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Документ Improvement of welding technology of high power turbine rotor(National Science Center "Kharkov Institute of Physics and Technology", 2024) Dmitrik, V. V.; Glushko, A. V.; Kasianenko, I. V.; Syrenko, T. O.; Baranova, T. A.; Asieieva, I. V.In order to solve the problem of increasing the reliability and increasing the service life of welded joints of rotors of high-power turbines of nuclear and thermal power plants, the technology of their manufacture was improved. The improved technology provided obtaining welded joints of rotors with improved characteristics of their original structure and higher mechanical and physical properties. The given properties were determined by comparing with similar properties that are characteristic of the welded connection of the rotor made according to standard technology. The improvement of the technology involved the modeling of welding heating of manufactured joints, which made it possible to optimize the parameters of the mode of automatic welding of the rotor made of 25Х2НМФА steel. For the first time, the thermal problem was solved as a conjugate one under the conditions of the Navier-Stokes and Fourier laws, which provided the results necessary for increasing the reliability of the rotors, as well as increasing their resource.Документ Creep pores in welded joints of steam pipelines(Springer Science+Business Media, LLC, 2023) Dmytryk, V. V.; Glushko, A. V.; Poznyakov, V. D.; Kasyanenko, I. V.Formation of creep pores and their transformation into creep cracks in the metal of welded joints of steam pipelines made of heat-resistant pearlite steels (12Kh1MF and 15Kh1M1F), with the long-term operation (over 270,000 h) under creep and low-cycle fatigue conditions (via repeated start-stop modes), largely depends on the structural and phase state of the welded joints. Welded joints are characterized by structural heterogeneity caused by welding heat. The heterogeneity increases with their further service life. This heterogeneity in the metal of welded joints is much greater than the heterogeneity of the base metal of the steam line, which has not been subjected to welding heat. In long-term operation, the structure of steam lines and their welded joints is transformed into a ferritic-carbide mixture at different rates. The rate of this transformation in the metal of welded joints is much higher than in the base metal of steam lines. It was found that the intensity of damage to the metal of welded joints by pores and creep cracks largely depends on the level of transformation of the initial structure into a ferritic-carbide mixture. It was found that creep pores are mainly formed along the boundaries of ߙ-phase grains and, to a lesser extent, along the grain body. We studied the peculiarities of physical and chemical processes occurring in the metal of welded joints of steam pipelines. We established a link between the self-diffusion of alloying elements (chromium, molybdenum, and vanadium) and the movement of dislocations. It was found that pore nucleation in the metal of welded joints occurs mainly at the boundaries of ferrite and bainite grains, where the coagulating carbides M23C6 and M7C3 are located rather than along the grain body. In the process of diffusion movement, vacancies, by merging, are transformed into microcontinuities that move in the direction of vacancy movement. It was found that the formation of creep pores in the metal of welded joints largely depends on its structural and phase state. Creep pores are most intensively formed in areas where the structure consists of tempering bainite, ferrite, and coagulating globularized pearlite. It was found that with an increase in the metal deformation of the zone of thermal influence of welded joints, the formation of creep pores is accelerated.Документ Recrystallization in the metal of welding joints of steam trucks(2019) Dmytryk, V. V.; Glushko, A. V.; Tsaryk, A. K.The recrystallization process in the structure of welded joints of steam pipelines from heat-resistant pearlitic steels, operated for a long time under creep conditions (Te = 545…585 °С, Рe = 20…25 MPa), reduces their performance. Studying the peculiarities of the recrystallization process will allow slowing down its passage, which is important for increasing the service life of welded joints of steam pipelines, which are characterized by the presence of a certain structural heterogeneity.Документ Improvement of the Mechanical Characteristics, Hydrogen Crack Resistance and Durability of Turbine Rotor Steels Welded Joints(2022) Balitskii, A. I.; Dmytryk, V. V.; Ivaskevich, L. M.; Balitskii, O. A.; Glushko, A. V.; Medovar, L. B.; Abramek, K. F.; Stovpchenko, G. P.; Eliasz, J. J.; Krolikowski, M. A.This article is devoted to the following issues: calculating the values of temperatures obtained by simulating welding heating and the subsequent implementation of the welding process at the given mode parameters made it possible to obtain a welded joint of the rotor with an improved initial structure and increased mechanical properties, hydrogen resistance and durability by up to 10–15%; simulating welding heating in the areas of fusion, the overheating and normalization of the HAZ and the formation of austenite grains; specified welding heating creates the conditions for the formation of new products of austenite decomposition in the form of sorbitol in the area of the incomplete recrystallization of the HAZ. In air and gaseous hydrogen, the destruction of the combined joints took place on the weld metal, as well as on the fusion areas, the overheating and the incomplete recrystallization of the HAZ of 20H3NMFA steel as the base metal. Structural materials have a relatively low strength and high fracture toughness in air. This is manifested in a significant reduction in the elongation (d), the area (y) and critical stress intensity factor (KIc) of welded joints and the endurance limit of cylindrical smooth rotor steel specimens, which were cut from transverse templates. Welded joints in the whole range of load amplitudes are sensitive to the action of hydrogen.