Vol 40, No 2 (2018)

The nanoindentation in the continuous stiffness measurement (CSM) mode was used to study the nucleation of the plasticity at the nanodeformation of the yttrium-aluminium garnet (YAG) having a low ((111) YAG single crystal after the annealing at the temperature of 1300°C) and a high (polycrystalline yttrium-aluminium garnet with a grain size of ~ 20 μm after the mechanical polishing) density of dislocations. For a sample having a high dislocations density a smooth elastoplastic transition was observed in the nanocontact as a result of the motion and multiplication of dislocations that are already present in the sample. For (111) YAG single crystal after annealing at the temperature of 1300°C an abrupt elastoplastic transition (pop-in) caused by a homogeneous nucleation of dislocations in the region under the contact was observed.

Metal and nitride coatings of high-entropy alloys (HEA) having different phase compositions produced by different methods were investigated. It is shown that for the high-entropy coatings is characteristic the presence of the nanostructured state, which in parallel with the cluster structure provides hardness for metal coatings ~ 10–19 GPa; for nitride coatings are characteristic 50–60 GPa and the modulus of inelastic buckling more than 300 MPa. The relation of the lattice parameters, which are defined experimentally, to the parameter of the lattice of the most refractory metal in the HEA reflects the level of the elastic modulus relative to the theoretically possible both in the cast HEA and in metal coatings on their base.

By simulating the pressureless sintering process, the thermal effects of FeCoCu pre-alloyed powders have been investigated. According to the notions of the Kissinger method, the activation energies in the expansion-shrinkage conversion stage are analyzed. Results show that with Fe content increasing, the specimens’ specific heat capacity values present the increasing trend. The 25%Fe–15%Co–60%Cu specimens have negative enthalpy value at 10°C/min and 20°C/min heating rate but positive values at 30°C/min. For the specimens with lower Cu content, the enthalpies are always positive. It is established that both the specific heat capacity and enthalpy are larger when at higher heating rates. The activation energy of the 65%Fe–15%Co–20%Cu specimens is 10 times higher than that of the 25%Fe–15%Co–60%Cu specimens and the 45%Fe–15%Co–40%Cu specimens.

The results are presented of the barothermal treatment studies of a WC–6Co hard alloy at high pressure (7 GPa). It is shown that such a treatment of hard alloy leads to the deterioration of the basic physico-mechanical characteristics, specifically the strength at the contact, and the coercive force, which is stipulated by the increase of the defects amount in the structure of the carbide phase of the hard alloy.

The paper addresses the effect of face roughness of cutting inserts made of diamond–tungsten carbide nanocomposite on cutting forces, vibration, and machined surface quality in finish turning of aluminum alloys and brass. The authors have substantiated the optimal cutting conditions to produce workpiece surfaces with the minimum roughness and waviness.

The influence of the explosive charge shell composition and the explosive charge modification by various compounds on the yield of DND and DS, content of impurities and their elemental composition has been studied. With proper choice compounds, one can increase the DS yield to 18.6 wt % and the DND yield to 7.6 wt %, reduce the amount of impurities down to 0.23 wt % in DS and to 0.3 wt % in DND. The phosphorus concentration was brought to 0.665 wt % in DS and to 0.244 wt % in DND; the boron content was brought to 0.96 wt % in DS and to 0.472 wt % in DND.

We would like to inform you that a sad mistake was made in one of our articles in “Journal of Superhard Materials”, 2018, vol. 40, no. 1, pp. 16–20. The article is “Mechanism of Functionalization of the Surfaces of Detonation Nanodiamonds: Mass-Spectrometric Investigation” by A. O. Pozdnyakov, A. P. Voznyakovskii, and A. V. Kalinin.