Electrical Contact Materials Research Articles

Current-carrying tribological behavior of textured Au/MoS2 coatings in vacuum

Sliding electrical contact has been widely used in spacecraft such as slip ring for solar windsurfing, and its service life directly affects that of the spacecraft. Au as a sliding electrical contact material has been widely used in aerospace equipment, but poor lubricity limits its service life. To address this issue, this study introduces MoS2 into the texturing holes of the Au coating, which can improve the lubricity, and maintain the continuity of Au and thus its conductivity. Additionally, the effect of texture density on the vacuum current-carrying tribological properties of the textured Au/MoS2 coating was investigated. The results indicate that texture not only reduces the mechanical properties of the coating but also affects the amount of MoS2 that can be filled. A high texture density greatly reduced the carrying capacity, leading to serious abrasive wear. However, low texture density results in serious adhesive wear owing to insufficient lubricity. Under an appropriate texture density, excellent vacuum current-carrying tribological behaviour can be achieved depending on the formation of a transfer film of MoS2 and Au, which maintains conductivity through Au and provides lubricity through MoS2. This study is of great significance in prolonging the service life of sliding electrical contacts and provides a new idea for the design of sliding electrical contact materials.

Simulation Calculation and Experimental Study on the Properties of Re-, In-, and Nb-Doped Ag/Ni Electrical Contact Materials

Simulation Calculation and Experimental Study on the Properties of Re-, In-, and Nb-Doped Ag/Ni Electrical Contact Materials

Influence of Ti2SnC content on arc erosion resistance in Ag–Ti2SnC composites

Abstract In this work, an Ag–Ti2SnC composite was fabricated by the hot-pressing sintering method, and the erosion behavior of Ag–Ti2SnC with volume percentages of 10–40% was studied at a load voltage of 10 kV. The arc life and breakdown current were observed at about 31–36 ms and 39 A, respectively. The cathode spot traveled the fastest on the surface of the Ag–40 vol% Ti2SnC composite. Due to emission center model, the temperature of the minor protrusions on the cathode surface increased, resulting in Ag ions, Ti ions, and Sn ions being generated. Combining with the ionized oxygen, Ag2O, AgO, TiO2, and SnO2 were formed on the eroded Ag–Ti2SnC surface after arc erosion. The research results will broaden the application range of Ag–Ti2SnC electrical contact material and enrich the arc erosion mechanism.

Study on extreme sulfuration behavior of brush-electroplated silver-graphene composite coatings as the electrical contact materials for the outdoor high-voltage isolating switch

The silver-graphene (Ag-G) composite coating was successfully prepared on the copper substrate via the method of cyanide-free brush plating. When the sulfuration temperature is increased from −70 °C to 45 °C, the sulfuration degree of the Ag-G composite coating fabricated in the composite solution with the optimal graphene content of 2 g L−1 gradually increase to a maximum. With increasing the sulfuration temperature to 90 °C, the sulfuration degree of the Ag-G composite coating has a small decrease in comparison with that of 45 °C. The Ag-G composite coating achieves excellent sulfuration, abrasion and corrosive resistance under extreme sulfuration temperatures, which is superior to pure Ag coating owing to the incorporation of graphene in the bulk. The sulfuration temperature and O2 content in the Na2S solution interactively determine the sulfuration resistance. The work provides novel high-performance Ag-based coating by employing a cyanide-free composite electrolyte for the possible practical application under different extreme environments.

Comprehensive Study on Carbon-Coated Silver for Improved Tribo-Electrical and Wetting Performance

The rise in electrification has considerably increased the demand for high-efficiency and durable electrical contact materials. Carbon nanoparticles (CNP) are a promising coating material due to their intrinsic transport properties (thus minimizing the impact on conductivity), their proven solid lubricity (potentially improving tribological performance), and their hydrophobic wetting behavior (potentially providing atmospheric protection). In this study, carbon nanotube and nanohorn coatings are produced via electrophoretic deposition on silver-plated surfaces, followed by tribo-electrical and wetting characterization. The proposed coatings do not negatively affect the conductivity of the substrate, showing resistance values on par with the uncoated reference. Tribo-electrical characterization revealed that the coatings reduce adhesive wear during fretting tests while maintaining stable and constant electrical contact resistance. Furthermore, CNP-coated surfaces show a hydrophobic wetting behavior toward water, with graphite and carbon nanotube (CNT) coatings approaching super-hydrophobicity. Prolonged exposure to water droplets during sessile drop tests caused a reduction in contact angle (CA) measurement; however, CNT coatings’ CA reduction after five minutes was only approximately 5°. Accordingly, CNP (specifically CNT) coatings show auspicious results for their application as wear and atmospheric protective barriers in electrical contacts.

Influence of nano-mechanical evolution of Ti 3AlC 2 ceramic on the arc erosion resistance of Ag-based composite electrical contact material

Influence of nano-mechanical evolution of Ti ₃AlC ₂ ceramic on the arc erosion resistance of Ag-based composite electrical contact material

Effect of TiB2 on properties and microstructures of Cu[sbnd]W electrical contact materials

The W skeletons were pressed by the cold isostatic pressing process, and CuW alloys with different TiB2 contents were prepared by the sintering and infiltration method. The effects of TiB2 addition on the microstructures, properties, vacuum breakdown performance, and arc motion characteristics of CuW alloys were investigated. The results show that the conductivity of CuW alloy decreases with the addition of TiB2, while the hardness increases. Compared with CuW alloy, this method improves the breakdown strength, reduces the chopping current and extends the arc life of CuW alloy. The anti-arc erosion performance of CuW alloy with the addition of TiB2 was enhanced. For CuW alloy containing TiB2, the electric breakdown occurs on the TiB2 phase at the edge of the W phase, the cathode spots are split, the arc is effectively scattered, and the ablation area after multiple breakdowns is larger, but the erosion pits are shallow and dispersed.

Microstructure and electrical contact properties of Al2O3-Cu/(Cr, Zr) composites

Al2O3-Cu/25Cr1Zr and Al2O3-Cu/25Cr3Zr electrical contact materials were fabricated by internal oxidation and fast hot press sintering. The prepared composites have uniform dense structure with over 98% density, 40.5 IACS% and 31.8 IACS% electrical conductivity, 141 HV and 154 HV hardness. TEM results show that internal oxidation during sintering generates diffusely distributed nanoparticles of γ-Al2O3, pinning dislocations and strengthening the matrix. In the 25 V DC, 10–40 A electrical contact tests, Al2O3-Cu/25Cr1Zr and Al2O3-Cu/25Cr3Zr composites show an increase in anode mass and a decrease in cathode mass, with the transfer direction of the material being from cathode to anode. Under the same experimental conditions, Al2O3-Cu/25Cr3Zr showed superior resistance to arc erosion. With the Zr content increased from 1 wt% to 3 wt%, the mass transfer of the electrical contact material decreased by 14.2%, 28.5%, 27.2%, and 8.2%, respectively, and the average arc duration was reduced from 0.4 ms to 0.24 ms, 4.35–2.46 ms, 4.91–3.53 ms, and 5.8–4.58 ms.

Study of ordered phase precipitation behaviour and hardening mechanism of Au-20Ag-10Cu alloy during deformation-aging treatment

With the rapid development of aerospace technology, the demand for a longer service life of Au-Ag-Cu alloy as conductive slip rings is increasing. Therefore, it is important to improve the hardness of the alloys in order to prolong their service life. Deformation-aging can improve the hardness of many alloys. The effect of the deformation-aging process of Au-20Ag-10Cu (wt%) alloy was investigated on the microstructure and properties, which characterized by DSC(Differential Scanning Calorimeter), XRD(X-ray Diffraction), EBSD(Electron Backscatter Diffraction), TEM(Transmission Electron Microscope) characterization techniques, microhardness and electrical conductivity testing methods. The results indicated that the microhardness increases and the conductivity decreases gradually with the increase of deformation rate. As the aging time increasing, the content of face-centered tetragonal AuCu I ordered phase increases, and thus the hardness increases gradually. The maximum hardness value of 307.44 HV was obtained after undergoing 70 % deformation and then aged at 300 ℃ for 16 h with the electrical conductivity values of 8.40 MS·m−1. This result indicated that both higher hardness and higher electrical conductivity of Au-20Ag-10Cu (wt%) alloy could be obtained, which ensures the requirements in the field of electrical contact materials.

Arc erosion behavior and mechanism of AgZrO2 electrical contact materials

In this study, the novel AgZrO2 electrical contact materials reinforced with different ZrO2 contents were successfully fabricated by powder metallurgy. The effect of ZrO2 content on arc erosion resistance of the AgZrO2 electrical contact materials was investigated, and the electrical conductivity and hardness were measured, as well as the arc erosion mechanism was discussed as well. Furthermore, the properties of AgZrO2 electrical contact material were also evaluated as compared to AgSnO2 electrical contact material. The results show that with increase of ZrO2 content, the hardness of AgZrO2 electrical contact materials gradually increases, while the electrical conductivity gradually decrease. The good comprehensive properties can be achieved at 8 wt%ZrO2. The electrical conductivity and hardness of Ag-8 wt%ZrO2 electrical contact material are 72.8%IACS and 77.9 HV, respectively. The AgZrO2 electrical contact materials with less than 8 wt% exhibit lower arc energy and shorter arc duration, as well as outstanding arc erosion resistance. However, an excess ZrO2 content causes obvious fluctuations on arc energy and duration, thereby resulting in more severe arc erosion. As compared to the Ag-8 wt%SnO2 electrical contact material, the Ag-8 wt%ZrO2 electrical contact material presents lower stable contact resistance, less arc energy, shorter arc duration and better interfacial bonding, thus exhibiting excellent resistance to arc erosion.

Erosion characteristics of WCu/Ti3SiC2 electrical contact materials by arc discharge in various ambient atmospheres

Arc erosion performances of electrical contacts are vital to guarantee the stable operation of electric power systems. In this work, arc erosion performances of WCu/Ti3SiC2 materials in SF6, CO2, O2, and Ar were systematically researched. Detachment of silicon layers from Ti3SiC2 occur in the 4 atm, Ti3SiC2 plays an important role in protecting the composites. Severe splashings and cavities are found on the eroded surfaces in CO2 and O2. Based on the arc energy densities and composition changes, arc erosion mechanisms of WCu/Ti3SiC2 in various atmospheres are proposed.

The Corrosion Behavior of Different Silver Plating Layers as Electrical Contact Materials in Sulfur-Containing Environments

Isolation switching devices are vital components in power grids. During their operational lifespan, these devices are prone to corrosion failure in atmospheric environments. To enhance conductivity and corrosion resistance, silver plating is applied to the contact surface of high-voltage switches. Common methods include graphite-Ag (G-Ag) coating, graphene-Ag (Gr-Ag) coating, and Ag-Sn coating. In this article, the corrosion resistance performance of silver plating, G-Ag coating, Gr-Ag coating, and Ag-Sn coating was studied. Firstly, adhesion tests were conducted on the plating layers. Subsequently, immersion experiments were performed to evaluate the corrosion resistance of the samples. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and laser confocal microscopy were used to analyze the morphology and elemental composition of the samples. Raman spectroscopy was used to analyze corrosion products. An electrochemical workstation was employed to study the electrochemical behavior of the samples. The adhesion results indicate that the adhesion of the plating layers is excellent. The immersion and electrochemical results showed the corrosion resistance order of the four Ag coatings was Ag-Sn coating > Gr-Ag coating > Ag coating > G-Ag coating.

Insights into nano-mechanical degradation behavior of Ag/Ti2AlC composite under different arc erosion stages

Serious arc erosion is the main reason for premature failure of the Ag-matrix composite electrical contact materials in actual service. Clarifying the structure and property degradation process is crucial for creating eco-friendly Ag/MAX electrical contacts and upgrading high-performance materials for low-voltage switch applications. In this study, the representative Ag/Ti2AlC electrical contacts were designed into three arc erosion stages (from 1 to 5610 cycles) by ex-situ arc discharging experiment, and the nanoindentation technique was then applied to in-depth analyze the evolution behavior of nano-mechanical properties by comparing nano hardness, modulus, creep, continuous stiffness, elastic/plastic deformation, and NanoBlitz 3D Mapping indentation results in different erosion stages. Finally, the inherent relationship among the structural dissociation of Ti2AlC, and compositional changes of Ag/Ti2AlC interface and nano-mechanical properties of composite was revealed, and the material degradation model and anti-arc erosion mechanism were proposed. This work further elucidates the intrinsic source of excellent arc erosion resistance and degradation process of Ag/Ti2AlC composite from the nano-mechanical perspective and lays a theoretical foundation for the future design and optimization of this material system.

Impact of alloying elements on generalized stacking fault energy and twinning of Ag-based alloys

The creep strength of Ag-based alloys can be remarkably enhanced through the formation of twin structures. In this study, the effects of alloying elements, including Sn, In, Zn, Cu, Zr, Ni, Ir, Cr, and W, on the formation enthalpy of point defects and the generalized stacking fault energy of Ag-based alloys were investigated using first-principles calculations. The formation enthalpy of point defects serves as a measure of the difficulty of alloying element doping in Ag-based alloys. Calculation results shows that the ability of alloying element doping to form point defects follows the order of Sn > In > Zn > Cu > Zr > Ni > Ir > Cr > W. The generalized stacking fault energy along the [112‾](111) slip direction in Ag-based alloys characterizes the competition between dislocation slip and twinning. As the formation enthalpy of point defects increases, the intrinsic stacking fault energy increases, leading to a decrease in twinning tendency. Once the formation enthalpy of point defects corresponding to the alloying element exceeds 1 eV, the intrinsic stacking fault energy and twinning tendency remain relatively unchanged. Comprehensive analysis shows that alloying elements Sn and In effectively reduce the intrinsic stacking fault energy and promote twinning, which aligns with the behavior observed in commonly used Ag–Sn–In electrical contact materials.

Enhanced mechanical and electrical performance of Ag-4wt%ZrB2 contact materials prepared with different-sized Ag powder

Ag-ZrB2 composite is a promising candidate used as electrical contact materials. So far, the effect of Ag particle size on the microstructure, properties and arc erosion behavior of Ag-based contact materials is unclear. In this work, the Ag-4 wt%ZrB2 contact materials were prepared with coarse and fine Ag powder utilizing wet mixing and spark plasma sintering. The microstructures and eroded morphologies of the Ag-4 wt%ZrB2 contact materials were characterized, the arc duration/energy, welding force and mass loss were investigated, and the effect of Ag particle size on arc erosion behavior was discussed as well. The results show that the fine Ag powder is beneficial for the uniform dispersion of the ZrB2 in the Ag matrix, and enhancement on the hardness and electrical conductivity. As compared to the Ag-4 wt%ZrB2 contact material prepared with the coarse Ag powder, the hardness and electrical conductivity of the Ag-4 wt%ZrB2 contact material prepared with the fine Ag powder are increased by 66.26% and 32.92%, respectively. Furthermore, the contact material prepared with fine Ag powder has a shorter break-arc duration and lower break-arc energy, as well as a smaller welding force and less mass loss, thereby exhibiting superior arc erosion and welding resistance.

Break-Arc Erosion and Material Transfer Behavior of Pt–Ir and Pt–Ir–Y Electrical Contact Materials under Different Currents

In order to explore the influence of rare earth element Y on the electrical contact properties of Pt–Ir alloys, Pt–10Ir–Y and Pt–25Ir–Y were prepared via arc melting combined with thermal processing, and electrical contact experiments were carried out with a DC voltage of 24 V and current ranging from 5 A to 25 A. Comparative analyses were conducted to analyze the changes in the break arc duration and arc energy, as well as the contact resistance before and after the addition of Y. The arc erosion surface morphology was characterized, and the transfer behavior of the alloys was discussed. The results show that at 5 A and 25 A, adding Y improves the stability of the arc duration of the Pt–Ir alloy, but it increases the overall arcing energy and decreases the stability. The contact resistance of the Pt–Ir alloy shows a clear partitioning phenomenon; the partitioning phenomenon disappears after the addition of Y, and the contact resistance fluctuates around the average value. The material transfer direction of the Pt–Ir alloy is affected by the current change, while the material transfer direction of the Pt–Ir–Y alloy is always from cathode to anode. The research results provide a reference for the performance optimization of Pt–Ir alloys.

Study on the electrical properties of Cu-based ECMs prepared by TiBN powder instead of W

In this work, TiBN and W were used as reinforced phases for Cu-based electrical contact materials. The microstructure, resistivity and arc corrosion resistance of Cu/TiBN and Cu/W alloys were investigated to understand the effect of TiBN and W doping on Cu/TiBN and Cu/W electrical contacts, respectively. Significant improvement in electrical conductivity, oxidation resistance and arc corrosion resistance of copper-based alloy was observed by TiBN reinforcement. Cu/TiBN composites showed good corrosion resistance to arc corrosion under atmospheric and salt spray conditions. The results showed the presence of large amount of TixOy, B2O3, N2 and other substances in Cu/TiBN system which are responsible for the improvement of arc corrosion resistance of Cu/TiBN system. The new Cu/TiBN electrical contact material showed great potential due to its excellent mechanical properties and arc corrosion resistance.

Properties of Ag-GNP silver-graphene composites and finite element analysis of electrical contact coupling field

By using powder metallurgy, new electrical contact materials of Ag-GNP with mass fractions of 0.2%–3% were created. The mechanical and electrical properties of the materials were studied, and the force-thermal-electric coupling fields of the electrical contact process were calculated using the finite element method. The findings demonstrate that GNP can greatly boost the material’s mechanical strength while also increasing its resistivity; nevertheless, concentration levels of less than 3 weight percent do not appreciably impair the silver matrix’s electrical conductivity. The finite element simulation gives the stress field, current density distribution, and temperature field during contact. A comparison of the theoretically calculated contact radius and the simulation results show the same trend of variation. Both the stress field and temperature field are enhanced with increasing GNP content. The temperature rise of the contact may be unfavorable when the GNP content is greater than 1 wt.%.

In situ observation and understanding of the arc erosion behavior of electrical contact materials

Abstract Arc erosion studies are carried out on electrical contact materials in the switching current experiment. A test rig is developed to capture the 2-D image and the 3-D profile of eroded silver tin oxide electrical contact material in situ. Image processing algorithms are specially presented to accurately recognize the features of erosion region. The initial small patch of erosion traces gradually evolves into the deep crater with the increment of switching cycle enabling a study of the arc erosion behavior. 2-D image, 3-D profile, and micro surface morphologies of the eroded contacts are analyzed and then related to the extent of erosion. The results show that the evolution process of central erosion region could be divided into the enlargement in breadth of contact surface and the extension in depth of contact profile. The end result of arc erosion is the net loss of contact material, which would lead to the substantial reduction of contact force and potential electrical contact instability.

Enhancement of Arc Erosion Resistance in AgCuO Electrical Contact Materials through Rare Earth Element Doping: First-Principles and Experimental Studies.

To investigate the stability and electrical and physical properties of undoped CuO and CuO doped with rare earth elements, electronic structures and elastic constants were calculated using first-principles density functional theory. Additionally, experimental verification was carried out on AgCuO and AgCuO-X (La, Ce, Y) electrical contacts, which were prepared using sol-gel and powder metallurgy methods. The contacts were tested under an 18 V/15 A DC resistive load using the JF04D contact material testing system. Arc parameters were analyzed, and three-dimensional surface profilometry and scanning electron microscopy were used to study the altered erosion morphology of the electrically contacted materials; moreover, the potential mechanisms behind their arc erosion behavior were investigated in depth. The results demonstrate that the doping of rare earth elements can improve the electrical conductivity and physical properties of the contacts, optimize the arc parameters, and enhance their resistance to arc erosion. Notably, AgCuO-Ce exhibited the highest electrical conductivity and the least amount of material transfer; moreover, it had excellent arc time and energy parameters, resulting in the best resistance to arc erosion. This study provides a theoretical basis for the screening of doping elements to enhance the performance of AgCuO contact materials and offers new ideas and scientific references for this field.