UDC 548.39:539.2
N. AND. Bondarenko, A. N. Zhukovsky, V. AND. Mechnyk (Kyiv)
Analysis of the main theories of sintering of materials. 2. Chemical reactions and nucleation processes. Basic principles of modeling sintering of superhard composite diamond-containing materials (review)
The basic kinetic equations for the description of surface chemical reactions and the formation of nuclei of new phases between components in multicomponent mixtures under conditions of high pressure and temperature are given. The physical interpretation of these equations is given and the basic provisions for describing the physical and chemical processes during sintering of superhard composite diamond-containing materials are formulated.
UDC 661.657.5
WITH. IN. Tkach, A. AND. Shulzhenko, N. P. Bezhenar, V. N. Tkach, S. AND. Bozhko, P. I. Kravchuk, O. P. Prussia (Kiev)
Electrical conductivity of composites of cubic boron nitride on a carbide substrate and the possibility of their electric spark cutting
The nature of the change in electrical resistance in the working layer of cubic boron nitride composites and at the interface with a hard alloy substrate, depending on the phase composition and distribution in the structure of electrically conductive and non-conductive phases, is investigated. Factors affecting the process of cutting plates by the electrospark method are analyzed.
UDC 621.9.048
AT. N. Grigoriev, I. AND. Podchernyaeva, A. D. Panasiuk, I. P. Neshpor, V. IN. Pasichny, A. P. Umansky, O. IN. Subbotyna (Kyiv)
Structural and phase transformations in ceramics of the SiC—Al2O3—ZrO2 system under the influence of concentrated solar radiation
The change in the composition, structure, and microhardness along the depth of the slag layer formed on the surface of the ceramics of the SiC—Al2O3—ZrO2 system when it is exposed to concentrated solar radiation in the air is studied. The formation of a gradient structure with an outer layer of mullite and a high (≈ 35 GPa) microhardness of the near-surface layer is shown, which decreases towards the base simultaneously with the increase in porosity.
UDC 539.4:620.2
M. G. Loshak, S. B. Polotniak, L. I. Aleksandrova (Kyiv)
The influence of the degree of contiguity of the carbide phase on the formation of the stress-strained state in hard alloys during cooling after sintering
Numerical modeling assessed the stress-strain state formed during cooling after sintering in individual structural elements of model tungsten alloys in which tungsten carbide grains are completely separated by cobalt interlayers or there is a continuous carbide framework, as well as in real alloys differing in the degree of carbide phase contiguity. A decrease in the degree of contiguity of the carbide phase leads to a decrease in the level of final stresses in the phase components of the alloy.
UDC 666.3:539.5
T. B. Serbeniuk, V. IN. Ivzhenko, V. B. Sverdun, I. P. Fesenko, V. AND. Chasnyk, R. WITH. Shmegera, T. AT. Prikhna (Kyiv)
Sintering of AlN—SiC composite material
Sintering of aluminum nitride with the addition of silicon carbide powder of different dispersion was carried out at normal pressure, using yttrium oxide as a sintering activator. It was shown that the shrinkage of AlN—SiC samples during sintering depends on the average particle size and silicon carbide content. The obtained ceramic composites based on aluminum nitride contain homogeneously distributed silicon carbide inclusions. X-ray phase analysis did not reveal any other phases in the sintered composites, except for aluminum nitride, silicon carbide and yttrium aluminum garnet. AlN—SiC composites have Vickers hardness HV (15kH) 13.2—15.6 GPa, crack resistance — 3.8—4.3 MPa·m0.5, thermal conductivity — 47—55 W/(m·K), dielectric constant — 10.9—14.9 (3 GHz), dielectric loss angle tangent — 0.13—0.50 (3 GHz).
UDC 539.89
WITH. AND. Vynogradov (Kyiv)
Analysis of the methodology of comparative testing of materials on Bridgman anvils (methodology of M. Wakatsuka)
On the basis of the similarity theory, an analysis of the method of comparative study of the mechanical properties of various materials by compression on flat Bridgman anvils, proposed by M. Wakatsuka, was carried out. It was shown that this technique does not meet the conditions that ensure the similarity of the stressed state, which correctly compares the mechanical properties of different materials. A modified formulation of M. Wakatsuka’s technique is proposed, which takes into account the conditions of similarity and allows not only to draw a conclusion about the qualitative ratio of yield strength values, but, knowing the dependence of the yield strength for one material, to determine this dependence for the second material in similar conditions.
UDC 621.923.4: 621.921.34: 621.318
IN. I. Lavrynenko (Kyiv) A. M. Brovchenko (Kirovohrad)
Investigation of the conditions for ensuring defect-free processing of hard magnetic alloys with STM wheels
The results of a study of the influence of the state of the cutting surface of wheels made of superhard materials on the productivity and quality of processing of magnetic hard alloys are presented. The conditions for achieving defect-free processing of alloys have been established. It is shown that according to the criterion of the minimum cutting force during grinding, the diamond ones are the best circles on a polymer bond with glass coating on the grains or without coating, and when cutting — circles on a galvanic bond.
UDC 621.891:681.7:539.621
D. IN. Tkachuk (Gomel) V. IN. Rogov, A. G. Vetrov (Kyiv)
Research of friction processes and cutting force during finishing of scintillator parts made of thermoplastic polymers with cutters with cutting elements made of diamond, sapphire, and zirconium ceramics
Friction processes and cutting force during fine microturning of polystyrene scintillator parts with cutters with diamond, sapphire, and zirconium ceramic cutting elements are investigated. The influence of the coefficient of friction and the angle of friction of the interacting tool and processed materials on the force of cutting, as well as the possibility of using sapphire and zirconium ceramics as tool materials instead of diamond to ensure the required condition of the machined surface of the parts, has been established.
UDC 621.928.4:621.921.1:621.922.34
G. AND. Petasiuk (Kyiv)
Comparative analysis of the adequacy of methods of quantitative assessment of the homogeneity of powders of superhard materials
The results of a comparative analysis of the homogeneity indicators provided by the system-criterion and other known methods are given. It has been established that indicators based on the system-criterion method react more adequately, sensitively and accurately to various changes in the quality of abrasive powders of superhard materials.
UDC 621.922
T. G. African (Havar, Armenia)
Assessment of the degree of orientation of abrasive grains in the abrasive-containing layer
A technique for estimating the degree of orientation of abrasive grains in the diamond-bearing layer based on the ratio of the sizes of their projections on the working surface of the wheel is proposed.