WO2023197469A1 - High-conductivity corrosion-resistant amorphous/nanocrystalline composite coexisting coating, and preparation method therefor and use thereof - Google Patents

Abstract

A high-conductivity corrosion-resistant amorphous/nanocrystalline composite coexisting coating, and a preparation method therefor and a use thereof. The preparation method comprises: using arc ion plating in combination with high-power impulse magnetron sputtering technology, taking a Cr target as an arc target, taking a Al target as a high-power impulse magnetron sputtering target, taking methane as a working gas, and depositing on a surface of a metal matrix to form a Cr-Al-C layer; and performing vacuum low-temperature heat treatment on the metal matrix on which the Cr-Al-C layer is deposited, thereby obtaining the high-conductivity corrosion-resistant amorphous/nanocrystalline composite coexisting coating. The coating has an amorphous structure and a nanocrystalline structure, and the amorphous structure is a mass-thickness fringe structure. According to the coating, the interface conductivity between the coating and the matrix is improved, the corrosion resistance is improved, and the coating has excellent conductivity and corrosion resistance in a harsh environment.

Description

Highly conductive and corrosion-resistant amorphous/nanocrystalline composite coating and its preparation method and application

This application is based on and requires the priority of the Chinese patent application with application number 202210394609.6 and the invention title "Highly conductive and corrosion-resistant amorphous/nanocrystal composite coexistence coating and its preparation method and application" submitted on April 15, 2022. right.

Technical field

This application belongs to the technical field of metal surface engineering protection, and relates to a highly conductive and corrosion-resistant amorphous/nanocrystalline composite coating and its preparation method and application. In particular, it relates to a highly conductive and corrosion-resistant amorphous/nanocrystalline (Cr- Al-C/Cr ₂ AlC) composite coexistence coating and its preparation method and application.

Background technique

In recent years, with the urgent need for automotive technological innovation and the rapid development of fuel cell technology, many governments and companies have been committed to promoting the development of fuel cell vehicles. Among them, proton exchange membrane fuel cells (PEMFCs) are the fifth generation of fuel cells after solid fuel cells. They have the advantages of high efficiency, energy saving, high specific energy, fast start-up at low temperature and high smooth operation. They are widely used in new energy vehicles and fixed/portable power supplies. It has developed rapidly and has been widely used in automobiles, aircraft, ships and other fields. However, due to its high cost, large size and other factors, its application in transportation, civil automobiles and other fields has been greatly restricted. In PEMFCs, the bipolar plate is a key functional component that separates the reaction gases and introduces the fuel reaction gases into the fuel cell through the flow field, collects and conducts current, and supports the membrane electrode. It is also responsible for the heat dissipation and drainage functions of the entire battery system. It occupies It accounts for 80% of the total mass of the fuel cell and about 18%-28% of the manufacturing cost. Therefore, the preparation of high-quality bipolar plates is a basic condition for reducing the production cost of PEMFCs, reducing the weight of the battery pack, and realizing the industrialization of fuel cells.

The traditional graphite bipolar plate has high processing costs and large volume, which limits its efficiency. Ultra-thin metal plates with excellent properties such as high electrical conductivity, high thermal conductivity, high mechanical strength, low stamping cost and low gas permeability are gradually replacing them. Graphite became the main material for bipolar plates. However, in the high temperature of the fuel cell and the acidic environment with a pH of about 2 to 3, dissolution and corrosion of the metal plates are inevitable. In particular, the penetration of metal ions into the proton exchange membrane causes a decrease in ion transmission efficiency and the corrosion products increase the interface contact resistance. Directly affects the output power and service life of the battery. Therefore, it has become an urgent need to functionally protect and modify the surface coating of metal bipolar plates to improve their conductivity and corrosion resistance.

In recent years, many scientific research teams have tried to prepare a variety of different corrosion-resistant conductive coatings, such as precious metal coatings, metal carbide coatings, conductive polymer composite coatings, amorphous carbon coatings, etc., which can significantly improve the performance of metal doublets. Plate performance. However, the high price of precious metal coatings limits its application. Due to the presence of grain boundaries and corrosive oxides in metal carbides, the conductive and corrosion resistance needs to be further improved. The preparation process of conductive polymers and amorphous carbon coatings Cumbersome steps limit further development. In addition, during the long-term service of PEMFCs, there are still great challenges for the coating to maintain high corrosion resistance and low interface contact resistance at the same time, which greatly affects the electric power, stability and life of the battery. Therefore, it is particularly urgent and important to research and develop new conductive and corrosion-resistant coatings to further improve its stability and interface conductivity in the PEMFC environment and reduce the attenuation of battery performance to promote the commercial development of PEMFC.

Contents of the invention

The main purpose of this application is to provide a highly conductive and corrosion-resistant amorphous/nanocrystalline composite coating and its preparation method and application, so as to overcome the shortcomings of the existing technology.

In order to achieve the foregoing invention objectives, the technical solutions adopted in this application include:

The embodiments of the present application provide a method for preparing a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating, which includes:

Provide metal substrate;

The arc ion plating composite high-power pulse magnetron sputtering technology is used, using the Cr target as the arc target, the Al target as the high-power pulse magnetron sputtering target, and methane as the working gas to deposit Cr- on the surface of the metal substrate. Al-C layer;

And, perform vacuum low-temperature heat treatment on the metal substrate on which the Cr-Al-C layer is deposited to obtain a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating;

The coating has an amorphous structure and a nanocrystalline structure, the amorphous structure is a thick stripe structure, the amorphous structure is Cr-Al-C; the nanocrystalline structure is a hexagonal phase layered structure, so The nanocrystal structure is Cr ₂ AlC MAX phase; the crystallinity of the coating is 20% to 80%.

The embodiments of the present application also provide a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating prepared by the aforementioned method, with a corrosion current density of 2.5 to 5.0×10 ^-8 A/cm ² and an interface contact resistance of 2 to 12.5 mΩ. ·cm ² , the thickness of the coating is 3 μm to 20 μm.

The embodiments of the present application also provide the use of the aforementioned highly conductive and corrosion-resistant amorphous/nanocrystalline composite coexistence coating in preparing fuel cell bipolar plates.

The embodiment of the present application also provides a surface modification method for a metal bipolar plate, which includes: using the aforementioned method to prepare a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating on the surface of the metal bipolar plate, thereby achieving Modification of metal bipolar plates.

Compared with the existing technology, the beneficial effects of this application are:

(1) This application uses arc composite high-power pulse magnetron sputtering technology to prepare Cr-Al-C coating, which not only takes advantage of the high deposition rate and large ion energy of arc ion plating, but also takes advantage of high-power pulse magnetron sputtering. It achieves the advantages of high plasma density, high ionization rate and controllable adjustment of deposited particle energy, so that the prepared coating not only has strong binding force with the substrate, but also is dense, has no columnar defects, has a smooth surface, and can Slows down the speed of electrochemical corrosion;

(2) The coating prepared by this application using inert atmosphere annealing technology has an amorphous/crystalline structure. The Cr-Al-C amorphous structure has no defects such as grain boundaries and dislocations, making it suitable for use in harsh environments such as acidity and high temperature. It lacks ion corrosion channels and has excellent corrosion resistance and protection properties; and the formed nanocrystalline Cr ₂ AlC is a large class of thermodynamically stable, layered high-performance ceramic materials with a close-packed hexagonal structure. The metallic bonds between Cr-Al make It has a high electronic state density at the Fermi level, which makes Cr ₂ AlC have good electrical conductivity. Combining the advantages of the two makes the coating have good electrical conductivity and corrosion resistance.

Description of the drawings

In order to explain the embodiments of the present application or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments recorded in this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a transmission electron microscope image of the Cr-Al-C/Cr ₂ AlC coating prepared in Example 1 of the present application;

Figure 2 is a selected area electron diffraction pattern of the Cr-Al-C/Cr ₂ AlC coating prepared in Example 1 of the present application;

Figure 3 is a selected area electron diffraction pattern of the Cr-Al-C layer prepared in Comparative Example 1 of the present application;

Figure 4 is a selected area electron diffraction pattern of the Cr-Al-C layer prepared in Comparative Example 2 of the present application;

Figure 5 is a selected area electron diffraction pattern of the Cr-Al-C layer prepared in Example 2 of the present application;

Figure 6 is a cross-sectional scanning electron microscope image of the Cr-Al-C/Cr ₂ AlC coating prepared in Example 3 of the present application;

Figure 7 is an XRD comparison chart of the coatings prepared in Example 1, Example 2, Example 3 and Comparative Example 1 of the present application;

Figure 8 is a comparison chart of the corrosion performance test of the coating layers prepared in Example 1, Example 2, Example 3 and Comparative Example 2 of the present application;

Figure 9 is a graph showing changes in contact resistance before and after corrosion of the coatings prepared in Example 1, Example 2, Example 3 and Comparative Example 1 of the present application.

Detailed ways

In view of the shortcomings of the prior art, the inventor of the present case was able to propose the technical solution of the present application after long-term research and extensive practice. The technical solution of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the present application. Examples, not all examples. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

Specifically, as one aspect of the technical solution of the present application, the preparation method of a highly conductive and corrosion-resistant amorphous/nanocrystalline composite coating includes:

Provide metal substrate;

The arc ion plating composite high-power pulse magnetron sputtering technology is used, using the Cr target as the arc target, the Al target as the high-power pulse magnetron sputtering target, and methane as the working gas to deposit Cr- on the surface of the metal substrate. Al-C layer;

And, perform vacuum low-temperature heat treatment on the metal substrate on which the Cr-Al-C layer is deposited to obtain a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating;

The coating has an amorphous structure and a nanocrystalline structure, the amorphous structure is a thick stripe structure, the amorphous structure is Cr-Al-C; the nanocrystalline structure is a hexagonal phase layered structure, so The nanocrystal structure is Cr ₂ AlC MAX phase; the crystallinity of the coating is 20% to 80%.

Specifically, the coating can also be recorded as Cr-Al-C/Cr ₂ AlC coating.

In some preferred embodiments, the preparation method specifically includes: using arc ion plating combined high-power pulse magnetron sputtering technology, placing the metal substrate in the reaction chamber, using the Cr target as the arc target, and the Al target as the high The power pulse magnetron sputtering target uses methane and inert gas as working gases to deposit a Cr-Al-C layer on the surface of the metal substrate. The bias voltage of the metal substrate is -30~-90V, and the high-power pulse duty cycle is The ratio is 20~50%, the average sputtering power of the Al target is 2000~3000W, the current of the Cr target is 20~50A, the input flow rate of methane is 15~20sccm, the input amount of inert gas is 150~200sccm, and the deposition The temperature is 150~300℃, and the deposition time is 60~300min.

Further, the inert gas is Ar gas, and is not limited thereto.

Further, the current of the Cr target is 40-50A.

Further, the target distance between the metal substrate and the Cr target is 15-20 cm, and the target distance between the metal substrate and the Al target is 5-10 cm.

Further, the thickness of the Cr-Al-C layer is 3 μm to 20 μm.

In some preferred embodiments, the preparation method specifically includes: filling the reaction chamber with an inert gas at a vacuum degree of 3×10 ^-4 Pa or less, and heating the reaction chamber at a heating rate of 5 to 10°C/min. The temperature is raised to 500°C to 550°C, and the metal substrate on which the Cr-Al-C layer is deposited is annealed for 0.1 to 1 hour, thereby forming the highly conductive and corrosion-resistant amorphous/nanocrystalline composite coexistence coating on the surface of the metal substrate. layer.

In some preferred embodiments, the material of the metal substrate includes any one or a combination of two or more of zirconium, tantalum, zirconium alloy, tantalum alloy, aluminum alloy, titanium, titanium alloy, stainless steel, and is not limited thereto.

In some preferred embodiments, the preparation method further includes: first cleaning and etching the metal substrate.

Another aspect of the embodiments of the present application also provides a highly conductive and corrosion-resistant amorphous/nanocrystalline composite coexistence coating prepared by the aforementioned method, with a corrosion current density of 2.5 to 5.0×10 ^-8 A/cm ² and an interface contact resistance of 2～12.5mΩ·cm ² , and the thickness of the coating is 3μm～20μm.

The formation of the MAX phase in this application needs to satisfy two processes: kinetics and thermodynamics. This application mainly focuses on kinetic research, which is the process of transition from amorphous state to crystalline state. Due to the relatively short annealing time, Cr and Al metal atoms at low temperatures It cannot be fully diffused and arranged to form a hexagonal MAX phase structure, so an amorphous and nano-coexistence structure will be formed.

Another aspect of the embodiments of the present application also provides the use of the aforementioned highly conductive and corrosion-resistant amorphous/nanocrystalline composite coexistence coating in preparing fuel cell bipolar plates.

Another aspect of the embodiment of the present application also provides a surface modification method for a metal bipolar plate, which includes: using the aforementioned method to prepare a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating on the surface of the metal bipolar plate. layer, thereby achieving modification of the metal bipolar plate.

The coating prepared by this application (amorphous/nanocrystalline composite Cr-Al-C/Cr ₂ AlC coating) is a coating on the surface of the substrate that has both good conductivity and corrosion resistance, and can meet the needs of many substrates. Protection requirements for electrical conductivity and corrosion resistance. For example, it can be used as a surface coating for stainless steel bipolar plates of proton exchange membrane fuel cells, because the thermal expansion of the crystal Cr ₂ AlC formed in the coating is 13.3×10 ^-6 K ^-1 compared with 17×10 ^-6 K ^-1 of SS316L Not far behind, this not only helps to improve the good adhesion between the substrate and the coating but also improves the corrosion resistance of the stainless steel bipolar plate and reduces its interface contact resistance.

The technical solution of the present application will be further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented based on the technical solution of the invention and provides detailed implementation modes and specific operating processes. However, the technical solution of the present application is The scope of protection is not limited to the following examples.

The experimental materials used in the following examples can be purchased from conventional biochemical reagent companies unless otherwise specified.

Example 1

In this embodiment, the substrate is a 316L stainless steel bipolar plate used for proton exchange membrane fuel cells, and the preparation method of the Cr-Al-C/Cr ₂ AlC coating on the surface of the substrate is as follows:

(1) Put the cleaned, degreased and dried 316L stainless steel bipolar plate substrate into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, introduce 180 sccm of argon gas into the vacuum chamber. The voltage was -60V, the linear anode ion source current was set to 0.8A, and the ionized argon ions were used to etch the substrate for 60 minutes.

(2) Using arc ion plating composite high-power pulse magnetron sputtering technology, the Cr target is used as the arc target, the arc target current is 40A, the Al target is used as the high-power pulse magnetron sputtering target, and the high-power pulse duty cycle is 25%, the average sputtering power of the Al target is 2500W, the target distance between the 316L stainless steel bipolar plate substrate and the Al target is 10cm, and the target distance between the Cr target and the Cr target is 18cm, the gas CH ₄ provides the C source, and the CH ₄ flow rate is 20 sccm , the argon flow rate is 200 sccm, the bias voltage of the substrate is -60V, the deposition temperature is 200°C, the deposition time is 150 min, and the thickness of the deposited Cr-Al-C layer is about 8 μm.

(3) Heat treat the 316L stainless steel bipolar plate with Cr-Al-C layer deposited under the protection of argon gas at an atmospheric pressure, with a heating rate of 8°C/min, an annealing temperature of 500°C, and a holding time of 0.5h, so that A Cr-Al-C/Cr ₂ AlC coating is formed on the surface of the 316L stainless steel bipolar plate, and the crystallinity of the coating is 40%.

Figure 1 is a transmission electron microscope image of the Cr-Al-C/Cr ₂ AlC coating prepared in this embodiment. It can be seen that the coating obtained after annealing contains crystalline and amorphous structures. The crystal structure appears black and amorphous. The structure shows a stripe structure, and the nanocrystals are the Cr ₂ AlC MAX phase formed. The MAX phase has a layered high-performance ceramic structure with a close-packed hexagonal structure; Figure 2 shows the Cr-Al-C/Cr ₂ AlC produced in this embodiment. From the selected area electron diffraction pattern of the coating, it can be seen that there is Cr ₂ AlC with a crystal structure in the coating, and there is also a halo formed by an amorphous structure.

Comparative example 1

This example is a comparative example of Example 1;

In this comparative example, the substrate is exactly the same as in Example 1, and the preparation method of the Cr-Al-C layer on the surface of the substrate is basically the same as that in Example 1. The difference is that the annealing treatment in step (3) is not performed. The crystallinity of the coating is 0%.

Figure 3 is the selected area electron diffraction pattern of the Cr-Al-C layer prepared in this comparative example. It can be seen that there is only a halo formed in the diffraction pattern, but no diffraction spots, indicating that there is no crystalline Cr in the formed Cr-Al-C layer. ₂ AlC has an amorphous structure.

Comparative example 2

This example is another comparative example of Example 1;

In this comparative example, the substrate is the same as Example 1, and the preparation method of the Cr-Al-C series MAX phase coating on the surface of the substrate is basically the same as that in Example 1, except for the annealing treatment in step (3). After 10 hours, the prepared coating is a Cr ₂ AlC layer, and the crystallinity of the coating is 100%; Figure 4 is the selected area electron diffraction pattern of the Cr ₂ AlC layer prepared in this comparative example. It can be seen that there is no halo in the diffraction pattern. The presence of rings indicates that the formed coating is completely crystallized and is Cr ₂ AlC.

Example 2

In this embodiment, the substrate is a 304 stainless steel bipolar plate used for proton exchange membrane fuel cells, and the preparation method of the Cr-Al-C/Cr ₂ AlC coating on the surface of the substrate is as follows:

(1) Put the cleaned, degreased and dried 304 stainless steel bipolar plate substrate into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, introduce 150 sccm of argon gas into the vacuum chamber. The voltage was -90V, the linear anode ion source current was set to 0.8A, and the ionized argon ions were used to etch the substrate for 60 minutes.

(2) Using arc ion plating composite high-power pulse magnetron sputtering technology, the Cr target is used as the arc target, the arc target current is 40A, the Al target is used as the high-power pulse magnetron sputtering target, and the high-power pulse duty cycle is 35%, the average sputtering power of the Al target is 3000W, the target distance between the 304 stainless steel bipolar plate substrate and the Al target is 8cm, the target distance between the 304 stainless steel bipolar plate substrate and the Cr target is 18cm, the gas CH ₄ provides the C source, and the CH ₄ flow rate is 20 sccm, the argon flow rate is 200 sccm, the bias voltage of the substrate is -90V, the deposition temperature is 200°C, the deposition time is 180 min, and the thickness of the deposited Cr-Al-C layer is about 10 μm.

(3) Heat treat the 304 stainless steel bipolar plate substrate with Cr-Al-C layer deposited under the protection of argon gas at an atmospheric pressure. The heating rate is 10°C/min, the annealing temperature is 500°C, and the holding time is 0.3h. , thereby forming a Cr-Al-C/Cr ₂ AlC coating on the surface of the 304 stainless steel bipolar plate substrate, and the crystallinity of the coating is 20%.

Figure 5 is a selected area electron diffraction pattern of the Cr-Al-C/Cr ₂ AlC coating prepared in this example. It can be seen that it is similar to Example 1. There is Cr ₂ AlC with a crystal structure and an amorphous structure in the coating. The halo formed.

Example 3

In this embodiment, the substrate is a 304 stainless steel bipolar plate used for proton exchange membrane fuel cells, and the preparation method of the Cr-Al-C/Cr ₂ AlC coating on the surface of the substrate is as follows:

(1) Put the cleaned, degreased and dried 304 stainless steel bipolar plate substrate into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, introduce 150 sccm of argon gas into the vacuum chamber. The voltage was -80V, the linear anode ion source current was set to 0.8A, and the ionized argon ions were used to etch the substrate for 60 minutes.

(2) Using arc ion plating composite high-power pulse magnetron sputtering technology, the Cr target is used as the arc target, the arc target current is 40A, the Al target is used as the high-power pulse magnetron sputtering target, and the high-power pulse duty cycle is 30%, the average sputtering power of the Al target is 2000W, the target distance between the 304 stainless steel bipolar plate and the Al target is 8cm, and the target distance between the Cr target and the Cr target is 18cm, the gas CH ₄ provides the C source, and the CH ₄ flow rate is 20 sccm , the argon flow rate is 200 sccm, the bias voltage of the substrate is -80V, the deposition temperature is 300°C, the deposition time is 160min, and the thickness of the deposited Cr-Al-C layer is about 8.6μm.

(3) Heat treat the 304 stainless steel bipolar plate substrate with Cr-Al-C coating deposited under the protection of argon gas at an atmospheric pressure. The heating rate is 5℃/min, the annealing temperature is 500℃, and the holding time is 1h. , thereby forming a Cr-Al-C/Cr ₂ AlC coating on the surface of the 304 stainless steel bipolar plate substrate, and the crystallinity of the coating is 80%.

Figure 6 is a cross-sectional scanning electron microscope image of the Cr-Al-C/Cr ₂ AlC coating prepared in this embodiment. It can be seen that the cross-section is smooth and there is no obvious columnar structure. The coating is closely combined with the substrate. The thickness of the coating is about 8.6μm.

The above-mentioned Example 1, Example 2, Example 3 and Comparative Example 1 were tested using XRD. As shown in Figure 7, it can be seen that only one steamed bun peak appears in the diffraction spectrum of the coating prepared in Comparative Example 1. , indicating that the coating prepared in the comparative example has an amorphous structure, which is consistent with the results of the selected area electron diffraction spectrum. In the XRD spectra of Examples 1, 2, and 3, Comparative Example 1 has sharp peaks, and the peak intensity changes. In addition, Example 1 can be seen from the characteristic peak of Cr ₂ AlC at 13.8°. , the coatings prepared in Example 2 and Example 3 all appear crystallized, but there are still uncrystallized parts.

An electrochemical standard three-electrode test system was used to measure the corrosion resistance of the substrate with a Cr-Al-C coating on the surface obtained in the above Example 1, Example 2, Example 3 and Comparative Example 2. The solution was 0.5M H ₂ S0 ₄ +5ppm HF solution, solution temperature is 80℃. The test results are shown in Figure 8. It can be seen from Figure 8: compared with Comparative Example 2, the corrosion current density in Example 1, Example 2, and Example 3 has significantly reduced, indicating that Example 1, Example 2. The Cr-Al-C/Cr ₂ AlC coating prepared in Example 3 has better corrosion resistance.

Figure 9 is a diagram showing the change in contact resistance of the coatings prepared in Example 1, Example 2, Example 3 and Comparative Example 1 before and after 24 hours of constant potential corrosion. It can be seen from Figure 9: Compared with Comparative Example 1 , Example 1, Example 2, and Example 3 all have smaller contact resistance before and after corrosion for 24 hours, which shows that the prepared Cr-Al-C/Cr ₂ AlC coating has better electrical conductivity.

Example 4

In this embodiment, the substrate is a 316L stainless steel bipolar plate used for proton exchange membrane fuel cells, and the preparation method of the Cr-Al-C/Cr ₂ AlC coating on the surface of the substrate is as follows:

(1) Place the cleaned, degreased and dried 316L stainless steel bipolar plate substrate into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, introduce 150 sccm of argon gas into the vacuum chamber. The voltage was -80V, the linear anode ion source current was set to 0.8A, and the ionized argon ions were used to etch the substrate for 60 minutes.

(2) Using arc ion plating composite high-power pulse magnetron sputtering technology, the Cr target is used as the arc target, the arc target current is 40A, the Al target is used as the high-power pulse magnetron sputtering target, and the high-power pulse duty cycle is 35%, the average sputtering power of the Al target is 3000W, the target distance between the 316L stainless steel bipolar plate substrate and the Al target is 8cm, and the target distance between the Cr target and the Cr target is 20cm, the gas CH ₄ provides the C source, and the CH ₄ flow rate is 20 sccm, the argon flow rate is 200 sccm, the bias voltage of the substrate is -90V, the deposition temperature is 150°C, the deposition time is 300 min, and the thickness of the deposited Cr-Al-C layer is about 20 μm.

(3) Heat treat the 316L stainless steel bipolar plate substrate with Cr-Al-C layer deposited under the protection of argon gas at an atmospheric pressure. The heating rate is 10°C/min, the annealing temperature is 550°C, and the holding time is 0.5h. , thereby forming a Cr-Al-C/Cr ₂ AlC coating on the surface of the 316L stainless steel bipolar plate substrate, and the crystallinity of the coating is 30%.

Example 5

In this embodiment, the substrate is a 316L stainless steel bipolar plate used for proton exchange membrane fuel cells, and the preparation method of the Cr-Al-C/Cr ₂ AlC coating on the surface of the substrate is as follows:

(1) Put the cleaned, degreased and dried 304 stainless steel bipolar plate substrate into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, introduce 150 sccm of argon gas into the vacuum chamber. The voltage was -80V, the linear anode ion source current was set to 0.8A, and the ionized argon ions were used to etch the substrate for 60 minutes.

(2) Using arc ion plating composite high-power pulse magnetron sputtering technology, the Cr target is used as the arc target, the arc target current is 40A, the Al target is used as the high-power pulse magnetron sputtering target, and the high-power pulse duty cycle is 35%, the average sputtering power of the Al target is 3000W, the target distance between the 316L stainless steel bipolar plate substrate and the Al target is 8cm, and the target distance between the Cr target and the Cr target is 18cm, the gas CH ₄ provides the C source, and the CH ₄ flow rate is 20 sccm, argon gas flow rate is 200 sccm, substrate bias voltage is -80 V, deposition temperature is 300°C, deposition time is 60 min, and the thickness of the deposited Cr-Al-C layer is about 3 μm.

(3) Heat treat the 316L stainless steel bipolar plate substrate with Cr-Al-C layer deposited under the protection of argon gas at an atmospheric pressure. The heating rate is 10°C/min, the annealing temperature is 550°C, and the holding time is 0.1h. , thereby forming a Cr-Al-C/Cr ₂ AlC coating on the surface of the 316L stainless steel bipolar plate substrate, and the crystallinity of the coating is 25%.

Example 6

In this embodiment, the substrate is a 304 stainless steel bipolar plate used for proton exchange membrane fuel cells, and the preparation method of the Cr-Al-C/Cr ₂ AlC coating on the surface of the substrate is as follows:

(1) Put the cleaned, degreased and dried 304 stainless steel bipolar plate substrate into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, introduce 150 sccm of argon gas into the vacuum chamber. The voltage was -90V, the linear anode ion source current was set to 0.8A, and the ionized argon ions were used to etch the substrate for 60 minutes.

(2) Using arc ion plating composite high-power pulse magnetron sputtering technology, the Cr target is used as the arc target, the arc target current is 40A, the Al target is used as the high-power pulse magnetron sputtering target, and the high-power pulse duty cycle is 50%, the average sputtering power of the Al target is 3000W, the target distance between the 304 stainless steel bipolar plate substrate and the Al target is 10cm, the target distance between the 304 stainless steel bipolar plate substrate and the Cr target is 20cm, the gas CH ₄ provides the C source, and the CH ₄ flow rate is 20 sccm, argon gas flow rate is 200 sccm, substrate bias voltage is -90 V, deposition temperature is 200°C, deposition time is 270 min, and the thickness of the deposited Cr-Al-C layer is about 15 μm.

(3) Heat treat the 304 stainless steel bipolar plate substrate with the Cr-Al-C layer deposited under the protection of argon gas at an atmospheric pressure. The heating rate is 10°C/min, the annealing temperature is 550°C, and the holding time is 1h. Thus, a Cr-Al-C/Cr ₂ AlC coating is formed on the surface of the 304 stainless steel bipolar plate substrate, and the crystallinity of the coating is 50%.

In addition, the inventor of the present case also conducted experiments with other raw materials, process operations, and process conditions mentioned in this specification with reference to the aforementioned embodiments, and achieved relatively ideal results.

It should be understood that the technical solution of the present application is not limited to the above-mentioned specific implementation cases. All technical modifications made based on the technical solution of the present application will fall within the scope of the present application without departing from the purpose of the present application and the scope protected by the claims. within the scope of protection applied for.

Claims (3)

1. A surface modification method for metal bipolar plates, characterized by including:

   Arc ion plating composite high-power pulse magnetron sputtering technology is used. The metal bipolar plate is placed in the reaction chamber, the Cr target is used as the arc target, the Al target is used as the high-power pulse magnetron sputtering target, and methane and inert are used. The gas is a working gas, and a Cr-Al-C layer is deposited on the surface of the metal bipolar plate. The bias voltage of the metal bipolar plate is -30~-90V, the high-power pulse duty cycle is 20~50%, and the Al The average sputtering power of the target is 2000~3000W, the current of the Cr target is 20~50A, the input flow rate of methane is 15~20sccm, the input amount of inert gas is 150~200sccm, and the deposition temperature is 150~300℃. Time is 60min～300min;

   And, when the vacuum degree is below 3×10 ^-4 Pa, inert gas is filled into the reaction chamber, and the temperature of the reaction chamber is raised to 500°C to 550°C at a heating rate of 5 to 10°C/min, which will have some effect on the deposition. The metal bipolar plate with the Cr-Al-C layer is annealed for 0.1 to 1 hour, thereby forming a highly conductive and corrosion-resistant amorphous/nanocrystal composite coating on the surface of the metal bipolar plate;

   Wherein, the coating is composed of amorphous and nanocrystalline structures that coexist, the amorphous structure is a thick stripe structure, the amorphous structure is Cr-Al-C; the nanocrystalline structure is a hexagonal phase layered structure , the nanocrystal structure is Cr ₂ AlC MAX phase; the crystallinity of the coating is 20% ~ 80%; the corrosion current density of the coating is 2.5 ~ 5.0×10 ^-8 A/cm ² , the The interface contact resistance of the coating is 2 to 12.5 mΩ·cm ² , and the thickness of the coating is 3 μm to 20 μm;

   The material of the metal bipolar plate is selected from any one or a combination of two or more of zirconium, tantalum, zirconium alloy, tantalum alloy, aluminum alloy, titanium, titanium alloy, and stainless steel.
2. The surface modification method according to claim 1, characterized in that: the current of the Cr target is 40-50A.
3. The surface modification method according to claim 1, characterized in that: the target distance between the metal bipolar plate and the Cr target is 15-20 cm, and the target distance between the metal bipolar plate and the Al target is 5-10 cm.

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