UDC 541.16
A. L. Ivanovsky (Yekaterinburg, Russia)
Microhardness of rhenium compounds with boron, carbon and nitrogen
Numerical estimates of Vickers microhardness HV were made for borides (ReB, ReB2, ReB4), carbides (Re4C, Re2C, ReC), nitrides (Re3N, Re2N, ReN, ReN2, ReN4), and also for some ternary diborides (Re1–хМхB2, М = W, Tc, Os, Ir) of rhenium, based on empirical correlation dependences of HV on the shear moduli G and Young’s moduli Y of these phases. The correlation between HV of these phases and their bulk compression moduli B and the so-called brittle-ductile behavior indices G/B was discussed.
Keywords: borides, carbides, rhenium nitrides, elastic moduli, microhardness, correlations, numerical estimates.
UDC 544.72:660.187
A. A. Efremov, P. M. Litvin, A. G. Gontar, S. P. Starik, V. M. Perevertaylo, I. V. Prokopenko, A. M. Kutsay, O. B. Loginova (Kiev)
Macro- and nanoscopic capillary effects on nanostructured real surfaces
The article presents the results of capillary force measurements on various diamond-like materials and allotropic modifications of carbon obtained using a scanning force microscope. The amplitude-frequency characteristics of the nanorelief of the studied surfaces were varied in a wide range by plasma-chemical treatments. The measurements of capillary forces are compared with the macroscopic values of the wetting angle. It is shown that the macroscopic wetting angle depends only on the averaged surface energy and weakly depends on the characteristics of the nanorelief, and nanocapillary forces correlate with both the surface relief parameters and the local wetting angle. The criteria for the multimeniscus mode of measuring capillary forces in surface force spectroscopy and the prospects for using this technique for energy mapping of a real surface are discussed in detail.
Keywords: atomic force spectroscopy, nanocapillary forces, macroscopic wetting angle, nanorelief, energy mapping of a real surface.
UDC 621.921.34-492.2:536.421.5:539.89
O. I. Chernenko, O. O. Bochechka, M. G. Loshak, L. I. Aleksandrova, T. O. Kosenchuk (m. Kiev)
The value of diamond powders synthesized in the Mg–Zn–B–C system
The value of diamond powders with a grain size of 125/100, synthesized in the Mg–Zn–B–C system at different concentrations of boron in the charge, was investigated.It is shown that the distribution of grain values according to the orientation of the soil is correctly described by the Weibull function. The value of diamond powders and reliable intervals for this value are determined. It has been established that its abundance in boron concentrations ranging from 1 to 40% (at.) is described by a function that has a minimum at 20%.
Key words: diamond synthesis, high pressure, boron, value indicator, Weibull subdivision function.
UDC 666.295:620.17
T. A. Prikhna, S. N. Dub, A. V. Starostina, M. V. Karpets (Kyiv)
T. Kabiech, P. Chartier (Potiers, France)
Mechanical properties of materials based on MAX phases of the Ti–Al–C system
The study of materials based on the MAX phase of Ti3AlC2 containing titanium carbide inclusions showed that with an increase in the content of the latter from 2 to 99% (by weight), the nanohardness and Young’s modulus increased from 2.0±0.4 to 23.6±1.2 GPa and from 137±21 to 447±11 GPa, respectively. The power exponent in the creep equation for these samples ranges from 104 to 140, indicating a weak dependence of the mechanical properties of the materials, and hence the MAX phase of Ti3AlC2, on the strain rate. For the samples consisting mainly of the MAX phase of Ti3AlC2, the formation of wide hysteresis loops was observed upon repeated loading/unloading of the indenter. This indicates large losses of elastic energy during cyclic deformation and, therefore, the prospects of using Ti3AlC2 as a damping material. The microhardness of the sample consisting of 98% Ti3AlC2 and synthesized at atmospheric pressure was 2.1 GPa under a load of 4.9 N, and its crack resistance was high (there were no cracks from the corners of the indentation even under a load of 149 N). The microhardness and fracture toughness of the material consisting of 71% Ti3AlC, 6% Ti2AlC and 23% TiC were 3.0±0.6 GPa and 4.3±1.4 MPa∙m1/2, respectively.
Keywords: MAX phase, mechanical properties, nanoindentation, creep.
UDC 621.762.045
A. P. Umansky, A. G. Dovgal, V. M. Kisel, Yu. I. Evdokimenko (Kyiv)
Structure and Wear Patterns of Coatings Made of Composite Metal-Ceramic Materials of the (SiC–Al2O3)–(Ni–Al) System
The structure of coatings made of composite material containing wear-resistant component SiC–Al2O3 and metallic binder Ni–Al obtained by high-speed air-fuel spraying on medium-carbon steels was investigated. The tribological characteristics of such coatings under friction conditions without lubricants in air were studied, the features and patterns of their wear mechanisms were determined.
Keywords: coating, ceramics, wetting, high-speed air-fuel spraying, wear resistance.
UDC 621.923
V. I. Kalchenko, N. N. Pogiba, D. V. Kalchenko (Chernigov)
Determination of cutting force components during deep grinding of surfaces of revolution with an oriented elbor wheel
A method for calculating the cutting force components during deep cylindrical grinding of stepped rollers, smooth cylindrical and other surfaces of revolution with an oriented elbor wheel is proposed, taking into account the parameters of the working surface of the wheel, as well as the influence of cutting and deforming edges, which helps to select optimal processing modes for one setup of surfaces of revolution of the “shaft” type. An example of calculating the cutting force components according to this method during deep high-speed grinding of a stepped roller with an oriented elbor wheel with optimization of the rotation angle is given. The normal component of the cutting force is calculated not only at the end face, but also at the periphery of the wheel, taking into account the influence of cutting and deforming edges.
Keywords: high-speed grinding, crossed axes, CBN wheel, cutting forces, cutting and deforming edges.
UDC 622.24.051:536.2:004.942
V. A. Dutka, A. L. Maistrenko, V. A. Lukash, O. V. Melnichuk, L. M. Virovets (m. Kiev)
Computer and experimental investigation of the hardness distribution of a steel body cut as a result of phase transformations during induction hardening
The results of numerical and experimental studies of the hardness distribution of the steel body of the carbide cut after induction hardening in the cores are presented. with various cold-blooded buildings. The heating mode for the cutting body was chosen in the same way as for the process of induction soldering of the carbide insert before the cutting body and the subsequent hardening. The results of calculating the hardness of different sections of the axial cut of the cutter body and experimental studies agree well with each other to confirm the adequacy of the numerical method.
Key words: computer modeling, inductive hardening, experimental research, phase transformation, hardness.
UDC 621.921.34
N. V. Novikov, G. P. Bogatyreva, G. D. Ilnitskaya, G. A. Petasyuk, A. M. Isonkin, I. N. Zaitseva (Kyiv)
The influence of homogeneity of synthetic diamond grinding powders on the performance of drilling tools
It is shown that sorting by the degree of defectiveness and additional classification with the allocation of narrow fractions of grain sizes of 400/355 and 250/220 diamond powders with magnetic properties obtained from diamonds synthesized in the presence of ferrocobalt, made it possible to obtain elite diamond powders of the AC160-E–AC65-E brands with high homogeneity in strength and geometric characteristics. Equipping drill bits with such powders allows increasing the performance of the tool when drilling hard rocks. It has been established that with an increase in the strength of powders of grades AC160-E–AC65-E and their homogeneity in strength, together with an increase in homogeneity in linear dimensions, the wear rate of crowns decreases.
Keywords: diamond powders, degree of defectiveness, homogeneity, strength, wear rate.