This study presents the results of investigating the influence of electron beam welding parameters – beam power, beam offset relative to the joint, welding speed, and scanning frequency – on the formation of butt joints between commercially pure titanium grade VT1-0 and nickel grade NP2. It is shown that the weld metal structure consists of various types of intermetallic compounds, eutectics, and solid solutions based on nickel and titanium, with their ratio determined by the degree of melting of the welded materials. High‑quality welded joints, free of cracks and lack of fusion, were obtained at nickel melting degrees of approximately 10, 55, and 85–90

The possibility of obtaining a combined titanium-steel construction by directed energy deposition using vanadium or vanadium/nickel interlayers has been investigated. Vanadium wire VnPr-1, nickel wire NP1 grade, and welding wires Sv-08G2S, 316L, and MSG NiFe-1 grades were used for deposition on the end of the titanium plate VT1-0. The use of vanadium as an interlayer deposited on titanium makes it possible to provide a joining with a stable structure, steady hardness distribution, and acceptable manufacturability. The content of dissolved titanium in the vanadium layer has a negative effect on the subsequent deposition of steel, nickel, or iron-nickel alloy. Therefore, the titanium content was reduced to a level of less than 0.5

The relevance of creating specialized computer programs that convert a virtual 3D model of an object into machine code (G-code) for controlling the process of 3D printing products from wire raw materials is substantiated. It is shown that for wire-based additive technologies, a fundamentally important requirement is to ensure the continuity of the surfacing trajectory within one section. A method for determining a continuous surfacing trajectory is proposed, the implementation of which requires two stages: performing a numerical analysis of a two-dimensional region with boundary conditions describing this section; and running a heuristic algorithm for the movement of the surfacing head, in which the direction of movement is selected based on the results of the analysis. The procedure for setting boundary conditions and an algorithm for numerically solving the boundary value problem of determining the field of the “height” function for each section are described. The principles of operation of the heuristic algorithm for selecting the direction of head movement based on the calculated height field and continuous determination of the proximity of adjacent layers and section boundaries are disclosed. An analysis of the algorithm operation is carried out using a section with holes as an example, and the potential of using numerical methods to calculate the change in the temperature field during the surfacing process is shown.

The work is devoted to the study of bimetallic structures “titanium-steel” by electron beam freeform fabrication with the use of niobium and copper interlayers. A metallographic study of the deposited interlayers is carried out. The hardness distribution over the samples is shown. Technological issues according to deposition of niobium on titanium and steel on copper are pointed out. Tensile testing results reveal that the obtained structures have an ultimate tensile strength of 150–228 MPa and the fracture is located at the niobium-copper alloy side or at the niobium interlayer. The need to reduce the titanium content in niobium due to the occurrence of intergranular penetration of copper is demonstrated.

The authors have conducted an investigation into the cooling of five distinct types of structured surfaces by means of a dispersed flow of distilled water. The modification of the heat transfer surface of the copper working section was conducted using a variety of methods, including mechanical processing and electron beam treatment at different parameters. Macrophotographs of the structured surface were obtained and their profiles were subsequently measured using a profilometer. Two series of experiments were conducted for each surface, with different coolant parameters. The excess pressure of the coolant at the nozzle inlet was in the range of 1.5 to 3.5 × 10⁵ Pa, the mass flow rate of the coolant (distilled water) was in the range of 4.0 to 6.1 × 10−3 kg/s, and the irrigation density varied within the range of 4.2 to 6.2 kg/(m2·s). The relationships between heat flux and heat transfer coefficient were compared for both modified and unmodified surfaces. The calculated thermophysical quantities were also represented graphically.

This study shows the need for a common structured approach to designing control systems for electron-beam welding, surfacing, and additive shaping plants. The main controlled parameters of the process are highlighted. The three-level hierarchical structure of the control system is described. The control processes are differentiated taking into account the process requirements for electron-beam treatment processes and the features of the vacuum system, the electron gun, and the positioning system, as well as the system of taking images of the treated area according to the signal of backscattered electrons. The types and quantitative characteristics of the parameters of the signals necessary for running the system are given. It is shown that it is effective to divide the control processes in three groups, depending on the requirements on the rapid response of the actuators, as well as on the need for synchronizing some processes with others over time. The presented differentiation is used to propose a method for selecting technical facilities for each of the mentioned groups. An example is provided of constructing a control system for an electron-beam process plant using hardware components available for purchase.

Methods for determining the diameter, focusing distance, and convergence angle of an electron beam used for vacuum electron-beam welding are considered. A technique is proposed for determining the boundaries of the electron flux using a continuous wavelet transform of the transverse integral beam profile of the beam obtained from its image on the residual gas in a vacuum chamber. The method is tested on a reference object, and the error in the linear dimensions of the beam is assessed. Quantitative dependences of the minimum beam diameter and focusing distance on the magnetic-lens current for two types of electron beam process installations are obtained. The features of the energy-density distribution in the region of converging and diverging beams are established. The results obtained make it possible to estimate the beam-power density and can be used to study the effect of process parameters on the shape and dimensions of the weld during electron-beam welding.

The erosion of nanostructured tungsten and titanium by high-heat plasma flux, laser, and arcing is investigated. To fabricate nanostructural fuzz layers and hierarchical granularity on the surfaces, samples were exposed to helium plasma in the steady-state plasma device PLM-M, which is a linear plasma trap of an eight-pole multicusp magnetic field with parameters similar to the scrape-off layer and divertor plasma in a tokamak. Arcing ignited with a Nd:YAG laser pulse on the target fuzzy surface in the helium plasma resulted in the melting of fibers and the creation of craters of several microns in depth and several tens of microns in diameter.

The mathematical formulation of electron beam melting and liquid metal transfer model in wire-based additive manufacturing with temperature dependencies of thermophysical properties is described. A description of the model algorithmic implementation based on the use of numerical methods for solving the Navier-Stokes equations system and the Volume of Fluid (VOF) method for tracking the free surface of a liquid on the cubic mesh cells is given. An iterative method for calculating the pressure field that ensures the fulfillment of the incompressibility condition for a viscous fluid is described. The paper also paid attention to the description of methodology for calculating the forces acting on the free surface of the melt, including surface tension forces and metal vapor pressure forces. One of the key elements of the proposed model is method for volumetric distribution of electron losses calculating, considering their scattering during the interaction of an electron beam with a curved melt surface. Electron beam focusing influence on the distribution of energy losses and the dynamics of penetration channel formation has been studied. An algorithm for visualizing the free surface of the melt based on the use of the Gaussian function, is described.

The article presents the developed technique of high-speed video recording of the combined-cycle gas channel and subsequent frame processing to obtain the dimensional characteristics of the combined-cycle gas channel. On the basis of this technique, dependences of the width of the weld at different depths were obtained depending on the current and welding speed. A pattern of dimensional characteristics of the steam-gas channel depending on the running energy and the dependence of the frequency of collapse of the steam-gas channel on the electron beam current at a constant welding speed of 40 m/h by the example of nickel and titanium alloys was revealed.

Low-frequency scanning electron beam welding (SEBW) is recently recognized as a possible control method for preventing the top concavity behavior in plate full penetration welding. However, due to a lack of understanding of the control of beam scanning in preventing concavity, the welding quality is difficult to control. In this study, the basic physics under different scanning frequencies was investigated. The results indicate the fundamental reason of improving the weld morphology is that the scanning can make the energy more dispersed. Specifically, due to the impact of recoil pressure and the nature of the weld pool, longitudinal scanning can promote the upstream flow of liquid metal and prevent the top concavity. However, when the scanning frequency reaches a certain threshold value, the effect of promoting the upwelling becomes weak. The threshold of the scanning frequency is 42.00 Hz for welding the 22-mm-thick 30HGSA steel in this study. When the scanning frequency is between 24.00 and 42.00 Hz, the process is in the Improvement Stage. Therefore, longitudinal scanning can effectively control the flow in the weld pool, and an appropriate scanning frequency is necessary to prevent the top concavity. These investigations can provide a better understanding of the effect of scanning on the top morphology.

The influence of the “saw-tooth” type electron beam sweep on the penetration shape during electron-beam welding of 30KhGSA high-strength steel with different welding modes was investigated. Using the instrumented indentation method, the distribution of Young’s modulus, as well as the characteristics of strength and plasticity in the welded joints cross-sections, was obtained. It has been found that in the weld metal there is a sharp increase in strength characteristics, while the plasticity ones are significantly reduced. The values of the Young’s modulus also varied over the cross-sections. The considerable decrease in this characteristic (up to 20%) was registered in the weld metal in comparison with the parent metal results.

The article presents the results of assessing the effect of the welding speed and the displacement of the electron beam relative to the joint on the mechanical heterogeneity of the weld metal of dissimilar welded joints of EP517 (Fe12Cr2NiMoWVNb) steel and 36NKhTYu (Fe36Ni12Cr3TiAl) alloy. Aging curves are plotted for the weld metal of welded joints made at electron beam welding (EBW) speeds of 30 m/h and 120 m/h, as well as for the weld metal of the welded joint made at a speed of 30 m/h with various electron beam displacements. An assessment of the change in the mechanical heterogeneity of the weld metal was carried out by the change in the standard deviation of the hardness values, and metallographic studies were also carried out. It was found that a decrease in the EBW speed leads to a decrease in the standard deviation of the results of measuring the hardness of the weld metal after aging from 45 to 14 HV5 or from 18% to 6%. It was also found that an increase in the displacement of the electron beam to alloy 36NKhTYu (Fe36Ni12Cr3TiAl) to 60% leads to an increase in the hardness of the weld metal from 225 to 305 HV5 (by 35%).

Проведен анализ структуры каналов управления установки для реализации процессов электронно-лучевого аддитивного формообразования на базе серийных электронно-лучевых сварочных установок. Рассмотрена актуальность решаемой задачи и описан метод ее решения. Предложен программно-аппаратный способ синхронизации каналов управления ЧПУ с каналами управления током пучка на базе программируемого контроллера ATmega328, который позволяет синхронизировать во времени каналы управления перемещения электронной пушкой и током пучка. Описан принцип работы разработанного устройства сопряжения, а также проведены эксперименты, показывающие работоспособность устройства. Проведены серии экспериментов по наплавке одиночных валиков из сплава ВТ6 и приведены осциллограммы параметров источников питания пушки, которые демонстрируют работоспособность разработанного метода.

In this work, two molybdenum-graphite X-ray targets for computed tomography/angiography devices were manufactured with usage of Ti-40Zr-8.5Nb-1.5Be filler metal and 1400 degrees C - 20 min brazing mode. To confirm the efficiency of the proposed brazing method, a mechanical test and simulated heating of the anodes were carried out, as well as a study of the evolution of the brazed joint under operating conditions. The brazed joint of the anodes showed stability and maintained integrity after tests. However, it is revealed that the long-term heat treatment of the brazed Mo/graphite joint leads to an increase in the amount of carbides in the seam, and also converts the seam into a refractory state by suppressing the formation of beryllium eutectic, while the cyclic heating mainly affects the recrystallization of the seam phases, leading to phase fragmentation. Shear strength tests after simulated heating show that the failure of the Mo/graphite joint occurs in the graphite element with cracking due to the infiltration of the filler metal into graphite through the open porosity. Infiltrates could provoke the occurrence of stresses during cyclic heating/cooling because of the difference in the CTE of graphite and carbide phases. Nevertheless, the joints remained integrity and showed a minimal strength of 23.4 +/- 2.5 MPa (after 20 heating cycles of 350 <-> 1400 degrees C) and 26.1 +/- 6.4 MPa (after vacuum annealing of 1400 degrees C - 8 h).

Studies of samples of graphite heat-shielding facing of the T-15MD tokamak chamber with stationary plasma loads in the PLM plasma device and high-power electron beams simulating loads during ELMs and transient processes were carried out. When the graphite facing samples were tested with plasma loads up to 2 MW/m2, their surface temperature reached more than 1200°C, the surface heating did not lead to cracking, a change in the relief, or significant erosion of the graphite surface. The plasma action led to the growth of a layer of highly porous carbon structures on the surface in the zone of contact with the plasma column. Irradiation of graphite with electron beams with a load of less than 12 MW/m2 did not lead to changes in the surface structure; at a load exceeding 24 MW/m2, the processes of erosion and cracking of the surface along the grain boundaries began. At thermal cyclic loads exceeding 380 MW/m2, effects of significant erosion were observed with a rate of material removal from the graphite surface up to 175 μm/s. The conducted experimental studies and tests are considered as the basis for using the investigated type of graphite as the facing of heat-shielding components of the divertor and the first wall for operation in the T-15MD tokamak.

The aim of this work was to braze molybdenum and graphite with Ti–40Zr–8.5Nb–1.5Be filler metal in order to demonstrate the possibility of its application for X-ray tube target brazing, further to investigate the joint microstructure using energy-dispersive X-ray spectroscopy (EDS), electron backscattered diffraction (EBSD), X-ray diffraction (XRD), and electron microscopy as well as to conduct shear and unbrazing tests. It is shown that the brazed joint consists of matrix from β-(Ti, Mo) solid solution, mixed ZrC and TiC carbide layers at the braze/graphite interface, and beryllides TiBe2 and MoBe2 located at the grain boundaries of β-(Ti, Mo). The presented data made it possible to propose a brazed joint formation mechanism and explain the concentration of beryllides at the grain boundaries during brazing, as well as the mixed carbide layer formation from the side of the graphite. The mechanical tests showed that Mo/graphite brazed joints have a shear strength of at least 28.0 ± 0.9 MPa. However, sample failure occurred through the graphite due to the graphite surface mechanical treatment and the presence of a ductile β-Ti phase in the joint. The evaluation of joint thermal properties was performed using unbrazing tests. The unbrazing temperature was 1882 °C, which was caused by formation of refractory phases during brazing. The microstructure study shows that unbrazing occurs through the β-(Ti, Mo) phase with grain boundaries and beryllides eutectic melting.

Combined tests of tungsten mock-ups with thermocyclic test in the electron beam facility with the load up to 50 MW/m² and subsequent irradiation with steady-state plasma load up to 1 MW/m² in PLM device have been carried out to simulate a material degradation under loads expected in a fusion reactor. Cracks of 1–5 microns and more have been formed on the surface of the tungsten during e-beam test. Melted layer observed in the area of e-beam hot spot load. Plasma load led to a formation of nanostructured layers on the surface.

A computer model has been developed to investigate the processes of heat and mass transfer under the influence of concentrated energy sources on materials with specified thermophysical characteristics, including temperature-dependent ones. The model is based on the application of the volume of fluid (VOF) method and finite-difference approximation of the Navier–Stokes differential equations formulated for a viscous incompressible medium. The “predictor-corrector” method has been used for the coordinated determination of the pressure field which corresponds to the continuity condition and the velocity field. The modeling technique of the free liquid surface and boundary conditions has been described. The method of calculating surface tension forces and vapor recoil pressure has been presented. The algorithm structure is given, the individual modules of which are currently implemented in the Microsoft Visual Studio environment. The model can be applied for studying the metal transfer during the deposition processes, including the processes with electron beam spatial oscillation. The model was validated by comparing the results of computational experiments and images obtained by a high-speed camera.