UDC 539.2.669.0176:669.018
G. WITH. Oleynyk (Kyiv)
Structural transformations during the formation of superhard materials based on initial powders of wurtzite boron nitride
Mechanisms of structural transformations that occur during sintering of materials obtained at high pressures and temperatures based on wurtzite boron nitride are considered. Depending on the sintering conditions, several types of microstructure can be formed in the material, differing in the quantitative content of polymorphic BN modifications, the size and substructure of the grains, and the structural state of the interfaces. It was concluded that the combination of high hardness (60–80 GPa) and fracture toughness (14–22 MPa×m1/2) of the material based on BNv (trade mark hexanit-R) is realized in the case of the formation of a microstructure with a high proportion of grains of a special structural state. Its features determine the presence in the material of intragranular interphase boundaries, interphase boundaries of the composite type, as well as the high stress level caused by these boundaries.
Key words: wurtzite, sphalerite, boron nitride, sliding, polymorphic transformation, sintering.
UDC 533.951:548.33
AND. IN. Kurdyumov, V. F. Brytun, V. IN. Yarosh, A. I. Danylenko, V. B. Zelyavskyi (Kyiv)
Influence of shock compression conditions on the transformation of graphite into lonsdaleite and diamond
The phase transformations of graphite into dense modifications of carbon during impact compression in cylindrical preservation ampoules (ores = 20–36 GPa, Tud = 1800–3500 K) were investigated. The dependence of the yield of lonsdaleite and diamond on the compression conditions was established. The obtained results are analyzed taking into account the mechanisms of the formation of dense phases, as well as the peculiarities of their shock-wave synthesis.
Key words: shock compression, graphite, phase transformations, lonsdaleite, diamond.
UDC 661.665.3:536.4
T. E. Letsoalo, J. E. Lowther (Johannesburg, South Africa)
Elastic and thermodynamic properties of potentially superhard carbon boride materials
Boron icosahedral structures are the basic building structures of many important hard borides and especially B4C. The structural and thermodynamic properties of B4C have been examined applying molecular dynamics simulation with the use of both ab initio and bond order Tersoff potentials. Various physical quantities of B4C including the elastic constants, thermal expansion coefficients, and specific heat have been examined.
Keywords: diamond, boron, electronic structure, elastic constants, molecular dynamics.
UDC 539.216:621.921.34
IN. WITH. Sedov, V. G. Ralchenko, A. AND. Khomych, A. I. Syzov, T. M. Zvukova, V. I. Konov (Moscow)
Stimulation of diamond nucleation on silicon substrates with a polymer precursor layer during deposition of diamond films in microwave plasma
It is shown that layers of a certain type of polymers deposited on a silicon substrate form diamond nanoparticles upon thermal destruction (along with sp2-coordinated carbon), which serve as crystallite nucleation centers during the subsequent deposition of diamond from the gas phase. Microcrystalline diamond films were synthesized using preceramic polymers poly(naphthylhydrocarbine) and poly(hydrocarbine) in a methane–hydrogen mixture in a microwave plasma.
Key words: diamond synthesis, diamond films, poly(naphthylhydrocarbene), poly(hydrocarbene), microwave plasma.
UDC 621.9.025.7-586:669.018.25:539.61
IN. AND. Zaloga, D. IN. Kryvoruchko (city of Sumy)
IN. I. Lebedev (Minsk, Belarus)
AT. AND. Pledge (Sumy)
Effect of nitrogen ion beam implantation on adhesive properties of VK8 hard alloy
The results of studies of the effect of nitrogen ion beam implantation on the adhesion properties of VK8 hard alloy are presented. The adhesive component of the friction coefficient was measured by the method of pressing a rotating indenter into the counterbody and it was shown that it decreases when the surface is modified by ion beam implantation of nitrogen, especially at contact pressures greater than the yield point of the counterbody.
Key words: friction, adhesion, ion implantation, hard alloy, stainless steel, indenter.
UDC 621.9
WITH. AND. Klymenko, A. WITH. Manokhin, Yu. AND. Melnychuk (Kyiv)
Wear and durability of a tool equipped with PSTM plates on the basis of KNB, during finishing turning of hardened steels with high feeds
The results of experimental studies of wear patterns of tools equipped with polycrystalline superhard materials based on cubic boron nitride in the conditions of high-performance finishing treatment of hardened steel with oblique cutters are presented. The influence of processing conditions on the durability of such tools was studied.
Key words: cutting tool wear, KNB-based tools, hardened steel, clean diagonal cutting, durability, cutting conditions.
UDC 621.9
IN. I. Lavrynenko (Kyiv)
IN. Yu. Malt (Dneprodzerzhinsk)
B. IN. Sytnyk, A. AND. Devitskyi, Yu. I. Nikitin, V. G. Poltoratskyi, O. AT. Pasichny, V. AND. Skryabyn (Kyiv)
Research on the possibilities of effective use of granular mineral concentrates as supporting elements in work layer of diamond circles
A study of the possibilities of effective use of supporting elements in the working layer of diamond wheels in the form of natural mineral granular concentrates to improve the operational characteristics of wheels in grinding processes is presented.
Keywords: support element, working layer, grinding wheel, rutile, staurolite, ilmenite, zircon, disten, quartz, diamond.
UDC 621.762:621.715:620.22
N. IN. Novikov, A. L. Maistrenko, N. M. Prokopiv (Kyiv)
Formation of diamond-hard alloy granules for use in rock-blasting tools
The technological process of forming diamond-hard alloy granules based on synthetic diamond powders and their sintering with the conditions of minimizing diamond softening is described. The requirements for the composition and structure of hard alloys used in granules to ensure reliable diamond retention are defined. Experimental baking of a composite layer based on diamond-hard alloy granules by the method of intensive electrosintering on the steel casings of inserts for rock-blasting tools was carried out.
Key words: diamond, diamond-hard alloy granules, granulation, softening, diamond retention, porosity, rock-breaking tools.
UDC 621.315
IN. I. Garlic (Kyiv)
High absorption of microwave energy at frequencies of 9.5–10.5 GHz in a system with highly elongated molybdenum grains in an aluminum nitride matrix
The high absorption of microwave energy obtained in a composite with an aluminum nitride matrix and highly elongated molybdenum grains at frequencies of 9.5–10.5 GHz is reported, and the possibility of using such composites as bulk vacuum absorbers for powerful microwave devices.
Key words: absorption of microwave energy, elongated grains, molybdenum, aluminum nitride.