UDC 661.868.1:004.94:62-987
O. P. Lyudvichenko*, O. O. Leshchuk, I. A. Petrusha
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*ludvial@ukr.net
Computer modeling of the influence of the concentration of components and the size of heaters on the thermal state of a high-pressure cell for studying the solubility of gallium nitride in iron (pp. 3-13)
Existing technologies for obtaining gallium nitride crystals are considered. The thermal state of a high-pressure apparatus cell used to study the solubility of gallium nitride in iron is modeled using the finite element method. The results of the calculations are presented as temperature fields in various elements of the apparatus. The influence of varying the wall thickness of the tubular heater and the change in the concentration of zirconium dioxide in axial heaters on the thermal state of the high-pressure cell was investigated. It was shown that when the wall thickness of the tubular heater changes, the temperature in the center of the cell changes linearly. An increase in the heater thickness leads to a slight (~ 2 °C) increase in the maximum temperature drop in the Armco-iron sample under study. The temperature drop at the characteristic points of the cell in the radial and axial directions decreases with an increase in the concentration of zirconium dioxide in the axial heaters. The optimal composition of the axial heaters for conducting experiments to study the solubility of gallium nitride in iron corresponds to the values of the ZrO2 and graphite concentrations of 60 and 40% (by mass), respectively.
Keywords: gallium nitride, high temperature, high pressure, high pressure apparatus (HPA), high pressure cell (HPCC), finite element method.
UDC 532.696:621.791.3:621.92
V. P. Krasovsky1, *, O. E. Shapiro2
1I. M. Frantsevich Institute for Problems of Materials Science, NAS of Ukraine, Kyiv, Ukraine
2Titanium Brazing. Inc., Columbus, USA
*vitalkras1955@gmail.com
Wetting and soldering of superhard materials based on dense modifications of BN with solder melts (pp. 14-24)
New data on the wetting of superhard materials based on dense modifications of BN with solder metal melts Zr–Ti–Ni, Ti–Zr–Cu–Ni and Cu–Sn–Ti by the lying drop method in the range of 900–1000 °C are presented. The wetting angles vary from 5 to 25° depending on the content of the active component (Zr, Ti) in the solder composition. The contact interface of metal melt/BN was investigated. The formation of nitrides and borides of Zr and Ti at the interface was established. Soldered joints of samples of BN with each other were obtained and the physical and mechanical characteristics of the joints for shear and bending were studied.
Keywords: boron nitride, wetting, brazing, titanium and zirconium, physical and mechanical characteristics, shear, bending.
UDC 620.22-621.921.34
B. T. Ratov1, V. A. Mechnyk2, *, Miroslaw Rucki3, E. S. Gevorkyan3, 4, M. O. Bondarenko2, V. M. Kolodnitsky2, **, V. O. Chyshkala3, 5, G. A. Kudaikulova1, A. B. Muzaparova1, D. L. Korystyshevsky2
1NAO “Kazakh National Research Technical University named after K. I. Satpayev”, Almaty, Kazakhstan
2Institute of Superhard Materials named after V. M. Bakul, NAS of Ukraine, Kyiv, Ukraine
3Kazimierz Pulaski University of Technology and Humanities in Radom, Poland
4Ukrainian State University of Railway Transport, Kharkiv, Ukraine
5V. N. Karazin Kharkiv National University, Kharkiv, Ukraine
*vlad.mechnik2019@gmail.com
**vasylkolod56@gmail.com
Composite materials Salmaz‒(WC‒Co)‒ZrO2 with improved mechanical and adhesive properties (pp. 25-43)
The structure, mechanical (hardness H, modulus of elasticity E) properties were studied, the parameters for determining the resistance of the material to elastic H/E and plastic H3/E2 deformations, the resistance to abrasive wear 1/(E2H), as well as the ability of the hard alloy matrix to retain diamond grains from falling out of composite diamond-containing materials (CBMs) 25Salmaz‒70.5WC‒4.5Co with different ZrO2 contents (in the range from 0 to 10% (by weight)), formed by the plasma-spark sintering method in the temperature range 20‒1350 °С at a pressure of 30 MPa for 3 min. The initial KAM has a coarse-grained structure with weak adhesion of diamond grains to the hard alloy matrix, is characterized by low values of H/E, H3/E2 and 1/(E2H), which is the cause of premature fallout of diamond grains. The presence of ZrO2 in the composition of the KAM prevents the processes of Oswald ripening and acts as a growth inhibitor, ensuring a decrease in WC grains, the formation of strong adhesion of diamond grains to the matrix and a significant increase in the parameters H/E, H3/E2 and 1/(E2H). As a result, the ability of the matrix to reliably hold diamond grains from premature fallout during the operation of the KAM increases. It is shown that the addition of zirconium dioxide in the amount of 10% (by weight) to the 25Salmaz‒70.5WC‒4.5Co composite led to an increase in the parameters H/E from 0.043 to 0.057, H3/E2 from 0.05 to 0.075 GPa, 1/(E2H) from 0.75×10-7 to 2.75×10-7 GPa-3 and the manifestation of signs of strong adhesion between diamond grains and the hard alloy matrix in the KAM samples.
Keywords: composite, tungsten carbide, cobalt, zirconium dioxide, concentration, composition, plasma-spark sintering, structure , properties, adhesion.
UDC 621.762.3
M. M. Prokopiv1, Yu. P. Ushchapovsky1, *, O. V. Kharchenko1, G. M. Kramar2, L. G. Bodrova2, G. P. Kysla3
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Ternopil National Technical University named after Ivan Pulyuy, Ternopil, Ukraine
3PrJSC “Plasmatek”, Vinnytsia, Ukraine
*gromurasls@gmail.com
The influence of the gas pressure increase rate during vacuum-compression sintering on the structure and properties of the VK6M hard alloy (pp. 44-52)
Using the technology of vacuum-compression sintering, which allows obtaining hard alloys with a high level of mechanical and operational properties, the influence of the rates of 0.08, 0.2 and 0.5 MPa/min of gas pressure increase to 5 MPa during vacuum-compression sintering on the structure and properties of the fine-grained VK6M hard alloy was investigated. A positive effect of increasing the gas pressure increase rate on the ultimate strength during bending and operational stability was established due to obtaining a finer-grained structure (dWC = 1.24 μm), reducing the residual microporosity to A1 0.02, increasing the form factor of carbide grains to 0.84, and reducing the intensity of gas desorption by 2.5–7.0 times. The ultimate strength for bending of the alloy sintered at a gas pressure increase rate of 0.5 MPa/min is 1.35 times higher than that of the alloy sintered at a gas pressure increase rate of 0.08 MPa/min and 1.5 times higher than that of the alloy sintered in vacuum, and the relative operational stability in the case of rough milling is 1.35 and 1.8 times higher, respectively.
Keywords: VK6M hard alloy, vacuum compression sintering, gas growth rate, microstructure, mechanical properties, operational stability.
UDC 539.89:666.657.5
Liang Cui1, 2, Wangxi Zhang1, 2, *, Baoyan Liang1, 2, Linlin Wang1, Mingli Jiao1
1Materials and Chemical Engineering School, Zhongyuan University of Technology, Zhengzhou, P.R. China
2Henan Joint International Research Laboratory of Diamond Engineering Technology, Zhengzhou, P.R. China
*zwxlby@126.com
HP-HT treatment of hexagonal boron nitride to enhance photocatalytic degradation of organic pollutants (pp. 53-58)
Hexagonal boron nitride (h-BN) solid waste obtained from high-pressure, high-temperature (HP-HT) synthesis of cubic boron nitride was used as a photocatalyst to study its degradation efficiency in organic pollutants. The results showed that the main phase of the solid waste was h-BN, which contained a small amount of impurity phases. The grains were irregular in shape and the grain size was about a few microns. Compared with commercial h-BN powder, the obtained h-BN waste had a higher absorption capacity in the entire visible light range. Under visible light irradiation, the removal ability of h-BN was very poor, but the addition of H2O2 improved the photocatalytic performance of waste h-BN and promoted the almost complete decomposition of methyl orange, rhodamine B, and methylene blue dyes in 30, 60, and 80 min, respectively.
Keywords: h-BN, waste, photocatalysis, H2O2, decomposition.
UDC 661.657.5
Xixi Hu1, Ailing Sun1, Yang Liu1, Shenglin Zhong1, Peicheng Mo1, 2, Yi Wu1, *1College of Materials Science and Engineering, Guilin University of Technology, Guilin, P.R. China
2Guangxi Key Laboratory of Superhard Material, China Nonferrous Metal (Guilin) Geology and Mining Co., Ltd., Guilin, Guangxi, P.R. China
*wuyi1958glut@126.com
Sintering of polycrystalline cubic boron nitride PcBN with addition of TiC0.5 and Al (pp. 59-69)
A polycrystalline cubic boron nitride (PcBN) with excellent mechanical properties was investigated, sintered using highly active TiC0.5 and metallic aluminum as a binder at high temperature and pressure. The effect of sintering temperature on the phase composition, microstructure, relative density and mechanical properties of PcBN composites was studied by X-ray diffraction, scanning electron microscopy and energy spectrum analysis. The results showed that under the conditions of low reaction temperature of 1400 °C and holding time of 10 min, a PcBN material with excellent properties was obtained. Strengthened phases such as Ti(C,N), TiB2 and AlN are stably present in the sintered material. In particular, the microhardness, flexural strength and fracture toughness of the sintered body initially increased and then decreased with increasing sintering temperature, their maximum values were 39.74 GPa, 1217 MPa and 8.78 MPa×m1/2, respectively.
Keywords: non-stoichiometric ratio, TiC0.5, PcBN, sintering at high temperature and pressure.
UDC 621.623
Yu. D. Filatov
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
filatov2045@gmail.com
New regularities of polishing surfaces of parts made of non-metallic materials (pp. 70-82)
As a result of the study of the mechanism of polishing precision surfaces of parts made of non-metallic materials using dispersed systems of micro- and nanoparticles of polishing pores pulley it was established that the formation of particles of the processed material sludge, particles of wear of the polishing powder and the lapping material is a consequence of the Förster resonant energy transfer, which occurs in the resonator formed by two parallel surfaces of the processed material and the lapping material. It is shown that with an increase in the Q-factor of the resonator, the polishing performance of non-metallic materials increases nonlinearly, and the roughness of the processed surfaces deteriorates. The relationship between the Q-factor and the optical length of the resonator is established and it is shown that the maximum values of the removal rate of the processed material, the intensity of wear of the polishing powder and the wear of the lapping surface are achieved when the optical length of the resonator is equal to an integer number of half-waves characteristic of nanoparticles of sludge, polishing powder and lapping material. It is shown that the polishing performance of parts made of non-metallic materials and the roughness of their polished surfaces depend extremely on the separation between the processed material, the polishing powder and the dispersed system by the dielectric constant.
Keywords: resonant energy transfer, material removal rate, roughness.
UDC 549.211.002.61:546.26.162
G. A. Petasyuk*, Yu. V. Sirota
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*petasyuk@ukr.net
Comparative analysis of grain shape characteristics and abrasiveness of natural impact and synthetic diamond powders (pp. 83-93)
A comparative quantitative analysis of grain shape characteristics and abrasiveness of natural impact and synthetic diamond powders was carried out. The features of the morphology of diamond powder grains that affect their abrasive ability were studied according to the following characteristics: shape and specific perimeter of the grain projection, their flattening coefficient, and the external specific surface area of the powder. The indicators of the differential shape similarity of the grain projection of the studied powders and their uniformity according to this characteristic as a sign of the quality of the powders were determined. The trend and degree of change in the indicators of the analyzed characteristics in the case of the transition from impact diamond powders to synthetic diamond powders were established. A joint quantitative analysis of the relationship between the detected trend of change in the characteristics of the grain morphology of the studied diamond powders of two types of material origin and the abrasive ability of the powders was carried out.
Keywords: diamond, impact, synthetic, grain, projection, shape similarity, flattening coefficient, specific surface area.
UDC 661.665.1:539.25:536.21
V. G. Kulych1, I. P. Fesenko1, *, M. O. Kovtyukh1, V. M. Tkach1, O. M. Kaydash1, E. F. Kuzmenko1, V. I. Chasnyk2, V. V. Ivzhenko1
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Orion Research Institute, Kyiv, Ukraine
*igorfesenko@ukr.net
Microstructure and Thermal Conductivity of Reaction-Sintered SiC (pp. 94-96)
The thermal conductivity of the dense structure of reaction-sintered silicon carbide, a ceramic material obtained by impregnating the SiC framework with silicon with subsequent carbidization of the liquid phase, was determined. The resulting SiC material has a thermal conductivity of 177 W/(m·K), which is 36% of the theoretically predicted value.
Keywords: silicon carbide, silicon infiltration, microstructure, thermal conductivity.