CN111519157B

CN111519157B - Preparation method and application of Cr-Al-C series MAX phase coating

Info

Publication number: CN111519157B
Application number: CN202010577774.6A
Authority: CN
Inventors: 马冠水; 汪爱英; 王振玉; 郭鹏; 李�昊
Original assignee: Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Ningbo Dun Ge Coating Technology Co ltd
Priority date: 2020-06-23
Filing date: 2020-06-23
Publication date: 2021-06-11
Anticipated expiration: 2040-06-23
Also published as: CN111519157A; WO2021259046A1

Abstract

The invention discloses a preparation method and application of a Cr-Al-C series MAX phase coating. First, a Cr-C layer is deposited on the surface of the substrate by arc ion plating, and the thickness of the Cr-C layer is 0.5 μm to 5 μm; then, an Al layer is deposited on the surface of the Cr-C layer by magnetron sputtering deposition, Al\Cr-C coating is obtained; finally, heat treatment is performed to obtain a Cr-Al-C MAX phase coating with (103) crystal plane preferential orientation. The coating has both good electrical conductivity and corrosion resistance. Compared with the prior art, the Cr-Al-C series MAX phase coating prepared by this method not only improves the interface conductivity with the substrate, but also Improved corrosion resistance, excellent conductive corrosion protection performance in harsh environments.

Description

Preparation method and application of Cr-Al-C series MAX phase coating

Technical Field

The invention belongs to the technical field of surface engineering protection, and particularly relates to a preparation method and application of a Cr-Al-C MAX phase coating.

Background

Unlike conventional transition metal nitrides/carbides, M_n+1AX_nThe phase (MAX phase) is a large class of thermodynamically stable, layered high performance ceramic materials with a hexagonal close packed structure, wherein M, A and X are located at different positions of the periodic Table of the elements, wherein M represents an early transition metal, A represents a main group IIIA or IVA element, and X represents C or N. The MAX phase layers are bonded by weak metal bonds between M atoms and A atoms. Unique interatomic combination mode and crystal structure, so that the MAX phase has metal and ceramicExcellent properties such as good electrical conductivity, thermal conductivity, self-healing properties, small thermal expansion coefficient, excellent thermal stability, oxidation resistance, acid and alkali corrosion resistance, and the like.

Cr₂AlC is a common compound in the MAX phase, belonging to the hexagonal system with the space group P63/mmc, and its crystal structure can be described as being composed of Cr with a rock-salt like structure₆The C sheet layer and the closely packed Cr group atom surface are alternately stacked in the C direction. At present, Cr₂The preparation of AlC coating is mainly carried out by spraying method and physical vapor deposition, but the prepared Cr₂The AlC coating has no preferred orientation, so that Cr and Al oxides are easily formed when the coating works for a long time under the severe conditions of acidity and the like, and the electric conduction and the corrosion resistance are reduced. The conductivity and corrosion resistance of the coating are the desired protective properties of the coating for many substrates.

In recent years, with the urgent need for the innovation of automobile technology, many governments and companies have been working on the development of fuel cell automobiles. Among them, Proton Exchange Membrane Fuel Cells (PEMFCs) are a new type of fuel cell that starts late among many fuel cells, have the advantages of high efficiency, energy saving, environmental protection, high specific energy, low-temperature fast start, and high smooth operation, are rapidly developed in the aspects of new energy vehicles and fixed/portable power sources, and have begun to be widely applied to the fields of ocean exploration, aerospace, and the like. In PEMFCs, bipolar plates are the key functional components that separate and direct the reactant gases through a flow field into the fuel cell, collect and conduct the current, and support the membrane electrodes, while also performing the heat dissipation and drainage functions of the entire cell system. Although the traditional graphite bipolar plate has the advantages of high conductivity and high corrosion resistance, the problems of high processing cost and large volume exist, and the use efficiency of the graphite bipolar plate is limited. Stainless steel metal sheets with excellent properties such as high electrical conductivity, high thermal conductivity, high mechanical strength, low stamping cost, and low gas permeability are gradually replacing graphite as the main material of bipolar plates. However, under the high-temperature and acidic environment with the pH value of about 2-3 of the fuel cell, the dissolution and corrosion of the polar plate cannot be avoided, and particularly, the ion transmission efficiency is reduced due to the fact that metal ions permeate into the proton exchange membrane, and interface contact resistance is increased due to corrosion products, so that the output power and the service life of the cell are directly influenced. Therefore, improving the conductivity and corrosion resistance of stainless steel metal plates is one of the key technologies to be overcome in the field of PEMFCs.

By adopting the surface coating technology, the conductivity and corrosion resistance of the stainless steel metal polar plate are improved on the basis of keeping the excellent mechanical property and strong processability of the polar plate, thereby ensuring the long-term effective operation of the battery. In recent years, various corrosion-resistant conductive coatings, such as noble metal coatings, metal carbide coatings, conductive polymer composite coatings, amorphous carbon coatings and the like, are prepared by various scientific research teams at home and abroad, and the performance of the metal bipolar plate can be remarkably improved. However, during long-term service of PEMFCs, the challenge of maintaining high corrosion resistance and low interfacial contact resistance of the coating is still large, which greatly affects the electric power, stability and lifetime of the battery. Therefore, research and development of a novel conductive corrosion-resistant coating, further improving its stability and interfacial conductivity in a PEMFC environment, and reducing degradation of cell performance, are particularly urgent and important to promote the commercialization development of PEMFCs.

Disclosure of Invention

In view of the above problems, the present invention is directed to a method for preparing a Cr-Al-C MAX phase coating layer, by which the electrical conductivity and corrosion resistance of the Cr-Al-C MAX phase coating layer can be improved.

In order to achieve the technical purpose, the inventor discovers, after a great deal of experimental research, that a Cr-Al-C series MAX phase coating is prepared by a method of combining an arc ion plating deposition technology and a magnetron sputtering deposition technology, and the specific process is as follows:

taking a Cr element simple substance target as an arc target, an Al element simple substance target as a direct current sputtering target, and carbon hydrogen gas as reaction gas to deposit on the surface of a substrate, and then carrying out heat treatment to obtain a Cr-Al-C series MAX phase coating;

in the process, arc ion plating deposition and magnetron sputtering deposition are separated, namely, firstly, a Cr-C layer is deposited by arc ion plating, then an Al layer is deposited on the surface of the Cr-C layer by magnetron sputtering deposition technology, finally, heat treatment is carried out, the high activity of Al is utilized to enable the Al to permeate into the Cr-C layer to form a Cr-Al-C MAX phase coating, and the Cr-C layer is controlled to reach a certain thickness, so that the Cr-Al-C MAX phase coating with the (103) crystal face preferred orientation can be obtained, and the corrosion resistance and the interface conductivity of the Cr-Al-C MAX phase coating are superior to those of the Cr-Al-C MAX phase coating prepared by the prior art.

Namely, the technical scheme provided by the invention is as follows:

a preparation method of a Cr-Al-C series MAX phase coating with (103) crystal face preferred orientation is characterized in that arc ion plating deposition and magnetron sputtering deposition are utilized, a Cr element simple substance target is used as an arc target, an Al element simple substance target is used as a direct current sputtering target, hydrocarbon methane gas is used as reaction gas to deposit on the surface of a substrate, and then heat treatment is carried out to obtain the coating; the method is characterized in that:

firstly, depositing a Cr-C layer on the surface of a substrate by arc ion plating deposition, wherein the thickness of the Cr-C layer is 0.5-5 microns;

preferably, the thickness of the Cr-C layer is 1 to 3 μm.

As one implementation mode, in the process of depositing the Cr-C layer, the thickness of the Cr-C layer is controlled by controlling the deposition time under the condition that other conditions are the same.

As another way of realization, in the process of depositing the Cr-C layer, the thickness of the Cr-C layer is controlled by controlling the current of the cathode arc target under the same other conditions.

Then, depositing an Al layer on the surface of the Cr-C layer by utilizing magnetron sputtering deposition to obtain an Al \ Cr-C coating;

finally, heat treatment is carried out to obtain the Cr-Al-C MAX phase coating.

Preferably, the etching treatment is carried out first, and then the Cr-Al-C series MAX phase coating preparation is carried out.

Preferably, the bias voltage of the substrate is-100V to-200V when the Cr-C layer is deposited.

Preferably, the current of the cathodic arc target is 50A to 100A, more preferably 65A to 90A, when the Cr-C layer is deposited.

Preferably, the thickness of the Cr-C layer is 1 to 3 μm.

Preferably, the thickness of the Al layer is 1 to 3 μm.

Preferably, when depositing the Al layer, the target power of the magnetron sputtering target is 2.0kW to 3.0kW, the bias voltage of the substrate is-100V to-200V, and the pressure of the deposition chamber is 10 mTorr to 20 mTorr.

Preferably, the heat treatment temperature is 400 to 550 ℃ and the time is 24 to 100 hours.

Preferably, the degree of vacuum during the heat treatment is less than 3X 10^-3Pa。

The base material is not limited, and includes Al, Ti or stainless steel.

Compared with the prior art, the invention adopts the method of combining cathodic arc ion plating deposition and magnetron sputtering deposition to gradually plate, and has the following beneficial effects:

(1) according to the invention, the Cr-Al-C MAX phase coating is formed by permeating Al into the Cr-C layer by utilizing the high activity of Al, so that the stability of each component in the Cr-Al-C MAX phase coating is improved, and the bonding degree between the Cr-Al-C MAX phase coating and a substrate is improved;

(2) the Cr-Al-C MAX phase coating prepared by optimizing the thickness of the Cr-C layer has the preferred orientation of (103) crystal planes, so that the interface conductivity between the coating and a substrate is improved, and the corrosion resistance is reduced. The coating prepared by the invention has the advantages that (103) crystal face preferred orientation is realized, and Cr, Al and C atoms are exposed, so that the coating is not easy to oxidize and has excellent corrosion resistance and protection performance in severe environments such as acidic environment, high temperature environment and the like.

Therefore, the Cr-Al-C MAX phase coating prepared by the method has excellent conductivity, and simultaneously has excellent corrosion resistance and protection performance under the environments of acidity, high temperature and the like, so that the Cr-Al-C MAX phase coating is a coating with good conductivity and corrosion resistance on the surface of a substrate, and can meet the protection requirements of the conductivity and the corrosion resistance of a plurality of substrates, for example, the Cr-Al-C MAX phase coating is used as a surface coating of a stainless steel bipolar plate of a proton exchange membrane fuel cell, so that the corrosion resistance of the stainless steel bipolar plate is improved, and the interface contact resistance of the stainless steel bipolar.

Drawings

FIG. 1 is a scanning electron micrograph of a Cr-Al-C MAX phase coating layer obtained in example 1.

FIG. 2 is a chemical composition energy spectrum of a MAX phase of Cr-Al-C system obtained in example 1.

FIG. 3 is an XRD contrast of the MAX phases of Cr-Al-C system obtained in example 1, comparative example 1 and comparative example 2.

FIG. 4 is a comparative graph of corrosion performance tests of Cr-Al-C based MAX phase coatings obtained in example 1, comparative example 1 and comparative example 2.

FIG. 5 is a graph showing the change in contact resistance before and after corrosion of Cr-Al-C MAX phase coatings obtained in example 1, comparative example 1 and comparative example 2.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1:

in this embodiment, the substrate is a 304 stainless steel bipolar plate for a pem fuel cell, and the Cr-Al-C MAX phase coating on the surface of the substrate is prepared as follows:

(1) putting the cleaned, deoiled and dried substrate into a cavity until the vacuum pressure in the cavity is 3.0 × 10^-5And introducing 100 standard milliliters per minute of argon into the vacuum chamber below the Torr, setting the current of a linear anode ion source to be 0.3A and the bias voltage of the substrate to be-100V, and etching the substrate by utilizing ionized argon ions for 30 min.

(3) Depositing a Cr-C transition layer by arc ion plating, wherein a cathode arc target provides a Cr source and a gas CH₄Providing a C source, and the current of the arc target is 90A, CH₄The flow rate was 10 standard ml/min, the argon flow rate was 300 standard ml/min, the substrate bias was-200V, the deposition time was 60min, and the thickness of the deposited Cr-C transition layer was about 3 μm.

(4) And depositing an Al coating on the surface of the Cr-C transition layer by adopting a magnetron sputtering method, providing an Al source for a magnetron sputtering target, controlling the target power to be 2.5kW, controlling the argon flow to be 200 standard milliliters per minute, controlling the air pressure to be 15Pa, controlling the bias voltage of the matrix to be-200V, controlling the deposition temperature to be room temperature (about 20 ℃) and depositing for 60min to obtain the Al \ Cr-C coating.

(5) And carrying out heat treatment on the substrate on which the Al \ Cr-C coating is deposited under the protection of argon at atmospheric pressure, wherein the heating rate is 5 ℃/min, the annealing temperature is 550 ℃, and the heat preservation time is 72 h.

FIG. 1 is a scanning electron micrograph of the Cr-Al-C series coating produced, and it can be seen that after annealing a smooth dense MAX phase coating is obtained.

FIG. 2 is a chemical composition energy spectrum of the obtained Cr-Al-C MAX phase coating, and it can be seen that the arc ion plating combined with the magnetron sputtering successfully deposits Cr and Al on the substrate.

Comparative example 1:

this example is a comparative example to example 1 above.

In this example, the substrate was completely the same as in example 1, and the method for producing the Cr — Al — C system MAX phase coating on the surface of the substrate was substantially the same as in example 1, except that the deposition time in step (3) was 2 min.

Comparative example 2:

this example is another comparative example to example 1 above.

In this example, the substrate was completely the same as in example 1, and the preparation method of the Cr — Al — C system MAX phase coating on the surface of the substrate was substantially the same as in example 1, except that the current of the arc target in step (3) was 20A.

FIG. 3 is an X-ray diffraction pattern of the coatings obtained in example 1, comparative example 1 and comparative example 2 above. As can be seen from FIG. 3, Cr was produced in each of example 1, comparative example 1 and comparative example 2₂AlC (002) and Cr₂A MAX phase coating of AlC (103); however, Cr obtained in example 1 was compared with comparative examples 1 and 2₂The AlC coating has a preferred orientation of the (103) crystal plane.

Measurement of Cr on the surfaces obtained in example 1, comparative example 1 and comparative example 2 described above using a three-electrode electrochemical test System₂Corrosion resistance of AlC coated substrates in solution 0.5M H₂SO₄+5ppm HF solution at a temperature of 80 ℃. The test results are shown in fig. 4, and it can be seen from fig. 4 that: the corrosion current density of the substrate in example 1 was significantly reduced compared to comparative examples 1 and 2, indicating thatThe MAX phase coating with preferred orientation (103) obtained in example 1 has better corrosion resistance.

FIG. 5 is a graph showing the change in contact resistance of the coatings obtained in example 1, comparative example 1 and comparative example 2 before and after 24h of potentiostatic corrosion, as can be seen from FIG. 5: the contact resistance before and after 24 hours of corrosion of example 1 was significantly reduced as compared with those of comparative examples 1 and 2.

Example 2:

in this embodiment, the substrate is a 316L stainless steel bipolar plate for a pem fuel cell, and the Cr-Al-C MAX phase coating on the surface of the substrate is prepared as follows:

(1) putting the 316L stainless steel substrate after cleaning, oil removing and drying into a cavity, and pressing the vacuum in the cavity at 3.0 multiplied by 10^-5Argon gas of 100 standard ml/min is introduced into the vacuum chamber, the current of a linear anode ion source is set to be 0.3A, the bias voltage of the substrate is set to be-200V, and the substrate is etched by ionized argon ions for 20 min.

(2) Depositing a Cr-C transition layer by arc ion plating, wherein a cathode arc target provides a Cr source and a gas CH₄Providing a C source, and the current of the arc target is 65A, CH₄The flow rate was 10 standard ml/min, the argon flow rate was 300 standard ml/min, the substrate bias was-200V, the deposition time was 30min, and the thickness of the deposited Cr-C transition layer was about 1.0. mu.m.

(4) And depositing an Al coating on the surface of the Cr-C transition layer by adopting a magnetron sputtering method, providing an Al source for a magnetron sputtering target, controlling the target power to be 2.5kW, controlling the argon flow to be 200 standard milliliters per minute, controlling the air pressure to be 15Pa, controlling the bias voltage of the substrate to be-100V, controlling the deposition temperature to be room temperature (about 20 ℃) and depositing for 20min to obtain the Al \ Cr-C coating.

(5) And carrying out heat treatment on the substrate on which the Al \ Cr-C coating is deposited under the protection of argon at atmospheric pressure, wherein the heating rate is 5 ℃/min, the annealing temperature is 500 ℃, and the heat preservation time is 100 h.

Example 3:

in this embodiment, the substrate is a 309 stainless steel bipolar plate for a pem fuel cell, and the Cr-Al-C MAX phase coating on the surface of the substrate is prepared as follows:

(1) putting the 309 stainless steel substrate after cleaning, degreasing and drying into a cavity, and pressing vacuum in the cavity at 3.0 multiplied by 10^- ⁵And introducing 100 standard milliliters per minute of argon into the vacuum chamber below the Torr, setting the current of a linear anode ion source to be 0.3A and the bias voltage of the substrate to be-150V, and etching the substrate by utilizing ionized argon ions for 30 min.

(3) Depositing a Cr-C transition layer by arc ion plating, wherein a cathode arc target provides a Cr source and a gas CH₄Providing a C source, and the current of the arc target is 90A, CH₄The flow rate was 10 standard ml/min, the argon flow rate was 300 standard ml/min, the substrate bias was-150V, the deposition time was 20min, and the thickness of the deposited Cr-C transition layer was about 1.0. mu.m.

(5) And carrying out heat treatment on the substrate on which the Al \ Cr-C coating is deposited under the protection of argon at atmospheric pressure, wherein the heating rate is 5 ℃/min, the annealing temperature is 450 ℃, and the heat preservation time is 60 h.

The scanning electron micrographs of the Cr-Al-C based coatings obtained in examples 2 and 3 above are similar to FIG. 1 and it can be seen that after annealing a smooth and dense MAX phase coating is obtained.

The chemical composition spectrum of the Cr-Al-C MAX phase coatings obtained in the above examples 2 and 3 is similar to that shown in FIG. 2, and it can be seen that arc ion plating combined with magnetron sputtering successfully deposited Cr and Al on the substrate.

The X-ray diffraction patterns of the Cr-Al-C MAX phase coatings obtained in the above examples 2 and 3 are similar to those shown in FIG. 3, and show that Cr is obtained₂The AlC coating has a preferred orientation of the (103) crystal plane.

Similar to example 1, the surfaces obtained from examples 2 and 3 above were measured to have Cr using a three-electrode electrochemical test system₂Corrosion resistance of AlC coated substratesThe solution was 0.5M H₂SO₄+5ppm HF solution at a temperature of 80 ℃. The test results show that the MAX phase coatings with preferred orientation (103) obtained in example 2 and example 3 have good corrosion resistance.

The graphs of the contact resistance changes of the coatings prepared in the above examples 2 and 3 before and after 24h of potentiostatic corrosion are similar to those shown in fig. 5, and show that the contact resistance changes little after 24h of corrosion.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a Cr-Al-C series MAX phase coating, using arc ion plating deposition and magnetron sputtering deposition, using a Cr elemental target as an arc target, an Al elemental target as a DC sputtering target, and a carbon Hydrogen gas is deposited on the surface of the substrate as a reactive gas, and then heat treated to obtain it; it is characterized by:

First, use arc ion plating to deposit a Cr-C layer on the surface of the substrate, and the thickness of the Cr-C layer is 0.5 μm to 5 μm;

Then, an Al layer is deposited on the surface of the Cr-C layer by magnetron sputtering deposition to obtain an Al\Cr-C coating;

Finally, heat treatment is performed to obtain a Cr-Al-C system MAX phase coating with a (103) crystal plane preferential orientation.

2 . The method for preparing a Cr-Al-C series MAX phase coating as claimed in claim 1 , wherein the substrate surface is first subjected to etching treatment, and then the Cr-Al-C series MAX phase coating is prepared. 3 .

3 . The method for preparing a Cr-Al-C based MAX phase coating according to claim 1 , wherein the thickness of the Cr-C layer is 1 μm˜3 μm. 4 .

4. The preparation method of the Cr-Al-C series MAX phase coating as claimed in claim 1, characterized in that: in the process of depositing the Cr-C layer, under the same other conditions, the Cr is controlled by controlling the deposition time. - the thickness of the C layer; or, under other conditions being the same, by controlling the current of the cathodic arc target to control the thickness of the Cr-C layer.

5 . The method for preparing a Cr-Al-C based MAX phase coating according to claim 1 , wherein when the Cr-C layer is deposited, the current of the cathodic arc target is 50A-100A. 6 .

6 . The method for preparing a Cr-Al-C based MAX phase coating as claimed in claim 5 , wherein when the Cr-C layer is deposited, the current of the cathodic arc target is 65A-90A. 7 .

7 . The method for preparing a Cr-Al-C based MAX phase coating according to claim 1 , wherein: when the Cr-C layer is deposited, the bias voltage of the substrate is -100V～-200V. 8 .

8 . The method for preparing a Cr-Al-C based MAX phase coating according to claim 1 , wherein the thickness of the Al layer is 1 μm˜3 μm. 9 .

9 . The method for preparing a Cr-Al-C based MAX phase coating according to claim 1 , wherein when the Al layer is deposited, the target power of the magnetron sputtering target is 2.0kW to 3.0kW, and the bias of the substrate is 2.0 kW to 3.0 kW. 10 . The pressure is -100V~-200V, and the deposition chamber pressure is 10~20mTorr.

10 . The method for preparing a Cr-Al-C series MAX phase coating according to claim 1 , wherein the heat treatment temperature is 400° C. to 550° C. and the time is 24 h to 100 h. 11 .

11. The method for preparing a Cr-Al-C based MAX phase coating according to claim 1, wherein the base material comprises Al, Ti or stainless steel.

12. A conductive and corrosion-resistant Cr-Al-C series MAX phase coating on the surface of a substrate, characterized in that: it is prepared by the preparation method according to any one of claims 1-11.

13. A stainless steel bipolar plate for a proton exchange membrane fuel cell, characterized in that: the surface of the stainless steel bipolar plate has a coating, and the coating uses the method described in any one of claims 1-11. Preparation method obtained.