UDC 546.26-162:541.183
A. V. Romanyuk (Vyshgorod) N. V. Novikov (Kyiv) Yu. I. Gorlov (Vyshgorod) G. P. Bogatyreva (Kiev)
Anomalous Properties of Diamonds and Chemical Reactivity of Their Surface
Based on a quantum-chemical study of the electronic structure of molecular models of diamond, an explanation is given for its extreme mechanical and thermal properties and high chemical passivity. It is shown that the hardness and elastic characteristics of diamond are determined not by the strength of the C—C chemical bonds, but by the repulsive (attractive) forces of carbon atoms during deformation of the material skeleton. Possible surface active centers are detailed, elementary chemical transformations on the diamond surface during its interaction with molecular oxygen are considered, and a conclusion is made about the predominantly heterolytic mechanism of oxidation reactions. A clear relationship is revealed between the hardness and chemical reactivity of diamond. It is shown that its chemical passivity is associated with high energy costs for deformation of the tetrahedral environment of framework carbon atoms during formation of transition complexes of C—C bond cleavage reactions.
UDC 544.722.54: 661.883.1: 661.657
V. M. Perevertaylo, O. I. Kaplunenko, E. V. Ishchenko, B. G. Mischanchuk, O. B. Loginova (Kiev)
Influence of the chemical state of the zirconium dioxide and boron nitride surface on adhesion in the solid—liquid contact system
The results of a study of the wettability of a number of zirconium dioxide and boron nitride modifications with liquids of different polarity (water, glycerin) are presented, depending on the method of surface treatment of these materials. Using the thermal desorption method, it was found that oxidation leads to surface destruction, and holding in vacuum stabilizes the surface layer.
UDC 620.193:546.271
A. P. Umansky, V. A. Lavrenko, S. S. Chuprov, S. A. Petrichenko (Kiev)
Mechanism of high-temperature oxidation of clad composite materials based on titanium diboride
The resistance of composite materials based on titanium diboride, clad with nickel and copper, to high-temperature oxidation in air was studied. It was shown that copper cladding does not significantly affect the oxidation process of composite materials, and nickel cladding leads to an increase in the temperature of the onset of their intense oxidation by 150 °C. This allows us to recommend composite materials based on titanium diboride, clad with nickel, for applying wear- and corrosion-resistant gas-thermal coatings.
UDC 620.186:537.311.3
S. V. Tkach, E. F. Kuzmenko, V. N. Tkach, A. G. Gontar, A. A. Shulzhenko (Kyiv)
Determination of the Specific Electrical Resistance of a Two-Layer Cutting Insert Based on cBN Using Digital Scanning Electron Microscopy
The article discusses the methodological features of measuring the specific electrical resistance of a composite material based on cubic boron nitride cBN using a scanning electron microscope probe. The change in the integral specific resistance of a two-layer cutting insert was studied when moving from a VK6 hard alloy substrate to a composite layer containing cBN, TiN, and AlN phases, as well as in local areas of the composite. Uniform distribution of the specific electrical resistance over the surface of the composite indicates the homogeneity of the material and can be used to test the quality of the cutting layer structure.
UDC 537.683:553.82
I. Kh. Abdukadirova (Tashkent)
The effect of reactor radiation on the absorption and luminescent properties of corundum
The effect of reactor radiation on some parameters of corundum, in particular, on its luminescent, absorption properties and structure, was studied using optical and X-ray spectroscopy methods. Dose dependences of changes in the intensity of a number of luminescence and color bands, characteristics of individual reflections and crystal lattice parameters were established. The presence of kinks and extrema in these dependences was revealed. The patterns of generation, thermal and photobleaching of some centers were determined, their nature was discussed. The values of activation energy and the contribution of radiation reabsorption were estimated. Acceleration of the process of radiation damage to corundum under the action of high fluences of reactor radiation, and the appearance of disordered regions in the crystal were detected. The results obtained are analyzed within the framework of existing models.
UDC 621.315.592
A. N. Katrusha, N. V. Novikov, S. A. Ivakhnenko, O. A. Zanevsky (Kyiv)
Features of the defect-impurity composition of synthetic diamond single crystals grown by the temperature gradient method
Synthetic diamond single crystals grown by the temperature gradient method from various growth systems were studied. Single crystals were identified that were close in their defect-impurity composition to natural diamonds of the IaA/Ib type. Qualitative dependences of the intensity of the IR absorption spectra of the studied synthetic diamond single crystals were established diamonds, their color and morphology from the concentration of boron impurity. The possibility of simultaneous presence in them of significant concentrations of paramagnetic impurity nitrogen (center C — donor), pairs of nitrogen-boron atoms in neighboring substitution positions (center D), and impurity boron — acceptor is shown. Such diamonds can be attributed to a new mixed type IIb/Ib.
UDC 621.923.042
M. N. Sheiko, O. V. Khimach (Kyiv)
Plunge dressing with diamond bars in the light of mechanical and statistical concepts of abrasive-diamond processing. Message 2. Some theoretical issues of operation of a tool with a non-uniform working surface
The main patterns of change in mechanical characteristics during plunge dressing with diamond stones, established by the authors and described in the previous message, for the first time, by using the apparatus of the mechanical-statistical theory of grinding, are supplemented by consideration of some theoretical issues of operation of a tool with a non-uniform working surface – with variable grain size and number of grains per unit area of the surface. The efficiency of such a tool is shown.
UDC 669.018.25: 620.178.16
N. A. Yurchuk, I. N. Diorditsa (Kiev)
Application of hot-pressed tungsten carbide hard alloy with a nickel binder for turning steel
The possibility of increasing the strength and performance properties of tungsten carbide hard alloy with a nickel binder VN8 by improving its structural state is shown. The results of alloy testing during steel turning are presented. The real possibility of using the VN8 alloy as a material for blade cutting tools is established.
UDC 621.919
Ya. B. Nemirovsky, L. I. Derevets, S. B. Polotnyak (Kyiv)
The influence of the geometry of the deforming element on its strength
The influence of the geometric parameters and loading conditions of the deforming elements used in deforming drawing on their structural strength is estimated numerically using the finite element method and a non-local strength criterion. It is shown that the influence of the working cone angle itself when changing in a fairly wide range on the magnitude of stresses was not observed, and the influence on the strength of the deforming element was taken into account by the height of the element, the length of the contact and the change in external loads.
UDC 622.24.051:536.2:004.942
V. A. Dutka, V. M. Kolodnitsky, S. D. Zabolotny, I. A. Sveshnikov, V. A. Lukash (metro Kiev)
Modeling the level of temperature in the rock elements of drill bits
A numerical modeling of the temperature level in the working elements of drill bits was carried out at different levels of the drilling zone cooling zone and for various materials. The influence of the operating modes of the tool on the distribution of temperature and the level of the thermal field in the cutting zone was observed. It has been shown that in working elements made of highly thermally conductive materials under intensive drilling conditions, the temperature level does not exceed the permissible level. It has been established that with a cyclic mode of operation of a tool, it is possible to significantly reduce the temperature level in its working elements to the same level as can be achieved in a continuous mode.
UDC 621.9.014
A. A. Vinogradov (Kyiv)
Calculation of tangential stress in the conditional plane of shear and forces on the rear surface of the tool when cutting metals
The methods of calculating tangential stress in the conditional plane of shear and forces on the rear surface of the tool by chip shrinkage and cutting force components, as well as by the force on the front surface of the tool are presented. An example of calculation is given for the case of cutting steel 40 in a wide range of feeds and speeds at a cutting depth of 4 mm.