Max-ag conductive composite coating and preparation method therefor

Abstract

Disclosed are a MAX-Ag conductive composite coating and a preparation method therefor. The conductive composite coating comprises a MAX phase and an Ag phase. The chemical formula of the MAX phase is Mn+1AXn, where M is a transition metal element, A is an Al element, X is a C or N element, and n is an integer ranging from 1 to 3. The MAX phase is of a strip-shaped structure, and the Ag phase is of a nanotwinned structure. The Ag phase aggregates at the grain boundaries of the MAX phase, and the conductive composite coating is of an Ag-wrapped MAX phase structure as a whole. In the present invention, the MAX phase coating is designed, by means of Ag doping, to have a heterogeneous grain shape. The doped Ag affects the growth of MAX phase grains, so that the MAX phase grains are of the strip-shaped structure. Furthermore, the doped Ag is of the nanotwinned structure, and fully wraps the MAX phase grains. Ag is continuously distributed at the MAX grain boundaries. Such a special structure may effectively reduce the scattering of electrons, provide a strong conductive path, and enable the coating to have excellent conductive properties.

Description

A MAX-Ag conductive composite coating and its preparation method Technical Field

[0001] The present invention relates to the technical field of surface engineering, in particular to a MAX-Ag conductive composite coating and a preparation method thereof. Background Art

[0002] As aerospace technology pursues larger, longer-range, and lighter weight capabilities, the use of composite materials is becoming increasingly widespread. However, because composite materials are inherently poor conductors, it is difficult to quickly dissipate the current trapped within the material during a lightning strike. However, with the increasing demand for all-weather launches for spacecraft, there are limitations to selecting launch windows to avoid lightning weather. Lightning can have destructive effects in multiple ways, including mechanical, environmental, and arcing. These include insulation breakdown, phase change, combustion, erosion, and structural distortion caused by arcing, as well as the adverse effects of electromagnetic field coupling on electronic and electrical equipment. Consequently, the demand for conductive protective coatings on surfaces is becoming increasingly urgent, and reliability requirements are also increasing.

[0003] MAX phases are a class of hexagonal, close-packed, ternary layered compounds. Their unique structure allows them to combine the advantageous properties of both metallic and ceramic materials, such as the high thermal conductivity, machinability, and plasticity of metallic materials, and the high strength, high melting point, good thermal stability, and oxidation resistance of ceramic materials. Recent research has demonstrated that MAX, as a coating material, exhibits promising application prospects in fuel cell bipolar plates, electromagnetic shielding and absorption, aerospace, and other fields. MAX phases exhibit moderate thermal stability. During arc discharge, they maintain their compositional and structural integrity below 1400°C; above 1400°C, they exhibit a tendency to slowly decompose and oxidize. Therefore, MAX phases are immune to premature loss and subsequent residual defects during arc erosion. Furthermore, the MAX phase's high thermal conductivity facilitates surface heat dissipation, preventing severe heat accumulation.

[0004] The resistivity of the MAX phase is higher than that of pure metals, and Ag has the best conductivity of all metals. Applying Ag as a composite element to a coating can increase its conductivity. For example, patent CN115896726A discloses a method for preparing a MAX-Ag phase composite coating. Using magnetron sputtering and composite cathode arc technology, a Cr-Al-C-Ag coating is deposited on the substrate surface. Annealing then produces a Cr2AlC-Ag composite coating with a composite structure of MAX phase and AlAg3. The MAX phase grains are equiaxed, and the Ag element is evenly distributed throughout the coating, forming no new conductive pathways. However, the resistivity of this composite coating still significantly differs from that of pure metals, placing higher demands on the conductivity of coatings in the field of electrical contacts in aerospace technology.

[0005] Summary of the Invention

[0006] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is how to reduce the resistivity of the MAX-Ag composite coating and improve the conductivity.

[0007] To achieve the above object, the present invention provides a MAX-Ag conductive composite coating, the conductive composite coating comprising a MAX phase and an Ag phase, wherein the chemical formula of the MAX phase is M n+1 AX n , wherein M is a transition metal element, A is an Al element, X is a C or N element, and n is an integer of 1 to 3. The MAX phase has a lamellar structure, the Ag phase has a nano-twin structure, the Ag phase is aggregated at the grain boundaries of the MAX phase, and the conductive composite coating as a whole has an Ag-wrapped MAX phase structure.

[0008] The present invention designs the MAX phase coating to have heterogeneous grain shape through Ag doping. The incorporation of Ag affects the growth of the MAX phase grains, making the MAX phase grains have a lath-like structure. At the same time, the incorporation of Ag presents a nano-twin structure, which fully wraps the MAX phase grains. Ag is continuously distributed at the MAX grain boundaries. This special structure can effectively reduce electron scattering, provide a strong conductive path, and give the coating excellent conductive properties.

[0009] Furthermore, the grain width of the MAX phase is 10 to 90 nm and the length is 25 to 300 nm. The present invention breaks through the restrictive relationship between strength and conductivity through the heterogeneous design of grain shape, thereby improving the strength and conductivity of the coating.

[0010] Furthermore, the aspect ratio of the MAX phase is between 2 and 7. Grain width mainly affects strength, while grain length mainly affects conductivity. When the aspect ratio is between 2 and 7, the coating has the best comprehensive performance in strength and conductivity.

[0011] Furthermore, the thickness of the Ag phase gathered at the grain boundary of the MAX phase is 1 to 20 nm. As the thickness of the Ag phase increases, the conductivity of the corresponding coating improves, but when the thickness of the Ag phase exceeds 20 nm, the strength of the coating decreases rapidly.

[0012] Furthermore, the MAX phase is selected from Cr2AlC, Cr2AlN, Ti2AlC, Ti2AlN, and Zr2AlC. This special structure is applicable to a variety of MAX phase coatings. Compared with pure MAX coatings, the conductivity of MAX-Ag conductive composite coatings can be increased by more than 2 times.

[0013] Furthermore, the Ag content in the conductive composite coating is 1-10 at.%. The coating requires less Ag content, significantly saves silver, and reduces material costs. Ag affects the mutual diffusion of elements in the coating, and too high an Ag content is not conducive to the formation of the MAX phase.

[0014] The present invention also provides a method for preparing the MAX-Ag conductive composite coating, comprising the following steps:

[0015] S1. providing a substrate, and sequentially performing mechanical polishing, ultrasonic cleaning, and glow cleaning on the substrate;

[0016] S2. Placing the substrate in a vacuum chamber, using a single-substance target of element M as an arc target, introducing a reaction gas providing element X and an inert gas, and depositing an MX layer using arc ion plating technology;

[0017] S3, using the A element and Ag composite target as a DC pulsed magnetron sputtering target, and using magnetron sputtering technology to deposit the A-Ag-X layer;

[0018] S4, repeating steps S2 and S3 2 to 20 times to form an MX / A-Ag-X alternating layer coating;

[0019] S5. Perform vacuum heat treatment on the alternating laminated coating obtained in step S4 to obtain a MAX-Ag conductive composite coating.

[0020] The present invention utilizes arc ion plating and magnetron sputtering to alternately deposit MX and A-Ag-X layers to create a coating with an alternating laminated structure. Vacuum heat treatment then allows Ag to influence the growth of MAX phase grains, transforming the originally equiaxed MAX phase grains into lath-shaped MAX phase grains. Ag, meanwhile, forms nanotwinned structures at the MAX phase grain boundaries, forming new conductive paths. This alternating laminated structure allows the coating to maintain this unique structure throughout the coating while maintaining overall compositional uniformity, ensuring strength and preventing defects.

[0021] Furthermore, in step S2, the substrate bias voltage is -50 to -200 V, the target-substrate distance between the substrate and the cathode arc target is 15 to 20 cm, the power of the cathode arc target is 1 to 3 kW, the current is 30 to 70 A, the flow rate of the reaction gas is 15 to 30 sccm, the flow rate of the inert gas is 150 to 200 sccm, and the deposition time is 5 to 30 min.

[0022] Furthermore, in step S3, the substrate bias voltage is -50 to -200 V, the target-substrate distance between the substrate and the DC pulse magnetron sputtering target is 10 to 15 cm, the power of the DC pulse magnetron sputtering target is 2 to 3.5 kW, the flow rate of the reaction gas is 15 to 30 sccm, the flow rate of the inert gas is 150 to 200 sccm, and the deposition time is 5 to 30 min.

[0023] The present invention controls the composition of each element in the coating by controlling the gas flow rate and coating parameters, and controls the coating thickness by deposition time. The prepared MAX-Ag conductive composite coating has good uniformity, fine grains inside the coating, and few crystal defects.

[0024] Furthermore, in step S5, the vacuum degree of the vacuum heat treatment is less than 2.0×10 -3 Torr, the temperature is 500-750℃, and the time is 30-360min. During the vacuum heat treatment, lamellar MAX phase grains are formed, and the conductive composite coating as a whole presents an Ag-wrapped MAX phase structure.

[0025] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The MAX-Ag conductive composite coating obtained by the present invention is designed by heterogeneous grain shape design of the MAX phase coating by Ag element doping, so that the MAX phase grains have a lath-like structure; at the same time, Ag is doped to form a nano-twin structure, which fully wraps the MAX phase grains; this special structure can effectively reduce the scattering of electrons, provide a strong conductive path, and give it excellent conductive properties.

[0027] (2) The present invention first prepares a coating with an alternating laminated structure to form an MX / A-Ag-X alternating laminated coating. During the annealing process, elements diffuse to generate MAX phase grains. Ag affects the growth of the MAX phase grains, causing the original equiaxed MAX phase grains to transform into lamellar MAX phase grains. The coating can form a special structure of Ag encapsulating the MAX phase as a whole, while maintaining the overall composition uniformity of the coating, ensuring strength and avoiding the formation of defects.

[0028] (3) The present invention precisely controls the coating thickness by controlling the coating time. The prepared MAX-Ag conductive composite coating has good uniformity, fine grains inside the coating, and few crystal defects. The conductivity of the MAX-Ag composite coating is more than twice that of the pure MAX coating, which improves the current dissipation rate and protects the substrate. It has broad application prospects in the fields of electrical contact and so on. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a transmission electron microscope image of the coatings prepared in Example 1 of the present invention and Comparative Example 1.

[0030] FIG2 is a schematic diagram of the microstructure of the coatings prepared in Example 1 of the present invention and Comparative Example 1.

[0031] FIG3 is a graph showing the XPS test results of the coatings prepared in Example 1 of the present invention and Comparative Example 1.

[0032] FIG4 is a graph showing the resistivity performance test results of the coatings prepared in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0034] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0035] It will be apparent to those skilled in the art that various modifications and variations can be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments derived from the present invention will be apparent to those skilled in the art.

[0036] A specific embodiment of the present invention provides a MAX-Ag conductive composite coating, which comprises a MAX phase and an Ag phase, and has an overall coating thickness of 10 to 100 μm.

[0037] The chemical formula of MAX phase is M n+1 AX n , where M is a transition metal element, A is an Al element, X is a C or N element, n is an integer of 1 to 3, and the MAX phase specifically includes Cr2AlC, Cr2AlN, Ti2AlC, Ti3AlC2, Ti4AlC3, Ti2AlN, Zr2AlC, etc.

[0038] Ag doping allows for heterogeneous grain shape design in the MAX phase coating. Ag influences MAX phase grain growth, resulting in a lamellar structure with grains ranging from 10 to 90 nm in width and 25 to 300 nm in length. The MAX phase preferably has an aspect ratio between 2 and 7. This heterogeneous grain shape design overcomes the constraints between strength and conductivity, thereby improving both strength and conductivity of the coating.

[0039] The Ag phase exhibits a nanotwinned structure, clustering at the MAX phase grain boundaries. The conductive composite coating exhibits an overall Ag-encapsulated MAX phase structure. Ag is continuously distributed at the MAX grain boundaries, forming new conductive pathways and imparting excellent electrical conductivity to the coating. Preferably, the Ag phase has a thickness of 1 to 20 nm to ensure excellent coating strength and electrical conductivity.

[0040] The Ag content in the conductive composite coating is relatively low, generally 1 to 10 at.%. The coating requires a relatively low Ag content, resulting in a significant silver-saving effect. However, excessively high Ag content is also detrimental to the formation of the MAX phase.

[0041] The preparation method of the MAX-Ag conductive composite coating comprises the following steps:

[0042] S1. Provide a substrate, and perform mechanical polishing, ultrasonic cleaning, and glow cleaning on the substrate in sequence.

[0043] In a specific embodiment, the substrate can be any one of pure titanium, titanium alloy, stainless steel, copper, aluminum oxide, and carbon fiber composite material, or a combination of two or more thereof.

[0044] The working conditions of glow cleaning are as follows: the working atmosphere is argon, the flow rate is 30-50 sccm, and the vacuum degree during sputtering is 2.0×10 -5 ~4.0×10 -5 Torr, the substrate is preheated to 100-300°C, the deposition bias is -100-250V, the linear anode ion source current is set to 0.2A, and the substrate glow cleaning time is 20-60min.

[0045] S2. The substrate is placed in a vacuum chamber, a single-substance target of element M is used as an arc target, reaction gas and inert gas providing element X are introduced, and an MX layer is deposited using arc ion plating technology.

[0046] In a specific embodiment, the substrate is preheated to 100-300°C, the substrate bias voltage is -50-200V, the substrate-to-cathode arc target distance is 15-20cm, the cathode arc target power is 1-3kW, the current is 30-70A, the reaction gas flow rate is 15-30sccm, the inert gas flow rate is 150-200sccm, and the deposition time is 5-30 minutes. By controlling the gas flow rate and coating parameters, the elemental composition of the coating can be adjusted, and by adjusting the deposition time, the coating thickness can be controlled.

[0047] S3. Using the A element and Ag composite target as a DC pulse magnetron sputtering target, the magnetron sputtering technology is used to deposit the A-Ag-X layer.

[0048] In a specific embodiment, the substrate bias voltage is -50 to -200 V, the distance between the substrate and the DC pulsed magnetron sputtering target is 10 to 15 cm, the DC pulsed magnetron sputtering target power is 2 to 3.5 kW, the reaction gas flow rate is 15 to 30 sccm, the inert gas flow rate is 150 to 200 sccm, and the deposition time is 5 to 30 minutes. By controlling the gas flow rate and coating parameters, the elemental composition of the coating can be adjusted, and by adjusting the deposition time, the coating thickness can be controlled.

[0049] S4. Repeat steps S2 and S3 2 to 20 times to form an MX / A-Ag-X alternating layer coating.

[0050] S5. Perform vacuum heat treatment on the alternating laminated coating obtained in step S4 to obtain a MAX-Ag conductive composite coating.

[0051] In a specific embodiment, the vacuum degree of vacuum heat treatment is less than 2.0×10 -3 Torr, temperature is 500-750℃, and time is 30-360min. During the vacuum heat treatment, lamellar MAX phase grains are formed, and the conductive composite coating as a whole has an Ag-wrapped MAX phase structure. During the vacuum heat treatment process, the MAX phase nucleates and grows. During the growth process, the presence of Ag has an inhibitory effect on its growth, so the grains grow in a direction parallel to Ag, forming lamellar MAX grains. At the same time, Ag has a high diffusion rate but does not react with the MAX phase, eventually forming a non-reactive interface that wraps the MAX phase grains. The alternating stacking structure enables the coating to form this special structure as a whole, while maintaining the overall composition uniformity of the coating, ensuring strength, and avoiding the formation of defects.

[0052] The technical effects of the present invention are described below with reference to specific embodiments.

[0053] Example 1

[0054] In this embodiment, the substrate is an alumina substrate, and the preparation method of the Cr-Al-C system MAX phase-Ag composite coating on the substrate surface is as follows:

[0055] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 3.0×10 -5 At a pressure of less than 100 Torr, 33.4 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -200 V, and the substrate was etched with ionized argon ions for 30 minutes.

[0056] (2) Arc ion plating was used to deposit the Cr-C layer in an Ar protective atmosphere of 200 sccm at a temperature of 150°C. A single Cr target was mounted on the arc source as a Cr source. The target power was 1.0 kW and the current was 60 A. The substrate bias was set to -150 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Cr-C layer.

[0057] (3) An Al-Ag-C layer was deposited by magnetron sputtering in a 200 sccm Ar protective atmosphere at a temperature of 150°C. The magnetron source was an AlAg (5 at.% Ag) target with a target power of 3.1 kW and a current of 7.0 A. The substrate bias was set to -150 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-C layer.

[0058] (4) Steps (2) and (3) were repeated 6 times to obtain a 6-layer alternating stacked coating of Cr-C / Al-Ag-C.

[0059] (5) The Cr-C / Al-Ag-C alternating layer coating was placed in an annealing furnace at a vacuum of less than 3.0×10 -5 Torr environment, and kept at 700℃ for 120min to obtain Cr2AlC-Ag composite coating.

[0060] Example 2

[0061] In this embodiment, the substrate is a carbon fiber composite material substrate, and the preparation method of the Cr-Al-C system MAX phase-Ag composite coating on the substrate surface is as follows:

[0062] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 2.0×10 -5 At a pressure below 200 Torr, 35 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -100 V, and the substrate was etched with ionized argon ions for 40 minutes.

[0063] (2) Arc ion plating was used to deposit the Cr-C layer in an Ar protective atmosphere of 150 sccm at a temperature of 200°C. A single Cr target was mounted on the arc source as a Cr source. The target power was 2.5 kW and the current was 50 A. The substrate bias was set to -100 V, 20 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted 15 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Cr-C layer.

[0064] (3) An Al-Ag-C layer was deposited by magnetron sputtering in an Ar protective atmosphere of 150 sccm at a temperature of 200°C. The magnetron source was an AlAg (2 at.% Ag) target with a target power of 2.8 kW and a current of 6 A. The substrate bias was set to -100 V, 20 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 15 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-C layer.

[0065] (4) Steps (2) and (3) were repeated 8 times to obtain an alternating stacked coating having 8 layers of Cr-C / Al-Ag-C.

[0066] (5) The Cr-C / Al-Ag-C alternating layer coating was placed in an annealing furnace at a vacuum of less than 2.0×10 -5 Torr environment, and kept at 650℃ for 200min to obtain Cr2AlC-Ag composite coating.

[0067] Example 3

[0068] In this embodiment, the substrate is a stainless steel substrate, and the preparation method of the Cr-Al-N system MAX phase-Ag composite coating on the substrate surface is as follows:

[0069] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 3.0×10 -5 Torr, 40 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -200 V, and the substrate was etched with ionized argon ions for 20 minutes.

[0070] (2) Arc ion plating was used to deposit the Cr-N layer in an Ar protective atmosphere of 150 sccm at a temperature of 200°C. A single Cr target was mounted on the arc source as a Cr source. The target power was 2 kW and the current was 70 A. The substrate bias was set to -200 V, 15 sccm of N2 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 20 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Cr-N layer.

[0071] (3) The Al-Ag-N layer was deposited by magnetron sputtering in an Ar protective atmosphere of 150 sccm at a temperature of 200°C. The magnetron source was an AlAg (6 at.% Ag) target with a target power of 2.5 kW and a current of 5 A. The substrate bias was set to -200 V, 15 sccm of N2 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 20 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-N layer.

[0072] (4) Steps (2) and (3) were repeated five times to obtain a coating layer having five layers of alternating Cr-N / Al-Ag-N.

[0073] (5) Place the Cr-N / Al-Ag-N alternating stacked coating in an annealing furnace at a vacuum degree of less than 2.0×10 -5 Torr environment, and kept at 750℃ for 60min to obtain Cr2AlN-Ag composite coating.

[0074] Example 4

[0075] In this embodiment, the substrate is a titanium alloy substrate, and the preparation method of the Ti-Al-C system MAX phase-Ag composite coating on the substrate surface is as follows:

[0076] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 2.0×10 -5 Torr, 50 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -50 V, and the substrate was etched with ionized argon ions for 60 min.

[0077] (2) Arc ion plating was used to deposit the Ti-C layer in an Ar protective atmosphere of 180 sccm at a temperature of 250°C. A single-element Ti target was mounted on the arc source as a Ti source. The target power was 2.8 kW and the current was 65 A. The substrate bias was set to -180 V, 20 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 25 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Ti-C layer.

[0078] (3) An Al-Ag-C layer was deposited by magnetron sputtering in an Ar protective atmosphere of 180 sccm at a temperature of 250°C. The magnetron sputtering source was an AlAg (6 at.% Ag) target with a target power of 3.2 kW and a current of 8 A. The substrate bias was set to -200 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 25 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-C layer.

[0079] (4) Steps (2) and (3) were repeated three times to obtain a three-layer Ti-C / Al-Ag-C alternating stacked coating.

[0080] (5) The Ti-C / Al-Ag-C alternating layer coating was placed in an annealing furnace at a vacuum of less than 2.0×10 -5 In a 30-400-torr environment, the Ti2AlC-Ag composite coating was obtained by heating at 700°C for 150 min.

[0081] Example 5

[0082] In this embodiment, the substrate is a copper substrate, and the preparation method of the Zr-Al-C system MAX phase-Ag composite coating on the substrate surface is as follows:

[0083] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 2.5×10 -5 Torr or less, 30 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -100 V, and the substrate was etched with ionized argon ions for 50 min.

[0084] (2) Arc ion plating was used to deposit the Zr-C layer in an Ar protective atmosphere of 150 sccm at a temperature of 100°C. A single-element Zr target was mounted on the arc source as the Zr source. The target power was 2 kW and the current was 50 A. The substrate bias was set to -100 V, 20 sccm CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 minutes. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Zr-C layer.

[0085] (3) An Al-Ag-C layer was deposited by magnetron sputtering in a 150 sccm Ar protective atmosphere at a temperature of 100°C. The magnetron sputtering source was an AlAg (1 at.% Ag) target with a target power of 2 kW and a current of 6 A. The substrate bias was set to -100 V, 20 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-C layer.

[0086] (4) Steps (2) and (3) were repeated 5 times to obtain a Zr-C / Al-Ag-C alternating layer coating.

[0087] (5) The Zr-C / Al-Ag-C alternating layer coating was placed in an annealing furnace at a vacuum of less than 2.0×10 -5 Torr environment, and kept at 500℃ for 360min to obtain Zr2AlC-Ag composite coating.

[0088] Example 6

[0089] In this embodiment, the substrate is a pure titanium substrate, and the preparation method of the Ti-Al-N system MAX phase-Ag composite coating on the substrate surface is as follows:

[0090] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 2.0×10 -5 Torr, 50 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -150 V, and the substrate was etched with ionized argon ions for 50 min.

[0091] (2) Arc ion plating was used to deposit the Ti-N layer in an Ar protective atmosphere of 200 sccm at a temperature of 150°C. A single-element Ti target was mounted on the arc source as a Ti source. The target power was 1.5 kW and the current was 40 A. The substrate bias was set to -50 V, 30 sccm of N2 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 5 minutes. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Ti-N layer.

[0092] (3) An Al-Ag-N layer was deposited by magnetron sputtering in a 200 sccm Ar protective atmosphere at a temperature of 150°C. The magnetron source was an AlAg (7 at.% Ag) target with a target power of 3.5 kW and a current of 9 A. The substrate bias was set to -50 V, 30 sccm N2 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 5 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-N layer.

[0093] (4) Steps (2) and (3) were repeated 10 times to obtain a coating layer having 10 layers of Ti-N / Al-Ag-N alternating layers.

[0094] (5) The Ti-N / Al-Ag-N alternating stacked coating was placed in an annealing furnace at a vacuum degree of less than 2.0×10 -5In a 30-400-torr environment, the Ti2AlN-Ag composite coating was obtained by keeping the temperature at 650℃ for 90min.

[0095] Comparative Example 1

[0096] In this comparative example, the substrate is an alumina substrate, and an Al target is used as a magnetron source to prepare a pure Cr2AlCMAX phase coating. The specific process is as follows:

[0097] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 3.0×10 -5 At a pressure of less than 100 Torr, 33.4 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -200 V, and the substrate was etched with ionized argon ions for 30 minutes.

[0098] (2) Arc ion plating was used to deposit the Cr-C layer in an Ar protective atmosphere of 200 sccm at a temperature of 150°C. A single Cr target was mounted on the arc source as a Cr source. The target power was 1.0 kW and the current was 60 A. The substrate bias was set to -150 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Cr-C layer.

[0099] (3) The Al-C layer was deposited by magnetron sputtering in a 200 sccm Ar protective atmosphere at a temperature of 150°C. The magnetron source was an Al target with a target power of 3.1 kW and a current of 7.0 A. The substrate bias was set to -150 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-C layer.

[0100] (4) Steps (2) and (3) were repeated 6 times to obtain a Cr-C / Al-C alternating laminated coating having 6 layers.

[0101] (5) The obtained Cr-C / Al-C alternating laminated coating was placed in an annealing furnace at a vacuum degree of less than 3.0×10 -5 Torr environment, and kept at 700℃ for 120min to obtain Cr2AlC coating.

[0102] Transmission electron microscopy (TEM) was used to analyze the microstructure of the coatings prepared in Example 1 and Comparative Example 1. The grain size and shape of the coatings were observed. The results are shown in Figure 1, and the structural diagram is shown in Figure 2. As can be seen from the left portion (a) of Figure 1 and the left portion (a) of Figure 2, the coating prepared in Comparative Example 1 is primarily composed of the Cr2AlC phase, and the equiaxed grains within the coating are uniform in size and densely arranged. As can be seen from the right portion (b) of Figure 1 and the right portion (b) of Figure 2, the coating prepared in Example 1 is primarily composed of the Cr2AlC phase and Ag. Due to the influence of Ag on the growth of MAX phase grains, the originally equiaxed MAX phase grains are transformed into lamellar MAX phase grains, and Ag is distributed at the grain boundaries of the MAX phase.

[0103] The chemical bond state of Ag on the surface of Example 1 and Comparative Example 1 was analyzed by X-ray photoelectron spectroscopy (XPS), and the results are shown in Figure 3. As shown in Figure 3, the Ag 3d 5 / 2 and Ag 3d 3 / 2 Peaks appear at 374.5eV and 368.5eV in the figure, and there is also Ag + The appearance of the peak indicates that the element Ag in the coating has Ag + There are two forms of Ag: Ag and elemental Ag. There is no peak in Comparative Example 1, indicating that there is no Ag element in the coating.

[0104] The resistivity of the coatings obtained in Example 1 and Comparative Example 1 before and after heat treatment was measured using a four-probe device. The results are shown in FIG4 . As shown in FIG4 , the resistivity of the deposited coating obtained in Comparative Example 1 is 292.8×10 -8 Ω·m, the resistivity of the deposited coating prepared in Example 1 is 188.7×10 -8 Ω·m, the resistivity of the deposited coating of Example 1 decreased by 35.5% compared with that of the deposited coating of Comparative Example 1; the resistivity of the annealed coating prepared in Comparative Example 1 was 118.8×10 -8 Ω·m, the resistivity of the annealed coating prepared in Example 1 is 48.9×10 -8 Ω·m, the resistivity of the annealed coating of Example 1 decreased by 58.8% compared with the annealed coating of Comparative Example 1. This proves that the continuous distribution structure of Ag at the MAX grain boundaries provides a strong conductive path, giving the coating excellent conductive properties.

[0105] Comparative Example 2

[0106] In this comparative example, the substrate is a high-temperature alloy substrate, and the preparation method of the Cr-Al-C series MAX-Ag phase composite coating on the substrate surface is as follows:

[0107] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 3.0×10 -5At a pressure of less than 100 Torr, 33.4 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -200 V, and the substrate was etched with ionized argon ions for 30 minutes.

[0108] (2) In an Ar protective atmosphere of 200 sccm and a temperature of 150°C, a Cr elemental target was installed on the arc source as a Cr source, with a target power of 1.0 kW and a current of 60 A; the magnetron source was an AlAg (5% atAg) target, with a target power of 3.1 kW and a current of 7.0 A; the substrate bias was set to -150 V, 25 sccm of CH4 was introduced, the gas pressure in the chamber was controlled to be 20 mTorr, and the deposition was carried out for 120 minutes. During the deposition process of the coating, the substrate was rotated at a uniform speed in the chamber to obtain a deposited Cr-Al-C-Ag coating.

[0109] (3) The deposited Cr-Al-C-Ag coating was placed in an annealing furnace at a vacuum of less than 3.0×10 -5 Torr environment, the Cr2AlC-Ag composite coating was prepared by keeping the temperature at 700℃ for 120min.

[0110] The coating prepared in this comparative example was subjected to phase structure detection using an X-ray diffractometer (XRD) with a scanning range of 5° to 90°. The results showed that the coating prepared in comparative example 1 consisted of a Cr2AlC phase and an AlAg3 phase, and Ag existed in the coating in the form of a compound.

[0111] The resistivity of the coating prepared in Comparative Example 2 before and after heat treatment was tested using a four-probe device. The results showed that the resistivity of the deposited coating prepared in Comparative Example 2 was 196.6×10 -8 Ω·m, the resistivity of the annealed coating prepared in Comparative Example 2 is 69.2×10 -8 Ω·m, the resistivity of the annealed coating of Comparative Example 2 decreased by 64.8% compared to the deposited coating of Comparative Example 2. The resistivity of the annealed coating of Example 1 decreased by 74.1% compared to the deposited coating of Example 1, and the resistivity of the annealed coating of Example 1 decreased by 29.3% compared to the annealed coating of Comparative Example 2. This indicates that the presence of Ag in the coating forms a new conductive path. Unlike the conductive mechanism of the coating of Comparative Example 2, the continuous distribution of Ag makes the conductive mechanism of the composite coating of the present invention exhibit metallic properties, and the conductive performance is improved by about 30%.

[0112] Comparative Example 3

[0113] In this comparative example, the substrate is an alumina substrate, and the magnetron source is an AlAg (20 at.% Ag) target. Except for increasing the Ag content of the magnetron target, other conditions are exactly the same as those of the above-mentioned Example 1. The specific process is as follows:

[0114] (1) Place the cleaned, degreased and dried substrate into the cavity and wait until the vacuum pressure in the cavity reaches 3.0×10 -5 At a pressure of less than 100 Torr, 33.4 sccm of argon gas was introduced into the vacuum chamber, the linear anode ion source current was set to 0.2 A, the substrate bias was set to -200 V, and the substrate was etched with ionized argon ions for 30 minutes.

[0115] (2) Arc ion plating was used to deposit the Cr-C layer in an Ar protective atmosphere of 200 sccm at a temperature of 150°C. A single Cr target was mounted on the arc source as a Cr source. The target power was 1.0 kW and the current was 60 A. The substrate bias was set to -150 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Cr-C layer.

[0116] (3) An Al-Ag-C layer was deposited by magnetron sputtering in a 200 sccm Ar protective atmosphere at a temperature of 150°C. The magnetron sputtering source was an AlAg (20 at.% Ag) target with a target power of 3.1 kW and a current of 7.0 A. The substrate bias was set to -150 V, 25 sccm of CH4 was introduced, and the pressure in the chamber was controlled to 20 mTorr. The deposition process lasted for 10 min. During the deposition process, the substrate was rotated at a constant speed in the chamber to obtain the deposited Al-Ag-C layer.

[0117] (4) Steps (2) and (3) were repeated 6 times to obtain a 6-layer alternating stacked coating of Cr-C / Al-Ag-C.

[0118] (5) The Cr-C / Al-Ag-C alternating layer coating was placed in an annealing furnace at a vacuum of less than 3.0×10 -5 In a 0.1-torr environment, the coating was kept at 700°C for 120 minutes. The test showed that no Cr2AlC phase was formed in the coating, which was due to the excessive amount of Ag, which affected the mutual diffusion of elements in the laminated structure.

[0119] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A MAX-Ag conductive composite coating, characterized in that: The conductive composite coating comprises a MAX phase and an Ag phase, wherein the chemical formula of the MAX phase is M n+1 AX n , wherein M is selected from one of Cr, Ti, and Zr, A is an Al element, X is a C or N element, and n is an integer of 1 to 3, the MAX phase is in a lath structure, the Ag phase is in a nano-twin structure, the Ag phase is aggregated at the grain boundary of the MAX phase, the conductive composite coating as a whole is in an Ag-wrapped MAX phase structure, the Ag content in the conductive composite coating is 1 to 10 at.%, and the preparation method of the MAX-Ag conductive composite coating comprises the following steps: S1. providing a substrate, and sequentially performing mechanical polishing, ultrasonic cleaning and glow cleaning on the substrate; S2, placing the substrate in a vacuum chamber, using a single target of the element M as an arc target, introducing a reaction gas and an inert gas providing the element X, and depositing an MX layer using an arc ion plating technique; S3, using the composite target of element A and Ag as a DC pulsed magnetron sputtering target, and using magnetron sputtering technology to deposit an A-Ag-X layer; S4, repeating steps S2 and S3 for 2 to 20 times to form an MX / A-Ag-X alternating laminated coating; S5. Perform vacuum heat treatment on the alternating laminated coating obtained in step S4 to obtain a MAX-Ag conductive composite coating.

2. The MAX-Ag conductive composite coating according to claim 1, characterized in that: The grain width of the MAX phase is 10-90 nm, and the length is 25-300 nm.

3. The MAX-Ag conductive composite coating according to claim 2, characterized in that: The grain aspect ratio of the MAX phase is between 2 and 7.

4. The MAX-Ag conductive composite coating according to claim 1, characterized in that: The thickness of the Ag phase gathered at the grain boundary of the MAX phase is 1 to 20 nm.

5. The MAX-Ag conductive composite coating according to any one of claims 1 to 4, characterized in that: The MAX phase is selected from one of Cr2AlC, Cr2AlN, Ti2AlC, Ti2AlN, and Zr2AlC.

6. A method for preparing the MAX-Ag conductive composite coating as claimed in claim 1, characterized in that: The following steps are involved: S1. providing a substrate, and sequentially performing mechanical polishing, ultrasonic cleaning and glow cleaning on the substrate; S2, placing the substrate in a vacuum chamber, using a single target of the element M as an arc target, introducing a reaction gas and an inert gas providing the element X, and depositing an MX layer using an arc ion plating technique; S3, using the composite target of element A and Ag as a DC pulsed magnetron sputtering target, and using magnetron sputtering technology to deposit an A-Ag-X layer; S4, repeating steps S2 and S3 for 2 to 20 times to form an MX / A-Ag-X alternating laminated coating; S5. Perform vacuum heat treatment on the alternating laminated coating obtained in step S4 to obtain a MAX-Ag conductive composite coating.

7. The method for preparing the MAX-Ag conductive composite coating according to claim 6, characterized in that: In the step S2, the substrate bias voltage is -50 to -200 V, the target-substrate distance between the substrate and the cathode arc target is 15 to 20 cm, the power of the cathode arc target is 1 to 3 kW, the current is 30 to 70 A, the flow rate of the reaction gas is 15 to 30 sccm, the flow rate of the inert gas is 150 to 200 sccm, and the deposition time is 5 to 30 min.

8. The method for preparing the MAX-Ag conductive composite coating according to claim 6, characterized in that: In the step S3, the substrate bias voltage is -50 to -200 V, the target-substrate distance between the substrate and the DC pulse magnetron sputtering target is 10 to 15 cm, the power of the DC pulse magnetron sputtering target is 2 to 3.5 kW, the flow rate of the reaction gas is 15 to 30 sccm, the flow rate of the inert gas is 150 to 200 sccm, and the deposition time is 5 to 30 min.

9. The method for preparing the MAX-Ag conductive composite coating according to claim 6, characterized in that: In step S5, the vacuum degree of the vacuum heat treatment is less than 2.0×10 -3 Torr, temperature is 500-750℃, time is 30-360min.

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