Ti-Nb-Zr / MAX phase / Cr-C-N multilayer composite coating bipolar plate and preparation method thereof

Abstract

The invention discloses a Ti-Nb-Zr / MAX phase / Cr-C-N multi-layer composite coating bipolar plate and a preparation method thereof. The multi-layer composite coating sequentially comprises a Ti-Nb-Zr alloy transition layer, an MAX phase middle layer and a Cr-C-N nano composite surface layer from inside to outside. According to the Ti-Nb-Zr / MAX phase / Cr-C-N multi-layer composite coating bipolar plate and the preparation method thereof, through the synergistic effect of the Ti-Nb-Zr alloy transition layer, the MAX phase middle layer and the Cr-C-N nano composite surface layer, the comprehensive optimization of the coating performance is realized: the Ti-Nb-Zr alloy transition layer provides excellent matrix adhesive force and stress buffer effect; the MAX-phase intermediate layer provides a main corrosion-resistant barrier and self-repairing capability; the Cr-C-N nano composite surface layer provides low contact resistance and good surface stability; and meanwhile, the interlayer stress is effectively reduced by utilizing the gradient transition region, the bonding strength and long-term stability of the coating are improved, and the comprehensive performance of the multi-layer composite coating bipolar plate is effectively improved.

Description

Technical Field

[0001] This invention relates to the technical fields of water electrolysis devices, bipolar plates, and coating materials, and in particular to a Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate and its preparation method. Background Technology

[0002] In recent years, hydrogen energy has received widespread attention as a clean energy carrier. Water electrolysis is an important way to produce green hydrogen, mainly including three technical routes: alkaline water electrolysis (ALK), proton exchange membrane water electrolysis (PEMWE), and anion exchange membrane water electrolysis (AEMWE).

[0003] Among the three water electrolysis technologies mentioned above, the bipolar plate, as a key component of the electrolyzer, undertakes multiple functions, including electrical conductivity, heat transfer, gas separation, and structural support. Metal bipolar plates, due to their excellent electrical and thermal conductivity, good mechanical strength, and ease of mass production, have become the ideal choice for water electrolysis devices.

[0004] However, in the harsh working environment of water electrolysis devices, metal bipolar plates face severe corrosion challenges: in PEMWE, bipolar plates are exposed to a strongly acidic environment (pH<2), high potential (up to 2V vs. SHE), and high temperature (80-90°C), resulting in extremely severe metal corrosion; in AEMWE, bipolar plates operate in a strongly alkaline environment (pH>13), where a loose and porous passivation layer easily forms on the metal surface, leading to increased contact resistance; in ALK, bipolar plates are immersed in 25-30% KOH solution for a long time, highlighting the problem of alkaline corrosion.

[0005] To address the aforementioned issues, preparing a protective coating on the surface of a metal bipolar plate is an effective way to improve its corrosion resistance and conductivity. Traditional coating technologies include noble metal coatings (such as platinum and gold), metal nitride coatings (such as TiN and CrN), and carbon-based coatings (such as DLC and graphene). However, these single coatings are difficult to simultaneously meet the complex working environment requirements of different water electrolysis technologies.

[0006] In recent years, MAX phase materials have attracted attention due to their dual properties of metals and ceramics. However, single MAX phase coatings still have shortcomings in terms of adhesion and interfacial contact resistance.

[0007] Therefore, there is an urgent need to develop a new type of multilayer composite coating structure to overcome the shortcomings of existing technologies and achieve comprehensive optimization of bipolar plate coating performance. Summary of the Invention

[0008] The purpose of this invention is to provide a Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate for water electrolysis devices and its preparation method, so as to solve the technical problem that metal bipolar plate coatings in the prior art are difficult to simultaneously meet the requirements of low contact resistance, high corrosion resistance and long-term stability.

[0009] To achieve the above objectives, one technical solution adopted by the present invention is: A Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate is provided, comprising: a metal substrate and a multilayer composite coating disposed on the surface of the metal substrate, wherein the multilayer composite coating comprises, from the inside to the outside: Ti-Nb-Zr alloy transition layer, wherein the atomic ratio of Ti, Nb and Zr in the Ti-Nb-Zr alloy transition layer is (40-60):(20-35):(15-30); The first gradient transition region is located between the Ti-Nb-Zr alloy transition layer and the MAX phase intermediate layer. Its composition includes Ti, Nb, Zr and Al. In the first gradient transition region, the content of Ti and Al gradually increases from the Ti-Nb-Zr alloy transition layer to the MAX phase intermediate layer, and the content of Nb and Zr gradually decreases from the Ti-Nb-Zr alloy transition layer to the MAX phase intermediate layer. The MAX phase intermediate layer includes Ti2AlC and / or Ti3AlC2; The second gradient transition region, located between the MAX phase intermediate layer and the Cr-CN nanocomposite surface layer, comprises Ti, Al, and Cr. In the second gradient transition region, the contents of Ti and Al gradually decrease from the MAX phase intermediate layer towards the Cr-CN nanocomposite surface layer, while the contents of Cr gradually increase from the MAX phase intermediate layer towards the Cr-CN nanocomposite surface layer. The Cr-CN nanocomposite surface layer has an atomic ratio of Cr, C, and N of (40-60):(20-40):(10-30).

[0010] In a preferred embodiment of the present invention, the metal substrate comprises one of stainless steel, titanium alloy, aluminum alloy or nickel-based alloy.

[0011] In a preferred embodiment of the present invention, the total thickness of the multilayer composite coating is 1.5-4.5 μm; preferably, the total thickness of the multilayer composite coating is 2.0-3.0 μm.

[0012] In a preferred embodiment of the present invention, the atomic ratio of Ti, Nb, and Zr in the Ti-Nb-Zr alloy transition layer is 50:30:20.

[0013] In a preferred embodiment of the present invention, the thickness of the first gradient transition region is 5-20 nm, and the thickness of the second gradient transition region is 5-20 nm.

[0014] In a preferred embodiment of the present invention, when the MAX phase intermediate layer is a composite structure of Ti2AlC and Ti3AlC2, the volume ratio of Ti2AlC to Ti3AlC2 is (1-3):(3-1), more preferably 1:1.

[0015] In a preferred embodiment of the present invention, the Cr-CN nanocomposite surface layer is a nanocomposite structure with nanocrystalline Cr(C,N) phase embedded in an amorphous carbon matrix; preferably, the nanocrystal size of the Cr-CN nanocomposite surface layer is 5-20 nm.

[0016] In a preferred embodiment of the present invention, the atomic ratio of Cr, C, and N in the Cr-CN nanocomposite surface layer is 50:30:20.

[0017] In a preferred embodiment of the present invention, the preparation steps of the Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate include: S1: Metal substrate pretreatment; S2: A Ti-Nb-Zr alloy transition layer is deposited on the surface of a metal substrate using pulsed laser deposition. S3: A first gradient transition region is deposited on the Ti-Nb-Zr alloy transition layer by pulsed laser deposition. S4: A MAX phase intermediate layer is deposited on the surface of the first gradient transition region using high-energy pulsed laser deposition. S5: A second gradient transition region is deposited on the surface of the MAX phase intermediate layer by a high-energy pulsed laser deposition method. S6: A Cr-CN nanocomposite surface layer was deposited on the surface of the second gradient transition zone using reactive pulsed laser co-deposition.

[0018] In a preferred embodiment of the present invention, the multilayer composite coated bipolar plate is applied in a water electrolysis device to improve the corrosion resistance and long-term stability of the bipolar plate and reduce the interfacial contact resistance.

[0019] The beneficial effects of this invention are as follows: Through the synergistic effect of the Ti-Nb-Zr alloy transition layer, the MAX phase intermediate layer, and the Cr-CN nanocomposite surface layer, the comprehensive optimization of coating performance is achieved: the Ti-Nb-Zr alloy transition layer provides excellent substrate adhesion and stress buffering effect; the MAX phase intermediate layer provides the main corrosion resistance barrier and self-healing ability; the Cr-CN nanocomposite surface layer provides low contact resistance and good surface stability; at the same time, the gradient transition region effectively reduces interlayer stress, improves the bonding strength and long-term stability of the coating, and effectively improves the comprehensive performance of the multilayer composite coating bipolar plate. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the structure of a Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to the present invention; Figure 2 These are test results of the interface contact resistance under 1.4 MPa pressure in embodiments and comparative examples of the present invention. Figure 3 These are corrosion current density test graphs of embodiments and comparative examples of the present invention; Figure 4 These are stability test graphs of embodiments and comparative examples of the present invention; Figure 5 This is the XRD diffraction pattern of the MAX phase of this invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1-5 The embodiments of the present invention include: A Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coating bipolar plate includes a metal substrate and a multilayer composite coating disposed on the surface of the metal substrate. The multilayer composite coating includes, from the inside to the outside: a Ti-Nb-Zr alloy transition layer, a MAX phase intermediate layer, and a Cr-CN nanocomposite surface layer. The atomic ratio of Ti, Nb, and Zr in the Ti-Nb-Zr alloy transition layer is (40-60):(20-35):(15-30). The MAX phase intermediate layer includes Ti2AlC and / or Ti3AlC2. The atomic ratio of Cr, C, and N in the Cr-CN nanocomposite surface layer is (40-60):(20-40):(10-30).

[0023] The outer side of the Ti-Nb-Zr alloy transition layer gradually and smoothly transitions to the MAX phase intermediate layer to form a first gradient transition region. That is, a first gradient transition region is provided between the Ti-Nb-Zr alloy transition layer and the MAX phase intermediate layer, such that the first gradient transition region includes the elements (or components) Ti, Nb, Zr and Al in the Ti-Nb-Zr alloy transition layer and the MAX phase intermediate layer.

[0024] Ti, Nb, and Zr are all metallic components in the Ti-Nb-Zr alloy transition layer, and Ti, Nb, Zr, and Al are also metallic components in the first gradient transition region.

[0025] In the first gradient transition region, the contents of Ti and Al gradually increase from the Ti-Nb-Zr alloy transition layer towards the MAX phase intermediate layer, while the contents of Nb and Zr gradually decrease from the Ti-Nb-Zr alloy transition layer towards the MAX phase intermediate layer. This results in the contents of Ti and Al in the first gradient transition region being greater than those in the Ti-Nb-Zr alloy transition layer, but less than or equal to those in the MAX phase intermediate layer. Furthermore, the contents of Nb and Zr in the first gradient transition region are less than or equal to those in the Ti-Nb-Zr alloy transition layer.

[0026] That is, based on the atomic ratio of Ti, Nb and Zr in the Ti-Nb-Zr alloy transition layer being (40-60):(20-35):(15-30), the content of Nb and Zr gradually decreases to 0 in the first gradient transition region, while the content of Ti and Al gradually increases, with the content of Al starting from 0 and increasing.

[0027] The outer side of the MAX phase intermediate layer gradually and smoothly transitions to the Cr-CN nanocomposite surface layer to form a second gradient transition region. That is, a second gradient transition region is set between the MAX phase intermediate layer and the Cr-CN nanocomposite surface layer, so that the second gradient transition region includes the elements (or components) Ti, Al, and Cr in the MAX phase intermediate layer and the Cr-CN nanocomposite surface layer.

[0028] Ti, Al, and Cr are all metallic components in the second gradient transition region.

[0029] In the second gradient transition region, the contents of Ti and Al gradually decrease from the MAX phase intermediate layer towards the Cr-CN nanocomposite surface layer, while the contents of Cr gradually increase from the MAX phase intermediate layer towards the Cr-CN nanocomposite surface layer. This results in the contents of Ti and Al in the second gradient transition region being less than or equal to the contents of Ti and Al in the MAX phase intermediate layer, and the contents of Cr in the second gradient transition region being less than or equal to the contents of Cr in the Cr-CN nanocomposite surface layer.

[0030] That is, the contents of Ti and Al gradually decrease to 0, and the contents of Cr gradually increase until the atomic ratio of Cr:C:N reaches (40-60):(20-40):(10-30).

[0031] By setting the first gradient transition zone and the second gradient transition zone mentioned above, the stress between layers can be reduced, and the bonding strength and long-term stability of the coating can be improved.

[0032] Furthermore, the metal substrate includes one of stainless steel, titanium alloy, aluminum alloy or nickel-based alloy, more preferably 316L stainless steel or TA1 pure titanium.

[0033] Furthermore, the total thickness of the multilayer composite coating is 1.1-4.5 μm, more preferably 1.8-3.0 μm.

[0034] In some embodiments of this application, the thickness of the Ti-Nb-Zr alloy transition layer is 0.1-0.5 μm, the thickness of the MAX phase intermediate layer is 0.5-2.0 μm, and the thickness of the Cr-CN nanocomposite surface layer is 0.5-2.0 μm.

[0035] In some other embodiments of this application, the thickness of the Ti-Nb-Zr alloy transition layer is 0.2-0.3 μm; the thickness of the MAX phase intermediate layer is 0.8-1.2 μm; and the thickness of the Cr-CN nanocomposite surface layer is 0.8-1.5 μm.

[0036] In some embodiments of this application, the atomic ratio of Ti, Nb, and Zr in the Ti-Nb-Zr alloy transition layer is 50:30:20.

[0037] In some embodiments of this application, the thickness of the first gradient transition region is 5-20 nm.

[0038] Furthermore, when the intermediate layer of the MAX phase is a composite structure of Ti2AlC and Ti3AlC2, the volume ratio of Ti2AlC to Ti3AlC2 is (1-3):(3-1), more preferably 1:1.

[0039] The thickness of the second gradient transition region is 5-20 nm.

[0040] Furthermore, the Cr-CN nanocomposite surface layer is a nanocomposite structure with nanocrystalline Cr(C,N) phase embedded in an amorphous carbon matrix.

[0041] In some embodiments of this application, the nanocrystal size of the Cr-CN nanocomposite surface layer is 5-20 nm.

[0042] In some embodiments of this application, the atomic ratio of Cr, C, and N in the Cr-CN nanocomposite surface layer is 50:30:20.

[0043] On the other hand, the present invention provides a Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate, the steps of which include: S1: Metal substrate pretreatment.

[0044] (S1.1) Mechanically polish the metal substrate until the surface roughness Ra ≤ 0.1 μm; (S1.2) The metal substrate is ultrasonically cleaned in acetone, ethanol and deionized water for 10-15 minutes each in sequence; (S1.3) Place the metal substrate in a vacuum chamber for Ar⁺ ion bombardment cleaning, with ion energy of 100-300eV and time of 5-15 minutes.

[0045] S2: A Ti-Nb-Zr alloy transition layer is deposited on the surface of a metal substrate using pulsed laser deposition.

[0046] In some embodiments of this application, the deposition conditions of the Ti-Nb-Zr alloy transition layer include: Target material: Ti-Nb-Zr alloy target or partitioned mosaic target, purity ≥99.9%; Background vacuum: ≤5×10⁻ 5 Pa; Working gas: High-purity argon, flow rate 15-40 sccm; Working pressure: 0.1-0.3 Pa; Laser source: Nd:YAG laser (wavelength 1064nm) or excimer laser (wavelength 248nm). Laser energy density: 2.5-5.0 J / cm²; Laser pulse frequency: 5-20Hz; Substrate temperature: 200-300°C; Substrate bias: -30 to -80V; Target-base distance: 50-80mm; Deposition time: 8-15 minutes.

[0047] S3: The first gradient transition region is deposited on the Ti-Nb-Zr alloy transition layer using pulsed laser deposition.

[0048] The preparation or deposition conditions of the first gradient transition zone are similar to those of the Ti-Nb-Zr alloy transition layer. The compositional gradient transition can be achieved simply by gradually adjusting the laser energy density and the target irradiation position.

[0049] Target material: Ti-Nb-Zr-Al alloy target or partitioned mosaic target, purity ≥99.9%; Background vacuum: ≤5×10⁻ 5 Pa; Working gas: High-purity Ar, 15–40 sccm; Operating pressure: 0.15–0.25 Pa; Laser source: Nd:YAG (1064 nm) or excimer (248 nm). Laser pulse frequency: 10–15 Hz; Target-base distance: 60–70 mm; Substrate temperature: 200–300 °C; Substrate bias: −30 to −80 V.

[0050] S4: A MAX phase intermediate layer is deposited on the surface of the first gradient transition region using high-energy pulsed laser deposition (HEPLD).

[0051] In some embodiments of this application, the deposition conditions for the MAX phase intermediate layer include: Target material: MAX phase composite target or partitioned target (Ti / Al / C region ratio strictly controlled); Laser parameters: energy density 3.0-6.0 J / cm², pulse width 10-30 ns, pulse frequency 10-30 Hz; Working pressure: 0.1-0.4 Pa; Substrate temperature: 400-550°C; Substrate bias: -20 to -60V; In some embodiments of this application, after deposition, the product is placed in a vacuum annealing process at 450-600°C for 0.5-1.5 hours to promote the formation of an ordered MAX phase crystal structure.

[0052] S5: A second gradient transition region is deposited on the surface of the MAX phase intermediate layer using high-energy pulsed laser deposition (HEPLD).

[0053] The preparation or deposition conditions of the second gradient transition zone are similar to those of the MAX phase intermediate layer. The compositional gradient transition can be achieved simply by gradually adjusting the laser energy density and the target irradiation position.

[0054] Target materials: MAX phase and Cr composite targets or partitioned targets (Ti / Al / C region ratio strictly controlled; if solid solution / doping is required). (Miscellaneous partitions can be introduced, such as Nb, Zr, or Si partitions). Background vacuum: ≤5×10⁻ 5 Pa; Working gas: High-purity Ar; Gas flow rate: 20–30 sccm; Operating pressure: 0.18–0.30 Pa; Laser source and parameters: HEPLD; Energy density 3.0–6.0 J / cm²; Pulse width 10–30 ns; Pulse frequency 10–30 Hz; Target-base distance: 60–70 mm; Substrate temperature: 400–550 °C; Substrate bias: −20 to −60 V; Substrate rotation: 5–20 rpm (uniform in-plane rotation, preserving thickness gradient); Pre-sputtering of target material: Pre-sputtering of substrate under shielding conditions for 2–5 minutes.

[0055] S6: A Cr-CN nanocomposite surface layer was deposited on the surface of the second gradient transition zone using reactive pulsed laser co-deposition.

[0056] In some embodiments of this application, the deposition conditions of the Cr-CN nanocomposite surface layer include: Target material: Cr-C composite target, purity ≥99.9%; Reactant gas: N2, with a flow rate accounting for 8-25% of the total gas flow rate; Working pressure: 0.1-0.5 Pa; Laser energy density: 3.0-5.5 J / cm²; Laser pulse frequency: 15-25Hz; Substrate temperature: 180-280°C; Substrate bias: -20 to -80V; Target-base distance: 60-90mm; Deposition time: 20-40 minutes.

[0057] On the other hand, the present invention provides a multilayer composite coated bipolar plate, which is applied in a water electrolysis device, thereby giving the bipolar plate excellent interfacial contact resistance (<8 mΩ·cm²), corrosion resistance (<0.5 μA / cm²) and long-term stability (>5000 hours). Example

[0058] This embodiment provides a Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate, the preparation method of which is as follows: (1) Substrate pretreatment A 316L stainless steel plate (100mm×100mm×1mm) was selected as the substrate and the following processes were performed sequentially: The surface was sanded step by step with SiC sandpaper up to 2000#, and then mechanically polished until the surface roughness Ra=0.08μm; Ultrasonic cleaning in acetone for 15 minutes removes organic contaminants; Ultrasonic cleaning in anhydrous ethanol for 15 minutes; Ultrasonic cleaning in deionized water for 15 minutes; After drying with nitrogen, immediately place it into the vacuum chamber; When the vacuum degree reaches 5×10⁻ 4 After Pa, argon gas is introduced to 0.5 Pa, and Ar⁺ ion bombardment cleaning is performed at an ion energy of 200 eV for 10 minutes.

[0059] (2) Deposition of Ti-Nb-Zr alloy transition layer The deposition conditions are as follows: Target configuration: Ti-Nb-Zr alloy partitioned target (75mm in diameter, purity ≥99.95%); Background vacuum: 2×10⁻ 5 Pa; Working gas: High-purity argon (99.999%), flow rate 25 sccm; Working pressure: 0.2 Pa; Laser source: Nd:YAG laser, wavelength 1064nm; Laser energy density: 3.5 J / cm²; Laser pulse frequency: 15Hz; Substrate temperature: 280°C; Substrate bias: -60V; Target-base distance: 65mm; Deposition time: 10 minutes; Under the above conditions, a Ti-Nb-Zr alloy transition layer with a thickness of 0.25 μm was deposited on the surface of a metal substrate, with an atomic ratio of Ti:Nb:Zr=50:30:20.

[0060] (3) Preparation of the first gradient transition region Two minutes before the Ti-Nb-Zr alloy transition layer deposition was completed, the laser focusing position was gradually adjusted to smoothly transition from the Ti-Nb-Zr region to the Ti-Al region, while the laser energy density was gradually increased to 4.0 J / cm², forming a gradient transition region with a thickness of about 8 nm.

[0061] (4) Deposition of the MAX phase intermediate layer The high-energy pulsed laser deposition (HEPLD) system was used, and the conditions included: Target material: Ti-Al-C three-zone distributed composite target (75mm in diameter); Laser parameters: energy density 4.0 J / cm², pulse width 20 ns, pulse frequency 20 Hz; Working pressure: 0.3 Pa; Substrate temperature: 500°C; Substrate bias: -40V; Target-base distance: 70mm; Deposition time: 22 minutes.

[0062] Under the above conditions, a MAX phase layer with a thickness of 1.0 μm was deposited on the surface of the first gradient transition zone. After deposition, it was vacuum annealed at 520°C for 1 hour to promote the formation of Ti2AlC and Ti3AlC2 phases and crystal ordering.

[0063] (5) Preparation of the second gradient transition region Three minutes before the MAX phase intermediate layer deposition was completed, the laser focus was gradually shifted from the Ti-Al-C region to the Cr-C region using a programmable laser beam scanning system, while the laser energy density was adjusted to 4.5 J / cm², forming a gradient transition region with a thickness of approximately 12 nm.

[0064] (6) Cr-CN nanocomposite surface layer deposition The deposition conditions are as follows: Target material: Cr-C composite target (75mm in diameter, purity ≥99.95%); Working gas: Ar / N2 mixed gas, Ar flow rate 20 sccm, N2 flow rate 8 sccm; Working pressure: 0.2 Pa; Laser energy density: 4.5 J / cm²; Laser pulse frequency: 20Hz; Substrate temperature: 230°C; Substrate bias: -50V; Target-base distance: 75mm; Deposition time: 25 minutes; Under the above conditions, a Cr-CN nanocomposite surface layer with a thickness of 1.2 μm was deposited on the surface of the second gradient transition zone, with an atomic ratio of Cr:C:N=50:30:20. Example

[0065] The difference between this embodiment and Embodiment 1 is that: The laser energy density was 3.0 J / cm² during the deposition of the Ti-Nb-Zr alloy transition layer; The thickness of the Ti-Nb-Zr alloy transition layer is 0.15 μm, and the atomic ratio is Ti:Nb:Zr=55:25:20; The laser pulse frequency of the MAX phase intermediate layer was adjusted to 18Hz, and the deposition time was 20 minutes. The thickness of the MAX phase intermediate layer is 0.8 μm, and it is mainly composed of Ti2AlC phase; The laser energy density of the Cr-CN nanocomposite surface layer is 4.2 J / cm². The Cr-CN nanocomposite surface layer has a thickness of 1.0 μm and an atomic ratio of Cr:C:N = 45:35:20. Example

[0066] The difference between this embodiment and Embodiment 1 is that: The substrate material is TA1 pure titanium; The laser source was replaced with an excimer laser (wavelength 248nm); The laser energy density was 4.0 J / cm² during the deposition of the Ti-Nb-Zr alloy transition layer; The thickness of the Ti-Nb-Zr alloy transition layer is 0.3 μm, and the atomic ratio is Ti:Nb:Zr=45:35:20; The laser pulse frequency of the MAX phase intermediate layer was adjusted to 25Hz, and the deposition time was 30 minutes. The thickness of the MAX phase intermediate layer is 1.5 μm, and the volume ratio of Ti2AlC to Ti3AlC2 is 1:2; The laser energy density of the Cr-CN nanocomposite surface layer is 5.0 J / cm². The Cr-CN nanocomposite surface layer has a thickness of 1.5 μm and an atomic ratio of Cr:C:N = 55:25:20.

[0067] Comparative Example 1 A 316L stainless steel substrate was used, and a single-layer TiN coating was deposited using pulsed laser deposition. The laser energy density was 3.8 J / cm², the pulse frequency was 20 Hz, and the thickness was 2.5 μm. Other process conditions were the same as in Example 1.

[0068] Comparative Example 2 Using a 316L stainless steel substrate, a single-layer Cr-CN coating was deposited using pulsed laser deposition. The laser energy density was 4.5 J / cm², the pulse frequency was 20 Hz, and the thickness was 2.5 μm. The composition and other process conditions were the same as those of the Cr-CN layer in Example 1.

[0069] Comparative Example 3 A 316L stainless steel substrate was used, and a MAX phase coating was directly deposited using pulsed laser deposition without a transition layer. The laser energy density was 4.0 J / cm², the pulse frequency was 20 Hz, and the thickness was 2.5 μm. Other process conditions were the same as those for the MAX phase layer in Example 1.

[0070] Performance testing The following performance tests were performed on the coated bipolar plates prepared in Examples 1-3 and Comparative Examples 1-3: 1) Interface contact resistance (ICR) test The contact resistance between the coating and the carbon paper was measured using the standard four-probe method under a pressure of 1.4 MPa. The results are as follows: Figure 2 As shown: - Example 1: ICR = 7.5 mΩ·cm²; Example 2: ICR = 8.2 mΩ·cm²; Example 3: ICR = 7.8 mΩ·cm²; - Comparative Example 1: ICR = 18.5 mΩ·cm²; - Comparative Example 2: ICR = 9.8 mΩ·cm²; - Comparative Example 3: ICR = 15.2 mΩ·cm².

[0071] 2) Electrochemical corrosion test Potentiodynamic polarization was tested in a 0.5 M H₂SO₄ + 0.2 ppm F⁻ solution. The results are as follows: Figure 3 As shown, the corrosion current density at 0.6V vs. SCE potential is: Example 1: 0.42 μA / cm²; Example 2: 0.55 μA / cm²; Example 3: 0.38 μA / cm²; - Comparative Example 1: 5.8 μA / cm²; - Comparative Example 2: 1.2 μA / cm²; - Comparative Example 3: 0.85 μA / cm².

[0072] 3) Long-term stability test The coated bipolar plate of Example 1 was subjected to constant potential (0.6V vs. SCE) testing in a simulated environment for 5000 hours. The results are as follows... Figure 4 As shown, the coating remained intact, the ICR increased from the initial 7.5 mΩ·cm² to 8.8 mΩ·cm², and the corrosion current density remained below 0.5 μA / cm².

[0073] 4) Coating structure characterization XRD analysis Figure 5 The results confirmed that the MAX phase intermediate layer is mainly composed of Ti2AlC and Ti3AlC2 phases. XRD analysis showed that the purity of Ti2AlC and Ti3AlC2 phases in the MAX phase intermediate layer prepared by the pulsed laser deposition method of the present invention reached more than 95%, and the content of secondary phase TiC was less than 5%, which is far superior to the MAX phase coating prepared by the traditional magnetron sputtering method (purity of about 75-80%).

[0074] Test results show that the Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate of the present invention has excellent comprehensive performance, low interfacial contact resistance, good corrosion resistance, and excellent long-term stability.

[0075] The beneficial effects of the Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate and its preparation method of the present invention are as follows: 1. This invention achieves comprehensive optimization of coating performance through the synergistic effect of the Ti-Nb-Zr alloy transition layer, the MAX phase intermediate layer, and the Cr-CN nanocomposite surface layer: the Ti-Nb-Zr alloy transition layer provides excellent substrate adhesion and stress buffering; the MAX phase intermediate layer provides the main corrosion resistance barrier and self-healing ability; and the Cr-CN nanocomposite surface layer provides low contact resistance and good surface stability. 2. The gradient transition zone designed in this invention effectively reduces interlayer stress, improves the bonding strength and long-term stability of the coating, and avoids peeling failure of the coating during service. 3. Precise composition control: Compared with the magnetron sputtering method commonly used in existing technologies, pulsed laser deposition (PLD) can achieve complete transfer of target composition, ensuring that the stoichiometry of the deposited film is consistent with that of the target. It is especially suitable for the deposition of ternary compounds with complex compositions such as MAX phase, and significantly improves the purity and structural order of MAX phase. 4. Low-temperature high-quality preparation: Compared with traditional methods, high-energy pulsed laser deposition can obtain high-quality MAX phase films at lower substrate temperatures (400-550°C), which is much lower than traditional CVD methods (above 1000°C) and solid-state reaction methods (800-1100°C), effectively avoiding thermal damage to the substrate material caused by high temperature. 5. The multilayer composite coating of the present invention has excellent comprehensive performance: interfacial contact resistance ICR≤8 mΩ·cm², corrosion current density at 2V working voltage≤0.5 μA / cm², and coating life>5000 hours; 6. The preparation method of the present invention is mature, the parameters are controllable, it is suitable for industrial mass production, and has good application prospects.

[0076] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate, characterized in that, include: A metal substrate and a multilayer composite coating disposed on the surface of the metal substrate, wherein the multilayer composite coating comprises, from the inside to the outside: Ti-Nb-Zr alloy transition layer, wherein the atomic ratio of Ti, Nb and Zr in the Ti-Nb-Zr alloy transition layer is (40-60):(20-35):(15-30); The first gradient transition region is located between the Ti-Nb-Zr alloy transition layer and the MAX phase intermediate layer. Its composition includes Ti, Nb, Zr and Al. In the first gradient transition region, the content of Ti and Al gradually increases from the Ti-Nb-Zr alloy transition layer to the MAX phase intermediate layer, and the content of Nb and Zr gradually decreases from the Ti-Nb-Zr alloy transition layer to the MAX phase intermediate layer. The MAX phase intermediate layer includes Ti2AlC and / or Ti3AlC2; The second gradient transition region, located between the MAX phase intermediate layer and the Cr-CN nanocomposite surface layer, comprises Ti, Al, and Cr. In the second gradient transition region, the contents of Ti and Al gradually decrease from the MAX phase intermediate layer towards the Cr-CN nanocomposite surface layer, while the contents of Cr gradually increase from the MAX phase intermediate layer towards the Cr-CN nanocomposite surface layer. The Cr-CN nanocomposite surface layer has an atomic ratio of Cr, C, and N of (40-60):(20-40):(10-30).

2. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, The metal substrate includes one of stainless steel, titanium alloy, aluminum alloy or nickel-based alloy.

3. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, The total thickness of the multilayer composite coating is 1.5-4.5 μm; preferably, the total thickness of the multilayer composite coating is 2.0-3.0 μm.

4. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, In the Ti-Nb-Zr alloy transition layer, the atomic ratio of Ti, Nb, and Zr is 50:30:

20.

5. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, The thickness of the first gradient transition region is 5-20 nm, and the thickness of the second gradient transition region is 5-20 nm.

6. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, When the MAX phase intermediate layer is a composite structure of Ti2AlC and Ti3AlC2, the volume ratio of Ti2AlC to Ti3AlC2 is (1-3):(3-1).

7. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, The Cr-CN nanocomposite surface layer is a nanocomposite structure with nanocrystalline Cr(C,N) phase embedded in an amorphous carbon matrix; preferably, the nanocrystal size of the Cr-CN nanocomposite surface layer is 5-20 nm.

8. The Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, In the Cr-CN nanocomposite surface layer, the atomic ratio of Cr, C, and N is 50:30:

20.

9. A Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, The preparation steps of the Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate include: S1: Metal substrate pretreatment; S2: A Ti-Nb-Zr alloy transition layer is deposited on the surface of a metal substrate using pulsed laser deposition. S3: A first gradient transition region is deposited on the Ti-Nb-Zr alloy transition layer by pulsed laser deposition. S4: A MAX phase intermediate layer is deposited on the surface of the first gradient transition region using high-energy pulsed laser deposition. S5: A second gradient transition region is deposited on the surface of the MAX phase intermediate layer by a high-energy pulsed laser deposition method. S6: A Cr-CN nanocomposite surface layer is deposited on the surface of the second gradient transition zone using reactive pulsed laser co-deposition.

10. A Ti-Nb-Zr / MAX phase / Cr-CN multilayer composite coated bipolar plate according to claim 1, characterized in that, This multi-layer composite coated bipolar plate is used in water electrolysis devices to improve the corrosion resistance and long-term stability of the bipolar plate and reduce the interfacial contact resistance.

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