Thermal Conductivity Calculations for Nanoparticles Embedded in a Base Fluid

The Prasher analytical model was used for calculating the thermal conductivity of the embedded nanoparticles of Al2O3, CuO, ZnO, and SiO2 in conventional fluids, such as water and ethylene glycol. The values that were obtained were used in the nanofluid theoretical models for comparison with experimental data, where good agreement was obtained. Liang and Li’s theoretical model was also used to calculate the thermal conductivity of these nanoparticles, where the results agreed with those obtained using the Prasher model. The effect of the liquid nanolayer thickness around the nanoparticles that was used to enhance the effective thermal conductivity of nanofluids was explained. The role of the nanoparticles’ surface specularity parameter, which was size-dependent, was clarified. This theoretical trend provides a simple method for estimating the thermal conductivity of nanoparticles and nanofluids.

Influence of the nanostructure of the functional layers of a multilayer coating on the wear of a carbide tool

The results of studies of the effect of nanolayer thickness on the wear of carbide tools are presented. The effect of nanolayer thicknesses on microhardness and fracture resistance of a multilayer coating during scratch testing is shown. The role of nanostructure in the processes of crack formation in multilayer coatings during cutting is revealed.

STRUCTURE AND CORROSION RESISTANCE OF VACUUM-ARC MULTI-PERIOD CrN/Cu, ZrN/Cu, AND NbN/Cu COATINGS

The structure and properties of vacuum-arc multi-period composite coatings of the MeN/Cu system (where Me is Cr, Zr, and Nb) are studied. It was found that at the smallest nanolayer thickness (about 8…10 nm) of composites in the layers of all systems, only a phase with an fcc lattice is formed, without a pronounced texture in the nitride layers. For ZrN and CrN, the phases with an fcc lattice are equilibrium, and for NbN, they are nonequilibrium. An increase in the thickness of nitride layers leads to the appearance of a texture in ZrN/Cu and CrN/Cu systems and the formation of an equilibrium ε-NbN phase in the layers of the NbN/Cu system. Tests for corrosion resistance in the environment of the formation of chloride ions showed that the coatings are anodic reaction. The best corrosion properties were obtained for coatings with the smallest layer thickness (about 8…10 nm).

Influence of the nanolayer structure of coatings on the cutting properties of tools

The paper is focused on the influence of the thickness of nanolayers in the Ti-TiN-(Ti,Cr,Al)N coating on the cutting properties of the tools during the turning of 09G2S silicon-manganese steel. Coatings with the nanolayer thicknesses of 302, 70, and 16 nm were considered. The conducted studies have revealed that a tool with a coating in which the nanolayer thickness is equal to 16 nm demonstrates the longest tool life. At the same time, for such tool, the wear pattern is more balanced, and signs of brittle fracture on the coating are less pronounced. The Ti-TiN- (Ti,Cr,Al)N coating with the nanolayer thickness of 16 nm provides an increase in the tool life by 3.5 times compared to an uncoated tool and by 1.3–1.5 times compared to the tools with the Ti-TiN-(Ti,Cr,Al)N coating with thicker nanolayers.