Molybdenum-based silver-plated composite material and PVD preparation method thereof

Abstract

The invention discloses a molybdenum-based silver-plated composite material and a PVD preparation method thereof, and belongs to the technical field of molybdenum-based composite materials. The PVD preparation method comprises the following steps: carrying out chemical cleaning and drying on a molybdenum sheet, and then carrying out ion source cleaning in a vacuum system to obtain a cleaned molybdenum sheet; performing ion source deposition and magnetron sputtering silver deposition on the cleaned molybdenum sheet to obtain a deposited molybdenum sheet; and ion source deposition is stopped, magnetron sputtering deposition continues, and the molybdenum-based silver-plated composite material is obtained. According to the obtained composite material, the molybdenum base material and the silver film layer are tightly, firmly and evenly combined, the silver film layer is compact and free of internal defects, meanwhile, other metal middle layers do not need to be introduced, the steps are simple, the production process is short, and the production efficiency is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molybdenum-based composite materials, in particular to a molybdenum-based silver-plated composite material and a PVD preparation method thereof. BACKGROUND

[0002] Molybdenum (Mo) as an important refractory metal, due to its high melting point, excellent high-temperature strength and rigidity, low thermal expansion coefficient, and good thermal and electrical conductivity, plays an irreplaceable role in high-end fields such as aerospace, nuclear power industry, and high-power electronic devices (such as microwave tube grid, heat dissipation substrate). However, molybdenum material itself has two inherent defects: first, poor corrosion resistance, especially under high temperature working conditions, it will rapidly oxidize to form volatile oxides, which seriously damages its structural integrity and service life; second, as an electrical contact material, its surface contact resistance is large and easy to fluctuate, and the brazing performance is also not ideal, which directly restricts its performance in long-term and high-reliability application scenarios.

[0003] To overcome the above limitations, plating silver on the surface of molybdenum substrate to obtain a molybdenum-based silver-plated composite material has been proven to be an effective solution. Silver (Ag) is the highest known electrical and thermal conductivity metal, and also has excellent weldability, low and stable contact resistance, and good arc erosion resistance. Applying a silver plating layer on the molybdenum substrate can perfectly combine the advantages of both: molybdenum provides mechanical support and thermal stability, and silver provides extremely high surface electrical / thermal conductivity, excellent brazing performance, improved wear resistance and friction reduction performance, and enhanced corrosion resistance.

[0004] However, achieving high-quality, high-bonding force molybdenum-based silver-plated surfaces faces great challenges. When prepared using traditional wet processes such as electroplating and chemical plating, a dense and chemically extremely stable natural oxide film is easily formed on the surface of molybdenum metal, which will seriously hinder the formation of a firm metallurgical bond between the silver plating layer and the molybdenum substrate, resulting in poor adhesion of the plating layer, which is easily peeled and flaked under the action of thermal cycling or mechanical stress. In addition, the wet process generates a large amount of cyanide or heavy metal-containing contaminated waste liquid, which is contrary to the current green and sustainable manufacturing philosophy.

[0005] Physical vapor deposition (PVD) technology, as an advanced dry plating method, has become an ideal choice for realizing high-performance silver functionalization of molybdenum-based surfaces due to its environmental friendliness, relatively low deposition temperature, high purity of the plating layer, strong controllability of composition and structure, and generally better adhesion of the plating layer than wet processes. However, the existing molybdenum-based silver-plated composite materials obtained using PVD technology still have many technical defects.

[0006] As the composite plating-annealing preparation method adopted by the prior art, a metal layer with good solid solubility with molybdenum, such as nickel, titanium or the like, is first deposited on the surface of the molybdenum substrate as an intermediate layer, then a silver layer is deposited on the intermediate layer by magnetron sputtering, and finally high-temperature annealing treatment is performed to promote interdiffusion between the layers to enhance the bonding force. This method has a complex and lengthy process flow, needs multiple deposition and annealing, has a long production cycle, low efficiency and high cost. Meanwhile, it needs to introduce an additional metal intermediate layer, which may change the electrical or thermal properties at the interface and make it difficult to obtain the most ideal structure.

[0007] Another prior art is a vapor deposition preparation method, which obtains a silver plating layer by sequentially vapor depositing a titanium film and a silver film on a molybdenum substrate and performing two annealing treatments. The bonding force between the obtained plating layer and the substrate is still poor, and it is difficult to form a reliable and effective bond. Meanwhile, the vapor deposition process itself has the defects of poor step coverage and poor uniformity, resulting in uneven thickness distribution of the plating layer on complex-shaped workpieces. In addition, the obtained silver film usually has low density and many defects, which affect its conductive, oxidation-resistant and long-acting protective properties as a functional plating layer.

[0008] In summary, the current molybdenum-based silver plating preparation method, especially the PVD-based preparation method, faces the technical problem of how to simplify the process flow, improve the production efficiency and ultimately obtain a silver plating layer with extremely high bonding strength, excellent uniformity and density under the premise of ensuring environmental friendliness and process controllability, to meet the stringent requirements of reliability and durability for high-end industrial applications. SUMMARY

[0009] In view of the defects of the prior art, the purpose of the present application is to propose a new molybdenum-based silver plating composite material and a PVD preparation method thereof. The preparation method can solve the problems of process complexity, long process cycle, low production efficiency caused by the introduction of a metal intermediate layer in the existing composite plating preparation method, and the problems of poor plating layer bonding force, difficulty in forming a reliable and effective bond between the molybdenum substrate and the film layer, poor step coverage and uniformity, and low film layer density caused by the existing vapor deposition preparation method.

[0010] The technical scheme of the present application is as follows: A PVD preparation method of a molybdenum-based silver plating composite material, comprising the following steps: (1) chemically cleaning a molybdenum sheet to remove inorganic oxides and / or organic contaminants on the surface thereof and activate the surface, and then drying to obtain a dried molybdenum sheet; (2) ion source cleaning the dried molybdenum sheet in a vacuum system to obtain a cleaned molybdenum sheet; (3) magnetron sputtering and ion source deposition of the cleaned molybdenum sheet to obtain a deposited molybdenum sheet; (4) Stop ion source deposition, continue silver deposition on the deposited molybdenum sheet by magnetron sputtering, and then cool to obtain the molybdenum-based silver-plated composite material.

[0011] In the above preparation method of the present invention, the chemical cleaning is a surface pretreatment of the molybdenum sheet, which can remove inorganic oxides and / or organic contaminants such as oxide scale, grease, and dirt present on the surface of the molybdenum sheet, improve the surface condition of the substrate, and provide good surface deposition conditions for subsequent ion source treatment and magnetron sputtering silver plating; the ion source cleaning can effectively remove physical adsorbed impurities on the surface-pretreated substrate and form a relatively loose atomic layer on its surface, allowing the adsorbed gases and organic matter to escape and generate an etching effect on the surface to form active sites. At the same time, it can roughen the substrate surface at the microscopic level, provide a good surface environment for film growth, and improve the bonding strength between the deposited film and the substrate; the magnetron sputtering can use ion bombardment of silver target material to sputter the target material into gaseous particles. At the same time, the energetic ion beam generated by the medium-energy assisted ion source bombards the substrate for auxiliary deposition. After auxiliary deposition for a period of time, magnetron sputtering deposition continues, and finally a silver plating layer with uniform thickness, density, and strong adhesion is deposited on the surface of the molybdenum substrate.

[0012] Among them, ion source-assisted deposition can bombard the deposited film with an energetic ion beam generated by an ion source during the deposition process, integrating ion implantation with film deposition, thereby significantly improving the optical, mechanical and environmental stability of the resulting coated film.

[0013] According to some preferred embodiments of the present invention, the cleaning agent used in the chemical cleaning includes acid, strong oxidizing liquid and deionized water, and the cleaning process uses gas blowing to ensure that the cleaning agent is in full contact with the surface of the molybdenum sheet.

[0014] According to some preferred embodiments of the present invention, the current of the ion source cleaning is 0.5-0.7A and the pulse duty cycle is 20-40%.

[0015] According to some preferred embodiments of the present invention, the ion source cleaning time is 5-7 minutes.

[0016] According to some preferred embodiments of the present invention, the ion beam current deposited by the ion source is 0.04-0.06A and the pulse duty cycle is 20-40%.

[0017] According to some preferred embodiments of the present invention, the deposition time of the ion source is 3-6 minutes.

[0018] According to some preferred embodiments of the present invention, the sputtering gas pressure of the magnetron sputtering is 0.4-0.6 Pa, the power is 3-5 kW, the bias voltage is 90-110 V, and the target-substrate distance is 80-100 mm.

[0019] According to some preferred embodiments of the present invention, the silver deposition time is 4-6 minutes.

[0020] According to some preferred embodiments of the present invention, the thickness of the molybdenum sheet in the molybdenum-based silver-plated composite material is 1-5 mm, and the thickness of the silver plating layer is 2-10 μm.

[0021] The present invention further provides a molybdenum-based silver-plated composite material prepared according to the above PVD preparation method.

[0022] In this molybdenum-based silver-plated composite material, the molybdenum substrate and the silver plating layer are tightly and firmly bonded without a transition layer. The resulting silver plating layer is dense, uniform, and free of internal defects.

[0023] The present invention has the following beneficial effects: This invention achieves efficient synergy between substrate surface pretreatment, ion source cleaning, ion beam assisted deposition, and vacuum magnetron sputtering coating, enabling deposited atoms to migrate to more energy-stable positions with sufficient kinetic energy, reducing surface and internal voids in the film layer, and obtaining a denser and more uniform film layer. At the same time, it improves the interfacial bonding strength between the film layer and the substrate, enhances the bonding force between the two, and makes the obtained film layer firmly adhered to the substrate. The preparation method of the present invention has simple steps, fewer sputtering processes, and does not require the introduction of other metal intermediate layers, resulting in a short production process and high production efficiency. Detailed Implementation

[0024] The technical solutions of the present invention will be further described below with reference to embodiments thereof. The embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0025] Example 1 Molybdenum-based silver-plated composite material was prepared using the following steps: (1) A molybdenum sheet with a specification of D35×T1.6mm (i.e., a circle with a diameter of 35mm and a thickness of 1.6mm) is placed in a cleaning tank and cleaned in sequence with hydrochloric acid, aqua regia and deionized water. During the cleaning process, gas blowing is used to make the cleaning agent fully contact the molybdenum base surface to remove the grease and organic contaminants on its surface and perform surface chemical pretreatment to activate the surface. After drying, a clean molybdenum sheet is obtained. (2) Place the clean molybdenum sheet into the magnetron sputtering equipment and evacuate to a high vacuum level of 8×10⁻⁶.-4 A high vacuum environment is formed by Pa, followed by anodic layer ion source cleaning to clean the surface of the molybdenum substrate. Nanoscale etching is then performed on the surface of the molybdenum substrate under high vacuum to remove adsorbed oxygen, slight contamination, and oxide layer. In the anodic layer ion source cleaning, the cleaning current of the ion source is 0.6A, the pulse duty cycle is 30%, and the cleaning time is 6min, resulting in a cleaned molybdenum sheet. (3) Silver was deposited on the cleaned molybdenum wafer by magnetron sputtering, and ion source deposition was performed simultaneously. The deposition time was 3 min to obtain the deposited molybdenum wafer. The magnetron sputtering gas pressure was 0.4 Pa, the power was 3.1 kW, the bias voltage was 100 V, the target-substrate distance was 80-100 mm, and the deposition time was 3 min. In the ion source deposition, the ion beam current was 0.05 A and the pulse duty cycle was 30%. (4) Stop ion source deposition and continue silver deposition on the molybdenum sheet by magnetron sputtering. The sputtering pressure is 0.5 Pa, the power is 4.4 kW, the bias voltage is 100 V, the target-substrate distance is 80-100 mm, and the deposition time is 5 min. Then, it is naturally cooled to below 50 °C in a high vacuum environment to obtain a silver-plated molybdenum sheet with a silver layer thickness of 5 μm, i.e., a molybdenum-based silver-plated composite material.

[0026] Example 2 Molybdenum-based silver-plated composite material was prepared using the following steps: (1) The molybdenum sheet with specifications of D35×T1.6mm was placed in a cleaning tank and cleaned in sequence with hydrochloric acid, aqua regia and deionized water. During the cleaning process, the cleaning agent was blown by gas to make full contact with the molybdenum base surface to remove the grease and organic contaminants on the surface and perform surface chemical pretreatment to activate the surface. After drying, a clean molybdenum sheet was obtained. (2) Place the clean molybdenum sheet into the magnetron sputtering equipment and evacuate to a high vacuum level of 8×10⁻⁶. -4 A high vacuum environment was created by applying Pa, followed by ion source cleaning of the anode layer. During the ion source cleaning, the cleaning current of the ion source was 0.6A, the pulse duty cycle was 30%, and the cleaning time was 3min, resulting in a cleaned molybdenum sheet. (3) Silver was deposited on the cleaned molybdenum wafer by magnetron sputtering, and ion source deposition was performed simultaneously. The deposition time was 3 min to obtain the deposited molybdenum wafer. The magnetron sputtering gas pressure was 0.4 Pa, the power was 3.1 kW, the bias voltage was 100 V, the target-substrate distance was 80-100 mm, and the deposition time was 3 min. In the ion source deposition, the ion beam current was 0.05 A and the pulse duty cycle was 30%. (4) Stop ion source deposition and continue silver deposition on the molybdenum sheet by magnetron sputtering. The sputtering pressure is 0.5 Pa, the power is 4.4 kW, the bias voltage is 100 V, the target-substrate distance is 80-100 mm, and the deposition time is 5 min. Then, the silver-plated molybdenum sheet with a silver layer thickness of 5 μm is obtained under high vacuum environment and naturally cooled to below 50 °C, i.e., molybdenum-based silver-plated composite material.

[0027] Example 3 Molybdenum-based silver-plated composite material was prepared using the following steps: (1) The molybdenum sheet with specifications of D35×T1.6mm was placed in a cleaning tank and cleaned in sequence with hydrochloric acid, aqua regia and deionized water. During the cleaning process, the cleaning solution was blown by gas to make full contact with the molybdenum base surface to remove the grease and organic contaminants on the surface and perform surface chemical pretreatment to activate the surface. After drying, a clean molybdenum sheet was obtained. (2) Place the clean molybdenum sheet into the magnetron sputtering equipment and evacuate to a high vacuum until the vacuum level reaches 8×10⁻⁶. -4 A high vacuum environment was created by applying Pa, followed by ion source cleaning of the anode layer. During the ion source cleaning, the cleaning current of the ion source was 0.6A, the pulse duty cycle was 30%, and the cleaning time was 6min, resulting in a cleaned molybdenum sheet. (3) Silver was deposited on the cleaned molybdenum wafer by magnetron sputtering, and ion source deposition was performed simultaneously. The deposition time was 3 min to obtain the deposited molybdenum wafer. The magnetron sputtering gas pressure was 0.4 Pa, the power was 3.1 kW, the bias voltage was 100 V, the target-substrate distance was 80-100 mm, and the deposition time was 3 min. In the ion source deposition, the ion beam current was 0.05 A and the pulse duty cycle was 30%. (4) Stop ion source deposition and continue silver deposition on the molybdenum sheet by magnetron sputtering. The sputtering pressure is 0.5 Pa, the power is 4.4 kW, the bias voltage is 100 V, the target-substrate distance is 80-100 mm, and the deposition time is 8 min. Then, it is naturally cooled to below 50 °C in a high vacuum environment to obtain a silver-plated molybdenum sheet with a silver layer thickness of 8 μm, i.e., a molybdenum-based silver-plated composite material.

[0028] The molybdenum-based silver-plated composite materials prepared in Examples 1-3 were subjected to coating adhesion tests: a 3M tape peel test was conducted. The 3M tape peel test method was as follows: 3M tape (681) was adhered to the coating and pressed firmly. After 10 seconds, the tape was peeled off with a force perpendicular to the coating direction. If the coating did not peel off, it indicates that its bonding strength was good. The results are shown in Table 1 below: Table 1. Test results of coating performance in the examples

[0029] As can be seen from Table 1, the silver coating in the molybdenum-based silver-plated composite material obtained by the present invention has good adhesion to the molybdenum substrate and is difficult to peel off.

[0030] Comparative Examples 1-3 were prepared by following the steps (1) and (4) of Examples 1-3 respectively (i.e., removing the steps (2) and (3) related to ion source cleaning and ion source assisted deposition) to obtain the molybdenum-based silver-plated composite materials of Comparative Examples 1-3.

[0031] Comparative examples 1-3 The prepared molybdenum-based silver-plated composite material underwent the same coating adhesion test and 3M tape peel test as in Examples 1-3. The results are shown in Table 2 below: Table 2. Performance test results of comparative coatings

[0032] Test results show that the molybdenum-based silver-plated composite material obtained without ion source cleaning and ion source-assisted deposition exhibits a significant decrease in both coating adhesion and coating peeling performance.

[0033] It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A PVD preparation method for a molybdenum-based silver-plated composite material, characterized in that, It includes the following steps: (1) The molybdenum sheet is chemically cleaned to remove inorganic oxides and / or organic contaminants from its surface and then surface activated, followed by drying to obtain a dried molybdenum sheet; (2) The dried molybdenum sheet is cleaned with an ion source in a vacuum system to obtain a cleaned molybdenum sheet; (3) The cleaned molybdenum sheet is subjected to magnetron sputtering and ion source deposition to obtain a deposited molybdenum sheet; (4) Stop ion source deposition, continue silver deposition on the deposited molybdenum sheet by magnetron sputtering, and then cool to obtain the molybdenum-based silver-plated composite material.

2. The PVD preparation method according to claim 1, characterized in that, The cleaning agents used in the chemical cleaning include acid, strong oxidizing liquid and deionized water. During the cleaning process, gas blowing is used to ensure that the cleaning agents come into full contact with the surface of the molybdenum sheet.

3. The PVD preparation method according to claim 1, characterized in that, The ion source cleaning current is 0.5-0.7A, the pulse duty cycle is 20-40%; and / or, the ion source cleaning time is 5-7 minutes.

4. The PVD preparation method according to claim 1, characterized in that, The ion beam current deposited by the ion source is 0.04-0.06A, the pulse duty cycle is 20-40%; and / or, the ion source deposition time is 3-6 min.

5. The PVD preparation method according to claim 1, characterized in that, The magnetron sputtering has a sputtering pressure of 0.4-0.6 Pa, a power of 3-5 kW, a bias voltage of 90-110 V, and a target-substrate distance of 80-100 mm; and / or the silver deposition time is 4-6 min.

6. The PVD preparation method according to claim 1, characterized in that, The thickness of the molybdenum sheet in the molybdenum-based silver-plated composite material is 1-5 mm, and the thickness of the silver plating layer is 2-10 μm.

7. The molybdenum-based silver-plated composite material prepared by the PVD preparation method according to any one of claims 1-6.

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