UDC 620.22-621.921.34
V. A. Mechnyk1, *, Miroslaw Rucki2, B. T. Ratov3, M. O. Bondarenko1, E. S. Gevorkyan4, V. M. Kolodnitsky1, **, V. A. Chyshkala5, O. M. Morozova4, V. G. Kulych1
1V. M. Bakuly Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Kazimierz Pulaski University of Technology and Humanities in Radom, Poland
3Kazakh National Research Technical University named after K. I. Satpayev, Almaty, Kazakhstan
4Ukrainian State University of Railway Transport, Kharkiv, Ukraine
5V. N. Karazin Kharkiv National University, Kharkiv, Ukraine
*vlad.me4nik@ukr.net
**vasylkolod56@gmail.com
Structure of Salmaz‒(WC‒6Co)‒ZrO2 composite materials formed by electric plasma-spark sintering method (pp. 3-28)
The influence of ZrO2 additives with different (from 0 to 10% (by weight)) content on the morphology, structure and retention of diamond grains by the hard alloy matrix of samples of composite diamond-containing materials (CBMs) of the Salmaz‒(WC‒6Co) system formed by electric plasma-spark sintering method in the temperature range of 20‒1350 °C at a pressure of 30 MPa for 3 min was studied. Stable correlations have been established between the content of the ZrO2 additive with the average WC grain size, microstructure parameters and the adhesion strength of diamond grains to the hard alloy matrix. It has been shown that for the initial sample Salmaz‒(WC‒6Co) a coarse-grained structure is formed in the hard alloy matrix with both direct contact of WC grains and large areas of cobalt bonding, which is the cause of weak adhesion between diamond grains and the hard alloy matrix and premature fallout of diamond grains from the matrix during its operation. After the addition of ZrO2 micropowder to the composite composition, a finer-grained structure with thin layers of cobalt bonding between WC grains is formed in the hard alloy matrix, which significantly enhances the adhesion between diamond grains and the hard alloy matrix. As a result, the ability of the hard alloy matrix to retain diamond grains from premature fallout during the operation of the CMM and their mechanical and operational properties increase. The greatest ability of the hard alloy matrix to retain diamond grains from premature fallout was observed at a ZrO2 content of 10% (by weight). Obtaining composites with ZrO2 additives provides significant economic benefits not only due to reduced energy consumption during the sintering process, but also due to a sharp decrease in the cost of composites.
Keywords: composite, tungsten carbide, cobalt, zirconium dioxide, concentration, composition, electric plasma-spark sintering, structure, adhesion.
UDC 666.3.7:620.193
D. V. Vedel*, P. V. Mazur, O. M. Grigoriev, L. M. Melakh, M. D. Bega, I. V. Kozak
Institute for Problems of Materials Science named after I. M. Frantsevich, NAS of Ukraine, Kyiv, Ukraine
*vedeldv@gmail.com
Preparation and Mechanical Properties of High-Entropy Ceramics (TiZrHfNbTa)C (pp. 29-38)
It is shown that for dense high-entropy ceramics (TiZrHfNbTa)C obtained by hot pressing, the optimal hot pressing temperature is 2000 °C. At lower temperatures, the presence of zirconium and hafnium oxides, as well as undissolved carbides, was observed in the composition of the ceramics. The strength of the obtained ceramics at room temperature was 394±72 MPa, at a temperature of 1600 °C – 119±31 MPa. It is shown that for pure carbides, a significant decrease in hardness was observed under increased load on the indenter, while for (TiZrHfNbTa)C, the preservation of hardness under any loads is characteristic. To obtain maximum values of hardness and strength of high-entropy ceramics (TiZrHfNbTa)C, it is necessary to reduce the amount of ZrO2 and HfO2 in the composition of the ceramic with a simultaneous decrease in grain size through the use of submicron powders and selection of technological modes of production.
Keywords: carbides, high-entropy ceramics, hot pressing, hardness.
UDC 629.045:621.431.3
L. B. Priymak, A. G. Dovgal*, V. V. Varyukhno
National Aviation University, Kyiv, Ukraine
*kalibr201@ukr.net
Study of wear resistance of new composite materials based on alumina of special tribotechnical purpose (pp. 39-47)
The structure and basic mechanical properties of a composite material based on corundum doped with graphite particles were studied. The tribotechnical behavior of the obtained composite under dry friction conditions in a pair with structural steel 45 under highly loaded tribocontact at low sliding speeds was studied. The values of wear intensity and friction coefficients for the obtained material were determined. The friction surfaces were studied and the wear mechanisms of the obtained material were determined. The prospects of using the specified material for friction joints operating in aggressive environments and not requiring lubrication were substantiated.
Keywords: composite material, ceramics, structure, grain size, wear resistance, wear mechanism.
UDC 621.763
E. S. Gevorkyan1, *, V. P. Nerubatsky1, R. V. Vovk2, V. O. Chyshkala2, M. V. Kyslytsia2
1Ukrainian State 2nd University of Railway Transport, Kharkiv, Ukraine
2Kharkiv National University named after V. N. Karazin, Kharkiv, Ukraine
*edsgev@gmail.com
Structure formation in silicon carbide–aluminum oxide composites during electroconsolidation (pp. 48-59)
A review of methods for improving hot pressing of SiC ceramics is conducted. The liquid-phase sintering method is described as a way to increase the physical and mechanical properties and reduce the energy consumption of the pressing process. An example of using liquid-phase sintering of ceramics based on silicon carbide by hot pressing by direct passage of electric current with the introduction of a small amount of oxide impurities is given. The features of structure formation and properties of a composite material based on silicon carbide micropowders obtained by hot pressing in a vacuum by heating with direct passage of high-amperage current through a graphite mold are presented. The microstructure and physical and mechanical properties of composites of different compositions were investigated. The optimal composition of the initial mixture and the most optimal sintering temperature were determined. A comparison of the physical and mechanical properties of the obtained composite materials was presented.
Keywords: silicon carbide, ceramics, hot pressing, electroconsolidation, liquid phase sintering, nanopowders.
UDC 669.018.25.9:661.665.2:66.046.564
Qianwei Zhang, Kaihua Shi*, Jinbao Gu, Kailin Dong,
Wei Zeng, Peng Wang, Yu Liao
Research and Development Center, Zigong Cemented Carbide Co. Ltd, Zigong, P.R. China
*zhangqianwei_lcy@outlook.com
**kaihua_shi@outlook.com
Effect of carbon content near the decarburization phase boundary on the physical and mechanical properties of WC–6 wt % Co hard alloy (pp. 60-69)
The effect of carbon content near the decarburization phase on the microstructure and mechanical properties of WC–6 wt % Co hard alloy obtained by traditional powder metallurgy methods was studied. The results of X-ray diffraction analysis showed that the content of the decarburization phase increases with decreasing carbon content. The WC–6 wt % Co hard alloy with lower carbon content has a finer WC grain size. The coercive force and hardness of the samples increase with decreasing grain size. The magnetic susceptibility and tensile strength of cobalt decrease with increasing content of the decarburization phase due to decreasing carbon content. The WC–6 wt. % Co hard alloy with high abrasion resistance and without significant decrease in tensile strength was obtained due to finer grains and decarburization phases.
Keywords: hard alloy, grain size, decarburization phase, abrasion resistance, tensile strength.
UDC 621.623
Yu. D. Filatov1, *, V. I. Sidorko1, A. Yu. Boyaryntsev2, S. V. Kovalyov1, V. A. Kovalyov1
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Institute of Scintillation Materials, NAS of Ukraine, Kharkiv, Ukraine
*filatov2045@gmail.com
Performance of polishing of polymer optical materials (pp. 70-80)
As a result of the study of the mechanism of polishing of polymer optical materials using dispersed systems of micro- and nano-particles of polishing powders, it was found that with resonant energy transfer from particles of the dispersed phase of the polishing dispersed system to the treated surface and in the opposite direction, the energy of sludge particles and wear particles is inversely proportional to the spectral separation between them. It is shown that during polishing of polymer materials using a dispersed system of nano-powders, the energies of sludge particles and wear particles decrease by 5 times in the case of increasing the spectral separation from 27 to 78 cm–1 and from 17 to 24 cm–1, respectively. When polishing using a dispersed system of micropowders, their energies decrease by 2–5 times in the case of increasing the spectral separation from 8 to 95 cm–1 and from 16 to 57 cm–1. In the case of decreasing the spectral separation between the processed material and the polishing powder, the volumes of sludge particles and wear particles, and accordingly the polishing performance and the wear intensity of the particles of the dispersed phase of the dispersed system, increase. It has been established that the polishing performance significantly depends on the efficiency of the Förster resonant energy transfer and increases in the case of decreasing the product of the ratios of the vibration frequencies of molecular fragments on the surface of the polishing powder particles and on the processed surface, as well as increasing the ratio of the lifetime of the clusters of polishing powder particles to the lifetime of the clusters of the processed surface in the excited state. It is shown that the results of theoretical calculations of the polishing efficiency of optical materials coincide with the experimental results with a deviation of 1–8%.
Keywords: polymer materials, resonant energy transfer, polishing efficiency.
UDC 621.9.025.7
A. S. Manokhin1, *, S. A. Klymenko1, **, V. O. Stolbovy1, 2, I. V. Kolodiy2, M. Yu. Kopeykina1, S. An. Klymenko1, K. V. Kamchatna-Stepanov a3, I. V. Serdyuk2
1V. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Institute of Solid State Physics and Materials Science, NC KhPTI, NAS of Ukraine, Kharkiv, Ukraine
3National Technical University “Kharkiv Polytechnic Institute”, Kharkiv, Ukraine
*the.manokhin@gmail.com
**atmu@meta.ua
Stress state in the cutting zone of a PcBN tool with a coating based on the TiAlSiYN system (pp. 81-92)
The residual stresses in vacuum-arc coatings of the TiAlSiYN system deposited on a PcBN base were investigated by X-ray diffractometry. Substructural characteristics were determined for the TiN phase and it was found that all the studied coatings have compressive stresses from –1.51 to –5.85 GPa, and significant (up to ε = 1.13 10–2) microstrains were also found at the micro level. Equivalent stresses Seqv in the contact layer of the tool material were determined in cases where the coating contains residual compressive stresses. The influence of residual stresses in protective coatings on equivalent stresses in the tool under the action of contact loads characteristic of the machining process was assessed. It was found that the presence of a compressive stress of –1.0 GPa in the coatings contributes to the reduction of equivalent stresses in dangerous points on the front surface of the tool in the initial cutting period. To reduce equivalent stresses on the side of the rear surface of the tool with significant (~ 0.3 mm) wear, coatings with residual compressive stresses of –3 GPa are optimal. The most significant decrease (from 1.9 to 0.5 GPa) of equivalent stresses at dangerous points on the front surface of the tool was observed in the presence of impact loads.
Keywords: PcBN tool, protective coatings, residual stresses, stress-strain state, contact loads.
UDC 539.533:546.27:661…461
V. L. Solozhenko
LSPM–CNRS, Université Sorbonne Paris Nord, Villetaneuse, France
*vladimir.solozhenko@univ-paris13.fr
On the hardness of boron subarsenide B12As2 (pp. 93-95)
The Vickers hardness of boron subarsenide B12As2 was predicted using three modern theoretical models and experimentally investigated by microindentation. The polycrystalline material has a hardness of about 31 GPa, so B12As2 belongs to the family of (super)hard phases.
Keywords: boron subarsenide, hardness, comprehensive compressive modulus.