CN111519157A - A kind of preparation method of Cr-Al-C series MAX phase coating and its application - Google Patents

Abstract

The invention discloses a preparation method and application of a Cr-Al-C MAX phase coating. 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; 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 with the preferred orientation of the (103) crystal face. The coating has good conductivity and corrosion resistance, and compared with the prior art, the Cr-Al-C MAX phase coating prepared by the method not only improves the conductivity of an interface between the Cr-Al-C MAX phase coating and a substrate, but also improves the corrosion resistance, and has excellent conductive corrosion-resistant protective performance in a harsh environment.

Description

A kind of preparation method of Cr-Al-C series MAX phase coating and its application

technical field

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

Background technique

Different from the traditional transition metal nitrogen/carbide, the Mn _{+ 1AXn} phase (MAX phase) is a large class of thermodynamically stable layered high-performance ceramic materials with a close-packed hexagonal structure, in which M, A and X are in the element Various positions on the periodic table, where M represents a pre-transition metal, A represents a main group IIIA or IVA element, and X represents C or N. The layers of the MAX phase rely on weak metal bonds between M atoms and A atoms. The unique interatomic bonding mode and crystal structure make the MAX phase have both the excellent properties of metals and ceramics, such as good electrical conductivity, thermal conductivity, self-healing, small thermal expansion coefficient, excellent thermal stability, anti-oxidation properties , acid and alkali corrosion resistance, etc.

Cr _{2 AlC} is a common compound in the MAX phase. It belongs to the hexagonal crystal system, and its space group is P63/mmc. It consists of alternating stacks in the c direction. At present, the preparation of Cr ₂ AlC coating is mainly by spraying method and physical vapor deposition, but the prepared Cr ₂ AlC coating has no preferred orientation, so it is easy to form Cr when the coating works under harsh conditions such as acid for a long time. Oxides with Al, resulting in reduced electrical conductivity and corrosion resistance. The conductivity and corrosion resistance of the coating are the protective properties of the coating required for many substrates.

In recent years, with the urgent need for automotive technological innovation, governments and companies in many countries are committed to promoting the development of fuel cell vehicles. Among them, proton exchange membrane fuel cells (PEMFCs) are a new type of fuel cell that started late among many fuel cells. Automotive, fixed/portable power sources have developed rapidly, and have begun to be widely used in marine exploration, aerospace and other fields. In PEMFCs, the bipolar plate is a key functional component that separates the reactant gas and introduces the fuel reactant gas into the fuel cell through the flow field, collects and conducts the current, supports the membrane electrode, and also undertakes the heat dissipation and drainage functions of the entire battery system. Although the traditional graphite bipolar plate has the advantages of high conductivity and high corrosion resistance, it has the problems of high processing cost and large volume, which restrict its use efficiency. Stainless steel metal plates with excellent properties such as high electrical conductivity, high thermal conductivity, high mechanical strength, low stamping cost and low gas permeability have gradually replaced graphite as the main material of bipolar plates. However, under the high temperature of the fuel cell and the acidic environment with pH of about 2 to 3, the dissolution and corrosion of the electrode plate are inevitable. In particular, the penetration of metal ions into the proton exchange membrane leads to a decrease in the ion transmission efficiency and the corrosion products will increase the interface contact resistance. Affect the output power and service life of the battery. 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.

The surface coating technology is adopted to improve the conductivity and corrosion resistance of the stainless steel metal plate while maintaining the excellent mechanical properties and processability of the stainless steel metal plate, thereby ensuring the long-term effective operation of the battery. In recent years, many scientific research teams at home and abroad have prepared a variety of different corrosion-resistant conductive coatings, such as precious metal coatings, metal carbide coatings, conductive polymer composite coatings, amorphous carbon coatings, etc. performance of bipolar plates. However, during the long-term service of PEMFCs, there are still great challenges in maintaining high corrosion resistance and low interfacial contact resistance of the coating, which greatly affects the electrical power, stability and life of the battery. Therefore, research and development of new conductive and corrosion-resistant coatings to further improve their stability and interfacial conductivity in the PEMFC environment and reduce the degradation of battery performance are particularly urgent and important for promoting the commercial development of PEMFC.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention aims to provide a preparation method of a Cr-Al-C series MAX phase coating, by which the electrical conductivity and corrosion resistance of the Cr-Al-C series MAX phase coating can be improved.

In order to achieve the above-mentioned technical purpose, the inventors have discovered through a large number of experimental explorations that the Cr-Al-C series MAX phase coating is prepared by using the combination of arc ion plating deposition technology and magnetron sputtering deposition technology, and the specific process is as follows:

The Cr element target is used as the arc target, the Al element target is used as the DC sputtering target, and the hydrocarbon gas is used as the reactive gas to deposit on the surface of the substrate, and then heat treatment to obtain the Cr-Al-C series MAX phase coating;

In this process, the arc ion plating deposition is separated from the magnetron sputtering deposition, that is, the Cr-C layer is first deposited by the arc ion plating, and then the Al layer is deposited on the surface of the Cr-C layer by the magnetron sputtering deposition technique, Finally, heat treatment is carried out, and the high activity of Al makes it infiltrate into the Cr-C layer to form a Cr-Al-C MAX phase coating, and by controlling the Cr-C layer to reach a certain thickness, the preferred orientation of the (103) crystal plane can be obtained. The Cr-Al-C series MAX phase coating has better corrosion resistance and interface conductivity than the Cr-Al-C series MAX phase coating prepared by using the prior art.

That is, the technical scheme provided by the present invention is:

A preparation method of a Cr-Al-C series MAX phase coating with a (103) crystal plane preferential orientation, utilizing arc ion plating deposition and magnetron sputtering deposition, using Cr elemental target as the arc target, Al elemental target As a DC sputtering target, hydrocarbon methane gas is deposited on the surface of the substrate as a reactive gas, and then heat-treated to obtain; 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;

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

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

As another implementation manner, in the process of depositing the Cr-C layer, under other conditions being the same, the thickness of the Cr-C layer is controlled by controlling the current of the cathodic arc target.

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-based MAX phase coating.

Preferably, the etching treatment is performed first, and then the Cr-Al-C series MAX phase coating is prepared.

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

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

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

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

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

Preferably, the heat treatment temperature is 400°C to 550°C, and the time is 24h to 100h.

Preferably, during the heat treatment, the degree of vacuum is lower than 3×10 ^-3 Pa.

The base material is not limited, including materials such as Al, Ti, or stainless steel.

Compared with the prior art, the present invention adopts the combination of cathodic arc ion plating deposition and magnetron sputtering deposition to gradually coat the layer, and has the following beneficial effects:

(1) The present invention utilizes the high activity of Al to infiltrate the Cr-C layer to form a Cr-Al-C series MAX phase coating, which not only improves the stability of each component in the Cr-Al-C series MAX phase coating, but also At the same time, the bonding degree between the Cr-Al-C system MAX phase coating and the substrate is improved;

(2) The Cr-Al-C series MAX phase coating obtained by optimizing the thickness of the Cr-C layer in the present invention has the (103) crystal plane preferential orientation, which not only improves the interface conductivity with the substrate, but also reduces the Corrosion resistance. This is because the coating prepared by the present invention has a preferred orientation of (103) crystal plane and exposes Cr, Al and C atoms at the same time, so it is not easily oxidized, and has excellent corrosion resistance and protection performance in harsh environments such as acid and high temperature.

Therefore, the Cr-Al-C series MAX phase coating prepared by the present invention has excellent electrical conductivity, and at the same time has excellent corrosion resistance and protection performance in acid, high temperature and other environments, so it is a kind of substrate surface with good performance Coatings with electrical conductivity and corrosion resistance can meet the protection requirements of many substrates for conductivity and corrosion resistance, such as the surface coating of stainless steel bipolar plates for proton exchange membrane fuel cells, thereby improving the corrosion resistance of stainless steel bipolar plates and reduce its interface contact resistance.

Description of drawings

1 is a scanning electron microscope image of the Cr-Al-C based MAX phase coating prepared in Example 1.

FIG. 2 is a chemical composition energy spectrum of the Cr-Al-C based MAX phase prepared in Example 1. FIG.

3 is a XRD comparison diagram of the Cr-Al-C based MAX phases prepared in Example 1, Comparative Example 1 and Comparative Example 2.

4 is a comparison diagram of the corrosion performance test of the Cr-Al-C based MAX phase coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2.

5 is a graph showing the change of contact resistance before and after corrosion of the Cr-Al-C based MAX phase coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2.

Detailed ways

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention.

Example 1:

In this embodiment, the substrate is a 304 stainless steel bipolar plate used in a proton exchange membrane fuel cell, and the preparation method of the Cr-Al-C series MAX phase coating on the surface of the substrate is as follows:

(1) Put the cleaned, degreasing and dried substrate into the chamber. When the vacuum pressure in the chamber is below 3.0×10 ^-5 Torr, pour 100 standard ml/min of argon into the vacuum chamber, and set up a linear anode The ion source current was 0.3A, the substrate bias was -100V, and the substrate was etched with ionized argon ions for 30min.

(3) The Cr-C transition layer is deposited by arc ion plating technology, wherein the cathode arc target provides the Cr source, the gas CH ₄ provides the C source, the current of the arc target is 90A, the flow rate of CH ₄ is 10 standard ml/min, and the argon gas The flow rate was 300 standard ml/min, the bias voltage of the substrate was -200V, the deposition time was 60 min, and the thickness of the deposited Cr-C transition layer was about 3 μm.

(4) The Al coating was deposited on the surface of the Cr-C transition layer by the magnetron sputtering method. The magnetron sputtering target provided the Al source, the target power was 2.5kW, the argon gas flow was 200 standard ml/min, and the control air pressure was 15Pa, the bias voltage of the substrate is -200V, the deposition temperature is room temperature (about 20°C), and the deposition time is 60min to obtain an Al\Cr-C coating.

(5) The Al\Cr-C coating substrate was heat-treated under one atmosphere of argon protection, the heating rate was 5°C/min, the annealing temperature was 550°C, and the holding time was 72h.

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

Figure 2 shows the chemical composition energy spectrum of the prepared Cr-Al-C series MAX phase coating. It can be seen that arc ion plating combined with magnetron sputtering successfully deposited Cr and Al on the substrate.

Comparative Example 1:

This example is a comparative example of the above-mentioned Example 1.

In this example, the substrate is exactly the same as in 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, the difference is that the deposition in step (3) The time is 2min.

Comparative Example 2:

This example is another comparative example of the above-mentioned Example 1.

In this example, the substrate is exactly the same as in Example 1, and the preparation method of the Cr-Al-C based MAX phase coating on the surface of the substrate is basically the same as that in Example 1, the difference is that the arc in step (3) The target current was 20A.

3 is an X-ray diffraction pattern of the coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2 above. It can be seen from FIG. 3 that the MAX phase coatings of Cr ₂ AlC (002) and Cr ₂ AlC (103) were all obtained in Example 1, Comparative Example 1 and Comparative Example 2; 2, the Cr ₂ AlC coating obtained in Example 1 has a (103) crystal plane preferential orientation.

A three-electrode electrochemical test system was used to measure the corrosion resistance of the substrates with Cr ₂ AlC coating on the surfaces obtained in Example 1, Comparative Example 1 and Comparative Example 2. The solution was a 0.5MH ₂ SO ₄ +5ppm HF solution, and the solution temperature is 80°C. The test results are shown in Figure 4. It can be seen from Figure 4 that compared with Comparative Example 1 and Comparative Example 2, the corrosion current density of the substrate in Example 1 is significantly reduced, indicating that Example 1 has a preferred The (103) oriented MAX phase coating has better corrosion resistance.

Figure 5 is a graph showing the change of contact resistance of the coatings prepared in the above-mentioned Example 1, Comparative Example 1 and Comparative Example 2 before and after potentiostatic corrosion for 24 hours. It can be seen from Figure 5 that: compared with Comparative Example 1 and Comparative Example 2 , the contact resistance of Example 1 before and after corrosion for 24 hours was significantly reduced.

Example 2:

In this embodiment, the substrate is a 316L stainless steel bipolar plate used in a proton exchange membrane fuel cell, and the preparation method of the Cr-Al-C series MAX phase coating on the surface of the substrate is as follows:

(1) Put the 316L stainless steel substrate after cleaning, degreasing and drying into the cavity. When the vacuum pressure in the cavity is below 3.0×10 ^-5 Torr, pour 100 standard ml/min of argon into the vacuum cavity, and set the The linear anode ion source current was 0.3A, the substrate bias was -200V, and the substrate was etched with ionized argon ions for 20 min.

(2) The Cr-C transition layer is deposited by arc ion plating technology, wherein the cathode arc target provides the Cr source, the gas CH ₄ provides the C source, the current of the arc target is 65A, the flow rate of CH ₄ is 10 standard ml/min, and the argon gas The flow rate is 300 standard ml/min, the bias voltage of the substrate is -200V, the deposition time is 30min, and the thickness of the deposited Cr-C transition layer is about 1.0μm.

(4) The Al coating was deposited on the surface of the Cr-C transition layer by the magnetron sputtering method. The magnetron sputtering target provided the Al source, the target power was 2.5kW, the argon gas flow was 200 standard ml/min, and the control air pressure was 15Pa, the bias voltage of the substrate is -100V, the deposition temperature is room temperature (about 20°C), and the deposition time is 20min to obtain an Al\Cr-C coating.

(5) The Al\Cr-C coating substrate was heat-treated under one atmosphere of argon protection, the heating rate was 5°C/min, the annealing temperature was 500°C, and the holding time was 100h.

Example 3:

In this embodiment, the substrate is a 309 stainless steel bipolar plate used in a proton exchange membrane fuel cell, and the preparation method of the Cr-Al-C series MAX phase coating on the surface of the substrate is as follows:

(1) Put the 309 stainless steel substrate after cleaning, degreasing and drying into the chamber. When the vacuum pressure in the chamber is below 3.0×10 ^{- 5} Torr, pour 100 standard ml/min of argon into the vacuum chamber, and set The linear anode ion source current was 0.3A, the substrate bias was -150V, and the substrate was etched with ionized argon ions for 30 min.

(3) The Cr-C transition layer is deposited by arc ion plating technology, wherein the cathode arc target provides the Cr source, the gas CH ₄ provides the C source, the current of the arc target is 90A, the flow rate of CH ₄ is 10 standard ml/min, and the argon gas The flow rate was 300 standard ml/min, the bias voltage of the substrate was -150V, the deposition time was 20 min, and the thickness of the deposited Cr-C transition layer was about 1.0 μm.

(4) The Al coating was deposited on the surface of the Cr-C transition layer by the magnetron sputtering method. The magnetron sputtering target provided the Al source, the target power was 2.5kW, the argon gas flow was 200 standard ml/min, and the control air pressure was 15Pa, the bias voltage of the substrate is -100V, the deposition temperature is room temperature (about 20°C), and the deposition time is 20min to obtain an Al\Cr-C coating.

(5) The Al\Cr-C coating substrate was heat-treated under the protection of one atmosphere of argon, the heating rate was 5°C/min, the annealing temperature was 450°C, and the holding time was 60h.

The scanning electron microscope images of the Cr-Al-C-based coatings prepared in the above Examples 2 and 3 are similar to those in Figure 1, and it can be seen that smooth and dense MAX phase coatings are obtained after annealing.

The chemical composition energy spectra of the Cr-Al-C MAX phase coatings prepared in the above-mentioned Example 2 and Example 3 are similar to those shown in Figure 2. It can be seen that arc ion plating combined with magnetron sputtering successfully combines Cr with Al. deposited on the substrate.

The X-ray diffraction patterns of the Cr-Al-C-based MAX phase coatings prepared in Example 2 and Example 3 are similar to those shown in Figure 3, showing that the obtained Cr ₂ AlC coatings have a (103) crystal plane preferred orientation .

Similar to Example 1, a three-electrode electrochemical test system was used to measure the corrosion resistance of the substrates with Cr ₂ AlC coating on the surface obtained in the above Examples 2 and 3, and the solution was 0.5MH ₂ SO ₄ +5ppm HF solution, The solution temperature was 80°C. The test results show that the MAX phase coatings with preferred orientation (103) prepared in Example 2 and Example 3 have good corrosion resistance.

The contact resistance change diagrams of the coatings prepared in the above-mentioned Examples 2 and 3 before and after potentiostatic corrosion for 24 hours are similar to those shown in Figure 5, which show that the contact resistance changes very little after 24 hours of corrosion.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the technical principles of the present invention, several improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

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-based MAX phase coating with a (103) crystal plane preferential orientation. 2. The preparation method of Cr-Al-C series MAX phase coating as claimed in claim 1, it is characterized in that: the substrate surface is first subjected to etching treatment, and then the Cr-Al-C series MAX phase coating is prepared; Preferably, the thickness of the Cr-C layer is 1 μm˜3 μm. 3. 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. 4. The preparation method of Cr-Al-C series MAX phase coating as claimed in claim 1, it is characterized in that: when depositing Cr-C layer, the electric current of cathodic arc target is 50A～100A, preferably 65A～90A; Preferably, when depositing the Cr-C layer, the bias voltage of the substrate is -100V to -200V. 5 . 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. 6 . 6 . 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 2.0kW to 3.0kW. The pressure is -100V～-200V, and the pressure of the deposition chamber is 10～20mTorr. 7 . 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. 8 . 8. 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. 9 . 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 described in any one of claims 1-8. 10. 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 1-8. Preparation method obtained.

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