UDC 621.9:621.928.4
O. O. Shulzhenko, T. O. Prikhna, G. D. Ilnytska, V. I. Lavrinenko*, O. I. Borymsky, O. M. Sokolov, V. M. Tkach, V. V. Smokvyna, I. M. Zaitseva, V. V. Tymoshenko
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*gil-ism@ukr.net
**lavrinenko@ism.kiev.ua
Comparison of dimensional, physical-mechanical and operational characteristics of synthetic diamond powders of grades AC6 and AC20 synthesized in the Ni–Mn–C and Fe–Si–C systems (pp. 3–16)
The dimensional, physical-mechanical and operational characteristics of diamond powders of grades AC6 and AC20 synthesized using Ni–Mn and Fe–Si solvent alloys are considered. It is shown that diamond powders obtained in the Ni–Mn–C and Fe–Si–C systems fundamentally differ in magnetic properties, as well as in the content of impurities and intracrystalline inclusions. For diamond powders of both systems, it was found that the alloy-solvent elements in the impurities and inclusions predominate and constitute 89–67% of the total amount of impurities and inclusions in diamond powders of the non-magnetic fraction, and of the magnetic fraction – slightly higher, and constitute 93–90%. Diamond powders of magnetic and non-magnetic fractions synthesized in the Ni–Mn–C and Fe–Si–C systems differ from each other in the value of specific magnetic susceptibility by approximately 10 times, in surface defects – by 1.5 times. The strength index of diamond grains of magnetic fractions of both systems is slightly higher compared to the strength of diamond grains of non-magnetic fractions due to the higher content of metal impurities and inclusions in them: for diamond powders synthesized in the Ni–Mn–C system, it increases by 1.25 times, and in the Fe–Si–C system – by 1.9 times. The wear resistance of wheels with diamond grains of the magnetic fraction synthesized in the Fe–Si–C system is 1.3 times higher compared to wheels with diamond grains of the non-magnetic fraction of the same system, and 2 times higher compared to wheels with diamond grains synthesized in the Ni–Mn–C system.
Keywords: physical and mechanical characteristics, synthetic diamond powders, magnetic properties, alloy-solvents, wear resistance of wheels.
UDC 661.685:621.762.5
Junxi Zhang*, Baiming Chen, Wu Yue, Hui Chen
School of Materials Engineering, Lanzhou Institute of Technology, Lanzhou Gansu, China
*57764866@qq.com
Phase composition, microstructure and wear properties of Ni/Ni3Si composites obtained by mechanical alloying (pp. 17–28)
The phase composition, microstructure and wear properties of Ni3Si and Ni/Ni3Si composites obtained by mechanical alloying using Ni and Si powders as raw materials were investigated. It was shown that Ni(Si) solid solution, intermediate phases Ni74Si26 and Ni31Si12 are formed during the ball milling process, and after 30 h of milling, nanocrystalline Ni3Si powder is formed. Based on the semi-empirical Miedema theory, the free energy of formation of various phases arising from mechanical alloying of mixed 3Ni–Si powders was calculated. The ordered Ni3Si phase is stable under equilibrium conditions and has the lowest enthalpy of formation during ball milling. Compared with monolithic Ni3Si, the Ni/Ni3Si composite has excellent friction coefficient and wear resistance, as well as high strength and impact toughness. With increasing load, the friction coefficient of the composite decreases, the wear rate of the composite first increases and then decreases. At a load of 10 N, the friction coefficient and wear rate of the composite are 0.246 and 5.23×10–4 mm3/(N×m), respectively. The main wear mechanism of the material changes from adhesive wear to abrasive wear with increasing load and exhibits significant tribo-oxidative wear at all loads.
Keywords: metal silicides, hot pressing, microstructure, friction and wear characteristics.
UDC 669.27-935.4:548.73
Zhongnan Xiang1, 2, Zhanjiang Li3, Hongbo Nie2, Fa Chang2, 3, Pinqiang Dai1, 3*
1College of Materials Science and Engineering, Fuzhou University, Fuzhou Fujian, China
2Xiamen Tungsten Co., LTD. Technology Center, Xiamen Fujian, China
3College of Materials Science and Engineering,Fujian University of Technology, Fuzhou Fujian, China
*pqdai@126.com
Effect of WC crystallinity on microstructure, properties and applications of WC–Co hard alloy (pp. 29–41)
The microstructure, properties and applications of WC–Co hard alloy obtained from WC powders of different crystallinity were compared. The results show that the crystallinity of various WC powders can be well investigated by X-ray diffraction, scanning electron microscopy and laser particle size measurement. The hardness of the hard alloy obtained from the WC powder with high crystallinity is slightly reduced, while the fracture toughness, transverse rupture strength, one-way compression strength and impact toughness are increased. Obtaining a WC raw material with high crystallinity is the basis for a high-performance hard alloy.
Keywords: WC crystallinity, microstructure, hard alloy, mining alloy.
UDC 661.865.4:54-19:544.225
Yulu Wan1, Cai Cheng1, Xu He2, Jing Chang1, *
1Institute of Solid State Physics, Sichuan Normal University, Chengdu, China
2Chengdu Textile College, Chengdu 611731, China
*changjing0394@163.com
Structural, electronic, mechanical and optical properties of LaIn3 under pressure: first-principles studies and calculations (pp. 42–56)
The structural, electronic, mechanical and optical properties of LaIn3 under pressure are systematically investigated using first-principles calculations based on density functional theory. Structural calculations show that cubic LaIn3 does not have a structural phase transition in the pressure range of 0–30 GPa. From the calculated electronic band structures and density of states, it is found that LaIn3 has a metallic character, and the bands crossing EF originate mainly from La-d states with some contribution from In-p states. The electrical conductivity and metallic properties gradually decrease with increasing pressure, and electron transfer becomes more difficult. The calculated elastic properties indicate that LaIn3 has mechanical stability and excellent mechanical properties in the considered pressure ranges. Moreover, the comparison of the two elastic constants C11 and C44 indicates that LaIn3 is more resistant to uniaxial compression than to shear deformation, and the values of Poisson’s ratio ν and B/G demonstrate that LaIn3 retains plastic behavior under pressure up to 30 GPa. In addition, the elastic anisotropy of LaIn3 under pressure was investigated. The optical properties and Debye temperature of cubic LaIn3 under pressure were also analytically predicted.
Keywords: first principles, electronic structure, elastic properties, optical properties, LaIn3.
UDC 537.226.1:666.3-1
D. V. Chasnyk1, V. I. Chasnyk2, *, O. M. Kaidash3, **
1Ukrainian Research Institute of Special Equipment and Forensic Examinations of the Security Service of Ukraine, Kyiv, Ukraine
2State Enterprise “Orion”, Kyiv, Ukraine
3V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv Kyiv, Ukraine
*vassiliyiv@gmail.com
**oka07@ism.kiev.ua
Estimation of dielectric permittivity in non-conducting composites by the content and morphology of conductive particles in the microwave frequency range (pp. 57–65)
For different values of relative dielectric permittivity e/ed in the insulator-spheroidal particle system, the relationship between the form factor and the volume content of conductive particles in the absence of macroscopic electrical conductivity has been theoretically established. Comparison of theoretical calculations of dielectric permittivity e with experimental data for the AlN–24% (by volume) Mo composite with conductive particles-spheres allowed us to correct the previously obtained e/ed ratios. The proposed new theoretical relationships take into account the mutual influence of conductive particles when approaching the percolation threshold and allow determining the dielectric permittivity of non-conductive composites from the volume content and morphology of conductive particles.
Keywords: conductive spheroidal particles, form factor, dielectric permittivity, percolation threshold.
UDC 620.22-621.921.34
V. A. Mechnyk1, *, M. O. Bondarenko1, V. M. Kolodnitsky1, **, V. I. Zakiyev2, I. M. Zakiyev2, E. S. Gevorkyan3, M. O. Kuzin4, O. S. Yakushenko2, I. V. Semak2
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2National Aviation University, Kyiv Kyiv, Ukraine
3Ukrainian State University of Railway Transport, Kharkiv, Ukraine
4Lviv Branch of Dnipro National University of Railway Transport named after Academician V. Lazaryan, Lviv, Ukraine
*vlad.me4nik@ukr.net
**vasylkolod56@gmail.com
Comparative study of mechanical and tribological characteristics of Fe–Cu–Ni–Sn composites with different CrB2 content under dry and liquid friction conditions (pp. 66–82)
The structure, phase composition, hardness, elastic modulus of sintered Fe–Cu–Ni–Sn–CrB2 composites and their tribological properties under dry and liquid friction conditions were investigated using X-ray diffraction, scanning electron microscopy, microindentation, and tribological testing methods. The results obtained showed that the microstructure, mechanical, and tribological properties of the composites depend on the CrB2 additive content. The Fe–Cu–Ni–Sn–CrB2 composites consisted of a-Fe, g-Fe, Cu phases and contained a certain proportion of the crystalline phases Cu9NiSn3, NiSn3 and CrB2. The hardness and elastic modulus of the composites practically do not depend on the friction medium (dry and liquid), while the friction force and wear rate vary. In terms of their mechanical and tribological properties, the Fe–Cu–Ni–Sn–CrB2 composites exceed the Fe–Cu–Ni–Sn composites. The addition of 2% (by mass) CrB2 to the 51Fe–32Cu–9Ni–8Sn composite resulted in a decrease in the friction force from 220 to 170 mN and the wear rate from 7.41·10–2 to 3.41·10–2 mm3·N–1·m–1 under dry friction conditions and, accordingly, from 200 to 140 mN and from 8.19·10–2 to 4.10·10–2 mm3·N–1·m–1 under liquid friction conditions. Further increase in the CrB2 concentration in the composites results in an increase in the wear rate. The mechanism of increased wear resistance of the composite containing 2% (by mass) CrB2 compared to the original composite is the formation of a finer-grained structure and optimal combination of hardness and elastic modulus. Fe–Cu–Ni–Sn–CrB2 composites can be used as a matrix material for composite diamond-bearing materials that are subject to severe wear.
Keywords: composite, concentration, structure, hardness, elastic modulus, tribological testing, dry and liquid friction, wear resistance.
UDC 621.623
Yu. D. Filatov*, V. I. Sidorko, S. V. Kovalev, V. A. Kovalev
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*filatov@ism.kiev.ua
The influence of rheological properties of the dispersed system on the polishing performance of optical glass and sieves (pp. 83–93)
As a result of the study of the regularities of polishing optical glass and sieves, it was found that the surface tension coefficient, the dynamic viscosity coefficient of the polishing dispersed system and the wetting angles of the surfaces of the treated surface and the lapping affect the thickness of the gap between them, and accordingly, the removal efficiency of the treated material and the roughness parameters of the treated surfaces. It is shown that the transfer energy is directly related to the volumetric wear coefficient, which determines the polishing performance, and the validity of the relationship between the volumetric wear coefficients and thermal conductivity depending on the specific heat capacity, transfer energy and temperature is confirmed. It has been found that increasing the thickness of the gap between the treated surface and the lapping leads to a decrease in the most probable size of the sludge particles and an improvement in the roughness of the polished surfaces.
Keywords: polishing, dispersed system, material removal rate, surface roughness.