Silver-tungsten carbide-carbon contact material and method for producing the same

Abstract

The application relates to the field of contact materials, in particular to a silver-tungsten carbide-carbon contact material and a preparation method thereof. The silver-tungsten carbide-carbon contact material is composed of a silver matrix, tungsten carbide particles uniformly dispersed in the silver matrix, and carbon fibers as a reinforcing phase and a solid lubricant; wherein the carbon fibers are randomly or directionally distributed in the silver matrix. In the application, the carbon fibers replace traditional graphite, the mechanical strength and arc erosion resistance of the material are significantly improved while the excellent anti-melting welding property is maintained, the contradiction that lubrication and reinforcement are difficult to be considered in traditional materials is effectively overcome, and the electrical life, contact reliability and comprehensive service performance of the prepared contact material are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of contact materials, and more particularly to a silver-tungsten carbide-carbon contact material and its preparation method. Background Technology

[0002] Silver-based contact materials are key components in low-voltage circuit breakers, contactors, and other circuit switching control equipment. Their performance directly affects the service life, breaking reliability, and operational safety of electrical equipment. Among various silver-based composite materials, the silver-tungsten carbide-carbon (AgWC-C) system has attracted widespread attention due to its combination of good electrical and thermal conductivity with a certain degree of resistance to arc erosion. In this material system, the silver matrix provides excellent conductivity, the hard tungsten carbide phase mainly plays a role in resisting arc erosion and wear, while the introduction of the carbon component (usually in the form of graphite) aims to improve anti-welding performance and prevent the contacts from sticking together when breaking large currents.

[0003] Although AgWC-C materials have shown certain application potential, the overall performance of materials prepared by existing technologies still has room for improvement under actual working conditions. A prominent contradiction lies in the fact that to achieve low contact resistance and temperature rise, a high purity and continuity of the silver matrix are desired; however, to improve arc erosion resistance and mechanical strength, a high content and uniform distribution of the hard tungsten carbide phase are required. While conventional mechanical mixing-powder metallurgy processes are simple, the significant density difference between silver powder and tungsten carbide powder easily leads to component segregation during mixing and subsequent processing, resulting in uneven distribution of tungsten carbide particles within the silver matrix. This inhomogeneity causes premature performance degradation in localized areas when the material is subjected to repeated arc impacts. For example, tungsten carbide-rich areas may become microcrack initiations due to high brittleness, while silver-rich areas may undergo plastic deformation or exacerbate arc erosion due to insufficient strength, ultimately limiting the improvement of the material's overall electrical life.

[0004] Furthermore, the introduction of carbon components also faces challenges. While commonly used micron-sized graphite powder can provide solid lubrication and improve weldability by forming a gas film or its own layered structure, graphite itself has low strength, and the interface between it and the silver matrix is ​​often weak. Under frequent arc thermal stress and mechanical impact, graphite particles easily detach from the matrix, not only weakening its lubrication effect, but also creating micropores that can become the starting point for arc concentration and material ablation. This also reduces the material's mechanical strength and affects the contact's impact toughness.

[0005] To address the uniformity issue, some studies have attempted to prepare composite powders using chemical methods, such as coating tungsten carbide particles with a silver layer, aiming to improve the wettability and distribution uniformity between the two phases. However, while these methods improve the uniformity of WC distribution, their contribution to the final densification and toughening of the material remains insufficient. In particular, the distribution state of the carbon component and its bonding strength with the matrix remain key factors affecting performance stability. Conventional pressing-sintering processes have limitations in achieving high material densification; a certain number of residual pores are unavoidable within the sintered body. These pores reduce the conductive cross-sectional area, leading to increased resistivity, and may become weak points for material failure under arcing.

[0006] Therefore, the art still anticipates improvements in AgWC-C contact materials and their preparation methods that can more effectively balance arc erosion resistance, weldability, and mechanical strength without sacrificing conductivity. In particular, it is desirable to improve the uniformity of the material's microstructure and its overall density, thereby enhancing its service stability and lifespan under harsh operating conditions. Existing solutions often struggle to simultaneously achieve multiple performance indicators; striking a good balance between process feasibility and performance optimization remains a key technical challenge. Summary of the Invention

[0007] This application aims to overcome the shortcomings of existing AgWC-C contact materials, which suffer from insufficient mechanical strength and unsatisfactory microstructure uniformity due to the use of graphite as the carbon component and the traditional powder mixing and sintering process. These shortcomings make it difficult to simultaneously achieve excellent resistance to arc erosion, low contact resistance, and high resistance to welding. Therefore, this application provides a silver-tungsten carbide-carbon contact material and its preparation method to overcome the above-mentioned deficiencies.

[0008] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution: Firstly, the present invention provides a silver-tungsten carbide-carbon contact material. It is composed of a silver matrix, tungsten carbide particles uniformly dispersed in the silver matrix, and carbon fibers as a reinforcing phase and solid lubricant; wherein the carbon fibers are randomly or oriented in the silver matrix.

[0009] As described in the background section, existing technologies generally use graphite as the carbon component source. While this satisfies the basic requirements for resistance to welding to some extent, the low strength of graphite itself and its poor interfacial bonding with the silver matrix have become bottlenecks restricting further improvement in the overall performance of the material. Specifically, graphite particles are prone to detachment from the matrix under the action of electric arc and mechanical stress, which not only weakens its lubrication function, but the resulting microscopic defects also accelerate the arc erosion and performance degradation of the material, making it difficult to improve the electrical life and mechanical reliability of the material in a coordinated manner. In addition, the inherent lack of uniformity in traditional mechanical powder mixing processes further amplifies the defects of weak interfacial bonding between components. Although some studies have attempted to improve the distribution uniformity of silver and tungsten carbide through methods such as chemical coating, they have failed to provide a fundamental solution to the inherent weaknesses of the carbon component itself.

[0010] It was against this technological backdrop that an innovative solution using carbon fiber as the core component was proposed. Unlike powdered graphite, carbon fiber, as a high aspect ratio and high-strength fiber material, fundamentally changes its role in composite materials. When carbon fiber is introduced into a silver matrix and uniformly dispersed, it is no longer merely a solid lubricant, but also a crucial reinforcing phase. Its fiber morphology allows it to effectively inhibit crack propagation through bridging and pull-out mechanisms, thereby significantly improving the material's toughness and resistance to mechanical impact. Simultaneously, carbon fiber retains the excellent solid lubrication properties of carbon materials, effectively preventing contact welding. This "dual-effect" design cleverly unifies the usually contradictory functions of "reinforcement" and "lubrication," resolving the core contradiction of traditional AgWC-C materials' difficulty in simultaneously achieving strength and weld resistance from the source of material design.

[0011] Ultimately, the technical solution yields significant and synergistic effects. Due to the reinforcing effect of carbon fiber on the matrix, the material's mechanical strength, arc erosion resistance, and fatigue resistance are greatly improved. Because of its uniform distribution and stable form, carbon fiber provides a more durable and stable lubrication effect compared to easily detached graphite particles, making its anti-welding properties more reliable. Simultaneously, the high uniformity of component distribution contributes to more stable electrical contact performance and lower contact resistance fluctuations. Therefore, this invention, through fundamental innovation in component morphology and careful control of microstructure, successfully and synergistically improves the overall performance of AgWC-C contact materials in a homogeneous material system, providing a non-obvious yet highly effective path to solving long-standing technical problems, distinct from all existing technologies.

[0012] Preferably, the product contains the following components by weight percentage: 70-85% silver, 12-27% tungsten carbide, and 0.5-5.5% carbon fiber.

[0013] Preferably, the carbon fiber has a length of 50-300 μm and a diameter of 5-15 μm.

[0014] Preferably, the tungsten carbide particles include micron-sized tungsten carbide and submicron-sized tungsten carbide; wherein, The micron-sized tungsten carbide has a particle size of 1-3 μm, and the submicron-sized tungsten carbide has a particle size of 0.1-1 μm.

[0015] This invention reveals that when using only tungsten carbide particles of a single size, the particle stacking creates numerous voids that need to be filled by a silver matrix. This weakens the overall support of the hard phase and may become a weak point in performance. However, by introducing submicron-sized particles with a specific particle size (0.1-1 μm), they can effectively fill the voids between micron-sized particles (1-3 μm), thereby significantly improving the packing density of the powder and laying the foundation for obtaining materials with higher density through subsequent sintering.

[0016] This higher density directly brings several synergistic benefits: on the one hand, it reduces electric field concentration and arc erosion initiation points caused by porosity, enhancing the material's arc resistance; on the other hand, the denser, more uniform matrix provides a more efficient stress transfer and less defective support environment for the carbon fiber reinforcement phase, allowing the reinforcing and lubricating effects of the carbon fibers to be fully realized, rather than being weakened by local porosity or structural inhomogeneity. Therefore, this combination of dual-scale tungsten carbide and the introduction of carbon fibers creates a synergistic reinforcement effect, working together to construct a composite material system with a more complete structure and more stable performance.

[0017] Preferably, the material further comprises additives, which are at least one of cobalt, nickel or rare earth oxides, and the total mass fraction of the additives is 0.1-3.0% (cobalt and nickel are usually added in the form of nitrates, etc., and then reduced in a hydrogen atmosphere after ball milling).

[0018] The addition of cobalt or nickel is mainly intended to improve the interfacial bonding strength between the silver matrix and the tungsten carbide hard phase by activating the sintering process. This is crucial for ensuring that the load is effectively transferred from the relatively soft silver matrix to the hard phase. The addition of rare earth oxides tends to agglomerate at the grain boundaries, which helps to inhibit grain growth, purify the interface, and improve the high-temperature stability of the material.

[0019] Furthermore, while the introduction of carbon fiber brings significant reinforcement, it also introduces a new and more complex interface, namely the interface between carbon fiber and silver / WC. The presence of additives indirectly but crucially strengthens the bonding force between carbon fiber and the surrounding matrix by optimizing the overall sintering behavior and matrix properties, reducing the risk of carbon fiber being pulled out of the matrix under stress, thus more fully realizing the function of carbon fiber as a "reinforcing phase".

[0020] Secondly, the present invention first provides a method for preparing the aforementioned silver-tungsten carbide-carbon contact material, comprising the following steps: S1. Silver-coated tungsten carbide composite powder was prepared by chemical coating method; S2. The composite powder and carbon fiber are ball-milled and mixed to obtain a mixture; S3. The mixture is subjected to warm pressing to obtain a green body; S4. The green blank is sintered to obtain a dense contact material.

[0021] Existing technologies typically employ a singular approach of mechanically mixing all raw materials. This method struggles to overcome the uneven mixing issues caused by the significant density difference between silver and tungsten carbide, and it also fails to adequately address the new challenges introduced by reinforcing materials like carbon fibers, which have high aspect ratios and are prone to agglomeration, such as difficulty in dispersion, random orientation, and weak bonding with the matrix. The present invention addresses these core process challenges by proposing a step-by-step, integrated, and optimized solution.

[0022] Specifically, the starting point of the method (S1) employs a chemical coating method to prepare silver-coated tungsten carbide composite powder, thereby fundamentally solving the problem of uniform distribution of the silver and tungsten carbide phases. By in-situ reducing the silver coating layer on the surface of tungsten carbide particles to form a uniform bond between the two phases at the nanoscale or microscale, the density segregation problem that traditional mechanical mixing cannot solve is completely avoided, resulting in a uniform initial microstructure for the material. However, simply achieving uniform mixing of silver and WC is insufficient to address the new challenges brought about by the introduction of carbon fibers. Therefore, in step S2, the previously obtained, homogenized Ag@WC composite powder is used as the "basic unit" and then ball-milled with carbon fibers. This step-by-step processing strategy has significant advantages: First, as a more fluid integral unit, Ag@WC composite powder, when mixed with fibrous carbon, can more effectively reduce component separation compared to mixing individual silver powder, WC powder, and carbon fiber. Second, through a precisely controlled ball milling process, not only can the uniform dispersion of carbon fibers be achieved, preventing their agglomeration, but mechanical force can also be used to moderately break the fibers and allow them to interweave between the composite powders, laying the foundation for the subsequent formation of an ideal three-dimensional spatial distribution.

[0023] After completing the fine preparation and uniform mixing of the powder, the method does not stop at conventional molding and sintering. Even with a uniform component distribution, traditional pressureless sintering struggles to completely eliminate porosity, especially when reinforcing materials like carbon fibers are present, which can impede diffusion paths. This often results in materials failing to achieve extremely high density. This is precisely where the value of warm pressing in step (S3) lies. Warm pressing applies intense plastic deformation to the sintered blank at a specific temperature, achieving near-complete densification, significantly reducing or even eliminating internal porosity, thereby greatly improving the material's conductivity and overall strength after sintering. More importantly, this process enables carbon fibers, which may be randomly distributed after ball milling, to exhibit a significant directional alignment effect, thus optimizing the anisotropy of mechanical properties and electrical and thermal conductivity in the pressure direction. This is crucial for contact surfaces that require resistance to current and mechanical stress in specific directions.

[0024] Therefore, in summary, this method ensures the uniform distribution of WC through chemical coating, providing a stable foundation for the introduction of carbon fibers; the specific ball milling process ensures the effective dispersion and bonding of carbon fibers; and the final hot pressing and sintering processes actively regulate the orientation of carbon fibers while achieving extremely high density, maximizing their reinforcing effect. These four steps are interconnected, mutually supportive, and work together to successfully realize the innovative concept of "carbon fibers as a reinforcing phase and solid lubricant," resulting in a significant and synergistic improvement in overall performance compared to materials prepared by traditional methods.

[0025] Preferably, in step S1, the chemical coating method is as follows: tungsten carbide powder is dispersed in silver nitrate solution, a reducing agent is added, and the mixture is reacted at 40-70°C to reduce the silver and coat it onto the surface of the tungsten carbide particles.

[0026] Preferably, in step S2, the ball milling is a wet ball milling process, the milling time is 2-10 hours, and the ball-to-material ratio is 2:1 to 5:1.

[0027] Preferably, in step S3, the temperature for warm pressing is 100-300℃ and the pressure is 250-400MPa.

[0028] Preferably, in step S4, sintering is carried out under a protective atmosphere, the sintering temperature is 800-950℃, and the holding time is 1-4 hours.

[0029] Therefore, this application has the following beneficial effects: First, by replacing traditional graphite with carbon fiber, the material maintains excellent resistance to welding while significantly improving its mechanical strength and resistance to arc erosion, effectively overcoming the contradiction of difficulty in balancing lubrication and reinforcement in traditional materials. Secondly, by adopting a strategy that combines chemical coating with a specific ball milling process, the problem of uniform distribution caused by large differences in density and morphology of multiphase components is fundamentally solved, laying a microscopic foundation for the stability of material properties. Furthermore, the innovative hot-pressing process not only greatly improves the density of the material and reduces the porosity, but also causes the carbon fibers to align in a specific direction, thereby achieving better mechanical and electrical properties in a specific direction. Ultimately, the synergistic effect of these process steps leads to significant improvements in the electrical life, contact reliability, and overall service performance of the prepared contact materials. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0031] Example 1 This embodiment provides a silver-tungsten carbide-carbon contact material and its preparation method.

[0032] Raw material preparation: silver nitrate (AgNO3, analytical grade), micron-sized tungsten carbide powder (WC, Fisher average particle size 2.0μm), short-cut carbon fibers (length about 150μm, diameter about 8μm), and hydrazine hydrate (N2H4·H2O, 85% aqueous solution) as reducing agents.

[0033] Preparation steps: Chemical coating (S1): 16.6 g of micron-sized tungsten carbide powder was dispersed in 2 L of deionized water, and an aqueous solution containing 170 g of silver nitrate was slowly added under vigorous stirring. Subsequently, excess hydrazine hydrate was slowly added dropwise in a 50 °C water bath, and the reaction was carried out for 2 hours. After the reaction was completed, the powder was filtered, washed, and dried to obtain silver-coated tungsten carbide (Ag@WC) composite powder. Ball milling (S2): The above Ag@WC composite powder was mixed with 2.5g of carbon fiber by wet ball milling. The milling medium was anhydrous ethanol, the ball-to-powder ratio was 3:1, the rotation speed was 150 rpm, and the milling time was 4 hours. The mixture was dried after ball milling to obtain the final product. Forming and sintering (S3): The mixture is hot-pressed into a green body at 200°C and 300MPa pressure; Hot extrusion (S4): The green compact is sintered in a hydrogen atmosphere at a temperature of 850°C for 2 hours to obtain the final dense contact material.

[0034] Example 2 This embodiment provides a silver-tungsten carbide-carbon contact material and its preparation method. The main difference between this embodiment and Embodiment 1 is the component content and hot extrusion temperature.

[0035] Raw material preparation: Add submicron-sized tungsten carbide powder (WC, average particle size 0.3μm) and cobalt nitrate (Co(NO3)2·6H2O).

[0036] Preparation steps: 20 g of micron-sized WC (2.0 μm) and 8.8 g of submicron-sized WC (0.3 μm) were dispersed in 2 L of deionized water. An aqueous solution containing 170 g of silver nitrate was slowly added under vigorous stirring. Subsequently, excess hydrazine hydrate was slowly added dropwise in a 70 °C water bath, and the reaction was allowed to proceed for 2 hours. After the reaction was complete, the mixture was filtered, washed, and dried to obtain silver-coated tungsten carbide (Ag@WC) composite powder. Ball milling (S2): The above composite powder was ball-milled together with 4.32g of carbon fiber and a cobalt nitrate aqueous solution (cobalt mass was 2.88g based on Co). The ball milling parameters were the same as in Example 1. After drying, the cobalt salt was reduced to metallic Co at 300°C under a hydrogen atmosphere. Forming and sintering (S3): The mixture is hot-pressed into a green body at 250°C and 350MPa pressure; Hot extrusion (S4): The green compact is sintered in a hydrogen atmosphere at a temperature of 880°C for 2 hours to obtain the final dense contact material.

[0037] Example 3 This embodiment provides a silver-tungsten carbide-carbon contact material and its preparation method. This embodiment aims to illustrate a feasible solution with lower silver content and higher carbon fiber content.

[0038] Raw material preparation: Same as in Example 2, but without adding cobalt salt.

[0039] Preparation steps: Chemical coating (S1): 30 g of micron-sized WC (3.0 μm) and 11.7 g of submicron-sized WC (0.8 μm) were dispersed in 2 L of deionized water. An aqueous solution containing 170 g of silver nitrate was slowly added under vigorous stirring. Subsequently, excess hydrazine hydrate was slowly added dropwise in a 50 °C water bath, and the reaction was carried out for 2 hours. After the reaction was complete, the mixture was filtered, washed, and dried to obtain silver-coated tungsten carbide (Ag@WC) composite powder. Ball milling and mixing (S2): Take the above composite powder and ball mill it together with 8.5g of carbon fiber. The ball milling parameters are the same as in Example 1; Forming and sintering (S3): The mixture is hot-pressed into a green body at 100°C and 400MPa pressure; Hot extrusion (S4): The green compact is sintered in a hydrogen atmosphere at a temperature of 900°C for 1.5 hours to obtain the final dense contact material.

[0040] Example 4 This embodiment provides a silver-tungsten carbide-carbon contact material and its preparation method. This embodiment demonstrates a combination of high silver content and low carbon fiber content, with the addition of rare earth oxides.

[0041] Raw material preparation: Yttrium oxide (Y2O3, nanoparticles, particle size ~50nm).

[0042] Preparation steps: Chemical coating (S1): 18.3 g of micron-sized tungsten carbide powder was dispersed in 2 L of deionized water, and an aqueous solution containing 170 g of silver nitrate was slowly added under vigorous stirring. Subsequently, excess hydrazine hydrate was slowly added dropwise in a 70 °C water bath, and the reaction was carried out for 2 hours. After the reaction was completed, the powder was filtered, washed, and dried to obtain silver-coated tungsten carbide (Ag@WC) composite powder. Ball milling (S2): The above composite powder was ball-milled together with 0.63g of carbon fiber and 0.13g of yttrium oxide nanoparticles. The ball milling parameters were the same as in Example 1. After drying, the cobalt salt was reduced to metallic Co at 300°C in a hydrogen atmosphere. Forming and sintering (S3): The mixture is hot-pressed into a green body at 300°C and 250MPa pressure; Hot extrusion (S4): The green compact is sintered in a hydrogen atmosphere at a temperature of 820°C for 3 hours to obtain the final dense contact material.

[0043] Example 5 This embodiment provides a silver-tungsten carbide-carbon contact material and its preparation method. This embodiment shows the lower limit of tungsten carbide content and uses nickel as an additive.

[0044] Raw material preparation: Nickel nitrate (Ni(NO3)2·6H2O).

[0045] Preparation steps: Chemical coating (S1): 12 g of micron-sized WC (1.0 μm) and 4.2 g of submicron-sized WC (0.2 μm) were dispersed in 2 L of deionized water. An aqueous solution containing 170 g of silver nitrate was slowly added under vigorous stirring. Subsequently, excess hydrazine hydrate was slowly added dropwise in a 40 °C water bath, and the reaction was carried out for 3 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain silver-coated tungsten carbide (Ag@WC) composite powder. Ball milling (S2): The above composite powder was ball-milled together with 6.75g of carbon fiber and a cobalt nitrate aqueous solution (4.05g of cobalt based on Co). The ball milling parameters were the same as in Example 1. After drying, the cobalt salt was reduced to metallic Co at 300°C under a hydrogen atmosphere. Forming and sintering (S3): The mixture is hot-pressed into a green body at 300°C and 280MPa pressure; Hot extrusion (S4): The green compact is sintered in a hydrogen atmosphere at a temperature of 800°C for 4 hours to obtain the final dense contact material.

[0046] Example 6 This embodiment provides a silver-tungsten carbide-carbon contact material and its preparation method. This embodiment uses cobalt and rare earth oxide additives in combination.

[0047] Raw material preparation: Same as in Examples 2 and 4.

[0048] Preparation steps: Chemical coating (S1): 20 g of micron-sized WC (3.0 μm) and 10.24 g of submicron-sized WC (0.1 μm) were dispersed in 2 L of deionized water. An aqueous solution containing 170 g of silver nitrate was slowly added under vigorous stirring. Subsequently, excess hydrazine hydrate was slowly added dropwise in a 50 °C water bath, and the reaction was carried out for 2 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain silver-coated tungsten carbide (Ag@WC) composite powder. Ball milling (S2): The above composite powder was ball-milled together with 2.16g of carbon fiber, 2.16g of yttrium oxide nanoparticles, and a cobalt nitrate aqueous solution (cobalt mass calculated as Co = 1.44g). The ball milling parameters were the same as in Example 1. After drying, the cobalt salt was reduced to metallic Co at 300°C under a hydrogen atmosphere. Forming and sintering (S3): The mixture is hot-pressed into a green body at 250°C and 380MPa pressure; Hot extrusion (S4): The green compact is sintered in a hydrogen atmosphere at a temperature of 920°C for 1 hour to obtain the final dense contact material.

[0049] Comparative Example 1 A comparative example is provided to show the effectiveness of the present invention.

[0050] Weigh out 77.5g of silver powder (particle size ~5μm), 20g of tungsten carbide powder (2.0μm), and 2.5g of graphite powder (particle size ~5μm). Dry mix the three powders mechanically for 2 hours. Then, press and sinter under the same conditions (850℃, 2 hours). The sintered blank is not subjected to hot extrusion.

[0051] Effect verification The materials obtained in Examples 1-6 and Comparative Example 1 were subjected to performance tests, and the results are shown in Table 1 below.

[0052] Table 1

[0053] As can be seen from Table 1 above, the materials prepared by the method of the present invention are significantly superior to the comparative examples of traditional mechanical mixing processes in terms of density, hardness and conductivity. Moreover, each embodiment can achieve excellent comprehensive performance under different parameters, which proves the broad scope of support of the claims of the present invention and the reproducibility of the technical effects.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A silver-tungsten carbide-carbon contact material, characterized in that, It is composed of a silver matrix, tungsten carbide particles uniformly dispersed in the silver matrix, and carbon fibers as a reinforcing phase and solid lubricant; wherein the carbon fibers are randomly or oriented in the silver matrix.

2. The silver-tungsten carbide-carbon contact material according to claim 1, characterized in that, By weight percentage, it contains the following components: 70-85% silver, 12-27% tungsten carbide, and 0.5-5.5% carbon fiber.

3. The silver-tungsten carbide-carbon contact material according to claim 1 or 2, characterized in that, The carbon fibers have a length of 50-300 μm and a diameter of 5-15 μm.

4. The silver-tungsten carbide-carbon contact material according to claim 1, characterized in that, The tungsten carbide particles include micron-sized and submicron-sized tungsten carbide; wherein... The micron-sized tungsten carbide has a particle size of 1-3 μm, and the submicron-sized tungsten carbide has a particle size of 0.1-1 μm.

5. The silver-tungsten carbide-carbon contact material according to claim 1, characterized in that, The material also includes additives, which are at least one of cobalt, nickel or rare earth oxides, and the total mass fraction of the additives is 0.1-3.0%.

6. A method for preparing the silver-tungsten carbide-carbon contact material as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Silver-coated tungsten carbide composite powder was prepared by chemical coating method; S2. The composite powder and carbon fiber are ball-milled and mixed to obtain a mixture; S3. The mixture is subjected to warm pressing to obtain a green body; S4. The green blank is sintered to obtain a dense contact material.

7. The method according to claim 6, characterized in that, In step S1, the chemical coating method is as follows: tungsten carbide powder is dispersed in silver nitrate solution, a reducing agent is added, and the mixture is reacted at 40-70°C to reduce the silver and coat it on the surface of the tungsten carbide particles.

8. The method according to claim 6, characterized in that, In step S2, the ball milling is a wet ball milling process, with a milling time of 2-10 hours and a ball-to-material ratio of 2:1 to 5:

1.

9. The method according to claim 6, characterized in that, In step S3, the temperature for warm pressing is 100-300℃ and the pressure is 250-400MPa.

10. The method according to claim 6, characterized in that, In step S4, sintering is carried out under a protective atmosphere at a temperature of 800-950℃ and a holding time of 1-4 hours.

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