Method for evaluating performance of arc ablated copper-tungsten contact material

Abstract

The invention discloses an arc ablation copper-tungsten contact material performance evaluation method, and belongs to the field of high-voltage switch equipment material testing. The method comprises the following steps: carrying out an ablation test on a material through a high-power pulse discharge system, and measuring a melting threshold value; mass loss before and after ablation is measured, and the ablation rate is calculated; a white light interferometer is used for collecting the three-dimensional shape of an ablation area, and the average melting depth is calculated; counting the maximum crack width of the surface by using a scanning electron microscope, and obtaining the maximum depth of the crack by observing the cross section; analyzing a microstructure by using back scattering electron diffraction, and counting a large-angle grain boundary proportion; and finally, selecting the six parameters as key indexes, and calculating a comprehensive performance score in combination with weight distribution. According to the method, a multi-dimensional evaluation system covering macroscopic thermal damage, surface topography characteristics and a microstructure is constructed, the limitation of single index evaluation is overcome, and accurate quantitative evaluation of arc ablation resistance and crack resistance of the copper-tungsten contact material is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of high-voltage switchgear material performance testing, specifically relating to a method for evaluating the performance of arc-eroded copper-tungsten contact materials. Background Technology

[0002] High-voltage switchgear, as the core unit of power system control and protection, directly affects the safety and stability of the power grid. During the opening and closing process of switchgear, the contact system must withstand the severe ablation and impact of high-energy electric arcs; therefore, the performance of the contact material is crucial. Copper-tungsten (Cu-W) composite materials, due to their excellent electrical and thermal conductivity, arc erosion resistance, and resistance to welding, have become the preferred contact material for high-voltage circuit breakers, load switches, and other equipment. In actual service environments, especially in SF6 gas insulation media, the contact surface experiences extreme transient high temperatures, particle bombardment, and complex chemical reactions, leading to mass losses such as melting, splashing, and evaporation of the material surface, accompanied by the initiation and propagation of microcracks caused by thermal stress. These cumulative damages can lead to increased contact resistance and decreased withstand voltage, potentially resulting in insulation breakdown or breaking failure. Therefore, establishing a scientific and accurate evaluation system for the ablation resistance performance of contact materials is of significant engineering importance for material selection, optimized design, and ensuring the safe operation of power equipment throughout its entire life cycle.

[0003] Current arc ablation performance evaluation techniques primarily focus on constructing experimental platforms to simulate real arc environments and rely on macroscopic physical quantities for characterization. For example, existing technologies (such as CN 117517563 A) disclose an arc ablation platform for copper-tungsten contact materials in high-voltage circuit breakers. By constructing charging, triggering, and observation modules, it can recreate the working environment of circuit breaker contacts in a laboratory setting, and use a precision balance to measure ablation mass loss and observe surface morphology using an electron microscope. Other technologies (such as CN 112986811 A) focus on the pressure-bearing limit of the tap changer top cover of converter transformers, testing the mechanical strength of the structure by simulating internal fault arcs. However, traditional material evaluation methods have significant limitations: First, the evaluation indicators are too singular and focus on macroscopic aspects, typically using only the "ablation rate" (mass or volume loss) as the main criterion. While the ablation rate reflects the overall wear resistance of the material, it cannot reveal the microscopic damage mechanism within the material. Studies have shown that materials with similar ablation rates can exhibit vastly different resistance to thermal shock crack propagation, with crack depth and density being the key factors leading to structural disintegration of the contact. Secondly, existing surface morphology observations are mostly qualitative descriptions, lacking systematic quantitative statistics on crack width, depth, and distribution density, and failing to establish a correlation between crack characteristics and the material's microstructure (such as grain orientation and grain boundary characteristics). For example, conventional methods neglect the influence of grain boundary angles on crack propagation resistance, making it impossible to explain why materials with certain microstructures exhibit superior macroscopic ablation resistance. Furthermore, due to the lack of a multi-dimensional comprehensive evaluation standard covering macroscopic losses, micromorphology, and internal structure, laboratory test results often deviate from actual long-term service performance, making it difficult to accurately guide the research and improvement of high-performance contact materials.

[0004] In summary, current technologies lack a quantitative evaluation method that can deeply integrate macroscopic ablation patterns with microscopic structural evolution. Overcoming the limitations of traditional single-index evaluation, addressing the inability of existing methods to accurately quantify microscopic crack characteristics and their intrinsic relationship with material crystal structure, and establishing a comprehensive evaluation system encompassing multi-dimensional indicators such as thermal damage threshold, macroscopic loss, microscopic crack morphology, and grain boundary characteristics to achieve a more accurate and scientific graded assessment of the ablation resistance of contact materials are pressing technical challenges in the field of high-voltage switch contact material testing. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned shortcomings and provide a method for evaluating the performance of arc-ablated copper-tungsten contact materials.

[0006] Firstly, a method for evaluating the performance of arc-ablated copper-tungsten contact materials, employing the following technical solution: A method for evaluating the performance of arc-ablated copper-tungsten contact materials, the method comprising the following steps: Step (1): Use a high-power pulsed power discharge system to generate an arc plasma to ablate the copper-tungsten contact material sample and determine the melting threshold T of the material. Step (2): Measure the sample mass before and after ablation and calculate the ablation rate R; Step (3): Use a white light interferometer to scan the ablation area, obtain the three-dimensional morphology, and calculate the average melting depth. ; Step (4): Observe the ablated surface of the material using a scanning electron microscope and count the maximum crack width. ; Step (5): Cut the sample from the center of the ablation zone, observe the cross-section, and obtain the maximum crack depth. ; Step (6): Perform backscattered electron diffraction test on the ablation surface of the material to analyze the grain orientation difference and count the proportion of large-angle grain boundaries G. Step (7): Select the melting threshold T, ablation rate R, and average melting depth. Maximum crack width Maximum crack depth The proportion of large-angle grain boundaries, G, is used as a key evaluation indicator. Combined with the weight allocation of each indicator, the comprehensive performance score P of the material is calculated.

[0007] Further, in step (1), the ablation test is conducted in a cavity filled with SF6 gas. A high-power pulsed power discharge system is used to perform arc ablation on samples with a surface roughness Ra≤1μm. The arc duration t is set to 1ms, and the arc plasma heat flux is 0.5 GW / m. 2 ~4GW / m 2 Adjustable within a range; Obtaining the melting threshold T of the material includes the following process: conducting arc ablation tests on the same material with different energies, gradually increasing the heat flux by 0.1 GW / m each time. 2 ~0.3 GW / m 2 The presence of liquid phase flow patterns or remelted spheroids on the surface is observed using an optical microscope as a criterion for determining melting, and the heat flux value at which the material begins to melt is recorded as the melting threshold.

[0008] Furthermore, in step (2), a precision electronic balance with an accuracy of 0.1 mg is used to weigh the sample before and after ablation. , According to the formula: ; Calculate the ablation rate; where S is the ablation area of ​​the sample and n is the number of ablation cycles; the ablation rate R is the average of three repeated tests of the same material under the same conditions.

[0009] Furthermore, in step (3), the white light interferometer uses a grid pattern to scan and observe the melting area on the target surface, wherein the average melting depth... The formula is: ; Where L is the sampling length of the sample measurement area; Z is the absolute value of the distance between the measurement point and the center line; and n is the number of sampling points along the x-direction.

[0010] Furthermore, in step (4), the accelerating voltage observed by the scanning electron microscope is 15kV, and the magnification is 500~5000 times; the width of the maximum crack is found under low magnification as... ; In step (5), the sample is cut from the center of the ablation zone using wire electrical discharge machining, and the maximum crack depth is obtained by observing and measuring the cross-section. ; In step (6), backscattered electron diffraction tests are performed on the ablated surface, and the percentage of large-angle grain boundaries G is obtained by counting the number of grain boundaries with an orientation difference greater than 15° between adjacent grains.

[0011] Furthermore, in step (7), before calculating the comprehensive performance score P, the standardized values ​​of each index are obtained by normalization. : For positive indices T and G, the standardized values ​​are: ; For the inverse indicator R, , and Standardized values: ; in, These are the measured values ​​for a single set of indicators. and These are the maximum and minimum values ​​of this indicator measured for similar materials.

[0012] Furthermore, in step (7), the comprehensive performance score P: ; Among them, the weighting coefficient The allocation is as follows: melting threshold T, weight 40%~60%; ablation rate R, weight 10%~20%; average melting depth. Weight 10%~20%, maximum crack width Weight 5%~15%, maximum crack depth The weight is 5%~15%, the proportion of large-angle grain boundaries is 1%~10%, and the sum of all weights is 100%.

[0013] Secondly, a device for evaluating the performance of copper-tungsten contact materials eroded by electric arc adopts the following technical solution: An evaluation device for the performance of arc-ablated copper-tungsten contact materials includes: The ablation test module is used to control the discharge system to obtain the melting threshold T of the material; The mass measurement module is used to obtain the mass before and after ablation and to calculate the ablation rate R. The morphology detection module is used to acquire the three-dimensional morphology of the ablation region and calculate the average melting depth. ; The crack analysis module is used to obtain and analyze the maximum crack width. and maximum crack depth ; The microstructure analysis module is used to acquire grain orientation data and calculate the proportion G of large-angle grain boundaries. The comprehensive evaluation module receives the above indicators as input parameters, performs normalization and weighting operations as described above, and outputs a comprehensive performance score P.

[0014] Thirdly, an electronic device adopts the following technical solution: An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, performs the steps of the method described above.

[0015] Fourthly, a computer-readable storage medium adopts the following technical solution: A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the method described above.

[0016] The beneficial effects of this invention are: This invention provides a method for evaluating the performance of copper-tungsten contact materials subjected to arc ablation. By constructing a multi-dimensional evaluation system that includes macroscopic thermal damage threshold, surface micromorphological features, and internal microstructure, the method significantly improves the accuracy and scientific rigor of copper-tungsten contact material performance evaluation. First, by determining the melting threshold through stepwise heat flux tests and calculating the ablation rate in conjunction with mass loss, the tolerance limit and macroscopic material loss of materials under different thermal shock conditions can be intuitively quantified. Second, by using a white light interferometer to obtain the average melting depth and combining it with a scanning electron microscope to statistically analyze the maximum surface crack width and the maximum cross-sectional crack depth, a three-dimensional characterization from three-dimensional volume loss to two-dimensional crack propagation risk is achieved, effectively capturing structural damage details that cannot be reflected by mass changes alone. Furthermore, by analyzing grain orientation through backscattered electron diffraction technology and introducing the key microscopic indicator of large-angle grain boundary ratio, based on the physical mechanism that large-angle grain boundaries can effectively hinder crack propagation and consume crack tip energy, the essential differences in the thermal shock fracture resistance of materials are revealed from the microscopic mechanism level. Finally, by weighted and quantified integration of the above indicators covering thermodynamic properties, morphological damage, and microscopic mechanisms, a comprehensive performance score is generated. This macro-micro combined evaluation method effectively eliminates the one-sidedness of a single indicator and can accurately distinguish materials with similar macroscopic performance but huge differences in service life, providing a highly reliable scientific basis for the selection and modification design of high-voltage switch contact materials. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A logic flowchart of the method for evaluating the performance of arc-ablated copper-tungsten contact materials provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the system structure used for conducting arc ablation tests in an embodiment of the present invention.

[0019] Figure 3 This is a three-dimensional surface morphology image of the copper-tungsten contact material obtained by white light interferometer testing after arc ablation in an embodiment of the present invention.

[0020] Figure 4 This is a scanning electron microscope (SEM) image showing the crack distribution on the surface of the copper-tungsten contact material in an embodiment of the present invention.

[0021] Figure 5This is a scanning electron microscope (SEM) image of the crack depth of the copper-tungsten contact material cross-section in an embodiment of the present invention.

[0022] Figure 6 This is a grain orientation pattern obtained from backscattered electron diffraction testing of a material surface according to an embodiment of the present invention.

[0023] Figure 7 This is a histogram of grain boundary angle distribution, representing the statistical results of backscattered electron diffraction analysis of grain orientation in an embodiment of the present invention.

[0024] Reference numerals: 1. Cavity; 2. Ablation material (sample); 3. Insulating sleeve; 4. Capacitor; 5. Electrode; 6. Arc plasma. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the present application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] In the following description, references to "some embodiments" refer to a subset of all possible embodiments; however, it is understood that "some embodiments" may be the same or different subsets of all possible embodiments and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the invention have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the invention pertain. The terminology used in the embodiments of the invention is for the purpose of describing the embodiments of the invention only and is not intended to limit the invention.

[0027] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0028] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0029] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value and an intermediate value within the stated range, as well as any other stated value or an intermediate value within the stated range, is also included within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in embodiments or test cases of the invention. All references to this specification are generally incorporated herein by reference to disclose and describe methods and / or materials associated with said references. In the event of any conflict with any incorporated reference, the contents of this application shall prevail.

[0031] It should be noted that all raw materials and / or reagents in the embodiments of the present invention were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0032] This embodiment proposes a method, apparatus, electronic device, and storage medium for evaluating the performance of arc-ablated copper-tungsten contact materials. The aim is to address the problem in existing technologies that rely solely on single indicators such as ablation mass loss, which are insufficient to accurately characterize the material's crack propagation resistance and long-term reliability under actual service conditions. This embodiment will describe the complete technical process of this evaluation method in detail.

[0033] I. Sample Preparation and Pretreatment Process Before evaluating the performance of arc ablation, the copper-tungsten (Cu-W) contact material must be prepared and pretreated in a standardized manner to eliminate the interference of sample size effect and initial surface state on the evaluation results.

[0034] First, the copper-tungsten composite material to be evaluated was selected. This material is typically prepared using powder metallurgy processes, including pressing of the tungsten powder framework, high-temperature sintering, and copper melt infiltration, or a mixed powder sintering process. To ensure the representativeness of the evaluation results, standard samples need to be extracted from the bulk material. Using wire electrical discharge machining (EDM), the copper-tungsten material was cut into pieces with dimensions of [size missing]. The rectangular block is selected for wire electrical discharge machining to minimize the macroscopic stress caused by mechanical cutting, but a recast layer will remain on the surface after cutting.

[0035] Therefore, mechanical polishing is necessary afterward. The cut block sample is fixed on a metallographic polishing machine, and different grits of wet sandpaper (e.g., from 400 grit, 800 grit, 1200 grit to 2000 grit) are used for progressive polishing. Water cooling is required during polishing to prevent frictional heat from softening or smearing the copper phase. After sandpaper polishing, diamond polishing paste is used for fine polishing until the surface of the sample to be ablated reaches a mirror finish, with strict control over surface roughness. This step is crucial because excessive surface roughness can exacerbate the random fluctuations of the arc spots, affecting the consistency of the ablation pit morphology. After polishing, the sample is ultrasonically cleaned in anhydrous ethanol or acetone solution for at least 10 minutes to remove residual oil, abrasive, and metal debris. After cleaning, it is dried with cold air and placed in a desiccator for later use.

[0036] II. Step 1: Arc Ablation Test and Determination of Melting Threshold (T) The core of this step lies in using a controllable arc plasma source to simulate the actual working conditions of high-voltage switch contacts and to determine the melting threshold T of the material. This is a key positive indicator characterizing the material's ability to resist the initiation of thermal damage.

[0037] 1. Experimental Apparatus and Environmental Setup The experiment used a high-power pulsed power discharge system. This system mainly consists of a high-voltage charging power supply, a multi-channel parallel pulse energy storage capacitor bank (in this embodiment, eight capacitors are connected in parallel), a high-power thyristor switch, a waveform modulation inductor, and a discharge electrode assembly.

[0038] The experiment was conducted inside a sealed arc chamber. First, the airtightness of the chamber was checked, and the air inside the chamber was evacuated to a predetermined vacuum level using a vacuum pump. Then, sulfur hexafluoride gas was introduced.

[0039] SF6 gas has excellent insulation and arc-extinguishing properties, making it the most commonly used insulating medium in high-voltage switchgear. Testing in this environment can best simulate the actual service environment of the contacts. Adjust the pressure valve to maintain the gas pressure in the chamber at the standard operating pressure (e.g., between 0.1MPa and 0.5MPa, depending on the specific simulated operating conditions).

[0040] 2. Arc parameter settings The core control parameters of the system are the arc heat flux and the arc duration.

[0041] (1) Time control: The duration of the arc is controlled by controlling the turn-on and turn-off logic of the thyristor or by adjusting the parameters of the LC oscillation circuit. The precise lock-in time is 1ms. 1ms was chosen to simulate half-wave current or specific short-term withstand processes under operating conditions, ensuring that heat is mainly concentrated in the surface layer, making it easier to observe surface effects.

[0042] (2) Energy control: The power supply system allows adjustment of the capacitor's charging voltage. According to the capacitor energy storage formula: ; Changing the voltage alters the total energy, thereby generating arcs with varying current densities through the discharge circuit, thus regulating the heat flux. The arc plasma heat flux regulation range designed for this system is 0.5 GW / m². 2 ~4 GW / m 2 .

[0043] 3. Procedure for determining the melting threshold T The melting threshold is determined using the "step-by-step pressure boosting method": (1) Initial loading: The first pre-treated sample is installed on the sample stage, and the initial discharge parameters of the system are set so that the arc heat flux generated is 0.5 GW / m 2 The discharge is triggered, generating a plasma arc that impacts the sample surface.

[0044] (2) Condition inspection: After the test, remove the sample or observe the area affected by the electric arc through the observation window on the cavity using an optical microscope or a high-powered magnifying glass. Focus on checking for melting traces, such as loss of surface gloss, appearance of tiny remelted spheroids, grain boundary manifestation, or liquid phase flow texture.

[0045] (3) Gradual loading: If at 0.5GW / m 2 If no melting phenomenon is observed, replace the sample with a new one of the same material (or the unablated area of ​​the same sample) and increase the heat flux by 0.2 GW / m. 2 (i.e., set to 0.7GW / m) 2 Repeat the above ablation and observation process.

[0046] (4) Threshold determination: based on 0.2GW / m 2 The heat flux was increased in increments (0.5, 0.7, 0.9...) until a certain heat flux level was reached, at which point a clear melting characteristic was observed on the material surface for the first time. The heat flux value at this critical state was recorded, which is the melting threshold of this copper-tungsten material. .

[0047] Melting threshold The higher the value, the less likely the material is to undergo phase change and liquefaction when subjected to electric arc thermal shock, and the better its thermal shock resistance. Therefore, this index is defined as a positive index in the subsequent evaluation system and has the highest weight.

[0048] III. Step 2: Calculation of ablation mass loss and ablation rate (R) After determining the melting threshold, the material needs to be ablated multiple times at a specific heat flux above the threshold (or at the standard test heat flux) to measure its mass loss. This step aims to obtain the ablation rate R, which is an inverse indicator reflecting the material's macroscopic loss resistance.

[0049] 1. Quality Measurement A precision electronic balance with an accuracy of 0.1 mg (i.e., one ten-thousandth of a gram) is used.

[0050] (1) Weighing before ablation: Place the cleaned and dried sample into the weighing chamber of the balance, and record the mass after the reading stabilizes. .

[0051] (2) Repeated ablation test: Set a fixed heat flux value that is sufficient to cause significant ablation (usually higher than the melting threshold, for example, 2 GW / m). 2 (Or selected according to actual working conditions). The sample is subjected to arc ablation under these conditions. To reduce random errors in a single test, it is specified that the same material be subjected to the same conditions. Secondary ablation test (usually) Note that here... This can be a continuous ablation of the same sample. Next, it can also be to Each different sample is ablated once. This implementation method recommends cumulative ablation of the same sample. To obtain a measurable mass difference, either averaging multiple samples. If single-sample cumulative ablation is used, ensure that loose surface deposits are cleaned after each ablation.

[0052] (3) Post-treatment and post-ablation weighing: After ablation, the sample surface will be covered with carbonized black ash, oxide powder, or loose particles that have re-condensed after splashing. These substances are not effective matrix materials and must be removed. The surface is gently brushed with a soft brush and then ultrasonically cleaned and dried again. Afterwards, the mass after ablation is measured using the same precision balance and recorded as follows: .

[0053] 2. Calculation of ablation rate R Based on the actual measured mass difference, the eroded area of ​​the sample, and the number of ablation cycles, calculate the mass loss rate per unit area and per ablation cycle, i.e., the ablation rate. The calculation formula is as follows: ; In the formula: : Sample mass before ablation (mg); Mass of the sample after ablation (mg); This refers to the amount of mass loss. ; Effective ablation area of ​​the sample surface (mm) 2 This area can be obtained by measuring the size of the electrode spot or the actual projected area of ​​the ablation pit. In standard experiments, the arc's effective range is usually relatively fixed. Number of ablation cycles.

[0054] The final The value is the arithmetic mean of the results of three independent repeated tests (i.e., three different samples of the same material). The smaller the value, the less mass the material loses under the action of an electric arc, and the better its ablation resistance.

[0055] IV. Step 3: Three-dimensional morphology characterization and average melting depth ( ) Measurement Mass loss only reflects the total loss amount and cannot reflect the depth and morphology of the ablation pit. The same mass loss, if shallow and widespread, has a smaller impact on contact life; however, if deep and pit-like ablation occurs, it can easily lead to contact perforation or electric field distortion. Therefore, this step introduces the concept of "average melting depth". "As a key evaluation indicator."

[0056] 1. Equipment selection and parameter settings Non-contact three-dimensional topography measurement was performed using a white light interferometer. White light interferometry utilizes the movement of interference fringes of light to calculate height information, and has the advantages of high longitudinal resolution (down to the nanometer level) and large lateral field of view, making it particularly suitable for measuring surface roughness and ablation pit morphology.

[0057] (1) Scanning Mode: Set the instrument to grid scanning mode or mosaic scanning mode to cover the entire ablation area. Set the pixel resolution to [value missing]. Pixels (or higher) to ensure sufficient lateral sampling density.

[0058] (2) Range setting: Select the vertical scanning interferometry (VSI) mode according to the estimated ablation depth. This mode is suitable for measuring steps or deep pits with large height differences (micrometer to millimeter level).

[0059] 2. Data Acquisition and Processing Place the ablation sample horizontally on the interferometer stage and adjust the focus until interference fringes are visible on the monitor. Start the scan; the instrument will automatically move the objective lens vertically and record the light intensity change of each pixel at different heights, thereby calculating the height coordinates of that point relative to the reference plane. .

[0060] Since arc ablation craters typically exhibit irregular bowl-shaped or crater-like forms with a deep center and shallow edges, simply measuring the maximum depth is easily affected by local spatter pits, resulting in randomness. Therefore, this method defines "average melting depth" to characterize the overall degree of erosion.

[0061] 3. Average melting depth Calculation From the acquired three-dimensional topographic data, one or more cross-sectional contour lines passing through the ablation center are selected. For each contour line, the instrument collects data along... Direction Height data of each sampling point Since the ablation pit is concave relative to the reference surface, If the value is negative, its absolute value is used in the calculation.

[0062] The physical average depth is a function of the contour. In measuring length Integral average over: ; In practical digital signal processing, the above integral is transformed into the summation and averaging of discrete data: ; In the formula: : No. The absolute value of the distance from each sampling point to the central baseline (unablated plane); The total number of valid sampling points along the measurement direction.

[0063] This physical quantity The calculation principle and surface roughness The arithmetic mean deviation is similar, but the physical meaning is different; here it specifically refers to the depth of material removal caused by ablation. The calculated... Similarly, the average value of multiple cross sections or multiple samples is taken.

[0064] The smaller the value, the shallower the ablation pit, and the stronger the material's resistance to deep erosion.

[0065] V. Step 4: Statistical analysis of surface cracks ( ) The instantaneous high temperature generated by an electric arc will produce enormous thermal stress on the material surface. Copper-tungsten materials are particularly problematic because of the significant difference in the coefficients of thermal expansion between copper and tungsten (copper approximately...). tungsten Surface cracks are highly susceptible to initiation at phase boundaries during rapid heating and cooling cycles. These surface cracks are precursors to contact material spalling and failure.

[0066] 1. Surface crack observation The cleaned ablation surface was observed using a scanning electron microscope.

[0067] (1) Parameter settings: Set the electron beam accelerating voltage to 15KV. This voltage value can excite sufficient secondary electron signals for morphological imaging, and at the same time has a certain penetration depth to help determine the crack direction. Adjust the working distance (WD) to about 10mm to obtain a good depth of field.

[0068] (2) Observation strategy: First, perform a panoramic scan of the entire ablation center and edge areas at a low magnification (e.g., 50x to 200x) to find areas with dense crack distribution. Figure 4 In the typical morphology shown, the main cracks usually exhibit a network distribution.

[0069] 2. Maximum crack width Measurement Locate the widest crack (one or several) under low magnification, then switch to high magnification (500x to 5000x) for fine focusing. Use the SEM's built-in measurement software or scale to measure and record the maximum vertical distance between the two crack walls. .

[0070] (1) Primary cracks and secondary cracks: During observation, cracks are found to be divided into two types. Primary cracks have a larger width (usually above 10 μm) and penetrate the grain; secondary cracks have a smaller width (<1 μm) and are mostly distributed at the tip of the primary crack or at the grain boundary. This evaluation method focuses on the maximum crack width. This is because it represents the location where stress release is most intense, and is the weakest link where serious failure can occur.

[0071] 3. Characterization of crack density Besides width, crack density is also an important indicator. This method uses the average distance between adjacent cracks to indirectly characterize crack density. Random cross-sections are made on the SEM image, and the distance between the cross-section and the crack intersection points is measured. The arithmetic mean of these distances is calculated. The lower the average distance between adjacent cracks, the more cracks per unit area, i.e., the greater the crack density.

[0072] VI. Step 5: Measurement of cross-sectional crack depth ( ) If surface cracks do not propagate deeper, the damage is manageable; however, if they propagate too deeply longitudinally, they will cause blocky material to detach. Therefore, it is necessary to destroy the sample to observe the internal cracks.

[0073] 1. Sample cutting and preparation To observe the cross-section, the sample needs to be cut along the centerline of the ablation pit. Mechanical shearing or heavy-duty sawing should not be used, as this may introduce new cracks. Electrical discharge wire cutting (EDM) must be employed, using a fine metal wire (such as molybdenum wire) for low-stress cutting via electrical discharge etching. After cutting, the cut surface will have rough discharge marks. The cut surface must be embedded face down in resin and re-ground and polished (as described in the sample pretreatment steps above) until the cross-section is smooth and free of scratches, exposing a clear matrix structure and crack paths.

[0074] 2. Cross-sectional observation and measurement The prepared cross-sectional sample was observed using a SEM. The focus was on scanning the central and edge regions at the bottom of the ablation pit (the edge typically has the greatest thermal stress gradient and the deepest crack). Figure 5 As shown, the path of the crack extending from the surface into the matrix is ​​observed.

[0075] Locate the deepest crack and measure the perpendicular distance from its tip to the surface baseline using an SEM ruler; record this distance as the maximum crack depth. This indicator is an inverse indicator; the smaller the value, the stronger the material's ability to prevent longitudinal crack propagation.

[0076] VII. Step 6: Microstructure Analysis and Statistical Analysis of Large-Angle Grain Boundary Ratio (G) The above indicators all reflect the material's performance after ablation. This step aims to explain the performance differences through microcrystalline characteristics and uses the proportion of large-angle grain boundaries, G, as a predictive positive evaluation indicator.

[0077] 1. EBSD Testing Principles Backscattered electron diffraction (BSED) is a crystallographic analysis technique performed in SEM. It obtains Kikuchi flower patterns excited by an electron beam striking a tilted sample surface and resolves the orientation information of the crystal lattice within a micro-region.

[0078] 2. Sample preparation requirements EBSD requires extremely high sample surface quality; the surface must be free of any residual stress layer. Therefore, in addition to mechanical polishing, vibratory polishing or argon ion beam polishing is recommended to thoroughly remove the amorphous deformation layer on the surface and ensure clear Kikuchi patterns.

[0079] 3. Data Collection and Analysis (1) Region selection: Select a typical scanning area in the unablated area of ​​the material.

[0080] (2) Scan settings: Set an appropriate step size. For fine-grained copper-tungsten materials, the step size is usually set to 0.1μm~0.5μm.

[0081] (3) Grain boundary definition and statistics: After data collection, orientation analysis software (such as Channel 5 or Aztec Crystal) is used for processing. The software calculates the misorientation angle between adjacent measurement points (i.e., adjacent grains). ).

[0082] Small angle grain boundaries (LAGB): usually defined as These grain boundaries are composed of dislocation arrays, have low energy, and are less effective at hindering crack propagation.

[0083] Large angle grain boundaries (HAGB): defined as These grain boundary structures are complex and have high interfacial energy. According to grain boundary engineering theory, large-angle grain boundaries can effectively deflect crack propagation paths and consume crack tip energy, thereby inhibiting intergranular fracture.

[0084] (4) Index Calculation: Calculate the length or number of all grain boundaries within the test area, and record the percentage of large-angle grain boundaries as follows: .Right now: ; The higher the value, the more strong grain boundaries there are in the material's microstructure, and theoretically, the better the performance in inhibiting crack initiation and propagation.

[0085] 8. Step 7: Comprehensive Performance Quantitative Evaluation Model Finally, the six key indicators obtained above (one macroscopic thermodynamic indicator, two macroscopic morphology indicators, two microscopic crack indicators, and one microscopic structure indicator) are summarized and weighted to obtain a unique comprehensive score. This allows for a clear and intuitive classification of material properties.

[0086] 1. Summary and Classification of Indicators (1) Positive indicators (the larger the better): melting threshold Large-angle grain boundary ratio .

[0087] (2) Reverse index (the smaller the better): ablation rate Average melting depth Maximum crack width Maximum crack depth .

[0088] 2. Data normalization processing Because the dimensions of each indicator are different (e.g. The unit is GW / m 2 , The unit is mg / mm 2 , These are percentages, and their numerical values ​​differ significantly in magnitude, making direct addition impossible. A range transformation method is needed to map all indicators to the [0, 1] interval to obtain standardized values. .

[0089] Suppose that in similar comparative materials (or historical databases), the maximum value of a certain indicator is... The minimum value is The measured value in this study was .

[0090] (1) For positive indicators (T,G): ; This formula ensures that the larger the measured value, the closer the score is to 1.

[0091] (2) For the reverse index (ablation rate) Average melting depth Maximum crack width Maximum crack depth ): ; This formula ensures that the smaller the measured value (the better the performance), the closer the score is to 1.

[0092] 3. Weight Allocation Based on the degree of influence of each indicator on the actual service life of the contact, this invention has established scientific weighting coefficients through extensive experimental verification. The weighting logic is as follows: Melting threshold T, weight The ablation rate R is 40%~60% with a weighting of 40%~60%. The average melting depth is 10%~20%. Weight The maximum crack width is 10% to 20%. Weight The maximum crack depth is 5% to 15%. Weight The proportion of large-angle grain boundaries is 5%~15%, with a weighting of G. It is 1% to 10%, and the sum of all weights is 100%.

[0093] In this implementation, the following is the optimal allocation of weights for each indicator: (1) Melting threshold ( ): This has the highest weight (50%). Because if a material melts at low heat flux, its subsequent resistance to ablation and cracking is meaningless; this is a critical threshold that determines its survival.

[0094] (2) Ablation rate ( Average melting depth ( ): Both account for 12.5%, totaling 25%. This represents the material's ability to resist material loss and morphological degradation, directly affecting the contact resistance and electrical life of the contacts.

[0095] (3) Maximum crack width ( Maximum crack depth ( ): Both account for 10%, totaling 20%. This represents the risk to the mechanical integrity of the material; cracks are the main cause of catastrophic damage (fracture).

[0096] (4) Proportion of large-angle grain boundaries ( ): accounting for 5%. As an auxiliary correction index for microscopic mechanisms, it is used to screen materials with better potential fatigue resistance when macroscopic properties are similar.

[0097] The total weights are: .

[0098] 4. Calculation of the overall score P Multiply the normalized value by the weight, sum the results, and then multiply by 100 to obtain the percentage score: ； Right now: .

[0099] 5. Results Evaluation according to Values ​​are used to classify materials: It has excellent performance and is recommended as a high-performance contact material.

[0100] It has good performance and can be used in normal working conditions.

[0101] Performance is acceptable, but usage scenarios need to be restricted.

[0102] Performance is substandard; it is recommended to eliminate or improve the process.

[0103] IX. Implementation of the Performance Evaluation Device for Arc-Ablated Copper-Tungsten Contact Materials Based on the above method, the present invention also provides an integrated evaluation device. This device mainly includes the following modules: 1. Ablation Test Module: This module includes an SF6 test chamber, a high-voltage pulse power supply, a capacitor bank, a trigger controller, and a heat flux adjustment knob. This module is responsible for executing step 1 and recording the input energy and melting phenomena.

[0104] 2. Mass Measurement Module: Includes a precision electronic balance interface connected to the central processing unit, automatically reading... and And based on the input and Automatic calculation .

[0105] 3. Shape Detection Module: Integrates a data interface for a white light interferometer. It receives 3D point cloud data, performs integration calculations using a built-in algorithm module, and outputs the result. .

[0106] 4. Crack Analysis Module: This is an image processing software module that receives image data from SEM. This module includes image recognition algorithms that can automatically identify crack edges and calculate the maximum width. and depth Alternatively, it may provide an interface for human-interactive measurement.

[0107] 5. Microstructure Analysis Module: The interface connects to EBSD analysis software to directly read grain boundary statistics and extract the proportion of large-angle grain boundaries. .

[0108] 6. Comprehensive Evaluation Module: This is the core processor of the device. It pre-stores historical extreme value data for various copper-tungsten materials. ) and preset weights Upon receiving the measured data from the aforementioned five modules, the system automatically performs normalization and weighted summation operations, ultimately outputting a comprehensive score on the display screen. And performance rating report.

[0109] Through the detailed description of the embodiments above, those skilled in the art can clearly understand and reproduce all the technical details of the present invention. This method, through rigorous experimental design and scientific data processing, achieves a comprehensive, objective, and quantitative evaluation of the ablation resistance of copper-tungsten contact materials.

[0110] Specific Implementation: Evaluation of the Arc Ablation Performance of a Copper-Tungsten Contact Material This embodiment aims to evaluate the arc erosion resistance of a copper-tungsten contact material used in high-voltage circuit breakers. The evaluation process strictly follows... Figure 1 The flowchart shown is followed.

[0111] 1. Sample preparation and experimental setup First, copper-tungsten composite material blanks were prepared using powder sintering and melt infiltration processes. The blanks were then cut into pieces with dimensions of [size missing]. A block sample. The sample is fixed on a polishing machine, and the surface to be ablated is then prepared. The surface is mechanically ground and polished until the surface roughness is reduced to a certain level. Clean and dry before use.

[0112] like Figure 2 As shown, an arc ablation test system was constructed. The system mainly consists of a sealed cavity (1), a sample of the material to be ablated (2), an insulating sleeve (3) for confining the arc, an energy storage capacitor (4), a discharge electrode (5), and the generated arc plasma (6). Before the test, the cavity (1) was evacuated and filled with 0.4 MPa of SF6 gas to simulate the real arc-extinguishing chamber environment.

[0113] 2. Determination of melting threshold (T) according to Figure 1 The process begins with a melting threshold test.

[0114] Start the high-power pulse power discharge system and set the arc duration t=1ms.

[0115] The initial arc heat flux is set at 0.5 GW / m. 2 .

[0116] Triggering discharge, the arc plasma (6) is ejected from the electrode (5) and impacts the surface of the sample (2).

[0117] After the test, the sample was taken out for observation, and no melting traces were found.

[0118] By replacing the sample with a new one made of the same material, the heat flux was increased by 0.2 GW / m in increments. 2 The experiments were conducted sequentially.

[0119] When the heat flux increases to 2.2 GW / m 2 At that time, obvious liquid phase flow and remelting traces were observed for the first time at the center of the sample surface.

[0120] Results recorded: The melting threshold of this copper-tungsten material was determined to be T = 2.2 GW / m. 2 .

[0121] 3. Ablation mass loss and melting depth test Under conditions above the melting threshold (heat flux set at 3.0 GW / m²), 2 Three repeated ablation tests were conducted on the same material sample.

[0122] Ablation rate (R): Measured using an electronic balance with an accuracy of 0.1 mg, the average mass loss from three tests was 1.2 mg. The ablation area is known. Approximately 20mm 2 With n=1 ablation cycles (single calculation), the calculated ablation rate R=0.06mg / mm 2 .

[0123] Average melting depth ( Using the MicroXAM-3D white light interferometer, select The pixel grid mode scans the ablation area.

[0124] Results analysis: such as Figure 3 As shown, a three-dimensional morphology image of the material surface was obtained. The image shows that the edges of the ablation pits are clear, and the central depression is obvious. Data in the image shows that the length and width of the ablation pits are distributed within 500 μm. Within a 1000 μm range, the surface height varies by -73.5 μm. 42.5 μm. The inner wall of the pit exhibits a clear height gradient.

[0125] Using the formula: ; right Figure 3 The average melting depth is obtained by integrating the data: .

[0126] 4. Statistical analysis of surface cracks The surface of the ablation sample was observed using a scanning electron microscope (SEM) at an accelerating voltage of 15 kV.

[0127] Results analysis: such as Figure 4 As shown, the material surface developed complex network cracks due to rapid heating and cooling. The main cracks and minute secondary cracks are clearly visible in the image.

[0128] Quantitative measurement: Locate the widest main crack under low magnification, then switch to high magnification for measurement, as shown by the white arrow in the figure, to measure the maximum crack width. .

[0129] Density characterization: Measuring the spacing between adjacent cracks, such as... Figure 4 The crack spacing is approximately 128 μm. This relatively small average spacing indicates a high crack density and intense stress release on the material surface.

[0130] 5. Measurement of cross-sectional crack depth The sample was vertically cut from the center of the ablation pit using wire electrical discharge machining to prepare a metallographic section, which was then observed under SEM.

[0131] Results analysis: such as Figure 5 As shown, the main cracks are primarily distributed at the edges and center of the ablation pit. This is because the temperature is highest at the center of the arc, but the temperature gradient is greatest at the edges, leading to thermal stress concentration at the edges and making it easier for deep cracks to initiate.

[0132] Quantitative measurement: Tracing the main crack shown in the figure, which extends from the surface into the interior of the matrix, the vertical distance from its tip to the surface is measured to obtain the maximum crack depth. This depth exceeds one-third of the sample thickness, indicating a risk of material fragmentation.

[0133] 6. Microstructure Analysis Backscattered electron diffraction (EBSD) was performed on the surface of the ablated sample.

[0134] Results analysis: Figure 6 The image shows the Kikuchi pattern quality map and grain boundary distribution map of the material surface. The irregular polygons in the image represent grains, and the lines between the grains represent grain boundaries.

[0135] Quantitative statistics: Figure 7 This is a histogram of grain boundary angle distribution. The horizontal axis represents grain boundary angles, and the vertical axis represents percentages. Statistical results show that small-angle grain boundaries ( ) accounted for 56.4%, large-angle grain boundaries (

[0136] (43.6%)

[0137] Result Record: Proportion of Large-Angle Grain Boundaries Although large-angle grain boundaries can hinder crack propagation, their proportion in this sample has not yet reached a dominant level (e.g., exceeding 60%), which explains why the crack propagated deeper in step 5.

[0138] 7. Comprehensive performance quantitative evaluation To arrive at the final score A set of historical test extreme values ​​of similar copper-tungsten materials were selected as the normalization benchmark (assuming...). and ), and calculate the above measured data.

[0139] (1) Data normalization: Assume the benchmark range for similar materials is as follows: Melting threshold (Positive): 1.0 3.0GW / m 2 Actual measured capacity: 2.2 GW / m 2 .but: .

[0140] ablation rate (Reverse): 0.02 0.10 mg / mm 2 The measured value was 0.06 mg / mm. 2 .but: .

[0141] Average melting depth (Reverse): 20 60μm. Actual measurement: 38.5μm. Therefore: .

[0142] Maximum crack width (Reverse): 5 25μm. Actual measurement: 17.4μm. Therefore: .

[0143] Maximum crack depth (Reverse): 0.5 2.0mm. Actual measurement 1.23mm. Therefore: .

[0144] Large angle grain boundary ratio (Positive): 20% 80%. Actual measurement: 43.6%. Therefore: .

[0145] (2) Weighted calculation: According to the weights set in this invention: .

[0146] .

[0147] .

[0148] .

[0149] 8. Results Analysis and Conclusions The overall score of this copper-tungsten material sample was 53.87 points. (Compared to the scoring criteria...) (The material was rated as "unqualified").

[0150] Reason: Although its melting threshold is acceptable (normalized value 0.6), its crack control performance is poor. Especially... Figure 4 The surface crack width is large (17.4 μm), and Figure 5 The internal crack depth was extremely deep (1.23 mm), resulting in a low normalized score. Furthermore, Figure 7The microstructure showed an insufficient proportion of large-angle grain boundaries (43.6%), which failed to effectively inhibit the propagation of cracks into deeper areas.

[0151] Recommendations for improvement: It is recommended to optimize the sintering process, increase the proportion of large-angle grain boundaries, or adjust the tungsten framework structure to improve its resistance to thermal shock crack propagation.

[0152] Through this embodiment, utilizing Figures 1 to 7 The test methods and data shown demonstrate that this method successfully identified the deep-seated hidden dangers (excessive crack depth) in the material, avoiding potential misjudgments based solely on ablation quality loss (which was moderate), and verifying the comprehensiveness and effectiveness of the evaluation method of this invention.

[0153] For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, but obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this invention.

Claims

1. A method for evaluating the performance of arc-ablated copper-tungsten contact materials, characterized in that, The method includes the following steps: Step (1): Use a high-power pulsed power discharge system to generate an arc plasma to ablate the copper-tungsten contact material sample and determine the melting threshold T of the material. Step (2): Measure the sample mass before and after ablation and calculate the ablation rate R; Step (3): Use a white light interferometer to scan the ablation area, obtain the three-dimensional morphology, and calculate the average melting depth. ; Step (4): Observe the ablated surface of the material using a scanning electron microscope and count the maximum crack width. ; Step (5): Cut the sample from the center of the ablation zone, observe the cross-section, and obtain the maximum crack depth. ; Step (6): Perform backscattered electron diffraction test on the ablation surface of the material to analyze the grain orientation difference and count the proportion of large-angle grain boundaries G. Step (7): Select the melting threshold T, ablation rate R, and average melting depth. Maximum crack width Maximum crack depth The proportion of large-angle grain boundaries, G, is used as a key evaluation indicator. Combined with the weight allocation of each indicator, the comprehensive performance score P of the material is calculated.

2. The method according to claim 1, characterized in that, In step (1), the ablation test is conducted in a cavity filled with SF6 gas. A high-power pulsed power discharge system is used to perform arc ablation on samples with a surface roughness Ra≤1μm. The arc duration t is set to 1ms, and the arc plasma heat flux is 0.5 GW / m. 2 ~4GW / m 2 Adjustable within a range; Obtaining the melting threshold T of the material includes the following process: conducting arc ablation tests on the same material with different energies, gradually increasing the heat flux by 0.1 GW / m each time. 2 ~0.3 GW / m 2 The presence of liquid phase flow patterns or remelted spheroids on the surface is observed using an optical microscope as a criterion for determining melting, and the heat flux value at which the material begins to melt is recorded as the melting threshold.

3. The method according to claim 1, characterized in that, In step (2), a precision electronic balance with an accuracy of 0.1 mg is used to weigh the sample before and after ablation. , According to the formula: ； Calculate the ablation rate; where S is the ablation area of ​​the sample and n is the number of ablation cycles; the ablation rate R is the average of three repeated tests of the same material under the same conditions.

4. The method according to claim 1, characterized in that, In step (3), the white light interferometer uses a grid pattern to scan and observe the melting area on the target surface, and the average melting depth is... The formula is: ； Where L is the sampling length of the sample measurement area; Z is the absolute value of the distance between the measurement point and the center line; and n is the number of sampling points along the x-direction.

5. The method according to claim 1, characterized in that, In step (4), the accelerating voltage observed by the scanning electron microscope is 15kV, and the magnification is 500~5000 times; the width of the maximum crack is found under low magnification as... ; In step (5), the sample is cut from the center of the ablation zone using wire electrical discharge machining, and the maximum crack depth is obtained by observing and measuring the cross-section. ; In step (6), backscattered electron diffraction tests are performed on the ablated surface, and the percentage of large-angle grain boundaries G is obtained by counting the number of grain boundaries with an orientation difference greater than 15° between adjacent grains.

6. The method according to claim 1, characterized in that, In step (7), before calculating the overall performance score P, the standardized values ​​of each indicator are obtained by normalization. : For positive indices T and G, the standardized values ​​are: ； For the inverse indicator R, , and Standardized values: ； in, These are the measured values ​​for a single set of indicators. and These are the maximum and minimum values ​​of this indicator measured for similar materials.

7. The method according to claim 6, characterized in that, In step (7), the comprehensive performance score P: ； Among them, the weighting coefficient The allocation is as follows: melting threshold T, weight 40%~60%; ablation rate R, weight 10%~20%; average melting depth. Weight 10%~20%, maximum crack width Weight 5%~15%, maximum crack depth The weight is 5%~15%, the proportion of large-angle grain boundaries is 1%~10%, and the sum of all weights is 100%.

8. A device for evaluating the performance of copper-tungsten contact materials subjected to arc ablation, characterized in that, include: The ablation test module is used to control the discharge system to obtain the melting threshold T of the material; The mass measurement module is used to obtain the mass before and after ablation and calculate the ablation rate R. The morphology detection module is used to acquire the three-dimensional morphology of the ablation region and calculate the average melting depth. ; The crack analysis module is used to obtain and analyze the maximum crack width. and maximum crack depth ; The microstructure analysis module is used to acquire grain orientation data and calculate the proportion G of large-angle grain boundaries. The comprehensive evaluation module is used to receive the above-mentioned indicators as input parameters, perform the normalization and weighting operations as described in any one of claims 6 to 7, and output a comprehensive performance score P.

9. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the steps of the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the steps of the method as described in any one of claims 1 to 7.

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