UDC 620.22-419.004.12:661.657.5:621.941
D.IN.Turkevich, V. Bushlya, J.-E. Ståhl (Lund, Sweden) I.AND.Petrusha, N.N.Beliavyna, V.WITH.Turkevich* (Kyiv)
*volodymyr.bushlya@iprod.lth.se
**vturk@ism.kiev.ua
HP-HT sintering, microstructure and properties of B6O-, TiC-containing composites based on cBN (pp. 3–16)
The possibility of using superhard boron suboxide B6O as a binder in composites with a low cBN content, characterized by higher mechanical characteristics than TiC, widely used in commercial materials, was studied. Using a high-pressure device of the “toroid” type at a pressure of 7.7 GPa in the temperature range from 1500 to 2000°C, composites with a cBN content of 60% (by volume) and a different composition of bonds, including B6O and TiC, were synthesized. With the use of electron microscopy, as well as X-ray phase analysis, the microstructure, phase and elemental composition of the obtained composites were studied. Their mechanical properties were studied using the indentation method. The workability of synthesized composites during turning of hardened cold-stamped steel has been established.
Keywords: superhard composites, cubic boron nitride, boron suboxide, titanium carbide.
UDC 621.921.34-419:536
L. Jaworska, P. Klimczyk, M. Szutkowska, P. Putyra, M. Sitarz, S. Cygan*, P. Rutkowski (Krakow, Poland)
*slawomir.cygan@ios.krakow.pl
Thermal resistance of PCD materials with borides bonding phase (p. 17–30)
In these studies, one group of PCD materials was prepared using diamond powder and 10 wt % of TiB2 and the second batch of the PCD material was prepared using a mixture of diamond powder with 5 wt % of TiB2 and 2 wt % of Co. The materials have been sintered using a Bridgman-type high-pressure apparatus at 8.0±0.2 GPa, at a temperature of 2000±50°C. Thermogravimetric (TG) measurements and Differential Thermal Analysis (DTA) have been carried out for diamond micropowders, TiB2 bonding phase, and sintered composites. The coefficients of friction for diamond composites in a sliding contact with an Al2O3 ceramic ball have been determined from the room temperature up to 800°C. Material phase compositions were analyzed for initial samples and after wear tests, at a temperature of 800°C. Raman spectra of diamond composites with borides bonding phases, observed for the first-order zone center modes of diamond and graphite during the heating up to 800°C in air have been presented. Thermal properties have been compared with the commercial diamond-cobalt PCD. It has been found that diamond with TiB2 and Co is the most resistant to the hardness changes at elevated temperatures and this material maintains the high hardness value up to 800 °C but it has a high coefficient of friction.
Keywords: PCD, TiB2 bonding phase, thermal stability, hardness, coefficient of friction.
UDC 669 017.3:539.893
IN.F. Brytun, V.IN. Yarosh, A.IN. Kurdyumov, A.I. Danylenko (Kyiv)
*britun@materials.kiev.ua
A comparative study of phases transformed into carbon under different shock compression schemes (pp. 31–39)
A comparative study of phase transformations in carbon graphite materials during shock compression was carried out according to two different schemes: in cylindrical ampoules with a central core in direct contact of explosives with the ampoule and in ampoules without a core with a thrown outer shell. It was established that a higher absolute yield of diamond is achieved during shock compression according to the second scheme, but, unlike the first scheme, the products of shock compression practically do not contain lonsdaleite or a dense amorphous phase. The conducted analysis showed that in the second case states with lower pressures but higher temperatures are realized, leading to the transformation of metastable phases into stable diamond.
Key words: shock compression, preservation ampoule, graphite, diamond, phase transformations.
UDC 661.65:661.55
IN. I. Kush*, S. N. Dub, R. WITH. Shmegera, Yu. IN. Orphan (Kyiv)
G. N. Tolmacheva (Kharkov)
*vkushch@bigmir.net
The method of multiple indentation for determining the hardness parameters of structurally heterogeneous materials (pp. 40–51)
The method of multiple indentation is proposed as a promising way of studying the surface properties of structurally heterogeneous bodies. It is applicable to a wide range of multiphase (including superhard) materials, ceramics and metals and allows to estimate the average values of the properties of individual phases and the composite as a whole, as well as the degree of inhomogeneity of the hardness of the sample at different scale levels. Such information is important when predicting the wear and machinability of structurally heterogeneous materials. Experimental and model results are presented, confirming the efficiency of the technique.
Keywords: hardness, indentation, structurally heterogeneous material, model, statistical analysis.
UDC 620.178.152:669.265.295
M. IN. Karpets, O. M. Myslyvchenko*, O. S. Makarenko, V. F. Gorban, M.O. Krapivka (Kyiv)
A. I. Degula (Sumy)
*karp@ipms.kiev.ua
**zvyagina-47@yandex.ru
The influence of nickel on the structure and phase composition of the high-entropy alloy VCrMnFeCoNiх (pp. 52–60)
The influence of nickel content on the phase composition, microstructure and hardness of high-entropy alloys VCrMnFeCoNiх (х = 0–3) was studied. The structure of the cast system consists of an fcc solid solution and an s-phase, both phases being multicomponent. An increase in the nickel content reduces the volume fraction of the s-phase. The microhardness of the alloys decreases from 12 GPa at x = 0 to 4.1 GPa at x = 3 as a result of a decrease in the amount of solid s-phase.
Keywords: sigma phase, crystal structure, solid solution, microhardness.
UDC 544.4, 544.723+661.183.1, 661.183.2
K. I. Veselovska, V. L. Veselovsky*, V. E. Diyuk, S. V. Gaidai, O. V. Ishchenko (Kyiv)
*veselovskyi.v@gmail.com
Modification of the surface of activated carbon by the method of gas-phase chlorination with carbon tetrachloride (pp. 61–66)
The modification of the surface of SKN activated carbon by the method of gas-phase chlorination with CCl4 vapor was studied. The effect of the reaction temperature on the amount of grafted chlorine in the temperature range of 200–500 °C, as well as the thermal stability of the attached chlorine, was studied. It has been shown that chlorination with CCl4 vapor in the gas phase leads to the grafting of up to 19.5 wt. % (5.5 mmol/g) of chlorine into the surface layer of coal. It has been established that amination of chlorine-containing samples of SKN leads to the replacement of surface halogen with nitrogen-containing groups in amounts up to 1.14 mmol/g.
Keywords: carbon materials, activated carbon, gas-phase chlorination, liquid-phase amination, surface modification.
UDC 621.922.02
D. Hessel, A. Karyazin* (Celle, Germany)
V. K. Starkov**, S. A. Ryabtsev, N. A. Horyn (Moscow, RF)
*alexey.karyazin@drkaiser.de
**v.starkov@stankin.ru
Rotation scheme of highly effective grinding wheels made of cubic boron nitride (pp. 67–76)
The kinematics of the rotary scheme for straightening grinding wheels with a cup-shaped rotating diamond wheel is studied. Examples of grinding with highly porous wheels made of cubic boron nitride on ceramic bonds of parts made of heat-resistant nickel and titanium alloys and high-alloyed steels show the advantages of such correction in comparison with correction by turning with diamond pencils.
Key words: rotary grinding, cubic boron nitride grinding wheel, cup-shaped diamond wheel, wheel durability, grinding time.
UDC 666.233
AND. N. Panova* (Kyiv)
IN. Yu. Dolmatov (St. Petersburg, Russia)
THERE ARE. IN. Ishchenko, G. G. Tsapyuk, A. AND. Bochecka (Kyiv)
M. IN. Veretennikova (St. Petersburg, RF)
V. Myllymaki (Vantaa, Finland)
THERE ARE. IN. Nikitin (Lesnoy, Russian Federation)
*annpanova@ukr.net
The influence of the conditions of synthesis of detonation nanodiamonds on the state of their surface layer (pp. 77–88)
Thermal desorption of volatile products from the surface of detonation nanodiamonds modified in the synthesis process was studied. It is shown that their possible doping has little effect on the nature and temperature range of the release of atomic oxygen, water, mono- and carbon dioxide. The spectrum of atomic oxygen has two maxima (250–300 and 550–650 °C), water – three maxima (50–80, 220–260 and 550–600 °C), CO – one maximum at 600–760 °C and CO2 – two maxima (200–270 and 520–660 °C). In phosphorus-containing detonation nanodiamonds, phosphine release was detected in the entire temperature range of exposure to them.
Keywords: detonation nanodiamonds, thermodesorption, alloying, surface modification, detonation synthesis, crystal lattice, functional groups.
UDC 620.178
AT. M. Suprun*, H. D. Ilnytska, V. M. Tkach, S. AT. Ivakhnenko (Kyiv)
*alona_suprun@mail.ru
Diamond Crystal Surface Cleaning Methods (pp. 89–93)
Methods for the step-by-step cleaning of diamond single crystals from surface contamination have been determined. The main processing stages are chemical surface cleaning, ion etching and ultrasonic cleaning. These methods ensured complete cleaning of the surface of diamond single crystals.
Keywords: diamond single crystals, chemical cleaning, surface, contamination.