UDC 661.883:536.45
T. O. Prikhna1, 4, *, A. S. Lokatkina1, P. P. Barvitsky1, M. V. Karpets1, 2, 4, S. S. Ponomarev3, A. A. Bondar4, B. Bukhner5, J. Werner5, R. Kluge5, V. E. Moshchil1, O. I. Borymsky1, L. M. Devin1, S. V. Rychev1, R. Khaber6, Zeynep Aiguzer Yasar6, B. Matovich7, M. Rutsky8, O. V. Prysyazhna1
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine Kyiv, Ukraine
3V. E. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kyiv, Ukraine
4I. M. Frantsevich Institute of Materials Science, NAS of Ukraine, Kyiv Kyiv, Ukraine
5Leibniz-Institut für Festkörper- und Werkstoffforschung, Dresden, Germany
6Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, USA
7Institute of Nuclear Sciences Vinča, Materials Science Laboratory, Belgrade University, Belgrade, Serbia
8Faculty of Mechanical Engineering, Kazimierz Pulaski University of Technology and Humanities in Radom, Radom, Poland
*prikhna@ukr.net
Structure, mechanical properties and high-temperature resistance of materials based on ZrB2 and HfB2 (pp. 3-20)
The structure, mechanical characteristics and high-temperature resistance in vacuum and in air sintered at high quasi-hydrostatic pressure (4.1 GPa) and by hot pressing (at a pressure of 30 MPa) of materials based on ZrB2 and HfB2 without additives and with additives of SiC and Si3N4 were investigated. It is shown that short-term (4 min) sintering under high pressure conditions at a relatively low (1800 °C) temperature allows to significantly improve the mechanical properties of materials compared to similar ones obtained by other methods (hot pressing and spark-plasma sintering). In the case of sintering at high (4.1 GPa) pressure, the addition of 20% (by mass) SiC to ZrB2 and 30% (by mass) SiC to HfB2 leads to a decrease in the specific gravity of ZrB2 and HfB2 and an increase in hardness (by 17 and 46%, respectively) and crack resistance (by 40 and 21%, respectively). In the case of adding SiC, solid solutions are formed due to the mutual diffusion of C and Si into the matrix phases of ZrB2 or HfB2 and a slight diffusion of Zr and Hf in the SiC-enriched region. During sintering of ZrB2 and HfB2 without additives at high pressure, the improvement of mechanical properties is explained by the formation of stronger bonds between grains in the sintered material. The addition of SiC to ZrB2 somewhat reduces the Young’s modulus, but increases the damping capacity of the resulting materials. The simultaneous addition of SiC and Si3N4 to ZrB2 leads to a lesser increase in hardness, but leads to a further increase in crack resistance. The melting point in vacuum of sintered ZrB2 and HfB2 turned out to be significantly higher than that of materials with SiC additives. The composite material made from a mixture of HfB2–30% (by mass) SiC had a density r = 6.21 g/cm3, microhardness HV(9.8 H) = 38.1±1.4 GPa, HV(49 H) = 27.7±0.24 GPa, HV(98 H) = 26.3±2.03 GPa, crack resistance KІс(9.8 H) = 8.2±0.2 MPa×m0.5, KІс(49 H) = 6.8±0.6 MPa×m0.5, KІс(98 H) = 6.4±0.11 MPa×m0.5, which is significantly higher than the similar characteristics of HfB2 sintered under the same conditions, but without additives.
Keywords: refractory borides, SiC, Si3N4, composites, ultrahigh-temperature materials, sintering under high pressures and temperatures, hot pressing, electron microscopy, mechanical properties, melting point in vacuum, high-temperature oxidation resistance.
UDC 621.921.34-492.2:539.89:621.762.5
O. O. Bochechka1, *, O. V. Kushch1, O. M. Isonkin1, G. A. Petasyuk1, O. I. Chernienko1, O. S. Osipov1, V. S. Gavrylova1, O. I. Borymsky1, Yu. Yu. Rumyantseva2
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Łukasiewicz Research Network – Krakow Institute of Technology, Krakow, Poland
*bochechka@ism.kiev.ua
The influence of the grain composition of diamond powder synthesized in the Mg–Zn–C system on the structure, physical-mechanical and operational properties of polycrystals sintered from it under high pressure (pp. 21-35)
Diamond was synthesized in the Mg–Zn–C system at a pressure of 8 GPa and a temperature of 1700 °C. After chemical purification of the synthesis product, the resulting diamond powder was classified by grain size. The influence of the ratio of coarse and fine fractions of diamond powder and sintering parameters on the structure and physical-mechanical properties of sintered diamond polycrystals was studied. The wear resistance of the obtained samples was studied by turning a cylindrical core of granite from the Korostyshiv deposit of the X drillability category. It is shown that high-pressure sintering of a mixture of coarse- and fine-dispersed synthesized diamond powders allows reducing the residual porosity by 2.46 times compared to sintering at the same pressure of diamond powders synthesized in systems based on iron group metals. The maximum hardness among the obtained polycrystalline samples, determined at a Knoop indenter load of 9.8 N, is 66 GPa, which is 87% of the hardness of a single crystal of natural diamond of type Ia (face (100)). The highest wear resistance is achieved by samples of diamond polycrystalline elements with a diameter of 15 mm and a height of 3 mm, sintered in an AVT “toroid 30” at a pressure of 8 GPa and a temperature of 1780 °C from a purified synthesis product in the Mg–Zn–C system, which is 5.6–10.9 times higher than the wear resistance of the control sample sintered from powder synthesized in the Ni–Mn–C system.
Keywords: diamond synthesis, diamond powder, high pressure, sintering, diamond polycrystal, hardness, granite core turning, wear resistance.
UDC 620.22-621.921.34:539.422.25
B. T. Ratov1, V. A. Mechnyk2, *, M. O. Bondarenko2, V. M. Kolodnitsky2, **, E. S. Gevorkyan3, 4, V. P. Nerubatsky4, A. G. Gusmanova5, B. V. Fedorov1, N. A. Kaldybayev6, M. T. Arshidynova5, V. G. Kulych2
1NAO “Kazakh National Research Technical University named after K. I. Satpayev”, Almaty, Kazakhstan
2V. M. Bakuly Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
3Kazimierz Pulaski University of Technology and Humanities in Radom, Radom, Poland
4Ukrainian State University of Railway Transport, Kharkiv, Ukraine
5Sh. Yesenov Caspian University of Technology and Engineering, Aktau, Kazakhstan
6M. Adishev Osh Technological University, Osh, Kyrgyzstan
*vlad.mechnik2019@gmail.com
**vasylkolod56@gmail.com
Features of the fracture surface structure of the Salmaz–(WC–Co)–ZrO2 composite as a result of impact loading (pp. 36-50)
The effect of the addition of ZrO2 micropowder (in the range from 0 to 10%) on the structural changes of the hard alloy matrix in the fracture region as a result of impact loading of a sample of the composite diamond-containing material (CBM) 25Salmaz–70.5WC–4.5Co (% by mass), formed by the spark plasma sintering method in the temperature range from 20 to 1350 °C at a pressure of 30 MPa for 3 min was studied. It was found that in the KAM sample without the ZrO2 additive, the structure of the hard alloy matrix has a form characteristic of brittle fracture, as evidenced by the smooth relief of the fracture surface. In this case, the fracture of the KAM sample occurs due to the splitting of the components of the hard alloy matrix, which leads to a decrease in its wear resistance. The introduction of the ZrO2 additive in an amount of 4% into the KAM composition causes a change in the structure of the fracture surface. On the fracture surface of the hard alloy matrix of the KAM sample, nanopores with a structural size of ~ 100–500 nm are formed due to viscous (pitting) fracture. At the same time, in addition to the formation of pits on the fracture surface of the hard alloy matrix, a highly developed relief is formed on the surface of the diamond grain, which is evidence of improved diamond retention and increased wear resistance of the composite. With a further increase of ZrO2 addition to 10% in the composition of the CAM, a more pronounced microrelief with the presence of deep pits and microcracks is formed on the fracture surfaces of the hard alloy matrix and diamond grain. It is proposed to use the type of relief of the fracture surface of sintered CAM samples during impact fracture at room temperature as an assessment of the strength characteristics of diamond retention.
Keywords: diamond retention, composite, composition, tungsten carbide, cobalt, zirconium dioxide, structure, spark plasma sintering.
UDC 621.762.242:546.271
Mehmet Bugdayci1, 2, *, Şeyma Güleç1
1Yalova University Chemical Engineering Dep., Yalova, Turkey
2Istanbul Medipol University Vocational School Construction Technology Dep., İstanbul, Turkey
*mehmetbug@gmail.com
Vacuum Carbothermal Synthesis of TiB2 (pp. 51-61)
The conditions for the formation of TiB2 by carbothermic reduction at lower temperatures were investigated using vacuum, mechanical activation, the effect of a functional additive, and different process durations. The optimal process duration was determined to be 4 h, and the optimal amount of functional additive was determined to be 5% (by weight) NaCl. The obtained samples were examined using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is shown that the unwanted phases were completely removed as a result of the reduction carried out after 16 h of ball mill operation, and the method of obtaining TiB2 by carbothermic reduction with additional processes is optimal.
Keywords: TiB2, carbothermic reduction, FactSage computational program, vacuum, ball mill.
UDC 621.923.7
Yu. D. Filatov1, *, V. I. Sidorko1, S. V. Kovalev1, A. Yu. Boyaryntsev2, V. A. Kovalev3, O. Ya. Yurchyshyn3
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Scintillation Materials Institute, NAS of Ukraine, Kharkiv, Ukraine
3National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine
*filatov2045@gmail.com
Dispersion of sludge nanoparticles during polishing of polymer optical materials (pp. 62-73)
As a result of the study of the patterns of interaction of sludge nanoparticles with nanoparticles of wear of polishing powder and lapping during polishing of polystyrene, polymethyl methacrylate and polyallyl diglycol carbonate using dispersed systems of micro- and nanopowders based on ab initio Calculations in accordance with the quantum theory of scattering have established that sludge nanoparticles are elastically scattered on wear nanoparticles. The differential scattering cross section has a maximum value at scattering angles of 0 and 180°, which exceeds its value for other angles by 2·104–5·104 times. It is shown that sludge nanoparticles during polishing move along the axis of the optical resonator between the treated surface and the lapping surface and scatter only forward and backward. It has been established that the total scattering cross section of sludge nanoparticles increases exponentially with increasing their concentration and significantly decreases with increasing size and kinetic energy of nanoparticles. With an increase in the Q factor of the resonator from 7.9 to 105.5, the total scattering cross section of sludge nanoparticles decreases exponentially from 120.8 to 0.6 Mb. It is shown that the calculated values of the total scattering cross section of sludge nanoparticles correlate with a high degree of accuracy with the experimentally determined material removal rate during polishing.
Keywords: polishing, polymeric materials, scattering of nanoparticles, resonator Q factor.
UDC 549.517.1:621.923
O. O. Vovk1, O. V. Voloshyn1, E. V. Slyunin1, L. I. Voloshyn2, *, S. I. Kryvonogov1, S. V. Nizhankovsky1
1Institute of Single Crystals, NAS of Ukraine, Kharkiv, Ukraine
2Institute of Scintillation Materials, NAS of Ukraine, Kharkiv, Ukraine
*sil.volyn@gmail.com
Material Removal Rate During Processing of Titanium-Doped Sapphire (pp. 74-85)
The effect of the content of titanium ions in titanium-doped sapphire crystals (Ti:sapphire, up to 0.2% (by weight) Ti) on the material removal rate and surface roughness at different stages of its processing was studied. It was found that the efficiency of material removal increases with increasing dislocation density in the crystal. It was found that with increasing titanium content in Ti:sapphire during grinding with a fixed abrasive, the material removal rate decreases, and in the case of grinding and polishing with a free abrasive, it increases due to disordering of the crystal structure and deterioration of the structural perfection of the crystals. Doping sapphire with titanium leads to a decrease in the value of the parameter of the surface roughness of the crystals at the grinding stage.
Keywords: sapphire, Ti:sapphire, grinding, mechanical polishing, chemical-mechanical polishing, material removal rate, surface roughness.
UDC 621.941
S. A. Klymenko*, S. An. Klymenko, M. Yu. Kopeykina, A. S. Manokhin, Yu. O. Melniychuk
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*atmu@meta.ua
Thermal phenomena on the front surface of a PcBN tool during turning of hardened steel (pp. 86-99)
The paper presents the results of determining the temperature at the flash spots on the front surface and the cutting temperature during turning of hardened steel with a PcBN tool of the VN group. Based on experimental data on the size of the chip-tool contact area, its topographic indicators and the level of loads on the front surface of the tool, a theoretical calculation of the temperature at the flash spots in the tool contact area was carried out. It was established that the change in temperature at the flash spots with increasing cutting speed is extreme: at a cutting speed of 2 m/s, the temperature value exceeds 2000 °C in the plastic and 1000 °C in the elastic parts of the contact area. Using the experimental and computational approach, the cutting temperature was determined, which increases with increasing cutting speed and reaches 1200 °C. It was proved that in the case of a decrease in the temperature at the flash spots under processing conditions with a cutting speed of more than 2 m/s, the intensity of the increase in the cutting temperature, which characterizes the average temperature at the tool contact area, decreases.
Keywords: flash point temperature, cutting temperature, PcBN tool, hardened steel, stress, area and topography of the contact area.
UDC 548.1
V. L. Solozhenko
LSPM–CNRS, Université Sorbonne Paris Nord, Villetaneuse, France
vladimir.solozhenko@univ-paris13.fr
On the crystal structure of superhard cubic BC2N (pp. 100-102)
Crystallochemical analysis and precise calculations of the mechanical properties of the recently proposed cubic diamond-like BC2N show that this hypothetical phase is not related to the experimentally synthesized cubic BC2N.
Keywords superhard B–C–N phases, structure, hardness, elastic moduli.
UDC 621.315
V. I. Chasnyk1, *, D. V. Chasnyk2, O. M. Kaidash3
1State Enterprise Scientific Research Institute “Orion”, Kyiv, Ukraine
2Ukrainian Scientific Research Institute of Special Equipment and Forensic Examinations of the Security Service of Ukraine, Kyiv, Ukraine
3V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
vassiliyiv@gmail.com
The Effect of Silicon Carbide Content on the Volume Resistivity of Freely Sintered AlN–SiC Composites (pp. 103-106)
It is reported that the volume resistivity of AlN–SiC composites decreases from 1.1∙108 to 3∙102 Ohm·cm when the silicon carbide content in them increases from 20 to 55% (by mass). In such composites with a SiC content of less than 50%, the porosity does not exceed 3% and does not have a significant effect on the electrical resistance value. The dependence of the electrical resistance on the SiC content is a straight line located at an angle to the abscissa axis, if the resistance values are given on a logarithmic scale.
Keywords: free sintering, aluminum nitride, silicon carbide, bulk electrical resistance.