Перегляд за Автор "Zdorenko, D.V."

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  • Ескіз
    Документ
    Methodology and results of the study of physical, mechanical and tribological characteristics of nitrided inner surfaces of long holes
    (Хмельницький національний університет, 2024) Stechyshyn, M.S.; Dykha, O.V.; Stechyshynа, N.M.; Zdorenko, D.V.
    Created control device physico-chemical and tribological characteristics of nitrided internal surfaces of long holes, which is a hollow pipe with radial holes made at a certain distance from its ends to ensure the ratio of the height of the center of the sample to the internal diameter of the pipe from 0 to 10 or more, which differs in that the height of the samples simulates the depth of the longitudinal holes, and the samples themselves to facilitate their fixation and to ensure the absence of electric spark discharge near the ends, they are installed with a certain tension. At the same time, the length of the cylindrical sample is equal to the thickness of the pipe wall.Thus, each sample is nitrided from two ends, which makes it possible to nitride from the outside and from the middle of the model at almost the same temperature, as well as to compare the results of nitriding of two surfaces (external and internal). At the same time, the difference in conditions is only in the location of these surfaces - external or internal. All other factors that could affect the results of the modification are practically identical. However, nitriding in a glow discharge with a constant current supply does not ensure the treatment of the inner surface uniformly throughout the entire depth, and with significant ratios of length to diameter (more than 4), the inner surface of the hole remote from the ends is practically not nitrided. Therefore, a process technology and a device for quality control of anhydrous nitriding in glow discharge (BATR) of long holes with cyclically switched power supply of the gas discharge chamber have been developed.
  • Ескіз
    Документ
    Theoretical foundations of glow discharge nitriding of internal local recesses on metallic surfaces
    (Хмельницький національний університет, 2025) Stechyshyn, M.S.; Dykha, O.V.; Skyba, M.Ye.; Zdorenko, D.V.; Liukhovets, V.V.
    This paper presents a comprehensive analysis of internal local recesses on metallic surfaces during glow discharge nitriding. Various types of recesses and their geometric features are studied to evaluate their impact on electric field concentration, which in turn affects the uniformity of surface modification. A field concentration criterion is introduced to quantify these effects, and an analytical framework is developed to describe the relationship between surface geometry and electric field parameters. The influence of the dimensions of internal recesses on field concentration is examined using numerical simulations. The results provide a deeper understanding of the mechanisms leading to localized variations in current density distribution on nitrided surfaces. The developed analytical tools are applicable for predicting and controlling electric field concentration indicators in glow discharge processes used for the surface modification of metallic components, which is critical for ensuring optimal mechanical and tribological properties.
  • Ескіз
    Документ
    Wear resistance of structural steels carbonitrated by the separate method
    (Хмельницький національний університет, 2025) Stechyshyn , M.S.; Dykha, O.V.; Zdorenko, D.V.; Oleksandrenko, E.G.
    The article investigates the influence of technological modes of separate carbonitriding of carbon steels on the thickness and microhardness of the hardened layer. Two hardening variants were investigated: first, carburizing of surfaces was carried out in argon-propane, and then nitriding in argon-nitrogen mixtures and vice versa. As the conducted studies have shown, the variant of the hardening technological process significantly affects the physical and mechanical characteristics of the hardened layer. In all two variants of the technological process, the hardened layer consists of a surface carbonitride zone and a diffusion zone of internal nitriding, but the properties of these zones are different in different variants of the technological process. Thus, when hardening steels according to the first mode, the thickness of the carbonitride zone is maximum, and the internal nitriding zone has a small thickness. This is explained by the fact that the carbonitride layer created on the steel surface at the first stage of processing performs the function of shielding the surface from the penetration of nitrogen ions into the surface layer of the metal. When hardening according to the second mode, the carbonitride zone has a slightly smaller thickness, but a more developed internal nitriding zone. In addition, carbonitriding according to the first mode leads to the formation of carbonitride inclusions in the diffusion zone in the form of a mesh, which significantly reduce the plasticity of the layer and under dynamic loads are centers of microcrack nucleation. It has also been established that a carbonitride ε − phase is formed on the surface of steels, which consists of carbonitrides of the type Fe2(N,C), Fe3(N,C), Fe4(N,C). The carbonitride zone has high hardness, high corrosion resistance, and increased wear resistance. The thickness of the carbonitride zone reaches a thickness of up to 25 microns. Under the carbonitride zone is the internal nitriding zone, which has a large thickness and is the main part of the carbonitrided layer. The internal nitriding zone consists of a nitrogenous solid solution of the base metal, its nitrides and nitrides of alloying elements. The dependences of thickness and microhardness on the technological parameters of carbonitriding of carbon steels obtained in the work: temperature, saturation time, composition of the gas medium, its pressure allow them to be optimized depending on the requirements of further operation