Yevgeniy Ostroverkh

The article presents one of the options for developing scientifically based recommendations for choosing a rational combination of the strength of the binder, the size of the diamond grain, the concentration of diamond grains with the physical and mechanical properties of different types of binders in the manufacture of diamond grinding wheels. The conducted studies have shown the feasibility of using detonation nanodiamond powders as a modifier of the polymer binder. The introduction of nanopowder into the polymer leads to an increase in microhardness by 23%, and the recommended mass fraction of nanodiamond should be about 1% of the weight of the binder. It is possible to use such polymer compositions in the diamond layer of standard grades, which theoretically will increase their hardness due to constant thermal conductivity.

The importance of developments to overcome friction and wear is largely due to the fact that the energy consumed by the manufacturing industry is almost a third of the total energy consumed. That is, the tribological aspect in the processes of diamond-abrasive processing is quite significant and must be taken into account. Recently, new modern developments have appeared in the literature that somewhat clarify this direction, both from the point of view of the diamond abrasive tool and the tribological behavior of various diamonds, including those with coatings. It is these developments that are covered further in our review of modern publications. Additive manufacturing (AM) methods have significant advantages for obtaining individual products and prototypes, allow to reduce costs, and also speed up the release of products to the market. Nowadays, this direction has begun to be used for diamond-abrasive tools. Of course, new binders for the working layer of the diamond tool have been developed for such energy-efficient AM technology. It is shown that the cutting forces and friction coefficients of microtextured diamond tools are significantly reduced. The tribological behavior of diamonds against various materials is fundamental for their use in the abrasive and bearing industries. It has been proven that, in comparison with ordinary diamond grains, porous diamond grains with an increased number of microedges effectively reduce the cutting force and heat generation. It is shown that the application of the effect of further mechanochemical influence during the coating of diamond abrasives, both on the diamond-bond boundary and on the contact of the surface of the diamond grain with the processed material, allows to increase the efficiency of the use of the diamond-abrasive tool. Attention is drawn to what kind of impurities are introduced into the contact zone during diamond-abrasive processing to change the tribological parameters. At the same time, the most widely used is h–BN, which with a layered crystal structure is one of the types of effective solid lubricants, especially at elevated temperatures. Attention has been paid to emerging materials such as graphene oxide and carbon dots (CD), a kind of carbon-based nanomaterials, which have been widely used as highly effective lubricant additives.

Modern research indicates the effectiveness of using abrasive and chemical-mechanical methods in polishing, taking into account the characteristics of the abrasives used. At the same time, for chemical-mechanical polishing (CMP), researchers consider two directions: the influence of different abrasives, i.e., emphasis on the mechanical component of CMP, and the influence of suspension, i.e., emphasis on the chemical component. As an abrasive for polishing, diamonds are used in the tool in the form of metallic Cu6Sn5 and polymer diamond film overlays, as well as with the use of a mixed abrasive suspension of cerium and diamond. The features of polishing Al2O3–SiO2 with mixed particles and pure – SiO2, as well as new abrasives of the core-shell type SiO2@A-TiO2 are separately considered. In new suspensions containing Fe, Al2O3, a new material is added - graphene oxide (GO), and deionized water is also used in CMP, and this is a certain modern research trend.

It was established that conditionally viscous-brittle tool materials (high-speed steels and hard alloys) behave in the same way with an increase in hardness: wheel wear and the specific energy consumption of their grinding decrease. As the hardness of brittle tool oxide-carbide ceramics increases, both wheel wear and the specific energy consumption of grinding, on the contrary, increase. That is, an increase in the hardness of viscous-brittle materials facilitates the separation of elementary chips, less energy is needed for this, and accordingly the wear of the wheel and the specific energy consumption of their grinding are reduced. On brittle ceramics, with increasing hardness, there is no change in chip removal, but harder sludge becomes more abrasive and, as a result, the wear of the wheel and the specific energy consumption of their grinding increase. The conclusion from the literature that hard and less plastic materials require relatively less specific energy for grinding is confirmed by us when comparing materials of approximately the same hardness - hard alloys and ceramics. In ceramics, the energy consumption of grinding is actually four times lower than that of hard alloys.

The analysis of modern research shows that when evaluating the specific energy intensity of the abrasive processing process, one should pay attention not only to the indicators of grinding power and material removal rate, but also to the indicator of the wear of the abrasive tool, which we will show below for the grinding tool made of superhard materials. It is shown that the traditional method of estimating the specific energy capacity based on the ratio of the grinding power to the processing productivity does not provide an adequate solution, since with it the specific heat capacity of processing exceeds the specific heat capacity of melting of the processing material by almost an order of magnitude. Therefore, it is the application of a new approach to the assessment of the specific energy intensity of diamond grinding, taking into account the wear of the working layer of the diamond wheel, and makes it possible to estimate the indicators of the specific energy intensity of grinding and the energy efficiency coefficient. It has been proven that when estimating the specific energy capacity of grinding metal-ceramic composite materials consisting of a low-melting and refractory component, the latent heat capacity of melting of the low-melting component should be taken as the basis. It is shown that the plastic mode of grinding occurs precisely when the specific energy capacity of grinding, taking into account the wear of the wheel, becomes close to the specific heat capacity of melting of a brittle material.

The purpose and characteristics of granular working media used in vibration processing operations are given. It is indicated that the purpose of granular media is their contact interaction with the processed part surface under conditions of various energy parameters. This interaction is accompanied by elastic-plastic deformation, micro-cutting, adhesion and mechanic-chemical processes. Indicators of technological and operational properties for various types of granular media are given, including the intensity of material removal from the processed surface, cutting ability, wear resistance and achieved surface roughness. The physical and technological parameters of granular media have been established, including deformability, hardness during finishing and hardening operations and surface roughness of the media granules. The influence of the parameters of processing media granules on the productivity of vibration treatment has been determined. It is shown that such parameters are the binding of the granules material, its wear resistance, grain material, granulation and the shape of individual granules. It is noted that the choice of granule sizes depends on two main factors such as: the necessity to obtain a given roughness and high productivity of vibration operations. It was revealed that to ensure high surface cleanliness, the use of small granules of the medium is required, but to obtain high productivity, the use of large granules is required. Approximate dependencies have been determined that relate the size and weight of granules of the processing medium and the processed parts. It is indicated that the best results in achieving high quality of the processed surface and sufficient productivity are provided by granular media with a shape close to a sphere. It is noted that granules in the form of cones, pyramids, prisms and other forms are used for the successful processing of hard-to-reach places in the form of small holes, straight and sharp angles in the interface of the surface of parts, niches or pockets. Such granules are specially manufactured from a mixture of grinding powders of various grain sizes and an inorganic binder based on clays. The features of the physical and technological parameters of processing media are given.

A comprehensive theoretical and experimental analysis of technological topographic adaptability is carried out, based on an idealized description of the topographic parameters of the working surface of the grinding wheel, their changes during its wear and experimental laser scanning of the working surface of the grinding wheel and the processed superhard material (SHM). It has been established that the protrusion height of diamond grains affects the intensity of destruction (removal) of stock through a change in the number of working grains and the actual contact area of the SHM with the working part of the grinding wheel surface. In a controlled grinding process, it is possible to stabilize the working height of the grains in any of the 3 stages of their wear intensity, equating this intensity with the intensity of removal of the intergranular bond. A method has been developed for determining the actual contact area of the working surface of the grinding wheel and changing its technological adaptability. It has been established that in the process of topographic adaptability, the actual contact area can change by several orders of magnitude, respectively, the specific pressure at the contact of diamond grains with the SHM will change, and, consequently, the nature and intensity of their mutual destruction.

This article provides information on modern developments in the direction of directed impact on the cutting surface of a diamond-abrasive tool and its contact zone in machining processes. For the most part, such processing is faced with issues of influence on the cutting surface of diamond tools, including ruling mechanical and electrophysical, taking into account the defectiveness of the diamonds that undergo processing, the directed influence on the surface of such diamonds, thermal and modification of the surface of diamonds. Such developments make it possible to significantly intensify processing processes and increase the efficiency of the diamond abrasive tool. That is why, in this review, the main attention is paid to the presentation of modern developments, known from scientific publications, mainly for the last 5 years, related to the above-mentioned issues.