Surface Engineering and Applied Electrochemistry最新文献

For a number of case-hardening low-carbon steels (16MnCrS5, 20MnV6, 18KhGT, 25KhGT, Е470), depending on the customer’s requirements, it is necessary to obtain stable fine austenite grains during high-temperature heating and long-term holding. The stability of the austenite grain size is ensured by microalloying of steel with a minimum sufficient amount of niobium within the limits according to the customer’s specification. This paper presents studies on mastering the technology of producing case-hardening steels with a stable austenite grain size with testing of changes in the ladle treatment technology. After adjusting the technology of ladle treatment of steel, the maximum size of austenite grain in the studied samples corresponded to 3–5 points. The results of metallographic studies show that adjusting the technology of ladle treatment of steel grade 16MnCrS5 did not allow to fully achieve the set goal, that is, to obtain an austenite grain size in case-hardening steel of no larger than 5 points. Taking into account the obtained results of metallographic studies after adjusting the technology of ladle treatment and microalloying of steel with niobium, a further strategy was developed to improve the technology of production of case-hardening steel grades resistant to the growth of austenite grains during high-temperature heating and long-term holding under the conditions at the of OAO BMZ—Management Company of BMK Holding.

Structural features of thin-layer coatings of fluorine-containing compounds formed on substrates of various nature depending on the chemical structure of oligomers, the nature of the substrate, and the conditions for the deposition of protective polymer-oligomeric layers have been studied. It is shown that the above parameters have a fundamental effect on the physicomechanical and chemical properties of coatings. The formation of liquid-crystalline phases in the structure of oligomeric coatings during the deposition of their metal substrates has been established. The use of energy factors for modifying coatings leads to an intensification of ordering processes in the structure of coatings, which should have a positive effect on the physical and mechanical properties of modified steel substrates.

The results of research showing the possibility of using aluminosilicates of man-made origin as mineral additives for concrete are presented. Processes of interaction of active mineral additives (dehydrated diatomite, Novosil active mineral additive) with Ca(OH)₂ have been investigated. The influence of additives on strength and physicochemical properties of cement stone has been estimated. It is shown that the components of the above additives are involved in the processes of cement hydration, which leads to the absorption of calcium hydroxide and the formation of a new phase in the form of calcium hydrosilicates.

The substructure, orientation, and morphology of thin β-SiC films formed on the surface of a vacuum cleavage (juvenile surface) and an air cleavage (nonjuvenile surface) of a silicon single crystal during carbidization in the process of carbon arc evaporation have been studied by TEM, RHEED, SEM, and AFM methods. The effect of the juvenile surface in the synthesis of β-SiC films on Si is shown, which manifests itself in the fact that the β-SiC phase nucleates uniformly on the juvenile surface, forming a nanocrystalline oriented film at 1123 K; on the nonjuvenile surface, the carbide phase is formed at the points of breakdown of a thin film of natural silicon oxide.

Results of structure, phase and element composition, and microhardness of the surface layer of Ti–6Al–4V alloyed by copper atoms under the action of compression plasma flows generated in nitrogen atmosphere are presented in this work. The findings showed that growth of the energy density absorbed by the surface layer in the region of 26–43 J/cm² led to diminishing of copper concentration from 20 to 4 at % in the alloyed layer. An alloyed layer with thickness of ~18 μm contained CuTi₂ and Cu₃Ti₂ intermetallides. Nitride δTiN was formed on the surface of the alloyed layer. Annealing at 750°С resulted in Cu₃Ti₂ decomposition.

The results of the main stages of research, development, and synthesis of multilayer polarizing coatings based on zirconium ZrO₂ and silicon SiO₂ oxides are presented. It has been established that the microstructure and optical properties largely depend on the technology of their production. The possibility of their use for the formation of antireflective coatings on the screen of the onboard computer of agricultural machinery is considered.

The influence of coating structure on corrosion resistance of Zn–Ni coatings in the salt fog chamber was studied by methods of X-ray phase analysis and electron scanning metallography. It is shown that the change of conditions of deposition of coatings leads to a strong change in their morphology. It has been established that the change of coating deposition conditions leads to a change in the phase composition of the coatings. It has been established that the coatings with fine-crystalline morphology having Ni₅Zn₂₁ phase in their composition have greater corrosion resistance.

Using the method of magnetron sputtering from a multicomponent target manufactured by hot pressing of a powder mixture, thin films of a high-entropy CoCrFeNiTi_x alloy on silicon substrates were first obtained. The microstructure and phase composition of these films have been studied. Resistive thin-film elements are made and their electrical resistance is measured at different temperatures. It is shown that the value of the electrical resistance of new resistive elements linearly depends on temperature with the negative temperature coefficient TCR = –4.66 × 10^–5 K^–1.

The results of dilatometric and structural studies of hypereutectic aluminum silicon alloys with a content of up to 30% silicon carbide in the test temperature range of 20–120°С are presented. The influence of modifying additives of silicon carbide on the nature of changes in the structure and temperature coefficient of linear expansion (TCLE) of the resulting composite is shown. The main technological conditions for obtaining the composite material of the Al–Si–SiC system are determined by sequential melting of aluminum at 660°С, followed by the addition of Al of 30% by weight SiC to the melt, by heating to 1250°С, and 10 min exposure and pouring the melt into the coquille, which allowed to obtain a composite material with TCLR 9.22 × 10^–6 °С^–1 in the specified temperature range.

The structural features of nanodispersed graphene particles obtained by various synthesis technologies have been studied. The surface physicochemical properties of graphene-like particles, as well as carbon particles obtained by SHS synthesis, have been evaluated. The surface morphology and topography was studied, the intermolecular interaction in composite materials was analyzed, and the influence of the concentration of nanodispersed graphene particles on the values of the coefficient of friction and physicomechanical characteristics of photopolymer composites was studied. The charge state of photopolymer composites was studied.