / cm 2 ), surface contact resistance is less than 1.55mΩ·cm 2 . Specific embodiment 3:

[0060] The titanium bipolar plates were ultrasonically degreased for 20 minutes using LT-T4030 industrial degreaser, followed by an ultrasonic rinse with distilled water for 10 minutes to ensure that there were no oil stains that could affect the next process. The plates were then polished using an ultrasonic + electrochemical composite polishing process to remove surface microscopic defects, achieving a surface roughness of less than 0.4μm. The plates were then ultrasonically rinsed with distilled water for 10 minutes to ensure a clean surface. The cleaned and polished plates were then placed in a vacuum chamber and etched for 60 minutes using high-energy argon ions generated by a titanium arc electron ion source. The etching pressure was 0.6Pa and the substrate was negatively biased at 5kV to remove the natural passivation film on the titanium bipolar plate substrate. A high-power pulsed magnetron sputtering power supply is then used to generate titanium metal plasma through instantaneous 2MW energy output. Under the action of negative pulse high voltage (high voltage amplitude 25kV, pulse width 30μs, pulse frequency 100Hz) on the titanium metal bipolar plate substrate, titanium ion implantation and deposition are achieved, forming a dense titanium mixed bottom layer with a thickness of 0.2-0.5μm. 20sccm acetylene and 30sccm nitrogen are introduced, and high-power pulsed magnetron sputtering is used to generate titanium metal plasma. Under the action of negative pulse high voltage (high voltage amplitude 25kV, pulse width 60μs, pulse frequency 50Hz) on the substrate, nitrogen and acetylene undergo ionization and chemical reaction under the action of titanium metal plasma, forming a titanium carbonitride layer with a thickness of 0.3μm to 0.5μm. Finally, the anode layer ion source is used to generate a carbon ion beam source, and then high-power pulsed magnetron sputtering is used to generate carbon plasma. Under the action of negative pulse high voltage on the substrate (high voltage amplitude 20kV, pulse width 20μs, pulse frequency 50Hz), a 0.5μm to 1μm thick carbon surface layer is deposited to achieve excellent strong bonding, high corrosion resistance, high conductivity and other composite coatings. The film-base bonding strength is 61N and the corrosion current density is 1.8μA / cm 2 ), surface contact resistance is less than 1.58mΩ·cm 2 .

[0061] An embodiment of the present invention provides a highly corrosion-resistant conductive composite coating for a titanium bipolar plate, a preparation method, and a bipolar plate. The composite coating comprises, from the inside out, a titanium mixed bottom layer, a gradient transition titanium carbonitride (TiCN) middle layer, and an amorphous carbon top layer. The titanium mixed bottom layer has a thickness of 0.2 μm to 0.5 μm and is formed by high-power pulsed magnetron sputtering combined with a 15 kV to 25 kV high-voltage pulsed target bias, through titanium ion implantation and deposition; the titanium carbonitride (TiCN) middle layer has a thickness of 0.3 μm to 0.5 μm and is deposited by high-power pulsed magnetron sputtering in a nitrogen and acetylene reaction atmosphere, wherein the nitrogen atomic content decreases from the titanium mixed bottom layer outward; the amorphous carbon top layer has a thickness of 0.5 μm to 1 μm and is deposited on the surface of the titanium bipolar plate by high-power pulsed magnetron sputtering assisted by an anode layer ion source.

[0062] The technical solution of the present invention can realize the preparation of a multi-layer structured highly corrosion-resistant conductive composite coating on the surface of a metal bipolar plate substrate, meet the high corrosion-resistant and conductive requirements of the titanium metal bipolar plate of hydrogen fuel cells, and improve the performance, life and reliability of hydrogen fuel cells.

[0063] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A highly corrosion-resistant conductive composite coating for a titanium bipolar plate, characterized in that: The composite coating comprises, from the inside to the outside, a titanium mixed bottom layer, a gradient transition titanium carbonitride (TiCN) middle layer and an amorphous carbon surface layer; The titanium mixed bottom layer has a thickness of 0.2 μm to 0.5 μm and is formed by high-power pulsed magnetron sputtering combined with 15 kV to 25 kV high-voltage pulsed target bias, and titanium ion implantation and deposition; The titanium carbonitride (TiCN) intermediate layer has a thickness of 0.3 μm to 0.5 μm and is deposited by high-power pulsed magnetron sputtering in a nitrogen and acetylene reaction atmosphere, wherein the nitrogen atomic content decreases from the titanium mixed bottom layer toward the outside; The amorphous carbon surface layer has a thickness of 0.5 μm to 1 μm and is deposited on the surface of the titanium metal bipolar plate by high-power pulsed magnetron sputtering assisted by an anode layer ion source.

2. The highly corrosion-resistant conductive composite coating for a titanium bipolar plate according to claim 1, characterized in that: The film-base bonding strength of the titanium mixed bottom layer is ≥51N, and the surface contact resistance of the amorphous carbon surface layer is ≤1.6mΩ·cm 2 , corrosion current density ≤ 2.0μA / cm 2 .

3. The highly corrosion-resistant conductive composite coating for a titanium bipolar plate according to claim 1, characterized in that: The C / N atomic ratio of the TiCN intermediate layer is regulated to be 0.6:1 to 1.9:1 by adjusting the flow rate ratio of acetylene to nitrogen, and the Vickers hardness is ≥2400 HV.

4. A method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate, characterized in that: The method comprises: S101, ultrasonically degreasing the titanium bipolar plates for 10 to 30 minutes using an industrial degreasing agent, and then ultrasonically rinsing them with distilled water for 10 to 30 minutes to remove oil stains; S102, performing ultrasonic-assisted electrochemical polishing on the surface of the titanium metal bipolar plate to achieve a surface roughness Ra of less than 0.4 μm; S103. In a vacuum chamber, using a titanium arc electron ion source to generate high-energy argon ions to etch and clean the cleaned and polished titanium bipolar plate at a working pressure of 0.3 Pa to 0.6 Pa, a negative bias voltage of 1 kV to 5 kV on the substrate of the titanium bipolar plate, and a time of 10 min to 120 min. S104, using a high-power pulsed magnetron sputtering power supply to generate titanium plasma, applying a negative pulse high voltage of 15 kV to 25 kV to the substrate of the titanium metal bipolar plate, with a pulse width of 10 μs to 100 μs and a frequency of 30 Hz to 300 Hz, to deposit a 0.2 μm to 0.5 μm titanium mixed bottom layer in an argon atmosphere; S105, using a high-power pulsed magnetron sputtering power supply to generate titanium plasma, applying a negative pulse high voltage of 15 kV to 25 kV to the substrate of the titanium metal bipolar plate, with a pulse width of 10 μs to 50 μs and a frequency of 30 Hz to 80 Hz, using nitrogen and acetylene as working gases, and depositing a titanium carbonitride intermediate layer of 0.3 μm to 0.5 μm in the nitrogen and acetylene mixed gas atmosphere; S106. Carbon plasma is generated by synergistically using the anode layer ion source and high-power pulse magnetron sputtering, and a negative pulse high voltage of 15kV to 20kV is applied to the substrate of the titanium metal bipolar plate. The pulse width is 10μs to 50μs, and the frequency is 30Hz to 80Hz. An amorphous carbon surface layer with a thickness of 0.5μm to 0.5μm is deposited in an argon + acetylene + hydrogen atmosphere.

5. The method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate according to claim 4, characterized in that: The argon working pressure of the etching cleaning is 0.5 Pa, the substrate negative bias voltage is 3 kV, and the time is 30 minutes.

6. The method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate according to claim 4, characterized in that: The flow rate ratio of nitrogen to acetylene is 1:1 to 1.5:1, and the working pressure is 0.03Pa to 0.3Pa. When the flow rate ratio of acetylene to nitrogen is 1:1, the contact resistance of the TiCN layer is the lowest.

7. The method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate according to claim 4, characterized in that: The working pressure of the argon + acetylene + hydrogen mixed atmosphere is 0.01Pa~0.1Pa.

8. The method for preparing a highly corrosion-resistant conductive composite coating for a titanium bipolar plate according to claim 4, characterized in that: The amount of hydrogen added is 3% to 8% by volume, which is used to suppress the internal stress of the amorphous carbon surface layer and improve the conductivity.

9. A hydrogen fuel cell titanium metal composite coating bipolar plate, characterized in that: The composite bipolar plate includes the highly corrosion-resistant conductive composite coating of a titanium metal bipolar plate according to any one of claims 1 to 3.

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