Vol 39, No 3 (2017)

Finite element method was used to calculate the distribution of temperatures in growth cells of the toroid TC-40 -type HPA. The experimental investigations of the process of growing type IIa diamond single crystals were performed in high-pressure cells with two growth layers. It is shown that in using the cell materials having appropriate properties and defined configuration of the system of the resistive heating the temperature gradients are 5.4–5.6°C/mm and the growth rate is 2.46 mg/h. The total weight of obtained structurally perfect type IIa diamond single crystals in the upper and lower growth layers is 1.18 and 1.13 carats, respectively, the nitrogen content in all grown crystals is 1–3 ppt.

The possibility of producing coatings of high entropic carbide by scattering multicomponent alloy in plasma of compressed vacuum–arc discharge has been shown. It is defined that the hardness of coatings from high-entropic carbide based on TiZrHfVNbTa multicomponent alloy is 43–48 GPa and exceeds the hardness of monocarbides of metals that enter into the composition of the alloy. The friction coefficient for the carbide high-entropic coating based on the TiZrHfVNbTa alloy at the loads 2.2 to 5.2 N is 0.14–0.16.

Coolant supplied by high pressure into the cutting zone has shown the lower thermal loads on the tool when machining difficult-to-cut materials as the Alloy 718. In this study, we investigate how the combination of high-pressure cooling and tool–surface modifications can lead to further improvements regarding tool life. The general approach is to enhance the coolant–tool interaction by increasing the contact area. Therefore, we machined cooling features into flank and rake faces of commercially available cemented tungsten carbide inserts. In this way, the surface area was increased by ~ 12%. After the cutting tests, the tools were analyzed by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Compared with conventional tools, the tool modifications reduced the flank wear by 45% for the investigated cutting parameters. Furthermore, we were able to significantly increase the cutting speed and feed rate without failure of the tool. The investigated surface modifications have great potential to enhance the productivity of metal cutting processes.

In this work the cutting tool temperature distribution that develops during turning of hardened cold-work tool steel is modeled on the basis of experimental data. The data obtained from a series of thermocouples, placed on a PCBN insert, into an anvil, and into a toolholder, were used as the input for the model. An inverse problem was solved, where the heat fluxes were computed. The temperature distribution was modeled for the case of new tools, as well as for the case of its development in the course of a tool wear. The reconstructed temperature distributions were in good agreement with the measured data. The heat flux through rake face was found to be reducing with the decrease of thermal conductivity of the tool material.

A methodology has been elaborated for controlling the structure formation in cutting-tool hard alloys during the plasma modification of their surfaces in order to produce an ultradispersed structure in the surface layer providing a high level of performance characteristics. The paper presents a block diagram of synthesis of modified layers with an ultradispersed structure, which includes a combination of theoretical, experimental, and technological investigations. The tool life testing of the modified tools has been carried out.

The results are presented on the investigation of the structure and mechanical properties of hot-pressed materials based on AlB₁₂C₂ powders of sizes 50–150 nm. It is shown that the consolidated materials having mechanical properties comparable with boron carbide may be produced at essentially lower (by 270–300°C) sintering temperatures. It has been established that the heating rate at compressing affects the stoichiometry of the impurity phase containing Al, B, O, which define the difference in mechanical properties of the materials (a decrease of the heating rate results in the insignifical decrease of the material hardness and increase of the fracture toughness).