UDC 620.22:621.921.34:661.657.5:539.533
Xiangting Ren, Xiaozhi Yan, Liping Wang, Yusheng Zhao, Shanmin Wang*
Department of Physics, Academy for Advanced Interdisciplinary Studies & Shenzhen Engineering Research Center for Frontier Materials Synthesis at High Pressure, Southern University of Science and Technology, Shenzhen, P. R. China
*yanxz@sustech.edu.cn
**wangsm@sustech.edu.cn
Strengthening of Superhard Materials by Nanostructure Engineering (pp. 3-30)
Traditional superhard materials, mainly diamond and cubic boron nitride, are used for scientific research and are used in many industries, especially as cutting and machining tools. Over the past few decades, enormous experimental efforts have been directed to the relentless search for new superhard systems with mechanical properties superior to traditional ones. On the other hand, it has been shown to be effective to enhance the mechanical properties of traditional superhard materials by nanostructuring. Experiments on the fabrication of nanostructured diamond and cubic boron nitride under high pressure and temperature conditions have shown record-breaking (~200 GPa) hardness values, almost twice that of their single-crystal counterparts (~110 GPa). These nanocrystalline forms of traditional superhard materials with enhanced toughness and thermal stability have great potential for the application of next-generation superhard materials. To date, knowledge about such nanostructured superhard materials is still insufficient, and there are many mysteries surrounding the formation mechanism, the influence of pressure and temperature on the growth of nanograins and defects (e.g., nanotwins), and the strengthening mechanism underlying the nanoinfluence on mechanical properties. This paper provides an overview of this relevant topic, which will provide important directions for further research on superhard materials.
Keywords: superhard materials, high pressure, hardness, nanomaterial.
UDC 666.233
V. Yu. Dolmatov1, *, O. N. Ozerin2, A. Vehanen3, V. Myllymäki3, A. O. Dorokhov4
1Federal State Unitary Enterprise “Special Design and Technological Bureau “Technologist”, St. Petersburg, Russia
2Federal State Budgetary Institution of Science Institute of Synthetic Polymeric Materials named after M. S. Enikolopov, RAS, Moscow, Russia
3“CarbodeonLtd. Oy”, Vaanta, Finland
4JSC “Plant “Plastmas”, Kopeysk, village Sovietov, Russia
*diamondcentre@mail.ru
On the question of the mechanism of formation of detonation diamonds (pp. 31-38)
The possibility of the formation of the prestructure of detonation nanodiamonds (DNA) in the plasma of the chemical reaction zone in the form of a fractal carbon network with the formation of a three-dimensional ordered carbon core at its nodes is shown, the density of the nodes should be within 2.5–3.2 g/cm3. When passing through the Chapman-Jouget plane, plasma carbon formations crystallized into DNA or amorphized. DNA formation occurred at a distance of 1/3–3/4 of the charge diameter from the detonation wave front. Under optimal conditions, ~ 20% (by mass) of the total carbon of the explosive was used for DNA formation.
Keywords: detonation nanodiamonds, formation mechanism, chemical reaction zone, Chapman-Jouget plane, condensed carbon, plasma, nanodiamond formation time.
UDC 621.921.34:548.53:66.097.3
Sang Jun Cha, Myong Chol Pak*, Kwang-Il Kim, Su Gon Kim
Department of Physics, Kim Il Sung University, Ryongnam Dong, Taesong District Pyongyang, Democratic People’s Republic of Korea
*myongcholpak@163.com
Characteristics of recrystallization of catalytic alloy and graphite in diamond synthesis (pp. 39-48)
The characteristics of recrystallization of catalytic alloy and graphite in the process of diamond synthesis under ultrahigh pressure and high temperature are considered. In the process of catalytic diamond synthesis, the metal is plastically deformed due to increasing pressure, and then recrystallizes as the temperature increases. During the recrystallization of the catalytic metal, graphite particles have a spherical shape in the region in contact with the catalyst, and an arbitrary shape outside this region. The distribution of the electron charge density and the cohesion energy of the cementite structure were calculated using the first-principles method for studying the interaction between transition metal elements and carbon atoms during high-temperature catalytic synthesis. Having determined the lattice parameter constants, the cohesion energy was obtained by subtracting the total energy of the crystal from the sum of the total energies of the atoms that make up the crystal and dividing it by the number of atoms. The effect of the catalyst on the synthesis of diamond was analyzed.
Keywords: diamond, catalyst, graphite, recrystallization, cohesion energy.
UDC 620.22-621.921.34
B. T. Ratov1, M. O. Bondarenko2, V. A. Mechnyk2, *, V. V. Strelchuk3, T. O. Prikhna2, V. M. Kolodnitsky2, **, A. S. Nikolenko3, P. M. Lytvyn3, I. M. Danilenko3, V. E. Moshchil2, E. S. Gevorkyan4, A. S. Kosminov1, A. R. Borash5
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
3V. E. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kyiv, Ukraine
4Ukrainian State University of Railway Transport, Kharkiv, Ukraine
5Sh. Esenov Caspian State University of Technology and Engineering, Aktau, Kazakhstan
*vlad.me4nik@ukr.net
**vasylkolod56@gmail.com
Structure and properties of vacuum hot-pressed sintered WC–Co composites with different CrB2 contents for drill bits (pp. 49-63)
Cold pressing methods with subsequent vacuum hot pressing formed composite samples with a diameter of 10 mm and a thickness of 8 mm based on tungsten carbide and cobalt with different (from 0 to 10% (by weight)) chromium diboride contents. A comprehensive study of the composites using traditional methods of testing mechanical properties in combination with digital optical, transmission and scanning atomic force microscopy methods allowed us to establish stable correlations between the content of the CrB2 additive with the average WC grain size, microstructure parameters, hardness and fracture toughness of the composites. For WC–6Co composites (% (by mass)), a coarse-grained structure was observed both with direct contact of WC grains and with large areas of cobalt bonding. The introduction of the CrB2 additive into the composite, on the contrary, allows the formation of thin (~ 100 nm) and extended layers of cobalt bonding even between small WC grains. It is shown that the CrB2 additive allows the formation of a finer-grained structure, the parameters of which can be purposefully controlled by changing its concentration. It was found that the introduction of the CrB2 additive into the composite in an amount of 4% (by mass) leads to a more than twofold increase in fracture toughness – from 4.4 to 9.8 MPa∙m1/2, with a slight decrease in hardness from 15.1 to 13.0 GPa. With further increase in CrB2 content from 4 to 10% (by weight), a gradual decrease in fracture toughness and hardness was observed.
Keywords: composite, tungsten carbide, cobalt, chromium diboride, composition, concentration, vacuum hot pressing, structure, hardness, fracture toughness.
UDC 537.534.2:679.826
Lei Zhang*, Fuming Deng, Zhenhai Guo
School of Mechanical Electronic and Information Engineering, China University of Mining and Technology, Beijing, P. R. China
*15036638883@163.com
Enhancing the adhesion of diamond coating to hard alloy by pre-treatment of the substrate surface structure with laser (pp. 64-77)
The instantaneous effect of high laser temperature on the surface of the substrate prepared for studying the topography of the microstructure, which causes melting of the surface structure, cooling and recovery, causing changes in the surface topography and surface microstructure of the substrate, was investigated. It is shown that after laser and ultrasonic pretreatment, the roughness of the tool surface increases significantly and a regular wavy texture appears, the number and size of defects in the zone of restoration of the shallow structure of the substrate increase significantly, forming a unique stereoscopic defective and wavy stepped structure, increasing the density and number of nuclei on the defects. The structure of the hole connectivity enhances the conditions for the growth of crystal nuclei, improves the mechanical adhesion of the coating and the substrate, and removes residual stresses in the surface layer of the substrate.
Keywords: laser pretreatment, microstructure topography, CVD diamond coating, microstructure restoration, coating adhesion.
UDC 621.921.34:666.233.08374
G. A. Petasyuk, O. O. Bochechka, Yu. V. Sirota
V. M. Institute of Superhard Materials Bakulya NAS of Ukraine, Kyiv, Ukraine
*petasyuk@ukr.net
**bochechka@ism.kiev.ua
***yatoris@gmail.com
Expanding the application capabilities of the search-analogue method for identifying the projection shape of abrasive powder grains (pp. 78-89)
The degree of perfection of the quantitative-object composition of the set of basic figure-analogues of the search-analogue method for identifying the projection shape of abrasive powder grains is investigated. In order to expand the application capabilities of the specified method, it is proposed to supplement the known list of basic figure-analogues with figures in the form of semi-regular octagons and dodecagons. An analytical presentation of simple criteria for form similarity to new basic figure-analogues is performed and the corresponding software is created. The results of testing the improved search-analogue method on standard grinding powders of synthetic diamond and electrocorundum are presented.
Keywords: diamond, grinding powder, grain, projection, shape similarity, identification, index.
UDC 546.22/.27:620.178.152.3
V. L. Solozhenko
LSPM–CNRS, Université Sorbonne Paris Nord, Villetaneuse, France
*vladimir.solozhenko@univ-paris13.fr
Hardness of new boron chalcogenides B12S and B12Se (pp. 90-93)
The hardness of polycrystalline boron chalcogenides, rhombohedral B12S and B12Se, was predicted using modern theoretical models and experimentally investigated using microindentation. Both two chalcogenides exhibit Vickers hardness of ~ 33 GPa, which exceeds that of boron carbide, and therefore belong to the family of (super)hard phases.
Keywords: boron chalcogenides, hardness, bulk modulus.