共查询到20条相似文献,搜索用时 46 毫秒
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P. P. Sharin M. P. Akimova S. P. Yakovleva A. M. Bolshakov V. I. Popov 《Russian Engineering Research》2019,39(12):1034-1042
The intermediate layer formed when diamond is in contact with metals that are active with respect to carbon—such as iron and titanium—is investigated in a vacuum furnace. The conditions in the furnace match those employed in sintering with copper impregnation of the hard-alloy matrix of diamond tools. The results may be used in developing compositions and technologies such that tool materials based on tungsten–cobalt hard-alloy powder have a high diamond content in the matrix. 相似文献
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以镍粉和钛粉为原料,采用自蔓延燃烧合成技术制备了多孔NiTi形状记忆合金,研究了压坯压力、镍含量、钛粉粒径等参数对合金孔隙尺寸、孔隙均匀性和显微组织的影响。结果表明:自蔓延燃烧合成的NiTi合金为螺旋分层结构;压坯压力在100~200 MPa范围内再经自蔓延燃烧合成的NiTi合金的孔隙均匀,且为三维连通结构,比较理想;镍质量分数为40%左右时,孔隙的分布和三维贯通性均较理想;当钛粉粒径较大时,出现了大量的液相和NiTi2、Ni3Ti等杂质相,反应很不充分,钛粉粒径在50~100μm之间为好。 相似文献
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M. Yu. Polyanchikova Yu. N. Polyanchikov D. V. Krainev N. I. Egorov 《Russian Engineering Research》2017,37(1):35-36
Results are derived regarding the influence of hard-alloy tool production by impact molding and high-temperature sintering on the dislocation density in tungsten-carbide and titanium-carbide powder. 相似文献
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In this paper, changes of microstructural characteristics of disperse systems during mechanical activation of zinc oxide (ZnO) have been investigated. ZnO powder was activated by grinding in a planetary ball mill in a continuous regime in air during 300 min at the basic disc rotation speed of 320 rpm and rotation speed of bowls of 400 rpm but with various balls‐to‐powder mass ratios. During ball milling in a planetary ball mill, initial ZnO powder suffered high‐energy impacts. These impacts are very strong, and large amounts of microstructural and structural defects were introduced in the milled powders. The morphology and dispersivity of particles and agglomerates of all powders were investigated by scanning electron microscopy and scanning transmission electron microscopy. The specific surface area of initial ZnO powder was determined as 3.60 m2 g?1 and it increased to 4.42 m2 g?1 in mechanically activated powders. An increase of the ball‐to‐powder mass ratio led to a decrease of particle dimensions as well as increased the tendency for joining into quite compact agglomerates, that is aggregates, compared with the very loose, soft initial agglomerates. The obtained results pointed out that activation of ZnO powders produces a highly disperse, nano‐scaled mixture of small particles, that is crystallites with sizes in the range of 10–40 nm. Most of these particles are in the form of aggregates with dimensions of 0.3–0.1 μm. The crystallite and aggregate size strongly depend on milling conditions, that is ball‐to‐powder mass ratio, as shown in this investigation. 相似文献
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This paper outlines the results of an experimental study of the influence of high hydrostatic pressure on the abrasive wear of hard-alloy materials based on tungsten carbide (~90% WC ± 10% Co), as well as alloys based on iron with high contents of chromium. A specially developed setup has been described in the paper that makes it possible to test materials under the hydrostatic pressure of up to 250 MPa at different friction speeds. An investigation of the surfaces of samples using the Scanning Electron Microscopy method has revealed that the main damage of alloy surface occurs due to the delamination and spalling of hard particles. It has been revealed that the hydrostatic pressure significantly influences the wear rate of the investigated materials. When the pressure increases to 200 MPa, the wear of materials with high contents of chromium increases seven times, while for the material based on tungsten carbide, it increases twice. 相似文献
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The erosion and abrasion characteristics of alumina coatings plasma sprayed under different spraying conditions 总被引:1,自引:0,他引:1
R. Westergrd L. C. Erickson N. Axn H. M. Hawthorne S. Hogmark 《Tribology International》1998,31(5):271-279
A series of plasma sprayed alumina coatings was evaluated regarding their erosion and abrasion characteristics. The coatings were deposited under different spraying conditions, using a commercial axial injection plasma spray system, and with powders of different grit sizes and crystallinity. A sintered bulk alumina and a conventionally sprayed coating, produced by a radial injection air plasma spray technique, were tested as reference materials. To evaluate the importance of energy input the coatings were produced using two different torch nozzle sizes and gas mixtures with a varied amount of hydrogen. The erosion and abrasion results indicate that hydrogen concentration, nozzle size and precursor powder type and size influence the tribological characteristics of the coatings. The wear resistance of the coatings seems to benefit from an increase in hydrogen concentration or torch nozzle size. The effect of precursor powder size on the wear resistance was more complex but indicates that sapphire powders of medium precursor sizes are advantageous to ordinary plasma spraying powders of alumina. 相似文献
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In this paper, a new single cone-cap plasticity with an isotropic hardening rule is presented for powder materials. A general form is developed for the cap plasticity, which can be compared with some common double-surface plasticity models proposed for powders in literature. The constitutive elasto-plastic matrix and its components are derived based on the definition of yield surface, hardening parameter and nonlinear elastic behavior, as a function of relative density of powder. Different aspects of the model are illustrated and the procedure for determination of powder parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of triaxial and confining pressure tests. 相似文献
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The main results from experimental research on the triboengineering characteristics of ultradispersed composite powder materials
are discussed. An experimental procedure for studying the triboengineering characteristics and yield stress of powder materials
is elaborated as applied to the processes of continuous forming of nanostructural solid items from metallic powders. 相似文献
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金属包覆型复合粉末及其在工程材料中的应用 总被引:3,自引:0,他引:3
金属包覆型复合粉末是一种壳-核状结构的粉末,兼有金属与非金属的性质,因而在众多领域得到广泛应用。在简述这种粉末制备方法的基础上,对化学镀法制备的粉末在陶瓷刀具、金刚石磨具、碳刷电极、摩擦片、电触头以及金属基复合材料、热喷涂粉末、减震材料等工程材料方面的研究现状进行了综述,并展望了其发展方向。 相似文献
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In this paper, a W-Ta thin-film thermocouple has been integrated on a diamond anvil cell by thin-film deposition and photolithography methods. The thermocouple was calibrated and its thermal electromotive force was studied under high pressure. The results indicate that the thermal electromotive force of the thermocouple exhibits a linear relationship with temperature and is not associated with pressure. The resistivity measurement of ZnS powders under high pressure at different temperatures shows that the phase transition pressure decreases as the temperature increases. 相似文献
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Surface durability has been reported to be the main factor affecting the tribological behavior of steam-oxidized sintered iron. In this paper, the influence of compaction pressure and powder grade on the surface durability of steam-treated sintered iron is analyzed. Specimens prepared from atomized powders in different sizes were compacted using four different pressures, sintered for 30 min at 1120°C and then subjected to a continuous steam treatment at 540°C for 2 h. The tribological characterization was carried out against a hard steel ball in a reciprocating wear test, in which the electrical contact resistance between the sliding surfaces was continually monitored. The processing parameters had a strong influence on the oxide durability, expressed in terms of the sliding distance required to achieve low contact resistance. High durability was always associated with high compaction pressure and smaller powder size. 相似文献
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A. N. Krasnovskii 《Journal of Friction and Wear》2013,34(3):221-224
The article presents the main results of an experimental study of the circular slipping of ultradispersed composite powder materials. The method is used in an experimental study of the coefficient of the circular slip of powder materials with respect to machining tools during the continuous working of volumetric nanostructural articles made from metal powders. 相似文献
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In this paper, analysis of ballistic behaviour of gun powder and flash powder of firework chemicals with different particle size have been carried out in a closed vessel to find out the maximum pressure when ignited. The experiment was carried out by changing the variables like sample composition, particle size, vessel volume. Works were carried out to synthesis of nanoflash powders and the particle sizes are 139.7 nm for KNO3, 94.5 nm for Al and 92.36 nm for S. The nanoflash powders are mixed with micron powders in different ratios and crackers are manufactured. The maximum pressure during the combustion of different samples and explosivity of the crackers are analysed. Results show that peak pressure is increased by 21.6% and explosive impulse is increased by 60% when burning of 100% nfp compared to 10% nfp cracker. 相似文献
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Y.-F. Tzeng C.-Y. Lee 《The International Journal of Advanced Manufacturing Technology》2001,17(8):586-592
This paper presents the effects of various powder characteristics on the efficiency of electrodischarge machining (EDM) SKD-11.
The additives examined include aluminium (Al), chromium (Cr), copper (Cu), and silicon carbide (SiC) powders that have significant
differences in their thermophysical properties. The machining mechanism with the addition of the foreign particles, the tool
wear rate (TWR), and the material removal rate (MRR) have been investigated. It was found experimentally that the particle
concentration, the particle size, the particle density, the electrical resistivity, and the thermal conductivity of powders
were important characteristics that significantly affected the machining performance in the EDM process. Proper addition of
powders to the dielectric fluid increased the MRR and, thus, decreased the TWR. Under the same particle concentration experiments,
the smallest suspended particle size led to the greatest MRR and, thus, the lowest TWR. Of the additives investigated, chromium
powder produced the greatest MRR and the lowest TWR, whereas the process without foreign particles has the converse effects.
The addition of copper powder to the dielectric fluid was found to make almost no difference to the pure kerosene EDM system. 相似文献
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Joanni E Savu R Valadares L Cilense M Zaghete MA 《The Review of scientific instruments》2011,82(6):065101
A tubular furnace specifically designed for growing nanostructured materials is presented in this work. The configuration allows an accurate control of evaporation temperature, substrate temperature, total pressure, oxygen partial pressure, volumetric flow and source-substrate distance, with the possibility of performing both downstream and upstream depositions. In order to illustrate the versatility of the equipment, the furnace was used for growing semiconducting oxide nanostructures under different deposition conditions. Highly crystalline indium oxide nanowires with different morphologies were synthesized by evaporating mixtures of indium oxide and graphite powders with different mass ratios at temperatures between 900 °C and 1050 °C. The nanostructured layers were deposited onto oxidized silicon substrates with patterned gold catalyst in the temperature range from 600 °C to 900 °C. Gas sensors based on these nanowires exhibited enhanced sensitivity towards oxygen, with good response and recovery times. 相似文献
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In the work, the wear rate of cutting tools made of hard alloy, cutting ceramics, and ultra-hard materials has been studied. The slowest wear rate is achieved using hard-alloy, with the bonding of hard-melting metal in the composition. 相似文献