A silver-nickel electrical contact and a method of making the same

Abstract

The application relates to a silver-nickel electric contact, and relates to the technical field of electric contact materials, which is made of the following raw material components: silver-nickel composite powder, nano tungsten powder, high-activity carbon source, tin-germanium pre-alloy powder and nano yttrium oxide. The tin-germanium pre-alloy powder, the nano tungsten powder and the high-activity carbon source are introduced to form a metastable (W, Sn, Ge) Cx ternary carbide transient intermediate phase, which is then decomposed and in-situ nano tungsten carbide reinforcing phases are formed; meanwhile, the separated tin-germanium liquid phase migrates to the surface to form a composite passivation film, so that the electrical stability, the arc ablation resistance and the corrosion resistance of the electric contact material are enhanced. The nano yttrium oxide is reduced to high-activity yttrium atomic oxygen impurity capturing clean interfaces in the sintering process, effectively pins the grain boundary, cooperates with the tungsten carbide reinforcing phase and the composite passivation film to guarantee the structural stability.

Description

Technical Field

[0001] This application relates to the field of electrical contact materials technology, and in particular to a silver-nickel electrical contact and its preparation method. Background Technology

[0002] Silver-nickel electrical contacts, as core components in low-voltage electrical appliances, play a crucial role in connecting and disconnecting current in devices such as contactors, relays, and air switches. Their performance directly determines the electrical stability, weld resistance, and service life of electrical equipment. However, as industrial equipment develops towards higher frequencies and larger currents, traditional silver-nickel electrical contacts are prone to problems such as material volatilization, increased contact resistance, and decreased corrosion resistance under long-term arc impact. Especially in harsh environments with sulfur content and high humidity, the formation of silver sulfide or nickel oxide films further exacerbates poor contact, leading to a surge in equipment failure rates.

[0003] In existing technologies, improvements to silver-nickel electrical contacts mainly focus on composition optimization and process innovation. Some studies improve the electrical stability of contacts by adding copper and graphite, utilizing the burn-resistance of copper and the lubricity of graphite. Other technologies employ nanocomposite coatings or multilayer structures to deposit a nickel-gold composite layer on the silver surface to enhance wear resistance and oxidation resistance. Furthermore, powder metallurgy, as the mainstream preparation process, can achieve a uniform distribution of the silver-nickel phase by controlling sintering temperature and pressure parameters. However, this method requires high purity of raw materials and precision of equipment, and it is difficult to completely eliminate internal porosity and inclusions. Although the above solutions extend contact life in specific scenarios, they still suffer from drawbacks such as insufficient compositional uniformity and limited resistance to sulfidation, making it difficult to simultaneously meet the dual requirements of high electrical stability and excellent corrosion resistance.

[0004] Therefore, developing a silver-nickel electrical contact that combines high electrical stability with excellent corrosion resistance is of great practical significance. Summary of the Invention

[0005] This application provides a silver-nickel electrical contact and its preparation method, which has the characteristics of high electrical stability and excellent corrosion resistance.

[0006] Firstly, the silver-nickel electrical contact provided in this application adopts the following technical solution: A silver-nickel electrical contact is made from the following raw material components in weight percentage: 1.5-2.0% nano-tungsten powder, 0.3-0.5% highly active carbon source, 1.5-2.5% tin-germanium pre-alloy powder, 0.2-0.3% nano-yttrium oxide, and the remainder being silver-nickel composite powder.

[0007] By adopting the above technical solution, the silver-nickel composite powder serves as the matrix, providing the material with excellent electrical and thermal conductivity, as well as the necessary mechanical strength. Meanwhile, the nano-tungsten powder and the highly active carbon source act as reactants in the hard phase, ultimately generating a dispersed tungsten carbide reinforcing phase in situ within the silver-nickel matrix to resist arc erosion and material migration.

[0008] To control the size and distribution of the tungsten carbide reinforcing phase, tin-germanium pre-alloy powder was introduced. The tin-germanium alloy possesses a low eutectic melting point of nearly 200°C, melting early in the sintering process to form a highly fluid liquid phase. This liquid phase acts as a highly efficient liquid-phase sintering aid, drawing surrounding solid powder particles closer together through capillary forces and wetting their surfaces, promoting rapid densification and improving the material's processability. More importantly, compared to traditional solid-solid reactions, tungsten and carbon atoms achieve higher solubility and diffusion rates in the tin-germanium liquid phase. This alters the tungsten carbide formation pathway, moving away from slow solid-phase diffusion. Instead, in the liquid phase, tungsten and carbon interact with tin and germanium atoms, rapidly forming a metastable (W, Sn, Ge)Cx ternary carbide transient intermediate phase. During this process, tin and germanium directly participate in the chemical bonding of the compound, achieving deep atomic-level integration with tungsten and carbon.

[0009] Subsequently, as the temperature rises further, this metastable ternary carbide decomposes, separating the tin-germanium liquid phase while simultaneously precipitating fine-sized, well-crystallized tungsten carbide nuclei in situ. This "dissolution-nucleation-decomposition" catalytic process ensures that the final tungsten carbide-reinforced phase possesses superior dispersion and uniformity, and its pinning and strengthening effect on the matrix far surpasses that of externally added tungsten carbide. It is precisely the catalytic mediation of the tin-germanium alloy that elevates the synergy between tungsten and carbon from a simple chemical ratio to the control of the reaction pathway and the microstructure of the products.

[0010] Building upon this foundation, the added nano-yttrium oxide is reduced to highly chemically active metallic yttrium during the sintering process. On one hand, these active yttrium atoms rapidly capture trace amounts of oxygen atoms inevitably present on the surface of newly formed tungsten carbide particles and at the silver-nickel grain boundaries, generating thermodynamically stable yttrium oxide particles. This deoxygenation and purification process cleanses the interface between the reinforcing phase and the matrix, enabling a clean and robust metallurgical bond and preventing the risk of particle breakage or detachment during application due to weak interfacial bonding. On the other hand, these dispersed and stable nano-yttrium oxide particles themselves act as excellent pinning phases, pinning the tungsten carbide particle surface and matrix grain boundaries, effectively inhibiting grain growth and structural evolution under long-term high-temperature arc exposure. Therefore, the introduced yttrium oxide strengthens the bond between the tungsten-carbon reaction products and the matrix while ensuring the long-term stability of the material's microstructure, resulting in excellent electrical stability and arc erosion resistance in the silver-nickel electrical contacts.

[0011] Finally, during the sintering holding stage, the tin-germanium liquid phase spontaneously migrates to the material surface driven by the temperature gradient. After cooling, a functional layer rich in tin and germanium is formed on the contact surface. When this layer comes into contact with air, it generates a composite oxide passivation film composed of SnO2 and GeO2. This film is dense, stable, and possesses good semiconductor conductivity. It effectively prevents deep oxidation of nickel on the contact, thus ensuring long-term stability of contact resistance. At the same time, it exhibits stronger chemical inertness to corrosive gases such as sulfides and chlorides commonly found in industrial environments, providing the contact with better corrosion resistance.

[0012] Optionally, the highly active carbon source is one of amorphous carbon powder, carbon nanotubes, or graphene.

[0013] By employing the above technical solution, amorphous carbon powder, due to its high reactivity, can rapidly dissolve and diffuse in a tin-germanium liquid-phase catalytic bed, quickly combining with tungsten atoms to ensure the sufficiency and efficiency of the tungsten carbide formation process, thereby guaranteeing the dispersion of the reinforcing phase. In addition to participating in the reaction as a carbon source, carbon nanotubes or graphene, with their unique nanostructure, retain a stable hybrid carbon skeleton after the reaction. This skeleton can be intercalated into the matrix, further enhancing the material's toughness while its excellent conductivity directly contributes to the current conduction capacity of the contacts. Furthermore, it synergistically forms a more robust conductive reinforcement network with the in-situ generated tungsten carbide, improving the material's resistance to arc erosion.

[0014] Optionally, in the silver-nickel composite powder, the weight of nickel accounts for 9.5-10.5% of the total weight of the silver-nickel composite powder.

[0015] By adopting the above technical solution, the weight of nickel accounts for 9.5-10.5% of the total weight of the silver-nickel composite powder, ensuring that the silver-nickel matrix has good conductivity while achieving optimized mechanical strength and arc erosion resistance. A nickel content below this range may lead to insufficient matrix strength, while an excessively high content will form a continuous nickel network, reducing the material's conductivity and exacerbating oxidation and material migration under arc conditions.

[0016] Optionally, in the tin-germanium pre-alloy powder, germanium accounts for 5-15% of the total weight of the tin-germanium pre-alloy powder.

[0017] By adopting the above technical solution, the weight of germanium accounts for 5-15% of the total weight of tin-germanium pre-alloy powder, which ensures that the tin-germanium pre-alloy can form a catalytic liquid phase with suitable fluidity and controllable total amount. If the amount of germanium is too low, the amount of eutectic liquid phase will be insufficient, which will weaken the sintering and catalytic effects; if the amount is too high, the excessive liquid phase may destroy the structural stability.

[0018] Optionally, the average particle size of the nano-tungsten powder is 50-150 nanometers.

[0019] By adopting the above technical solution, the particle size range of 50-150 nanometers enables tungsten powder to have the best dissolution and diffusion rate in the tin-germanium liquid phase. If the particle size is too large, the dissolution will be slow and the reaction will be incomplete; if it is too small, it will easily agglomerate.

[0020] Optionally, the average particle size of the nano-yttrium oxide is 20-80 nanometers.

[0021] By adopting the above technical solution, yttrium oxide in this particle size range has a higher specific surface area and chemical activity, ensuring that it is fully reduced to highly active yttrium atoms during the sintering process of the preparation process, thereby efficiently capturing and fixing interfacial oxygen impurities and generating dispersed and stable nano-yttrium oxide.

[0022] Optionally, the average particle size of the tin-germanium pre-alloyed powder is 1-10 micrometers.

[0023] By adopting the above technical solution, this particle size range ensures that the pre-alloyed powder can achieve a highly uniform dispersion distribution in the silver-nickel matrix, laying the foundation for the subsequent formation of a continuous liquid-phase catalytic network. At the same time, powder of this size can quickly and uniformly reach its low eutectic melting point and melt into a liquid phase, avoiding both the agglomeration or premature oxidation that may occur with excessively fine powder and the localized liquid-phase enrichment and compositional segregation caused by excessively coarse powder.

[0024] Secondly, this application provides a method for preparing a silver-nickel electrical contact, comprising the following steps: S1. Mix silver-nickel composite powder, nano-tungsten powder, highly active carbon source, tin-germanium pre-alloy powder and nano-yttrium oxide to obtain a uniform mixed powder; S2. The S1 mixed powder is loaded into a discharge plasma sintering mold. Under vacuum or inert atmosphere protection, the mixed powder is pressurized and heated by discharge plasma sintering process to 800-950℃ and held for 5-15 minutes. The powder is then cooled to room temperature in the furnace to obtain the formed silver-nickel electrical contact.

[0025] By employing the aforementioned technical solution, the spark plasma sintering process, through the coupling effect of pulsed current and axial pressure, first promotes the rapid densification of the mixed powder, creating ideal conditions for subsequent in-situ reactions. During the sintering process at 800-950℃, the instantaneous high-temperature field and plasma activation environment provided during preparation efficiently trigger the melting of the tin-germanium pre-alloy powder, forming a catalytic liquid phase. This promotes the dissolution and diffusion of tungsten and carbon atoms within the liquid phase, thereby ensuring the formation of the metastable ternary carbide intermediate phase and the subsequent in-situ, uniform precipitation of the nano-tungsten carbide reinforcing phase. Simultaneously, it effectively activates nano-yttrium oxide, fully leveraging its interface purification and grain boundary pinning effects. Finally, the electric field and temperature gradient of this process also drive the surface migration of the tin-germanium liquid phase, achieving an improvement in the overall material performance.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. By introducing tin-germanium pre-alloy powder, its low melting point allows it to form a highly active liquid-phase catalytic environment in the early stages of sintering. This promotes the rapid dissolution and diffusion of nano-tungsten powder and highly active carbon sources, forming a metastable (W, Sn, Ge)Cx ternary carbide transient intermediate phase. Subsequently, this phase decomposes and precipitates in situ fine-sized, dispersed nano-scale tungsten carbide reinforcing phase. This mechanism not only ensures the uniformity of the hard phase, thereby improving the material's resistance to arc erosion, but more importantly, after completing its catalytic function, the tin-germanium liquid phase migrates to the surface, forming a SnO2 / GeO2 composite passivation film. This film plays a role in stabilizing contact resistance and providing resistance to environmental corrosion, achieving enhancement from bulk reinforcement to surface protection. 2. By introducing nano-yttrium oxide, which is reduced to highly active yttrium atoms during sintering, an interface regulation effect is achieved. These yttrium atoms can capture and fix oxygen impurities on the surface of tungsten carbide particles and at silver-nickel grain boundaries, generating stable nano-yttrium oxide particles. This purifies and strengthens the interfacial bonding between the reinforcing phase and the matrix, preventing the detachment of the reinforcing phase. On the other hand, these in-situ formed yttrium oxide particles can effectively pin grain boundaries, inhibiting grain growth under high-temperature electric arc conditions and ensuring the long-term stability of the structure. Detailed Implementation

[0027] Example 1 A silver-nickel electrical contact is made from the following raw material components by weight percentage: 1.5% nano-tungsten powder, 0.3% highly active carbon source, 1.5% tin-germanium pre-alloy powder, 0.2% nano-yttrium oxide, and the remainder being silver-nickel composite powder; Among them, the highly active carbon source is amorphous carbon powder; in the silver-nickel composite powder, nickel accounts for 10% of the total weight of the silver-nickel composite powder; in the tin-germanium pre-alloy powder, germanium accounts for 10% of the total weight of the tin-germanium pre-alloy powder; the average particle size of the tin-germanium pre-alloy powder is 1-10 micrometers; the average particle size of the nano-tungsten powder is 50-150 nanometers; and the average particle size of the nano-yttrium oxide is 20-80 nanometers.

[0028] A method for preparing a silver-nickel electrical contact includes the following steps: S1. Mix silver-nickel composite powder, nano-tungsten powder, highly active carbon source, tin-germanium pre-alloy powder and nano-yttrium oxide to obtain a uniform mixed powder; S2. The S1 mixed powder is loaded into a discharge plasma sintering mold. Under vacuum or inert atmosphere protection, the mixed powder is pressurized and heated by discharge plasma sintering process to 800-950℃ and held for 5-15 minutes. The powder is then cooled to room temperature in the furnace to obtain the formed silver-nickel electrical contact.

[0029] Example 2 A silver-nickel electrical contact differs from Example 1 in that it is made from the following raw material components by weight percentage: 1.8% nano-tungsten powder, 0.4% highly active carbon source, 2% tin-germanium pre-alloy powder, 0.25% nano-yttrium oxide, and the remainder being silver-nickel composite powder.

[0030] Example 3 A silver-nickel electrical contact differs from Example 1 in that it is made from the following raw material components by weight percentage: 2.0% nano-tungsten powder, 0.5% highly active carbon source, 2.5% tin-germanium pre-alloy powder, 0.3% nano-yttrium oxide, and the remainder being silver-nickel composite powder.

[0031] Comparative Example 1 A silver-nickel electrical contact differs from Example 1 in that the raw material components do not contain nano-tungsten powder.

[0032] Comparative Example 2 A silver-nickel electrical contact differs from Example 1 in that its raw material components do not contain a highly active carbon source.

[0033] Comparative Example 3 A silver-nickel electrical contact differs from Example 1 in that nano-tungsten powder and a highly active carbon source are replaced with an equal amount of tungsten carbide.

[0034] Comparative Example 4 A silver-nickel electrical contact differs from Example 1 in that the tin-germanium pre-alloy powder is replaced with an equal amount of tin powder.

[0035] Comparative Example 5 A silver-nickel electrical contact differs from Example 1 in that the tin-germanium pre-alloy powder is replaced with an equal amount of germanium powder.

[0036] Comparative Example 6 A silver-nickel electrical contact differs from Example 1 in that the raw material components do not contain nano-yttrium oxide.

[0037] Comparative Example 7 A silver-nickel electrical contact differs from Example 1 in that the weight of nickel in the silver-nickel composite powder accounts for 5% of the total weight of the silver-nickel composite powder.

[0038] Comparative Example 8 A silver-nickel electrical contact differs from Example 1 in that the weight of nickel in the silver-nickel composite powder accounts for 15% of the total weight of the silver-nickel composite powder.

[0039] Comparative Example 9 A silver-nickel electrical contact differs from Example 1 in that: in the tin-germanium pre-alloy powder, the weight of germanium accounts for 15% of the total weight of the tin-germanium pre-alloy powder.

[0040] Comparative Example 10 A silver-nickel electrical contact differs from Example 1 in that the average particle size of the tin-germanium pre-alloyed powder is 10-20 micrometers.

[0041] Detection example The electrical stability and corrosion resistance of silver-nickel electrical contacts were tested according to GB / T 5588-2017 "Technical Conditions for Silver-Nickel and Silver-Iron Electrical Contacts". The specific test results are shown in Table 1.

[0042] Table 1

[0043] As shown in Table 1 of the performance test data for Examples 1-3 and Comparative Examples 1-5, the introduction of tin-germanium pre-alloy powder, with its low melting point, creates a highly active liquid-phase catalytic environment in the early stages of sintering. This promotes the rapid dissolution and diffusion of nano-tungsten powder and highly active carbon source, forming a metastable (W, Sn, Ge)Cx ternary carbide transient intermediate phase. This phase then decomposes and precipitates in situ fine-sized, dispersed nano-scale tungsten carbide reinforcing phase. This mechanism not only ensures the uniformity of the hard phase, thereby improving the material's resistance to arc erosion, but more importantly, after completing its catalytic function, the tin-germanium liquid phase migrates to the surface, forming a SnO2 / GeO2 composite passivation film. This film plays a role in stabilizing contact resistance and providing resistance to environmental corrosion, achieving enhancement from bulk reinforcement to surface protection.

[0044] As shown in Table 1 of Examples 1-3 and Comparative Example 6, the introduction of nano-yttrium oxide, which is reduced to highly active yttrium atoms during sintering, plays a role in interface regulation. These yttrium atoms can capture and fix oxygen impurities on the surface of tungsten carbide particles and at the silver-nickel grain boundaries, generating stable nano-yttrium oxide particles. This purifies and strengthens the interfacial bonding between the reinforcing phase and the matrix, preventing the detachment of the reinforcing phase. On the other hand, these in-situ formed yttrium oxide particles can effectively pin grain boundaries, inhibiting grain growth under high-temperature electric arc, and ensuring the long-term stability of the structure.

[0045] As shown in Table 1 of the performance test data for Examples 1-3 and Comparative Examples 7-8, the nickel content ensures that the silver-nickel matrix achieves optimized mechanical strength and arc erosion resistance while maintaining good electrical conductivity. A nickel content below this range may result in insufficient matrix strength, while an excessively high content will form a continuous nickel network, reducing the material's conductivity and exacerbating oxidation and material migration under arc conditions.

[0046] As shown in Table 1 of the performance test data for Examples 1-3 and Comparative Examples 9-10, the weight of germanium as a percentage of the total weight of the tin-germanium pre-alloy powder ensures that the tin-germanium pre-alloy can form a catalytic liquid phase with suitable fluidity and controllable total amount. If the weight is too high, the excess liquid phase may damage the structural stability. Tin-germanium pre-alloy powder Excessively coarse particle size can lead to localized liquid phase enrichment and component segregation in the material.

[0047] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A silver-nickel electrical contact, characterized in that, It is made from the following raw material components by weight percentage: 1.5-2.0% nano tungsten powder, 0.3-0.5% highly active carbon source, 1.5-2.5% tin-germanium pre-alloy powder, 0.2-0.3% nano yttrium oxide, and the remainder is silver-nickel composite powder.

2. The silver-nickel electrical contact according to claim 1, characterized in that, The highly active carbon source is one of amorphous carbon powder, carbon nanotubes, or graphene.

3. A silver-nickel electrical contact according to claim 1, characterized in that, In the silver-nickel composite powder, nickel accounts for 9.5-10.5% of the total weight of the silver-nickel composite powder.

4. A silver-nickel electrical contact according to claim 1, characterized in that, In the tin-germanium pre-alloy powder, germanium accounts for 5-15% of the total weight of the tin-germanium pre-alloy powder.

5. A silver-nickel electrical contact according to claim 1, characterized in that, The average particle size of the nano-tungsten powder is 50-150 nanometers.

6. A silver-nickel electrical contact according to claim 1, characterized in that, The average particle size of the nano-yttrium oxide is 20-80 nanometers.

7. A silver-nickel electrical contact according to claim 1, characterized in that, The average particle size of the tin-germanium pre-alloyed powder is 1-10 micrometers.

8. A method for preparing a silver-nickel electrical contact according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix silver-nickel composite powder, nano-tungsten powder, highly active carbon source, tin-germanium pre-alloy powder and nano-yttrium oxide to obtain a uniform mixed powder; S2. The S1 mixed powder is loaded into a discharge plasma sintering mold. Under vacuum or inert atmosphere protection, the mixed powder is pressurized and heated by discharge plasma sintering process to 800-950℃ and held for 5-15 minutes. The powder is then cooled to room temperature in the furnace to obtain the formed silver-nickel electrical contact.

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