UDC 538.945:539.893
T. A. Prikhna, V. E. Moshchil, S. N. Dub, V. B. Sverdun (Kyiv) A. Zhola, J. Rabier (Poitiers, France) Ks. Shaw (Grenoble, France) V. Gavalek, D. Litzkendorf, T. Habisreuter (Jena, Germany)
Processing and oxygen saturation of fused textured ceramics YBaCuO under high and elevated pressures and temperatures
It was found that textured ceramic materials YBa2Cu3O7–ð when saturated with oxygen under elevated (up to 10–16 MPa) pressure and high (700–900 °C) temperatures in a relatively short (72 h) time reach a record level of superconducting (at 77 K in the ab plane Y123 jc ≈ 100 kA/cm2 (0 T), 55 kA/cm2 (2 T) and Hirr 9.5 T) and mechanical (microhardness up to HV = 7.6 GPa and crack resistance up to K1c = 4.4 MPa m0.5 at a load of 4.9 N) properties. This is explained by the formation of a nanostructure of twins serving as pinning centers for vortices of the non-superconducting phase (twinning density ≈ 20–35 μm–1), as well as the formation of a significantly smaller number of microcracks (< 0.2 μm–1) and the prevention of the formation of macrocracks.
Keywords: fused textured ceramics, dislocations, twins, critical current, high pressure, superconducting properties, pinning force.
UDC 666.792.34:539.89
D. A. Stratiychuk, V. Z. Turkevich, N. N. Belyavina, M. A. Tonkoshkura, A. S. Osipov, T. N. Belyaeva (Kiev)
Crystal structure of binary aluminum borides synthesized under high pressure and temperature conditions
Phase formation in the Al−B system under high pressure and temperature conditions and the crystal structure of aluminum borides formed in it were studied. The existence of AlB16, AlB25, AlxB12 borides was established by X-ray diffraction and scanning electron microscopy. It was shown that the crystal structures of the boron-rich AlB16, AlB25, AlxB12 phases synthesized under high pressure are closely related to the crystal structures of known boron modifications.
Keywords: aluminum borides, high pressure, X-ray structural analysis.
UDC 621.921.34
M. G. Loshak, L. I. Aleksandrova (Kyiv)
The influence of the magnitude of the load applied to the tip on the results of measuring the hardness of superhard materials
The magnitude of the load applied to the Vickers diamond tip when measuring the hardness of superhard composite materials is substantiated. It is shown that a load of 5 N during hardness tests provides optimal capabilities for accurate measurement of the indentation and the absence of destruction near it.
Keywords: composite superhard materials, hardness, load on the tip, accuracy of indicators.
UDC 620.178.015
Yu. V. Milman, E. M. Pidgornyuk, A. N. Katrusha, S. I. Chugunova, A. A. Golubenko, S. A. Ivakhnenko (Kiev)
Mechanical properties of type IIb synthetic diamond at 900 °C
The mechanical properties of type IIb synthetic diamond obtained by the temperature gradient method were studied at 900 °C using indenters with different angles between the axis and the pyramid face. A deformation curve was plotted in stress–total deformation coordinates. It was shown that deformation of diamond is accompanied by strain hardening with a linear dependence of flow stress on the degree of plastic deformation. It was found that the microhardness and crack resistance values of the studied synthetic diamond and natural diamond, as well as their deformation mechanism, do not differ significantly.
Key words: indenter, hardness, plasticity, elastic deformation, plastic deformation, Young’s modulus.
UDC 621.9: 621.923
V. I. Lavrinenko (m. Kiev)
Structurally changes the surface ball of the contact surfaces of the circle with NTM and the virus, which can be sampled as a source of increased wear resistance (spit storage)
The formation of the structurally changed surface ball of the contact surfaces of the circle from the supersolid materials and the process that is processed under the infusion of electrophysical processing methods has been observed. It has been shown that the creation of melts on these surfaces changes both their electrophysical and tribotechnical characteristics, and creates a solution for increasing the wear resistance of contact surfaces.
Key words: electrode melts, structural changes in the surface ball, tribotechnical characteristics, contact surface, wear resistance.
UDC 621.923
V. V. Gabitov, P. G. Matyukha (Donetsk)
Productivity and specific cost of internal plunge diamond grinding of hard alloy with periodic electrical discharge effects
The effect of diamond wheel grain size on the productivity and specific cost of internal plunge grinding using an elastic scheme of hard alloy VK15 was studied. It was found that periodic electrical discharge action on the working surface of the wheel with optimal periodicity provides an increase in processing productivity by 396 ‰ and a decrease in specific cost by 305% compared to grinding without such action.
Keywords: internal plunge grinding, elastic scheme, processing productivity, specific costity.
UDC 621.941
L. N. Devin, A. A. Osadchiy (Kyiv)
Improving the performance characteristics of CBN cutters by increasing their damping properties
A design of a tool with special inserts made of damping materials with increased vibration damping capacity has been developed. The influence of damping properties on the vibration amplitude, tool life of CBN cutters and the roughness of the machined surface has been studied.
Keywords: vibrations, damping properties, cubic boron nitride, logarithmic decrement of vibrations, wear, vibration acceleration, finishing turning, hardened steel.
UDC 621.921.34; 666.233.004.14
Y. Le Godec, O. O. Kurakevych, P. Munsch (Paris, France) G. Garbarino, M. Mezouar (Grenoble, France) V. L. Solozhenko (Villetaneuse, France)
Effect of nanostructure on compressibility of cubic BN
Compressibility of high-purity nanostructured cBN has been studied under quasi-hydrostatic conditions at 300 K up to 35 GPa using diamond anvil cell and angle-dispersive synchrotron powder X-ray diffraction. It has been found that the data fit to the Vinet equation of state yields the values of the bulk modulus B0 of 375(4) GPa with its first pressure derivative B0´ of 2.3(3), thus, the nanometer grain size (≈ 20 nm) results in a decrease of the bulk modulus by ≈ 9‰.
Keywords: nanostructure, cubic boron nitride, equation of state, superhard materials.
UDC 661.665.1; 536.421.1:53.092
P. S. Sokolov, V. A. Mukhanov, T. Chauveau, V. L. Solozhenko (Paris)
On the Melting of Silicon Carbide under Pressure
The melting of silicon carbide was studied at pressures of 5–8 GPa and temperatures up to 3300 K and it was found that SiC melts congruently, and its melting curve has a negative slope of –44±4 K/GPa.
Keywords: silicon carbide, melting, high pressure, Si–C system.