Wear resistance of Zr/WC composite coatings on Cr12MoV steel surface by electric spark deposition

Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.

Effects of silver powder particle size on the microstructure and properties of Ag-Yb_2O_3 electrical contact materials prepared by spark plasma sintering

mg-Yb203 electrical contact materials were fabricated by spark plasma sintefing （SPS）. The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope （OM）, and the fracture morphologies were observed by scanning electron microscopy （SEM）. The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder （5 ktm）, homogeneous and fme microstmcture was obtained by fine silver powder （_〈0.5-1am）. At the same time, the electrical conductivity, microhardness, and tensile strength of the sin- tered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples （both by free and coarse silver powders） is more than 95%. The fracture characteristics are ductile.

Electric and mechanical performances of Bi_(0.5)Sb_(1.5)Te_(3) prepared by spark plasma sintering

Thermoelectric(TE)materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely.The thermoelectric effects hold great potential for application in power generation and refrigeration.Bi_(2)Te_(3)and its alloys are well known as best TE materials currently available near room temperature.This paper studies respectively the effects of spark plasma sintering(SPS)on electric performance of Bi_(0.5)Sb_(1.5)Te_(3)thermoelectric materials that are prepared through vacuum melting and ball milling.Through X-ray Diffraction and cold field emission scanning electric microscope s4800,the phase constituent and microstructure of the TE materials samples were analyzed.Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature(from 300 to 500℃)and pressure(from 30 to 60 MPa),and the density and mechanical strength of Bi_(0.5)Sb_(1.5)Te_(3)thermoelectric material increase,too.

Electrical Conductivity of Spark Plasma Sintered W-Cu and Mo-Cu Composites for Electrical Contact Applications

Tungsten copper and molybdenum copper composites, with weight percent copper in the range of 20% - 40%, have been produced using the spark plasma sintering (SPS) technique. Other specimens having similar compositions were also developed using the conventional techniques of Liquid Phase Sintering (LPS) and Infiltration. Electrical conductivity measurements showed that the specimens produced by the SPS process had substantially higher levels of electrical conductivity than those produced by the other methods. Relative density measurements showed that the SPS specimens achieved very high densification, with relative densities in the range of 99.1% - 100%. On the other hand, the specimens produced by LPS and infiltration had relative densities in the range of 88% - 92% and 96% - 98% respectively. The superior conductivity of the SPS specimens has been attributed to the virtually full densification achieved by the process. The effect of porosity on electrical conductivity has been discussed and three standard models were assessed using results from porous sintered skeletons of pure tungsten and pure molybdenum.

Electric Spark Sensitivity of Polynitro Compounds. Part V. A Relationship between Electric Spark and Impact Sensitivities of Energetic Materials

The spark energy, E ES , required for 50 percent initiation probability of 41 polynitro compounds was determined. The relationships between the E ES values and impact sensitivity, expressed as drop energies E d of the "first reaction", were established and discussed. The conclusion is made that depending on intermolecular interaction factors in crystals of energetic materials, the mechanism of impact energy transition to the reaction centre of their molecule can be differ from that of transition of energy of electric spark.

Thermal-electrical Coupled Analysis and Experimental Investigation on Spark Plasma Sintering of SiC Ceramics

Finite element simulations were conducted to study the mechanism of spark plasma sintering. The spark plasma sintering of SiC ceramics was simulated by the Marc software based on the load current curve and temperature-time curve deserved by SPS experiment. The concept of equivalent radiation coefficient was presented and applied during the simulation. The temperature distribution regularity of SiC ceramics sintered by SPS technology was got by thermal-electrical coupled finite element simulation. The experimental results show that by thermal-electrical coupled finite element analysis, the temperature rising and distribution regularity of nonconductive material can be preferable forecasted in the sintering process of SPS. In the initial stage of the heat preservation, the temperature of the central part of the sample has achieved sintering temperature, but now, the temperature of the sample is not uniform. The temperature for each part of the die is also quite different and the sample temperature in the center is higher than that in the edge. In the end of heat preservation, the central temperature of the sample is 50 ℃higher than the required sintering temperature, and the temperature gap for each part of the die decreases gradually.

Reactive synthesis Ti （CN） -based metal ceramic coating by electric-spark deposition

Electric-spark deposition （ESD） was adopted for depositing a Ti（ CN） -based ceramic coating on the TC4 titanium alloy substrate using a laboratory-developed electric-spark deposition system, a nitrogen-sealed atmosphere and graphite electrode. The surface morphology, microstructure, interfacial behavior between the coatings and substrate, phase and element composition of the coatings were investigated by scanning electron microscope （ SEM ） , X-ray diffraction （ XRD ） , X-ray photoelectron spectroscopy （ XPS ） and Auger electron spectroscopy （ AES ） . Microhardness profile was measured with a Vickers microhardness tester. The results show that metallurgical bond between the coating and substrate is realized and the phase of coatings are made up of Ti（ CN ） spherocrystal and dendritic crystal, TiV and C. Ti（ CN） ceramic particles, which is in-situ synthesized by the reaction among titanium from the substrate, carbon from the graphite electrode and nitrogen from the shielding nitrogen gas, is about 600 mn and distributes dispersively among the coatings. Microharduess profile falls off with the coatings thickness increasing and the highest microhardness values of the superficial coating could be up to 1 496HV, which is six times more than that of the substrate.

Relationship between Electric Spark Sensitivity of Cyclic Nitramines and Their Molecular Electronic Properties

On the basis of the structural and electronic properties of 14 different cyclic nitramine molecules, two types of formulas are employed to predict their electric spark sensitivity. One contains the minimum Mulliken charges of nitro group, the ratio of hydrogen to oxygen, and the ratio of carbon to oxygen; the other contains the lowest unoccupied molecular orbital energy, the ratio of hydrogen to oxygen, and the ratio of carbon to oxygen. Using these two types of formulas, we calculate the electric spark sensitivity of these 14 cyclic nitramine molecules, and compare them with the experimental data and previous theoretical values. And our investigations show that the former type of formula is better than the latter on predicting the electric spark sensitivity for cyclic nitramine molecules.

A new look on the electric spark sensitivity of nitramines

Electric spark energy,E_(ES),for a 50%probability of initiation of the 14 nitramines was determined using a measuring instrument in which the electrodes are in direct contact with the sample.Indirectly proportional relationships were established between the logarithm of the E_(ES)values and the length of the longest N-N bond in the nitramine molecule.This finding is compatible with the mechanism of the first step in the electro-reduction of the nitramine grouping.Directly proportional relationships were found to exist between the E_(ES)values and the crystal lattice free volumes,ΔV(i.e.an increase in theΔV values increases the nitramine's resistance to electric sparks)but there were several nitramines with the opposite course of this relationship.Also a semilogarithic relationships between the E_(ES)values and a ratio of intrinsic volumes of molecule,V_(int),to theΔV values were described as well as ambiguous linear dependence between these energies and a sum of the positive and negative extremes of the molecular surface electrostatic potentials,V_(S,∑).Several nitramines studied(always the same ones)display roughly the same distribution in the coordinate systems of relationships with lengths of the longest N-N bonds,the Vint/ΔV ratio and the sum V_(S,∑)as the independent variables.It was found that,typically,such relationships start from a single identical point,in effect a point corresponding to data for a structural unit from which tho studied nitramines can be hypothetically generated,and/or are converging on another point,often the one corresponding to the data for HNIW.All the findings point to a fundamental influence of the intermolecular forces on reactivity of nitramines exposed to electric sparks.

DK7732-1 Electric Spark CNC Wire-Cuffing Machine

The machine tool is one of the new products developed and produced by the Shanghai No.8 Machine Tool Plant. It adopts a lift adjustable wiretrame and molybdenum filament tensioning mechanism with large cutting thickness and high machining precision. It is equipped with an advanced IBM-PC 386 microcomputer-controlled system, with strong performance and CRT display. Man/

DK7763A Digitalcontrolled Electric Spark Wire Cutter

The DK7763A digital-controlled electric spark wire cutter, developed by the Tianjin Tianyi Digital-controlled Machinery Holdings Co. Ltd, is used in processing large modules and large precision parts. In 1995 it was awarded the title of state-level new product. It has a T-type body,rational Structure and

Formation of Diffuse and Spark Discharges in Nonuniform Electric Field in Elevated Pressure Gases

Diffuse and spark discharges are formed and studied during breakdowns with nonuniform electric field in nitrogen,air,and argon at elevated pressures and pulse repetition frequency of 400 Hz.Negative-polarity voltage pulses of the amplitude 20 kV,width at the base of 15 ns and rise time of 2 ns are applied to the electrode with a small radius of curvature.In the conditions of generation of runaway electron beams and X-rays,a CCD camera records the time of the diffuse discharge formation and its duration prior to its transition to a spark one.In all three gases,the diffuse discharge is formed during the time not exceeding 1 ns,when the bright spots appear on cathode in argon and air resulting in the beginning of the spark channel propagation.

Electric ignition energy evaluation and the energy distribution structure of energy released in electrostatic discharge process

Ignition energy is one of tbe important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters （the maximum power, duration of discharge process） of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%-14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy.

Determination of the Trigger-Electrode Position for the Field-Distortion Spark Gap

The optimal axial position of the trigger-electrode of the field-distortion spark gap is investigated through electric field calculation. The electric fields of the gap are calculated when locating trigger-electrode at different positions. It is shown that if the distance d between the trigger electrode and the low electric potential electrode is greater than 1.3 mm, the maximum field intensity occurs at the edge of the trigger-electrode, which will facilitate the generation of multi-channel discharge. According to calculated results, the working characteristics of the gap is investigated and it shows that when d=1.4 mm the field distortion gap can be triggered reliably.

Enhancing high-temperature oxidation resistance of nickel superalloy obtained by laser powder bed fusion via reactive electric spark treatment

The high-temperature oxidation resistance of the nickel superalloy prepared by the laser powder bed fusion(LPBF)has been significantly increased as a result of in-situ formation of a thermal barrier layer(α-Al_(2)O_(3)+CaMoO4)during oxidative annealing of surface layers modified by electric spark treatment(EST).The reactive EST of the LPBF-built items based on nickel EP741NP alloy was carried out with low-melting Al−12%Si,Al−6%Ca−0.6%Si and Al−7%Ca−1%Mn electrodes.It was found that under EST done by Al−7%Ca−1%Mn electrode an intermetallic(β-NiAl+γ'-Ni3Al)15μm-thick layer reinforced by spherical oxide(CaMe)O nanoparticles was formed.Formation of that structure increases the wear resistance of LPBF nickel superalloy by 4.5 times.Further oxidative annealing at 1000°C leads to a formation of continuous two-layered coating with an inner layer ofα-Al_(2)O_(3) and an outer layer of CaMoO4,which together act as an effective barrier preventing the diffusion of oxygen into the bulk of the superalloy.

基于Spark的电力设备在线监测数据可视化方法

大数据可视化可以实现海量电力设备在线监测数据中各种属性、运行状态等电力特征信息的图形、图像化直观呈现,为设备运行状态的及时有效监控分析提供有力保障。因此,本文提出一种基于Spark的电力设备在线监测数据可视化方法,为实现大数据环境下的电力设备在线监测数据的状态信息快速提取,在Spark大数据计算平台上,建立了基于设备状态评估指标体系与模糊C均值聚类(FCM)的电力设备状态信息提取算法。针对数据的多维、时序特性,构建三维平行散点图的数据可视化展现形式,实现电力设备在线监测数据信息全貌的可视化展现。将该方法运用于吉林省某风电场的风电机组在线监测数据集,实验结果证明了该方法的有效性。

基于Spark和IPPSO_LSSVM的短期分布式电力负荷预测算法

为了提高电力负荷预测的精度,应对单机运算资源不足的挑战,提出一种改进并行化粒子群算法优化的最小二乘支持向量机短期负荷预测模型。通过引入Spark on YARN内存计算平台,将改进并行粒子群优化(IPPSO)算法部署在平台上,对最小二乘支持向量机(LSSVM)的不确定参数进行算法优化,利用优化后的参数进行负荷预测。通过引入并行化和分布式的思想,提高算法预测准确率和处理海量高维数据的能力。采用EUNITE提供的真实负荷数据,在8节点的云计算集群上进行实验和分析,结果表明所提分布式电力负荷预测算法精度优于传统的泛化神经网络算法,在执行效率上优于基于Map Reduce的分布式在线序列优化学习机算法,且提出的算法具有较好的并行能力。

一种基于Spark的大数据匿名化系统实现

分组匿名化框架是一类经典的数据匿名化技术,它通过构造匿名记录的组,使得同一组内的不同数据无法被识别区分,从而达到隐私防护的效果。电力行业大数据分析涉及电力企业核心数据、用户隐私数据,其数据敏感度更强,传统的数据匿名化系统已经无法满足电力行业大数据业务应用和安全防护的需要。基于此,设计并实现了一种基于Spark的新型大数据匿名化系统,提供对Hadoop平台上多种数据格式的支持,并有效提高对大数据的匿名化处理效率。

基于Spark框架的电力大数据清洗模型

针对电力大数据清洗过程中的提取统一异常检测模式困难、异常数据修正连续性及准确性低下等问题,提出了一种基于Spark框架的电力大数据清洗模型。首先基于改进CURE聚类算法获取正常簇;其次,实现了正常簇的边界样本获取方法,并设计了基于边界样本的异常识别算法;最后通过指数加权移动平均数实现了异常数据修正。通过对某风电场风力发电监测数据进行了数据清洗实验分析,验证了清洗模型的高效性、准确性。

Microstructural characterization and dry sliding wear behavior of spark plasma sintered Cu-YSZ composites

In the present study, yttria stabilized zirconia （YSZ） reinforced Cu matrix composite specimens were produced by spark plasma sintering （SPS）. For comparison, pure Cu specimen was also produced in the same conditions. The effect of particles content on microstructure, relative density, electrical conductivity, and Vickers hardness was evaluated. The pin-on-disk test was also performed to determine dry sliding wear behavior of specimens under different wear conditions. After sliding wear tests, the worn surfaces were examined by field emission scanning electron microscopy （FE-SEM）. Microstructural study showed satisfactory distribution of reinforcement particles in copper matrix. The relative density up to 95%was obtained for all specimens. By increasing YSZ content from 0 to 5% （volume fraction）, the electrical conductivity of specimens decreased from 99.2%IACS to 65%IACS, correspondingly. The hardness of Cu-5%YSZ composite specimen was two times greater than that of pure copper. The volume loss and wear rate of pure Cu specimen were 1.48 mm^3 and 1.5±10^-3 mm^3/m under 50 N applied load and 1000 m sliding distance. However, for composite containing 5% YSZ particles, these values dropped to 0.97 mm^3 and 0.9±10^-3 mm^3/m, respectively. Moreover, the friction coefficient of specimens was changed from 0.6 to 0.4. The worn surface and debris observation indicate local plastic deformation and delamination as dominant wear mechanisms for pure copper, while oxidation and ploughing for composite specimen. Accordingly, it can be concluded that the Cu-YSZ composite could be a good candidate for the electrical contact applications in relays, contactors, switches and circuit breakers requiring good electrical and thermal conductivity and capability to resist wearing.