MODIFICATION OF HEAT-RESISTANT OXIDES AND CHLORIDES OF GRAIN SURFACES OF SYNTHETIC DIAMOND GRINDING POWDERS FOR APPLICATION IN GRINDING TOOLS

Further development of modern technologies of diamond processing is connected with application in the diamond tool of powders with new unique properties, special morphology of grains, with the increased chemical and thermal stability. To increase the heat resistance of diamonds, they are covered with a metal (metallization) or glass-ceramic layer, or introduced into the reaction mixture used in the synthesis of diamonds, alloying additives of certain elements. Recently, other methods of coating to increase the heat resistance of diamonds have been developed, such as: vacuum ion-plasma sputtering, epitaxial synthesis, magnetron sputtering, the method of liquid-phase deposition. The latter method is promising for modifying the grain surface of grinding powders of superhard materials by heat-resistant inorganic non-metallic coatings, as it is the most economically advantageous. Determining the features of the technology of modification by the method of liquid-phase application of heat-resistant inorganic coatings (oxides and chlorides of metals and nonmetals) on the surface of grains of grinding powders of synthetic diamond brand AC6, used for grinding tools in mechanical engineering. Modification was performed by the isothermal method of liquid-phase application of saturated solutions of both heat-resistant oxides (В2О3, Al2O3), chlorides (СаСl2, NaCl, MgCl2, FeCl3), and their mixtures (В2О3+СаСl2, В2О3+NaCl). Based on the analysis of the results of the research, it can be stated that the application of coatings of inorganic substances (some oxides and chlorides) increases the heat resistance of synthetic diamond grinding powders. Modification allows to reduce expenses of diamonds in wheels at grinding. Conditions for modification of heat-resistant oxides and chlorides, as well as their mixtures, grain surface of synthetic diamond grinding powders are determined. Modification of the surface of diamond grains with a combination of B2O3+Al2O3 is guaranteed to double the wear resistance of diamond wheels. It is established that in all cases of modification the roughness of the parameter Ra decreases. It is determined that by changing the surface modifier of diamond grains it is possible to affect the bearing capacity of the rough surface obtained by grinding. The development of effective ways to increase the heat resistance of grinding powders made of superhard materials, primarily abrasive grinding powders made of synthetic diamond powders, helps to improve the quality of the grinding tool.

Investigation of the accuracy of the manipulator of the robotic complex constructed on the basis of cycloidal transmission

The object of research is modern robotic systems used in hotspots. In their arsenal, such mobile works are equipped with manipulators with high-precision hinges, which provide accurate positioning of the gripper (object of manipulation). Considering ground-based robotic complexes with a wheel or caterpillar base, the implementation of the process of manipulation on a stationary basis, a number of problem areas were identified that affect the accuracy of positioning. In the course of research and analysis of modern robotic complexes, their circuit and design of components and mechanisms that provide the necessary qualities and parameters. The problem of developing high-precision hinges is central to the creation of efficient ground-based robotic systems. The methodology of kinematic research of rotary hinges of the manipulator for the ground robotic complex is stated. The analysis of influence of deformations of material of impellers of not involute transfer on accuracy of positioning of a final subject is carried out. A kinetostatic analysis of the manipulator circuit was performed and the maximum moments acting in the hinged units on the drive unit were determined, which allowed to make a quantitative assessment using the Solidworks software package. The mathematical model of construction of transfer and definition of accuracy of a rotary knot for a ground robotic complex, with use of cycloidal transfer without intermediate rolling bodies is investigated and developed. Mathematical modeling and taking into account the features of mechanical processes occurring in the manipulator, allows to increase the technical level of robotic complexes. Ways of improvement are defined for maintenance of a progressive design of the manipulator that not only will satisfy necessary technical characteristics, but also will allow to simplify manufacturing technology. Modern technologies and materials (stereolithography, carbon fiber, superhard materials) make it possible to implement advanced designs of spatial drive systems. Therefore, work in this direction is relevant, as robotic mechanical complexes for special purposes are widely used when performing work in emergencies.

Defining the true hardness of materials harder than single crystal diamond

With the development of new synthesis methods and chemistries, a number of new superhard materials have been reported to be harder than diamond. While such materials are highly desirable due to their wide-ranging applications, there are some inherent uncertainties in the methods utilized to determine and define the hardness of such materials. In this paper, we employed the Vickers Hardness Tester to measure the hardness of nine ceramic and superhard materials within a well-defined criteria and methodology, for the reliable assessment of the hardness of these new superhard materials. These findings and the developed testing method have broad implications in the characterizing of new and emerging superhard materials, leading to new discoveries.

MODELING THE INFLUENCE OF METAL PHASE IN DIAMOND GRAINS ON SELF-SHARPENING OF GRINDING WHEELS ON CERAMIC BONDS

The article presents the results of theoretical studies using finite element modeling, which made it possible to determine the rational characteristics of diamond wheels based on ceramic and polymer bonds. The effect of the parameters of the diamond-bearing layer on the change in its stress-strain state in the process of microcutting of hard alloys and superhard materials has been studied. It is established that the determining factor in the occurrence of critical stresses during grinding is the temperature in the cutting area, the increase of which in the presence of metal phase inclusions in diamond grains with high values of thermal expansion coefficient can lead to destructive stresses in grains and, consequently, their premature destruction. It is advisable to use diamond grains with a minimum content of metal phase and the use in the manufacture of synthetic diamonds solvent metals with a low value of this coefficient, which will significantly increase the use of potentially high resource diamond grains.

Dislocation-mediated shear amorphization in boron carbide

The failure of superhard materials is often associated with stress-induced amorphization. However, the underlying mechanisms of the structural evolution remain largely unknown. Here, we report the experimental measurements of the onset of shear amorphization in single-crystal boron carbide by nanoindentation and transmission electron microscopy. We verified that rate-dependent loading discontinuity, i.e., pop-in, in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events reveals an exceptionally small activation volume, slow nucleation rate, and lower activation energy of the shear amorphization, suggesting that the high-pressure structural transition is activated and initiated by dislocation nucleation. This dislocation-mediated amorphization has important implications in understanding the failure mechanisms of superhard materials at stresses far below their theoretical strengths.