Fuel cell metal bipolar plate with multi-layer composite gradient coating and preparation method of fuel cell metal bipolar plate

Abstract

The invention discloses a fuel cell metal bipolar plate with a multi-layer composite gradient coating and a preparation method of the fuel cell metal bipolar plate, and relates to a preparation method of a surface coating of a fuel cell metal bipolar plate. The problem that a metal bipolar plate in a fuel cell is poor in corrosion resistance is solved. The Ti / TiN / TiCN multi-layer composite gradient is prepared on a substrate through a multi-arc ion plating technology by regulating and controlling parameters such as air pressure and flow of nitrogen and methane, the coating is composed of a pure Ti base layer and a transition layer with three to five periods, a gradient multi-layer structure is adopted, TiN metal nitride with good conductivity is adopted, and the conductivity of the coating is greatly improved. The interface contact resistance is reduced, meanwhile, the permeation of corrosive liquid and the further corrosion of the corrosive liquid to the coating and the matrix material are effectively prevented, the corrosion resistance of the metal bipolar plate in an acid environment is remarkably improved, and the interface contact resistance of the surface of the metal bipolar plate under the working pressure of a fuel cell is reduced.

Description

Technical Field

[0001] The invention relates to a method for preparing a surface coating of a metal bipolar plate of a fuel cell. Background Art

[0002] Bipolar plates (BPP) are one of the key components of proton exchange membrane fuel cells (PEMFC). Among them, metal bipolar plates have the advantages of good comprehensive performance and simple preparation process, which can effectively reduce the manufacturing cost of fuel cells. They mainly include stainless steel, titanium alloy and other types. For stainless steel bipolar plates, they lack long-term stability and reliability in the acidic environment (pH = 2-3) inside the fuel cell, are easily affected by corrosion, and have a high surface contact resistance. Solving these problems is crucial to promoting the development and commercial application of fuel cell technology. People have adopted a series of methods to improve its performance. Among them, depositing a corrosion-resistant conductive coating on the surface of metal bipolar plates is a very effective method. With this goal in mind, various types of coatings have gradually been studied and applied by researchers at home and abroad.

[0003] Feng et al. used closed-field unbalanced magnetron sputtering technology to coat pure aC coating on the surface of 316L stainless steel, and immersed it in a corrosion solution of 0.5 mol / L H2SO4+2 mg / L HF at 80 °C for potentiodynamic polarization test; compared with uncoated SS316L, the coating-modified SS316L showed higher corrosion resistance potential, and the corrosion current density was significantly reduced to 1.85 μA / cm 2 , ICR is lower than that of untreated SS316L (Feng K, Cai X, Sun H, et al. Carbon coated stainless steel bipolar plates in polymer electrolyte membrane fuel cells[J]. Diamond and related materials, 2010, 19(11): 1354-1361), but this technology has problems such as high process difficulty and difficulty in controlling structural micro-defects.

[0004] Su et al. studied the effect of CrCx coating deposited on SS316L surface by radio frequency unbalanced magnetron sputtering technology on BPs (where x is the acetylene flow rate). 25 The corrosion current density (Icorr) of the coating is the lowest, only 0.07 μA·cm -2 , and the interface contact resistance (ICR) is only 7.27mΩ·cm 2 , which is attributed to CrC 25The coating has low surface roughness and small cluster size; TiN, CrN and TiAlN coatings were deposited on 316L stainless steel, and among the three bipolar plates with different coatings, the stainless steel bipolar plate with CrN coating has the best performance considering the comprehensive conductivity and corrosion resistance (Su YL, Kao WH, Chang GY. Tribological, Anti-corrosion, and Electrical Conductivity Properties of CrCx Coatings Deposited on Stainless Steel 316L and Used as Metal Bipolar Plates for Fuel Cells [J]. Journal of Materials Engineering and Performance, 2022, 32 (8): 3739-3754.). With a single coating structure, the microscopic defects generated during the coating deposition process cannot be effectively filled, and the coating is retained, and the best coating corrosion resistance cannot be obtained.

[0005] Kahraman et al. used PVD technology to deposit TiN and CrN coatings on a variety of stainless steels and found that the bipolar plates had better surface quality after the coatings were deposited. The surface hydrophobicity and corrosion resistance were greatly improved. The corrosion current density of 316Ti stainless steel bipolar plates was even as low as 0.2μA·cm after the CrN coating was deposited. -2 [Kahraman H, Cevik I, Dündar F, et al. The Corrosion Resistance Behaviors of Metallic Bipolar Plates for PEMFC Coated with Physical Vapor Deposition (PVD): An Experimental Study [J]. Arabian Journal for Science and Engineering, 2016, 41 (5): 1961-1968.] Similarly, the use of a single coating structure cannot achieve the best coating corrosion resistance and has high requirements on the substrate material.

[0006] Patent CN107681173A proposes a point-shaped conductive coating and preparation process for fuel cell metal plates, which has strong corrosion resistance, especially high potential corrosion resistance, and has good conductivity. Under long-term corrosion, the coating contact resistance will not increase, and has good durability. Compared with traditional electroplating gold or meteorological deposition of precious metal films, this coating structure can greatly reduce the use of precious metals and reduce production costs. However, there are problems such as high process technology difficulty and high equipment requirements. Summary of the invention

[0007] In order to solve the problem of poor corrosion resistance of metal bipolar plates in fuel cells, the present invention proposes a fuel cell metal bipolar plate with a multi-layer composite gradient coating and a preparation method thereof. The present invention gives full play to the advantages of the metal nitride coating and improves the durability of the metal nitride coating in the fuel cell environment.

[0008] The fuel cell metal bipolar plate with a multi-layer composite gradient coating and a preparation method thereof of the present invention comprises a substrate and a Ti / TiN / TiCN multi-layer composite gradient coating;

[0009] The Ti / TiN / TiCN multilayer composite gradient coating is composed of a base layer, a transition layer, and a surface layer in order from bottom to top; the base layer is pure Ti; the transition layer is composed of 3-5 TiN / TiCN layers, in which the TiCN layer is located on the upper surface of the TiN layer; and the surface layer is TiCN;

[0010] The preparation method of the fuel cell metal bipolar plate with gradient coating of the present invention is carried out according to the following steps:

[0011] 1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate;

[0012] The degreasing treatment uses acetone; the ultrasonic cleaning uses alcohol and deionized water in sequence, using alcohol ultrasonic cleaning for 15 minutes and using deionized water ultrasonic cleaning for 15 minutes;

[0013] The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning is 900-1000V, and the sputtering cleaning time is 10-15min;

[0014] The substrate is stainless steel or titanium alloy;

[0015] Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate;

[0016] The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600-650V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 5-15min;

[0017] 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment;

[0018] The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1500-1750sccm, the gas pressure is 0.6-1.8Pa, the substrate bias is 600-650V, the duty cycle is 15-25%, the target current of the titanium target is 50-60A, and the deposition time is 5-15min;

[0019] 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment;

[0020] The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 100-120sccm, the gas pressure is 0.6-1.8Pa, the substrate bias voltage is 150-200V, the duty cycle is 15-25%, the target current of the titanium target is 50-60A, and the deposition time is 3-10min;

[0021] 5. Repeat steps 3 and 4 to obtain a transition layer composed of 3-5 TiN / TiCN layers;

[0022] 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed;

[0023] The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 40-50V, target current of titanium target is 35-40A, duty cycle is 15-25%, nitrogen flow rate is 200-300sccm, methane flow rate is 700-750sccm, gas pressure is 0.6-1.8Pa, and deposition time is 10-20min.

[0024] The principles and beneficial effects of the present invention are:

[0025] Compared with the prior art, the present invention prepares a Ti / TiN / TiCN multilayer composite gradient on a substrate by multi-arc ion plating technology by regulating parameters such as gas pressure, flow rates of nitrogen and methane. The coating is composed of a pure Ti base layer and three to five periods of transition layers, adopts a gradient multilayer structure, and uses TiN metal nitride with good conductivity, which reduces the interface contact resistance while effectively preventing the penetration of corrosive liquid and its further corrosion to the coating and substrate material, significantly improves the corrosion resistance of the metal bipolar plate in an acidic environment, and reduces the interface contact resistance on the surface of the metal bipolar plate under the working pressure of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a fuel cell metal bipolar plate with a gradient coating prepared in Example 1;

[0027] Figure 2 The dynamic point potential polarization curves of the gradient coating in the fuel cell metal bipolar plate with gradient coating prepared under different gas pressures;

[0028] Figure 3 The contact resistance curve of the gradient coating in the fuel cell metal bipolar plate with gradient coating prepared under different gas pressures. DETAILED DESCRIPTION

[0029] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0031] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0032] Specific implementation method 1: The fuel cell metal bipolar plate with a multi-layer composite gradient coating and the preparation method thereof in this implementation method is composed of a substrate and a Ti / TiN / TiCN multi-layer composite gradient coating;

[0033] The Ti / TiN / TiCN multilayer composite gradient coating is composed of a base layer, a transition layer and a surface layer in order from bottom to top; the base layer is pure Ti; the transition layer is composed of 3-5 TiN / TiCN layers, in which the TiCN layer is located on the upper surface of the TiN layer; and the surface layer is TiCN.

[0034] This embodiment has the following beneficial effects:

[0035] In this embodiment, a Ti / TiN / TiCN multilayer composite gradient is prepared on a substrate by multi-arc ion plating technology. The coating is composed of a pure Ti base layer and three to five periods of transition layers. It adopts a gradient multilayer structure and uses TiN metal nitride with good conductivity. While reducing the interface contact resistance, it effectively prevents the penetration of corrosive liquid and its further corrosion to the coating and substrate material, significantly improving the corrosion resistance of the metal bipolar plate in an acidic environment and reducing the interface contact resistance on the surface of the metal bipolar plate under the working pressure of the fuel cell.

[0036] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: the substrate is stainless steel or titanium alloy.

[0037] Specific implementation method three: This implementation method is different from specific implementation method one or two in that the thickness of the base layer, TiCN layer, TiN layer and surface layer are 100-200 nm respectively.

[0038] Specific embodiment 4: The preparation method of the fuel cell metal bipolar plate with a multi-layer composite gradient coating in this embodiment is carried out according to the following steps:

[0039] 1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate;

[0040] The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning is 900-1000V, and the sputtering cleaning time is 10-15min;

[0041] The substrate is stainless steel or titanium alloy;

[0042] Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate;

[0043] The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600-650V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 5-15min;

[0044] 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment;

[0045] The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1500-1750sccm, the gas pressure is 0.6-1.8Pa, the substrate bias is 600-650V, the duty cycle is 15-25%, the target current of the titanium target is 50-60A, and the deposition time is 5-15min;

[0046] 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment;

[0047] The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 100-120sccm, the gas pressure is 0.6-1.8Pa, the substrate bias voltage is 150-200V, the duty cycle is 15-25%, the target current of the titanium target is 50-60A, and the deposition time is 3-10min;

[0048] 5. Repeat steps 3 and 4 to obtain a transition layer composed of 3-5 TiN / TiCN layers;

[0049] 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed;

[0050] The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 40-50V, target current of titanium target is 35-40A, duty cycle is 15-25%, nitrogen flow rate is 200-300sccm, methane flow rate is 700-750sccm, gas pressure is 0.6-1.8Pa, and deposition time is 10-20min.

[0051] Compared with the prior art, this embodiment prepares a Ti / TiN / TiCN multilayer composite gradient on a substrate by multi-arc ion plating technology by regulating parameters such as gas pressure, nitrogen and methane flow rates. The coating is composed of a pure Ti base layer and three to five periods of transition layers, adopts a gradient multilayer structure, and uses TiN metal nitride with good conductivity. While reducing the interface contact resistance, it effectively prevents the penetration of corrosive liquid and its further corrosion to the coating and substrate material, significantly improves the corrosion resistance of the metal bipolar plate in an acidic environment, and reduces the interface contact resistance on the surface of the metal bipolar plate under the working pressure of the fuel cell.

[0052] Specific implementation method five: This implementation method is different from specific implementation method four in that: acetone is used for degreasing treatment in step one; alcohol and deionized water are used for ultrasonic cleaning in sequence, with alcohol ultrasonic cleaning for 15 minutes and deionized water ultrasonic cleaning for 15 minutes.

[0053] Specific embodiment 6: This embodiment is different from specific embodiment 4 in that: the ion sputtering cleaning process in step 1 is to dry the substrate after ultrasonic cleaning, and then put it into the multi-arc ion plating furnace chamber, and evacuate the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning is 1000 V, and the sputtering cleaning time is 9 minutes.

[0054] Specific implementation method seven: This implementation method is different from specific implementation method four in that: the multi-arc ion plating process for pure titanium base layer deposition in step 2 is: turn on the titanium target, the substrate bias is 600V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 15min.

[0055] Specific embodiment eight: This embodiment differs from specific embodiment four in that: the multi-arc ion plating process for depositing the TiN layer in step three is: the nitrogen flow rate is 1750sccm, the gas pressure is 0.6Pa, the substrate bias is 600V, the duty cycle is 15%, the target current of the titanium target is 58A, and the deposition time is 14.4min.

[0056] Specific embodiment nine: This embodiment differs from specific embodiment four in that: the multi-arc ion plating process for depositing the TiCN layer in step four is: the methane flow rate is 120sccm, the gas pressure is 0.6Pa, the substrate bias is 150V, the duty cycle is 15%, the target current of the titanium target is 58A, and the deposition time is 3.5min.

[0057] Specific embodiment ten: This embodiment differs from specific embodiment four in that: the multi-arc ion plating process for TiCN surface deposition in step six is: the substrate bias is 50V, the target current of the titanium target is 40A, the duty cycle is 15%, the nitrogen flow rate is 278sccm, the methane flow rate is 720sccm, the gas pressure is 0.6Pa, and the deposition time is 10.5min.

[0058] Example 1

[0059] The preparation method of the fuel cell metal bipolar plate with gradient coating in this embodiment is carried out according to the following steps:

[0060] 1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate;

[0061] The degreasing treatment uses acetone; the ultrasonic cleaning uses alcohol and deionized water in sequence, using alcohol ultrasonic cleaning for 15 minutes and using deionized water ultrasonic cleaning for 15 minutes;

[0062] The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning was 1000 V, and the sputtering cleaning time was 9 min; the substrate was mounted on a sample fixture 130 mm away from the target in the coating system;

[0063] The substrate is stainless steel;

[0064] Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate;

[0065] The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 15 minutes;

[0066] 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment;

[0067] The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1750 sccm, the gas pressure is 0.6 Pa, the substrate bias voltage is 600 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 14.4 min;

[0068] 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment;

[0069] The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 120 sccm, the gas pressure is 0.6 Pa, the substrate bias voltage is 150 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 3.5 min;

[0070] 5. Repeat steps 3 and 4 to obtain a transition layer composed of three TiN / TiCN layers;

[0071] 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed;

[0072] The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 50V, target current of titanium target is 40A, duty cycle is 15%, nitrogen flow rate is 278sccm, methane flow rate is 720sccm, gas pressure is 0.6Pa, and deposition time is 10.5min.

[0073] Figure 1 Schematic diagram of a fuel cell metal bipolar plate with a gradient coating prepared in Example 1; Figure 2 The P-1 curve shown in Example 1 shows that the gradient coating prepared on the surface of the stainless steel bipolar plate in 0.5M H2SO4+5ppm HF simulated fuel cell cathode environment has an electrochemical potential scanning corrosion potential of 0.11V and a corrosion current of 0.18μA·cm -2 .like Figure 3 The P-1 curve shown in FIG. 1 shows that when the loading load is 1.4 MPa (test pressure), the contact resistance between the gradient coating prepared on the surface of the stainless steel bipolar plate in Example 1 and the carbon paper is 8.44 mΩ·cm 2 .

[0074] Example 2

[0075] The preparation method of the fuel cell metal bipolar plate with gradient coating in this embodiment is carried out according to the following steps:

[0076] 1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate;

[0077] The degreasing treatment uses acetone; the ultrasonic cleaning uses alcohol and deionized water in sequence, using alcohol ultrasonic cleaning for 15 minutes and using deionized water ultrasonic cleaning for 15 minutes;

[0078] The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning was 1000 V, and the sputtering cleaning time was 9 min; the substrate was mounted on a sample fixture 130 mm away from the target in the coating system;

[0079] The substrate is stainless steel;

[0080] Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate;

[0081] The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 15 minutes;

[0082] 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment;

[0083] The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1750 sccm, the gas pressure is 1 Pa, the substrate bias voltage is 600 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 14.4 min;

[0084] 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment;

[0085] The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 120 sccm, the gas pressure is 1 Pa, the substrate bias voltage is 150 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 3.5 min;

[0086] 5. Repeat steps 3 and 4 to obtain a transition layer composed of three TiN / TiCN layers;

[0087] 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed;

[0088] The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 50V, target current of titanium target is 40A, duty cycle is 15%, nitrogen flow rate is 278sccm, methane flow rate is 720sccm, gas pressure is 1Pa, and deposition time is 10.5min.

[0089] like Figure 2 The P-2 curve shown in Example 2 shows that the gradient coating prepared on the surface of the stainless steel bipolar plate in 0.5M H2SO4+5ppm HF simulated fuel cell cathode environment has an electrochemical potential scanning corrosion potential of 0.12V and a corrosion current of 0.12μA·cm -2 .like Figure 3 The P-2 curve shown in FIG. 1 shows that when the loading load is 1.4 MPa, the contact resistance between the gradient coating prepared on the surface of the stainless steel bipolar plate in Example 2 and the carbon paper is 1.82 mΩ·cm 2 .

[0090] Example 3

[0091] The preparation method of the fuel cell metal bipolar plate with gradient coating in this embodiment is carried out according to the following steps:

[0092] 1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate;

[0093] The degreasing treatment uses acetone; the ultrasonic cleaning uses alcohol and deionized water in sequence, using alcohol ultrasonic cleaning for 15 minutes and using deionized water ultrasonic cleaning for 15 minutes;

[0094] The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning was 1000 V, and the sputtering cleaning time was 9 min; the substrate was mounted on a sample fixture 130 mm away from the target in the coating system;

[0095] The substrate is stainless steel;

[0096] Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate;

[0097] The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 15 minutes;

[0098] 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment;

[0099] The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1750 sccm, the gas pressure is 1.4 Pa, the substrate bias voltage is 600 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 14.4 min;

[0100] 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment;

[0101] The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 120 sccm, the gas pressure is 1.4 Pa, the substrate bias voltage is 150 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 3.5 min;

[0102] 5. Repeat steps 3 and 4 to obtain a transition layer composed of three TiN / TiCN layers;

[0103] 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed;

[0104] The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 50V, target current of titanium target is 40A, duty cycle is 15%, nitrogen flow rate is 278sccm, methane flow rate is 720sccm, gas pressure is 1.4Pa, and deposition time is 10.5min.

[0105] like Figure 2 The P-3 curve shown in Example 3 shows that the gradient coating prepared on the surface of the stainless steel bipolar plate in 0.5M H2SO4+5ppm HF simulated fuel cell cathode environment has an electrochemical potential scanning corrosion potential of 0.16V and a corrosion current of 0.44μA·cm -2 .like Figure 3 The P-3 curve shown in FIG. 1 shows that when the loading load is 1.4 MPa, the contact resistance between the gradient coating prepared on the surface of the stainless steel bipolar plate in Example 3 and the carbon paper is 2.61 mΩ·cm 2 .

[0106] Example 4

[0107] The preparation method of the fuel cell metal bipolar plate with gradient coating in this embodiment is carried out according to the following steps:

[0108] 1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate;

[0109] The degreasing treatment uses acetone; the ultrasonic cleaning uses alcohol and deionized water in sequence, using alcohol ultrasonic cleaning for 15 minutes and using deionized water ultrasonic cleaning for 15 minutes;

[0110] The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning was 1000 V, and the sputtering cleaning time was 9 min; the substrate was mounted on a sample fixture 130 mm away from the target in the coating system;

[0111] The substrate is stainless steel;

[0112] Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate;

[0113] The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 15 minutes;

[0114] 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment;

[0115] The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1750 sccm, the gas pressure is 1.8 Pa, the substrate bias voltage is 600 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 14.4 min;

[0116] 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment;

[0117] The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 120 sccm, the gas pressure is 1.8 Pa, the substrate bias voltage is 150 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 3.5 min;

[0118] 5. Repeat steps 3 and 4 to obtain a transition layer composed of three TiN / TiCN layers;

[0119] 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed;

[0120] The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 50V, target current of titanium target is 40A, duty cycle is 15%, nitrogen flow rate is 278sccm, methane flow rate is 720sccm, gas pressure is 1.8Pa, and deposition time is 10.5min.

[0121] like Figure 2 The P-4 curve shown in Example 4 shows that the gradient coating prepared on the surface of the stainless steel bipolar plate in 0.5M H2SO4+5ppm HF simulated fuel cell cathode environment has an electrochemical potential scanning corrosion potential of 0.11V and a corrosion current of 0.49μA·cm -2 .like Figure 3 The P-4 curve shown in FIG. 1 shows that when the loading load is 1.4 MPa, the contact resistance between the gradient coating prepared on the surface of the stainless steel bipolar plate in Example 4 and the carbon paper is 5.05 mΩ·cm 2 .

Claims

1. A fuel cell metal bipolar plate with a multi-layer composite gradient coating, characterized in that: A fuel cell metal bipolar plate with a multi-layer composite gradient coating and a preparation method thereof The fuel cell metal bipolar plate is composed of a substrate and a Ti / TiN / TiCN multi-layer composite gradient coating; The Ti / TiN / TiCN multilayer composite gradient coating is composed of a base layer, a transition layer, and a surface layer in order from bottom to top; the base layer is pure Ti; The transition layer is composed of 3-5 TiN / TiCN layers, in which the TiCN layer is located on the upper surface of the TiN layer; the surface layer is TiCN.

2. The fuel cell metal bipolar plate with a multi-layer composite gradient coating according to claim 1, characterized in that: The substrate is stainless steel or titanium alloy.

3. The fuel cell metal bipolar plate with a multi-layer composite gradient coating according to claim 1, characterized in that: The thicknesses of the base layer, TiCN layer, TiN layer and surface layer are 100-200 nm respectively.

4. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 1, characterized in that: The preparation method of the fuel cell metal bipolar plate with a multi-layer composite gradient coating is carried out in the following steps:

1. Degreasing, ultrasonic cleaning and ion sputtering cleaning are sequentially performed on the substrate; The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the furnace chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning is 900-1000V, and the sputtering cleaning time is 10-15min; The substrate is stainless steel or titanium alloy; Second, a multi-arc ion plating process is used to deposit a pure Ti base layer on the substrate; The multi-arc ion plating process for pure titanium base deposition is as follows: the titanium target is turned on, the substrate bias voltage is 600-650V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 5-15min; 3. Depositing a TiN layer on the pure titanium base layer using a multi-arc ion plating process in a nitrogen environment; The multi-arc ion plating process for depositing the TiN layer is as follows: the flow rate of nitrogen is 1500-1750sccm, the gas pressure is 0.6-1.8Pa, the substrate bias is 600-650V, the duty cycle is 15-25%, the target current of the titanium target is 50-60A, and the deposition time is 5-15min; 4. Depositing a TiCN layer on the TiN layer using a multi-arc ion plating process in a methane environment; The multi-arc ion plating process for depositing the TiCN layer is as follows: the flow rate of methane is 100-120 sccm, the gas pressure is 0.6-1.8 Pa, the substrate bias voltage is 150-200 V, the duty cycle is 15-25%, the target current of the titanium target is 50-60 A, and the deposition time is 3-10 min; 5. Repeat steps 3 and 4 to obtain a transition layer composed of 3-5 TiN / TiCN layers; 6. Depositing a TiCN surface layer on the transition layer by a multi-arc ion plating process in a methane and nitrogen environment to obtain a Ti / TiN / TiCN multilayer composite gradient coating is completed; The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 40-50V, target current of titanium target is 35-40A, duty cycle is 15-25%, nitrogen flow rate is 200-300sccm, methane flow rate is 700-750sccm, gas pressure is 0.6-1.8Pa, and deposition time is 10-20min.

5. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 4, characterized in that: In step 1, acetone is used for degreasing treatment; alcohol and deionized water are used for ultrasonic cleaning in sequence, with alcohol ultrasonic cleaning for 15 minutes and deionized water ultrasonic cleaning for 15 minutes.

6. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 4, characterized in that: Step 1 The ion sputtering cleaning process is as follows: drying the substrate after ultrasonic cleaning, and then placing it into a multi-arc ion plating furnace chamber, and evacuating the chamber until the vacuum degree is less than 6×10 -3 Pa, the substrate bias voltage for ion sputtering cleaning is 1000 V, and the sputtering cleaning time is 9 minutes.

7. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 4, characterized in that: The multi-arc ion plating process for pure titanium base deposition in step 2 is as follows: the titanium target is turned on, the substrate bias voltage is 600V, the target current of the titanium target is 60A, the duty cycle is 15%, and the deposition time is 15min.

8. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 1, characterized in that: The multi-arc ion plating process for depositing the TiN layer in step 3 is as follows: the nitrogen flow rate is 1750 sccm, the gas pressure is 0.6 Pa, the substrate bias is 600 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 14.4 min.

9. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 4, characterized in that: The multi-arc ion plating process for depositing the TiCN layer in step 4 is as follows: the flow rate of methane is 120 sccm, the gas pressure is 0.6 Pa, the substrate bias is 150 V, the duty cycle is 15%, the target current of the titanium target is 58 A, and the deposition time is 3.5 min.

10. The method for preparing a fuel cell metal bipolar plate having a multi-layer composite gradient coating according to claim 4, characterized in that: Step 6: The multi-arc ion plating process for TiCN surface deposition is as follows: substrate bias voltage is 50 V, target current of titanium target is 40 A, duty cycle is 15%, nitrogen flow rate is 278 sccm, methane flow rate is 720 sccm, gas pressure is 0.6 Pa, and deposition time is 10.5 min.

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