Method of making silver tungsten contact material resistant to arc erosion and material

Abstract

The application discloses a preparation method of a silver-tungsten contact material resistant to arc ablation and the material. In the method, silver is electrolessly plated, wherein tungsten powder is subjected to electroless plating treatment to form a silver coating layer on the surface of the tungsten powder, and silver-coated tungsten powder is obtained; hot-press sintering is performed on the silver-coated tungsten powder in a vacuum environment to obtain a tungsten skeleton, and the silver coating layer serves as a buffer medium to avoid direct contact of the tungsten powder with extrusion deformation; and skeleton infiltration is performed on the tungsten skeleton and silver sheets stacked together in a reducing atmosphere to obtain the silver-tungsten contact material, wherein the silver coating layer participates in silver phase penetration and eliminates internal stress of the skeleton when the silver coating layer is melted.

Description

Technical Field

[0001] This invention relates to the field of electrical contact materials technology, and in particular to a method for preparing a silver-tungsten contact material resistant to arc erosion, as well as the material itself. Background Technology

[0002] Contacts are critical components in power switches used for connecting, carrying, and breaking current. They must not only ensure low loss and low temperature rise during long-term current flow but also withstand the thermal and mechanical shock of electric arcs generated during switch opening and closing. Silver-tungsten alloys, possessing both the high conductivity of silver and the high melting point of tungsten, are widely used as contact materials in low-voltage switchgear. In terms of manufacturing processes, contact materials prepared by melt infiltration have a tungsten skeleton structure and strong resistance to arc erosion, thus making them widely adopted. However, in conventional melt infiltration processes, tungsten powder is first pressed into a green blank by adding a forming agent, then the forming agent is removed at high temperature, and the green blank is sintered into a skeleton for subsequent silver infiltration. In this process, the addition and removal of the forming agent not only increases production costs but may also lead to carbon impurity contamination, deteriorating the conductivity of the contact material and causing spalling and ablation. Existing technologies cannot simultaneously avoid carbon contamination and stress residue problems. Therefore, optimizing the manufacturing process of silver-tungsten contact materials and developing contact materials with excellent resistance to arc erosion are of great significance for improving the lifespan and reliability of switchgear.

[0003] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] This invention provides a method for preparing a silver-tungsten contact material resistant to arc erosion and the material itself, which does not require the addition of a molding agent and significantly alleviates the residual stress inside the tungsten skeleton.

[0005] A method for preparing a silver-tungsten contact material resistant to arc erosion includes:

[0006] Chemical silver plating involves chemically plating tungsten powder to form a silver coating layer on the surface of the tungsten powder, thereby obtaining silver-coated tungsten powder.

[0007] Hot pressing sintering, wherein the silver-coated tungsten powder is hot-pressed and sintered in a vacuum environment to obtain a tungsten skeleton, and the silver coating layer serves as a buffer medium to prevent the tungsten powder from being directly squeezed and deformed. Skeleton infiltration: Under a reducing atmosphere, the tungsten skeleton and silver sheet are stacked and infiltrated to obtain silver-tungsten contact material. The silver coating layer participates in silver phase infiltration during melting to eliminate internal stress in the skeleton.

[0008] In the preparation method of the silver-tungsten contact material resistant to arc erosion, the chemical silver plating includes dispersing tungsten powder in a solution containing silver ions, adjusting the pH to an alkaline environment, adding a reducing agent to carry out a reduction reaction, and after the reaction is completed, solid-liquid separation, washing and drying are performed to obtain silver-coated tungsten powder with uniformly coated nano-silver particles on the surface.

[0009] In the preparation method of the silver-tungsten contact material resistant to arc erosion, the silver ion-containing solution is a silver nitrate solution, the reducing agent is an ascorbic acid solution, tungsten powder and silver nitrate solution are added to a reaction vessel and magnetically stirred to mix them evenly, then sodium hydroxide solution is added to the reaction vessel while maintaining magnetic stirring, and ascorbic acid solution is added to the reaction vessel for reduction.

[0010] In the preparation method of the silver-tungsten contact material resistant to arc erosion, the mass ratio of silver nitrate to tungsten powder is (79-316):1000, the mass ratio of silver nitrate to ascorbic acid is 1:(5.75-11.5), the solution pH value is between 9 and 11, and the water bath temperature of the reduction reaction is 90℃.

[0011] In the preparation method of the silver-tungsten contact material resistant to arc erosion, the heating rate during hot pressing sintering is 25℃ / min, the sintering temperature is 750–950℃, the holding time is 10–30 min, and the applied pressure is 4.5–8 MPa.

[0012] In the preparation method of the silver-tungsten contact material resistant to arc erosion, the heating rate during melting and infiltration is 5℃ / min, the melting and infiltration temperature is 1050–1200℃, and the holding time is 1–3 h; the reducing atmosphere is hydrogen.

[0013] In the preparation method of the silver-tungsten contact material resistant to arc erosion, the flow rate of the reducing atmosphere is 20 sccm.

[0014] A silver-tungsten contact material is formed by the aforementioned method for preparing an arc-resistant silver-tungsten contact material.

[0015] In the aforementioned silver-tungsten contact material, there is no stress concentration due to extrusion deformation inside the tungsten skeleton, the silver-tungsten interface is densely bonded, and the silver-tungsten contact material does not exhibit molten silver droplet splashing or sheet-like peeling under arc ablation conditions.

[0016] In the silver-tungsten contact material, after being subjected to 5 cycles of 200 A DC arc interruption, the mass loss rate is reduced by ≥40% compared with the control sample without silver coating, and the surface morphology is intact without protruding particles.

[0017] Compared with existing technologies, this invention has the following advantages: This invention produces a tungsten skeleton in one step through hot-pressing sintering, eliminating the need for adding and removing forming agents. This avoids structural defects such as pores and cracks formed inside the tungsten skeleton due to rapid vaporization during forming agent removal. It also prevents carbon residue caused by insufficient removal of forming agents and the formation of carbide impurities from the reaction with tungsten during high-temperature removal. Carbon residue and brittle carbide impurities hinder silver penetration and its interfacial bonding with the tungsten skeleton. The hot-pressing sintering process for tungsten skeleton formation reduces carbon contamination, improves the conductivity of the contact material, improves the internal structure of the material, and reduces the risk of contact sheet peeling and ablation caused by carbon impurities or brittle carbides. A layer of silver particles is coated onto the surface of tungsten powder through chemical plating. Due to the soft texture and good ductility of silver, the silver coating on the surface of the tungsten particles promotes the full flow and uniform rearrangement of the tungsten particles during the hot-pressing sintering process, replacing the lubricating effect of the forming agent and avoiding the problems of uneven particle density and localized pore formation within the tungsten skeleton. In addition, during the hot-pressing sintering process for preparing the tungsten skeleton, the tungsten particles do not come into direct contact with each other. The extrusion deformation is mainly borne by the silver coating on the surface of the tungsten powder, which avoids residual stress inside the tungsten. The deformation and stress of the silver will be fully released in the form of melting into liquid during the melting and infiltration process. This solves the problem of large-scale precipitation, enrichment and splashing of molten silver caused by internal stress in the silver-tungsten contact under the action of electric arc, and improves the resistance to fusion welding and resistance to electric arc erosion of the silver-tungsten contact. Attached Figure Description

[0018] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0019] In the attached diagram:

[0020] Figure 1 SEM images of the prepared silver-coated tungsten powder, from left to right: W@Ag5, W@Ag10, and W@Ag20;

[0021] Figure 2 The images show the surface of the prepared silver-tungsten contact materials after arc ablation. From left to right, they are silver-tungsten contact materials prepared by W, W@Ag5, W@Ag10, and W@Ag20.

[0022] Figure 3 This is a schematic diagram showing the mass loss of the prepared silver-tungsten contact material after arc ablation.

[0023] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0024] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0025] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0026] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0027] like Figures 1 to 3 As shown, the preparation method of the arc-erosion-resistant silver-tungsten contact material includes,

[0028] Chemical silver plating involves chemically plating tungsten powder to form a silver coating layer on the surface of the tungsten powder, thereby obtaining silver-coated tungsten powder.

[0029] Hot pressing sintering, wherein the silver-coated tungsten powder is hot-pressed and sintered in a vacuum environment to obtain a tungsten skeleton, and the silver coating layer serves as a buffer medium to prevent the tungsten powder from being directly squeezed and deformed. Skeleton infiltration: Under a reducing atmosphere, the tungsten skeleton and silver sheet are stacked and infiltrated to obtain silver-tungsten contact material. The silver coating layer participates in silver phase infiltration during melting to eliminate internal stress in the skeleton.

[0030] In a preferred embodiment of the method for preparing an arc-erosion resistant silver-tungsten contact material, the chemical silver plating process includes dispersing tungsten powder in a solution containing silver ions, adjusting the pH to an alkaline environment, adding a reducing agent to carry out a reduction reaction, and after the reaction is completed, performing solid-liquid separation, washing, and drying to obtain silver-coated tungsten powder with uniformly coated nano-silver particles on its surface.

[0031] In a preferred embodiment of the preparation method of the silver-tungsten contact material resistant to arc erosion, the silver ion-containing solution is a silver nitrate solution, the reducing agent is an ascorbic acid solution, tungsten powder and silver nitrate solution are added to a reaction vessel and magnetically stirred to mix them evenly, then sodium hydroxide solution is added to the reaction vessel while maintaining magnetic stirring, and ascorbic acid solution is added to the reaction vessel for reduction.

[0032] In a preferred embodiment of the preparation method of the silver-tungsten contact material resistant to arc erosion, the mass ratio of silver nitrate to tungsten powder is (79-316):1000, the mass ratio of silver nitrate to ascorbic acid is 1:(5.75-11.5), the solution pH is between 9 and 11, and the water bath temperature for the reduction reaction is 90°C.

[0033] In a preferred embodiment of the method for preparing an arc-resistant silver-tungsten contact material, the heating rate during hot pressing sintering is 25°C / min, the sintering temperature is 750–950°C, the holding time is 10–30 min, and the applied pressure is 4–8.5 MPa.

[0034] In a preferred embodiment of the method for preparing an arc-resistant silver-tungsten contact material, the heating rate during melting and infiltration is 5°C / min, the melting and infiltration temperature is 1050–1200°C, and the holding time is 1–3 h; the reducing atmosphere is hydrogen.

[0035] In a preferred embodiment of the method for preparing an arc-resistant silver-tungsten contact material, the flow rate of the reducing atmosphere is 20 sccm.

[0036] A silver-tungsten contact material is formed by the aforementioned method for preparing an arc-resistant silver-tungsten contact material.

[0037] In the preferred embodiment of the silver-tungsten contact material, there is no stress concentration due to extrusion deformation inside the tungsten skeleton, the silver-tungsten interface is densely bonded, and the silver-tungsten contact material does not exhibit molten silver droplet splashing or sheet-like peeling under arc ablation conditions.

[0038] In a preferred embodiment of the silver-tungsten contact material, after being subjected to 5 cycles of 200 A DC arc interruption, the mass loss rate of the silver-tungsten contact material is reduced by ≥40% compared to the control sample without a silver coating, and the surface morphology is intact without protruding particles.

[0039] In one embodiment, the method includes the following steps:

[0040] (1) Silver plating of tungsten powder: Tungsten powder and silver nitrate solution are added to the reaction vessel and magnetically stirred to make them evenly mixed. Then sodium hydroxide solution is added to the reaction vessel while magnetic stirring is maintained. Ascorbic acid solution is added to the reaction vessel for reduction and silver-coated tungsten powder is obtained by separation.

[0041] (2) Sintering of tungsten skeleton: hot pressing sintering is used to sinter and solidify silver-coated tungsten powder in a vacuum environment to obtain tungsten skeleton.

[0042] (3) Skeleton melting and infiltration: Under a reducing atmosphere, the pre-sintered tungsten skeleton and silver sheet are stacked and placed in a high-temperature sintering furnace for melting and infiltration. Further settings are as follows: in step (1), the mass ratio of silver nitrate to tungsten powder is (79-316):1000, the mass ratio of silver nitrate to ascorbic acid is 1:(5.75-11.5), the solution pH is between 9 and 11, the water bath temperature of the reduction reaction is 90℃, and the silver-coated tungsten powder needs to be washed with water, washed with anhydrous ethanol and vacuum dried after the reaction is completed. Further settings are as follows: in step (2), the temperature is raised to 750-950℃ at a heating rate of 25℃ / min, the applied pressure is 4-8.5MPa, and the holding time is 10-30min. Further settings are as follows: in step (3), the temperature is raised to 1050-1200℃ at a heating rate of 5℃ / min, the holding time is 1-3h, and the reducing atmosphere is hydrogen or ammonia decomposition atmosphere. The tungsten skeleton is prepared by hot pressing and sintering, eliminating the need for adding and removing forming agents, avoiding residual carbon impurities and carbide formation, improving the internal structure of the contact material, and reducing the risk of spalling and ablation. Simultaneously, chemical silver plating prevents deformation between tungsten particles, avoiding excessive residual stress inside the contact and the resulting severe spalling and ablation problems. The silver-tungsten contact material provided by this invention is free of internal defects and impurities, and exhibits excellent resistance to arc erosion.

[0043] Example 1

[0044] A method for preparing a silver-tungsten contact material includes the following steps:

[0045] (1) Add 0.79g of silver nitrate to the reaction vessel and stir until dissolved. Then add 10g of tungsten powder to the reaction vessel and stir for 1 hour. The magnetic stirring speed is 700-900 rpm.

[0046] (2) While stirring, add sodium hydroxide solution dropwise to the container until the solution pH reaches 9, and gradually add 19.75 ml of ascorbic acid solution with a concentration of 230 g / L to the container;

[0047] (3) Heat the container in a water bath for 3 hours at a temperature of 90°C and a magnetic stirring speed of 300-500 rpm;

[0048] (4) The powder at the bottom of the container was washed three times by centrifugation with deionized water and then washed three times by centrifugation with anhydrous ethanol. The resulting powder was then vacuum dried to obtain silver-coated tungsten powder (W@Ag5).

[0049] (5) Pour the W@Ag5 powder described in step (4) into a graphite mold, place the mold in a plasma sintering furnace, evacuate and pressurize it. When the pressure reaches 8.5 MPa, heat it to 750°C at a heating rate of 25°C / min, hold it for 30 min, and then cool it with the furnace to obtain a tungsten skeleton.

[0050] (6) Place the skeleton in a ceramic boat, place the molten silver sheet on the tungsten skeleton, and place it in a high-temperature sintering furnace with a reducing atmosphere, the reducing atmosphere being hydrogen with a flow rate of 20 sccm, and heat it to 1050°C at a heating rate of 5°C / min. After holding at the temperature for 3 hours, cool it with the furnace to obtain the silver-tungsten contact material (Ag / W@Ag5).

[0051] The graphite mold and ceramic boat are coated with a boron nitride coating.

[0052] The SEM image of W@Ag5 powder obtained by the silver-tungsten contact material preparation method in Example 1 is shown below. Figure 1 As shown in Figure a, the surface of the micron-sized tungsten powder is coated with a large number of nano-silver particles.

[0053] Example 2

[0054] A method for preparing a silver-tungsten contact material includes the following steps:

[0055] (1) Add 1.58g of silver nitrate to the reaction vessel and stir until dissolved. Then add 10g of tungsten powder to the reaction vessel and stir for 1 hour. The magnetic stirring speed is 700-900 rpm.

[0056] (2) Keep stirring and add sodium hydroxide solution dropwise to the container until the pH value of the solution reaches 10. Gradually add 60 ml of ascorbic acid solution with a concentration of 230 g / L to the container.

[0057] (3) Heat the container in a water bath for 3 hours at a temperature of 90°C and a magnetic stirring speed of 300-500 rpm;

[0058] (4) The powder at the bottom of the container was washed three times by centrifugation with deionized water and then washed three times by centrifugation with anhydrous ethanol. The resulting powder was then vacuum dried to obtain silver-coated tungsten powder (W@Ag10).

[0059] (5) Pour the W@Ag10 powder described in step (4) into a graphite mold, place the mold in a plasma sintering furnace, evacuate and pressurize it. When the pressure reaches 5.65 MPa, heat it to 850°C at a heating rate of 25°C / min, hold it for 20 min, and then cool it with the furnace to obtain a tungsten skeleton.

[0060] (6) Place the skeleton in a ceramic boat, place the molten silver sheet on the tungsten skeleton, and place it in a high-temperature sintering furnace with a reducing atmosphere, the reducing atmosphere being hydrogen, the atmosphere flow rate being 20 sccm, and heat it to 1100℃ at a heating rate of 5℃ / min. After holding at the temperature for 2 hours, cool it with the furnace to obtain the silver-tungsten contact material (Ag / W@Ag10).

[0061] The graphite mold and ceramic boat are coated with a boron nitride coating.

[0062] The SEM image of W@Ag10 powder obtained by the silver-tungsten contact material preparation method in Example 2 is shown below. Figure 1 As shown in Figure b, the surface of the micron-sized tungsten powder is coated with a large number of sheet-like silver nanoparticles.

[0063] Example 3

[0064] A method for preparing a silver-tungsten contact material includes the following steps:

[0065] (1) Add 3.16g of silver nitrate to the reaction vessel and stir until dissolved. Then add 10g of tungsten powder to the reaction vessel and stir for 1 hour. The magnetic stirring speed is 700-900 rpm.

[0066] (2) While stirring, add sodium hydroxide solution dropwise to the container until the solution pH reaches 11, and gradually add 158 ml of ascorbic acid solution with a concentration of 230 g / L to the container;

[0067] (3) Heat the container in a water bath for 3 hours at a temperature of 90°C and a magnetic stirring speed of 300-500 rpm;

[0068] (4) The powder at the bottom of the container was washed three times by centrifugation with deionized water and then washed three times by centrifugation with anhydrous ethanol. The resulting powder was then vacuum dried to obtain silver-coated tungsten powder (W@Ag20).

[0069] (5) Pour the W@Ag20 powder described in step (4) into a graphite mold, place the mold in a plasma sintering furnace, evacuate and pressurize it. When the pressure reaches 4MPa, heat it to 950℃ at a heating rate of 25℃ / min, hold it for 10min, and then cool it with the furnace to obtain a tungsten skeleton.

[0070] (6) Place the skeleton in a ceramic boat, place the molten silver sheet on the tungsten skeleton, and place it in a high-temperature sintering furnace with a reducing atmosphere, the reducing atmosphere being hydrogen with a flow rate of 20 sccm, and heat it to 1200℃ at a heating rate of 5℃ / min. After holding it at that temperature for 1 hour, cool it with the furnace to obtain the silver-tungsten contact material (Ag / W@Ag20).

[0071] The graphite mold and ceramic boat are coated with a boron nitride coating.

[0072] The SEM image of W@Ag20 powder obtained by the silver-tungsten contact material preparation method in Example 3 is shown below. Figure 1 As shown in Figure c, the surface of the micron-sized tungsten powder is coated with a large number of nano-silver particles.

[0073] Example 4

[0074] A method for preparing a silver-tungsten contact material includes the following steps:

[0075] (1) Pour 10g of tungsten powder into a graphite mold, place the mold in a plasma sintering furnace, evacuate and pressurize it. When the pressure reaches 5.65MPa, heat it to 850℃ at a heating rate of 25℃ / min, hold it for 20min, and then cool it with the furnace to obtain a tungsten skeleton.

[0076] (2) The skeleton is placed in a ceramic boat, the molten silver sheet is placed on the tungsten skeleton, and then placed in a high-temperature sintering furnace with a reducing atmosphere, the reducing atmosphere being hydrogen, the atmosphere flow rate being 20 sccm, the temperature is raised to 1100℃ at a heating rate of 5℃ / min, and after holding for 2 hours, the silver-tungsten contact material is obtained by cooling with the furnace.

[0077] The graphite mold and ceramic boat are coated with a boron nitride coating.

[0078] Example 5

[0079] The arc erosion resistance of the silver-tungsten contact material prepared above was investigated. A frustum-shaped silver-tungsten contact material was obtained by turning, and the larger base of the frustum was welded onto a copper pillar. Using a simulated electrical contact device, under a DC current of 200A, with the silver-tungsten contact material as the anode (moving contact) and graphite as the cathode (stationary contact), and the two contacts 5 mm apart, an arc erosion experiment was conducted in air. Each group of contact materials underwent 5 cycles of opening and closing.

[0080] The morphology of the silver-tungsten contact material prepared above after arc ablation is as follows: Figure 2 As shown, the silver-tungsten contact material prepared from pure W exhibits numerous particles and protrusions on its surface and sides. This is because during the hot-pressing sintering process to prepare the tungsten skeleton, the W particles are deformed under pressure, resulting in significant residual stress within the skeleton. This internal deformation stress is released under the thermal-mechanical action of the electric arc, driving the precipitation of molten silver to the surface and sides. In contrast, the silver-tungsten contact materials prepared from W@Ag5, W@Ag10, and W@Ag20 exhibit complete ablation morphology, with no large particles or protrusions on their surface and sides. This is because the tungsten powder, after chemical plating, has its surface-coated silver bearing the deformation during skeleton sintering, while the W particles remain undeformed. Consequently, the contact material does not experience stress-driven molten silver precipitation under the action of the electric arc, thus optimizing its resistance to arc ablation.

[0081] The mass loss of the silver-tungsten contact material prepared above due to arc ablation is as follows: Figure 3 As shown, compared to contact materials prepared from pure tungsten powder, contact materials prepared from silver-coated tungsten powder exhibit significantly reduced mass loss. Under the action of an electric arc, the contact loses material in the form of evaporation and droplet splashing. Since the contact material prepared from silver-coated tungsten powder does not precipitate liquid silver, it avoids the severe mass loss caused by large droplet splashing, thus demonstrating excellent resistance to arc erosion.

[0082] Furthermore, the nanoscale continuous silver coating layer (thickness controllable between 5–10 wt%) formed on the surface of tungsten powder in this invention plays three key roles in subsequent processes: Carbon-free binder replacement: It completely replaces traditional organic molding agents such as paraffin and polyethylene, eliminating the carbon source at its origin and avoiding the formation of brittle carbides such as WC (high hardness, poor conductivity, and easy to become the starting point for arc erosion) caused by carbon residue during the sintering removal stage; Stress buffer medium: The melting point of silver (961℃) is slightly higher than the upper limit temperature of hot pressing sintering (950℃), exhibiting high plasticity in the 750–950℃ range. During hot pressing, the silver layer preferentially undergoes plastic flow and deformation, effectively isolating the rigid contact between tungsten particles, absorbing and dispersing mechanical stress into the silver phase, and avoiding micro-cracks and residual stress concentration in the tungsten skeleton; Interface activation layer: The silver coating layer is rich in nanoscale active silver particles (SEM). Figure 1 (Confirmed) It significantly increases the contact area and chemical activity of the tungsten-silver interface, providing a high diffusion channel for subsequent melting and infiltration, and promoting rapid and uniform penetration of silver liquid.

[0083] Sintering stage: Vacuum environment (≤10) -2 Under hot-press sintering at 1050–1200°C, the silver coating undergoes directional plastic flow under pressure, guiding the tungsten particles to rearrange uniformly, forming a skeletal structure with interconnected pores and a uniform density distribution (compared to the localized densification and stress concentration observed in pure tungsten powder sintering in Example 4). During the melting and infiltration stage: when the temperature is raised to 1050–1200°C, the silver coating and the outer silver sheet melt synchronously. The liquid silver not only fills the skeletal pores but also, through capillary action and flow shear force, completely releases the elastic / plastic strain energy "stored" in the silver phase during the sintering stage. This process achieves "stress dissolution," fundamentally eliminating molten silver splashing caused by internal stress driven by arc thermal shock. Figure 2 , Figure 3 Empirical evidence: The W@Ag sample surface has no protruding particles, and the mass loss is reduced by ≥40%. The final material forms an ideal structure of "continuous support of tungsten skeleton + three-dimensional interpenetration of silver phase": the tungsten skeleton is free of carbon contamination and deformation defects, ensuring the integrity and resistance to welding of the high-melting-point skeleton; the silver-tungsten interface is a clean metallurgical bond (without a carbide isolation layer), the conductive path is unobstructed, and the temperature rise during current flow is reduced; the internal stress is close to zero, and the energy is uniformly dissipated during arcing, avoiding droplet splashing and sheet-like peeling caused by local overheating.

[0084] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for preparing a silver-tungsten contact material resistant to arc erosion, characterized in that, Includes the following steps: Chemical silver plating involves chemically plating tungsten powder to form a silver coating layer on the surface of the tungsten powder, thereby obtaining silver-coated tungsten powder. Hot pressing sintering, wherein the silver-coated tungsten powder is hot-pressed and sintered in a vacuum environment to obtain a tungsten skeleton, and the silver coating layer serves as a buffer medium to prevent the tungsten powder from being directly squeezed and deformed. Skeleton infiltration: Under a reducing atmosphere, the tungsten skeleton and silver sheet are stacked and infiltrated to obtain silver-tungsten contact material. The silver coating layer participates in silver phase infiltration during melting to eliminate internal stress in the skeleton.

2. The method for preparing an arc-erosion-resistant silver-tungsten contact material according to claim 1, characterized in that, Preferably, the chemical silver plating process includes dispersing tungsten powder in a solution containing silver ions, adjusting the pH to an alkaline environment, adding a reducing agent to carry out a reduction reaction, and after the reaction is completed, performing solid-liquid separation, washing, and drying to obtain silver-coated tungsten powder with uniformly coated nano-silver particles on its surface.

3. The method for preparing an arc-erosion-resistant silver-tungsten contact material according to claim 2, characterized in that, The silver ion-containing solution is a silver nitrate solution, and the reducing agent is an ascorbic acid solution. Tungsten powder and silver nitrate solution are added to the reaction vessel and magnetically stirred to mix them evenly. Then, sodium hydroxide solution is added to the reaction vessel while maintaining magnetic stirring. Finally, ascorbic acid solution is added to the reaction vessel for reduction.

4. The method for preparing an arc-erosion-resistant silver-tungsten contact material according to claim 3, characterized in that, The mass ratio of silver nitrate to tungsten powder is (79-316):1000, the mass ratio of silver nitrate to ascorbic acid is 1:(5.75-11.5), the pH value of the solution is between 9 and 11, and the water bath temperature for the reduction reaction is 90℃.

5. The method for preparing an arc-erosion-resistant silver-tungsten contact material according to claim 1, characterized in that, During hot pressing sintering, the heating rate is 25℃ / min, the sintering temperature is 750–950℃, the holding time is 10–30 min, and the applied pressure is 4–8.5MPa.

6. The method for preparing an arc-erosion-resistant silver-tungsten contact material according to claim 1, characterized in that, The heating rate during melting and infiltration is 5℃ / min, the melting and infiltration temperature is 1050–1200℃, and the holding time is 1–3 h; the reducing atmosphere is hydrogen.

7. The method for preparing an arc-erosion-resistant silver-tungsten contact material according to claim 1, characterized in that, The flow rate of the reducing atmosphere is 20 sccm.

8. A silver-tungsten contact material, characterized in that, It is formed by the preparation method of the silver-tungsten contact material resistant to arc erosion according to any one of claims 1-7.

9. The silver-tungsten contact material according to claim 8, characterized in that, There is no stress concentration due to extrusion deformation inside the tungsten skeleton, the silver-tungsten interface is densely bonded, and the silver-tungsten contact material does not exhibit molten silver droplet splashing or sheet-like peeling under arc ablation conditions.

10. The silver-tungsten contact material according to claim 8, characterized in that, After being subjected to five cycles of 200 A DC arc interruption, the silver-tungsten contact material showed a mass loss rate that was ≥40% lower than that of the control sample without a silver coating, and the surface morphology was intact without protruding particles.

Images