Optimization of titanium matrix composites (TMCs) relies on precise control of in-situ reactions and interfacial bonding. This study reports the first identification of the TiBxCy interphase in Ti-64/B4C metal-matrix composites fabricated via direct metal deposition, providing critical insights into microstructural evolution and mechanical enhancement. Systematic variation of laser energy density, substrate preheating, and ceramic concentration (10-15 wt.% B4C) reveals three distinct local environments around B4C particles. An intermediate energy density (14.3 J/mm2, 15 wt.% B4C) achieves superior wear resistance and microhardness (830 HV0.3), resulting in a coating with more than twice the wear resistance of the Ti-64 substrate driven by balanced ceramic dissolution and TiBxCy formation. Advanced characterization, including synchrotron radiation diffraction and scanning electron microscopy, confirms the role of TiBxCy in strengthening interfacial bonding. Substrate preheating mitigates thermal stresses without altering phase composition, enabling defect-free coatings. These findings establish a framework for tailoring TMCs for aerospace and high-performance applications, highlighting the critical influence of energy density and ceramic concentration on wear resistance and hardness.

Introduction. Traditionally, the most common technology for producing parts from nickel alloys involves casting followed by heat treatment to achieve the required phase composition. Significant disadvantages of this method include the segregation of chemical elements, the presence of large undesirable inclusions such as Laves phase and eutectic structures, and the non-uniform distribution of strengthening phases throughout the workpiece cross-section. At the same time, many complex-shaped parts are assembled into a single combined structure using welding. An analysis of the hardening characteristics of nickel alloys and the products derived from them suggests that additive manufacturing techniques are a promising approach for fabricating such workpieces. The structure and phase composition of the material volumes formed via layer-by-layer deposition will differ significantly from those obtained by conventional methods. In the case of producing combined structures using additive methods, identifying the patterns of structure and phase composition formation becomes an even more complex challenge. Therefore, the purpose of this work is to identify the structural features of "steel - nickel alloy - steel" gradient layers fabricated by direct metal deposition. The study examines dissimilar joints produced using the "Welding and Surfacing Complex based on a Multi-Coordinate Arm and a Fiber Laser" at the S.A. Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences, employing direct metal deposition technology. Research methods. A Carl Zeiss Axio Imager A1m light microscope and a Carl Zeiss EVO 50XVP scanning electron microscope, equipped with an INCAX-Act energy-dispersive X-ray spectroscopy (EDS) attachment, were utilized for microstructural investigations of the fabricated layers. Phase composition analysis of the samples was performed using an ARLX'TRA X-ray diffractometer. Microhardness testing was conducted using a Wolpert Group 402 MVD Vickers hardness tester. Results and discussion. It was observed that the maximum layer height (up to 7 mm) was achieved when implementing the following parameters: 1,000 W laser power with a scanning speed of 35 mm/s, and 1,500 W laser power with a scanning speed of 15 mm/s. In the first case, minimal material mixing at the fusion boundary was noted. In all fabricated compositions, defects in the form of unmelted powder particles were observed, as well as cracks in the first steel layers. During the deposition of Inconel 625 onto 316L stainless steel, the transition zone exhibited solidification modes consistent with the formation of iron-based alloys, specifically FA (ferrite-austenite), AF (austenite-ferrite), and A (austenite) sequentially. When depositing 316L stainless steel onto Inconel 625, the transition zone exhibited a solidification mode characterized by the formation of only the austenite phase. The microhardness values were found to be 230 +/- 15 HV for 316L stainless steel and 298 +/- 20 HV for Inconel 625.

The study investigates the effects of substrate preheating temperature on the structural-phase composition and microhardness of titanium matrix composites obtained using direct laser deposition. To fully investigate the substrate heating aspect, synchrotron radiation is employed along with conventional microstructure diagnostics techniques, which allows obtaining information about the structure of the substance at the micro and macro levels. Key findings indicate that preheating of the substrate prevents cracking while changing the structural and phase state, which affects the increased microhardness. The study reveals a direct correlation between the secondary phases (such as TiB, TiB 2 , TiC, and B 4 C) growth and the increase in microhardness of the metallic matrix. The paper also emphasizes the formation of Ti 3 Al intermetallic compound. This research provides critical insights into the relationship between laser processing conditions, microstructure, and mechanical properties of laser-deposited coatings. The novel use of synchrotron radiation paves the way for more detailed and accurate material characterization in material science and surface engineering.

The electrical resistivity of 12Х18Н10Т stainless steel specimens was measured in the course of compression and heating under stepwise shock compression. A mathematical simulation of the obtained experimental data was conducted. The simulation allowed switching to specific values and reconstructing the volume–temperature dependence of the electrical resistivity of steel at high pressures of 25–65 GPa and temperatures of 350–950 K. Semi-empirical regularities were identified that permit the prediction of the total effect of a decrease in the electrical resistivity of 12Х18Н10Т steel upon compression and its increase upon heating. The outcomes of the electrical resistivity tests on shock-compressed and heated steel are evaluated in comparison with the existing literature data on similar experiments conducted under atmospheric pressure and high temperatures.

Introduction. Laser surfacing is one of the leading trends in the field of additive technologies, which consists in layer-by-layer build of material using a laser as an energy source. To obtain a high-quality product, it is necessary to select the optimal building parameters correctly. The problem is that such optimization is necessary for all equipment, since minor differences in its characteristics can make significant changes in the parameters of layer-by-layer build. In order to determine the optimal build mode, it is enough to analyze the effect of various equipment parameters on the characteristics of single tracks. Therefore, the purpose of this work is to determine the most important parameters of laser radiation that affect the surfacing process and the optimal mode for building a single track of chromium-nickel steel. The work investigated single tracks obtained by laser surfacing of powder from austenitic chromium-nickel steel AISI 316L. The optimization factors included such characteristics as laser power, beam speed, flow rate of supplied powder and laser spot size. The wavelength of laser radiation was 1.07 μm. Research methods. To determine the quality and geometric dimensions of single tracks, the macrostructure of cross sections of specimens was studied using metallography and scanning electron microscopy methods. Results and discussion. It is established that the optimal mode for growing single tracks of steel AISI 316L is characterized by a laser radiation power of 1,250 W and a scanning speed of 25 mm/s. In this case, the optimal powder consumption rate is 12 g/min, and the laser spot size is 4.1 mm. The work shows that the powder consumption and laser spot size have the greatest influence on the coefficient of effective use of powder material. By changing it, the surfacing performance can be increased by 10–15 %.

This work investigates the effect of the temperature of the substrate additional heating on the structural-phase composition of an Inconel 718 coating obtained by direct laser growth. Using synchrotron radiation diffraction in the Debye-Scherrer geometry, it was shown that an additional heating temperature of the substrate of $750{ }^{\circ} \mathrm{C}$ leads to a more intense formation of the strengthening $\gamma^{\prime \prime}$ phase, as well as Laves phases with the stoichiometry ($\mathbf{N i}, \mathbf{C r}$, $\mathrm{Fe}) \mathbf{2}(\mathbf{N b}, \mathrm{Mo}, \mathrm{Ti})$. Also, as a result of a decrease in the temperature gradient formed during laser cladding and a decrease in the cooling rate of the melt pool, the structure of the formed material changed. The material obtained without additional heating is characterized by the presence of columnar dendrites in the structure located towards the substrate. Additional heating of the substrate up to $750{ }^{\circ} \mathrm{C}$ contributed to a change in the structure of the sample and the formation of larger dendrites without a preferred direction. In both cases, at the boundaries of the dendrites, segregation of a large number of elements forming the Laves phases occurred: $\mathrm{Nb}, \mathrm{Mo}, \mathrm{Ti}$. The internal material of dendrites is characterized by a high content of $\mathrm{Al}, \mathrm{Cr}, \mathrm{Fe}$ and Ni.

Dimensionless parameters and scaling laws that describe the geometric dimensions of a cermet weld bead formed during direct metal deposition are determined. A Ti64 titanium alloy and ceramics (silicon carbide, SiC) with different volume fractions are used as a powder mixture. A model for estimating the thermophysical parameters of a heterogeneous material is proposed. It is shown that, regardless of the volume fraction of ceramics, the dimensionless geometric parameters of a single track (depth, width, and height) depend on two dimensionless parameters: normalized enthalpy and the Peclet number. Also, these dependences can be approximated by algebraic expressions.

This work presents a study on the additive manufacturing of functionally graded metal-ceramic materials based on Ti64 with boron fibers and particles. For the first time, the phase composition of the obtained composite was investigated using synchrotron radiation. It was shown that during laser exposure and in situ synthesis, boron dissolves in the titanium matrix, forming secondary compounds such as TiB and TiB2. An increase in the microhardness of the formed material compared to the titanium alloy was established. High-speed impact tests on the Ti64-B samples were conducted using an electrodynamic mass accelerator. It was shown that the use of boron fibers in the metallic matrix reduces the depth of the crater created during impact testing by 40% compared to the Ti64 reinforcement-free coating.

Experiments were carried out on multiple shock wave compression and subsequent storage of powdered samples of boron carbide. The samples were subjected to the stepwise shock compression. Steel-tungsten capsule was used for saving of shocked samples. The maximum pressures in the sample under study reached 70 GPa. X-ray phase analysis, electron microscopy, and X-ray spectral microanalysis of boron-carbide samples before and after loading were performed. It is shown that as a result of the impact of dynamic pressures P-tr = 63(7) GPa and temperatures T-tr = 1600(200) K, new reflexes appear on the X-ray diffraction patterns of the shocked boron-carbide samples, which are presumably due to the formation of graphite and tungsten borides. Assessment of the temperature and pressure at the beginning of physical and chemical transformations and melting of powdered boron carbide under stepwise shock compression is discussed.

This study presents a comparative analysis of the shape and microstructure of individual tracks formed from AISI 316 L stainless steel using laser surface cladding (LSC) and direct metal deposition (DMD) methods. The research aims to identify the relationship between laser radiation parameters (laser spot size, radiation power, scanning speed) and geometric characteristics of created tracks. The result shows that the change in the geometric characteristics of single tracks (depth, width, and height) can be related to two dimensionless parameters: normalized enthalpy H and Peclet number Pe. Based on the experimental data summary, the limiting values of the conditions for realizing keyhole melting (H > 2, Pe < 10) and heat conduction (H < 2, Pe > 10) were determined.

In situ electrical resistivity measurements are performed on samples of iron with a hexagonal close–packed lattice (ε–Fe), compressed and heated by stepwise shock loading. Equations of state for ε-Fe are constructed. The obtained experimental results are mathematically simulated in the hydrocode based on the developed equations of state. The modeling results are used to reconstruct the volumetric–temperature dependence of the ε–Fe electrical resistivity at pressures of ≈20–70 GPa and temperatures of ≈750–950 K. The volume–temperature dependence of the ε-Fe thermal conductivity coefficient is calculated according to the Wiedemann–Franz law. The results obtained for the electrical and thermal conductivity of shock compressed and heated ε-Fe are compared with literature experimental and theoretical data for iron and silicon iron.

Laser processing is an effective post-treatment method for modifying the structure and improving the properties of cold-sprayed coatings. In the present work, the possibility of fabricating a hard and wear-resistant Ti-based cermet coating by cold spray followed by laser remelting was studied. A mixture of titanium and chromium carbide powders in a ratio of 60/40 wt.% was deposited by cold spray onto a titanium alloy substrate, which ensured the formation of a composite coating with a residual chromium carbide content of about 12–13 wt.%. The optimal values of laser beam power (2 kW) and scanning speed (75 mm/s) leading to the qualitative fusion of the coating with the substrate with minimal porosity and absence of defects were revealed. The microstructure and phase composition of as-sprayed and remelted coatings were examined with SEM, EDS and XRD analysis. It was shown that the phase composition of the as-sprayed coating did not change compared to the feedstock mixture, while the remelted coating was transformed into a β-Ti(Cr) solid solution with uniformly distributed nonstoichiometric TiCx particles. Due to the change in microstructure and phase composition, the remelted coating was characterized by an attractive combination of higher microhardness (437 HV0.1) and lower specific wear rate (0.25 × 10−3 mm3/N × m) under dry sliding wear conditions compared to the as-sprayed coating and substrate. Laser remelting of the coating resulted in a change in the dominant wear mechanism from oxidative–abrasive to oxidative–adhesive with delamination.

The realization of schemes for measuring rapidly changing resistances in dynamic (explosive) experiments is considered. Practical schemes of two-wire and four-wire resistance measurement techniques are presented. The results of the application of the described techniques in an explosive experiment are presented.

An overview of laser welding methods and additive manufacturing technologies used in modern mechanical engineering is given, and the main trends and aspects of these technologies are discussed. Laser welding processes of thermally hardened aluminum alloys and problems of obtaining high-strength welded joints are considered. The additive growth of heterogeneous materials is analyzed taking into account the dimensionless parameters determining the structure of materials fabricated by additive manufacturing.

Pioneering studies on the additive manufacturing of a cermet heterogeneous material using SiC ceramic fiber were carried out. Unique studies of the damage staging (cratering) and the transition to the destruction of the formed material during high-speed impact created with the help of an electrodynamic mass accelerator have been carried out. It has been shown that the use of ceramic fiber in a metal matrix reduces the impact crater depth by 22% compared to material with ceramic particles. For the first time, the phase composition of the resulting composite was studied using synchrotron radiation. It was shown that, as a result of laser exposure, silicon carbide SiC is dissolved in the titanium matrix with the formation of secondary compounds of the TiC and Ti5Si3C types. It has been established that the use of SiC ceramic fibers leads to their better dissolution, in contrast to the use of SiC ceramic particles, with the formation of secondary phase compounds, and to an increase in mechanical characteristics.

Results of theoretical and experimental investigations of physical and mechanical properties of a heterogeneous material based on the TiB ceramics and Ti–6Al–4V metallic alloy obtained by means of selective laser melting are reported. Elastic properties of the heterogeneous structure under analysis are described by the method of conditional moments. Young’s modulus of the created heterogeneous material based on the titanium alloy and titanium boride is measured. The experimental data are found to be in good agreement with the numerical predictions.

The paper presents the results of experimental studies on the synthesis of a metal-matrix composite by direct laser deposition, including the assessment of optimum irradiation modes to make such a material free of defects (pores, cracks, etc.). It is shown that in-situ synthesis is provided by laser irradiation of a powder mixture composed of polycrystalline boron and titanium alloy Ti64 in a ratio of 1 : 9 wt %. According to X-ray diffraction analysis with synchrotron radiation, scanning electron microscopy, and nanoindentation, the deposited material contains second phases in the form of TiB and TiB2 ceramics. According to mechanical tests, the elastic modulus and the hardness of the Ti64 metal matrix are E-av = 159.7 GPa and H-av = 7 GPa, and those of synthesized particles (whiskers) are E-av = 321.6 GPa and H-av = 19.7 GPa, respectively.

In this work, the process of laser surface cladding was used for deposition of multilayer coatings using repetitively pulsed CO2 laser radiation. As a material for deposition a powder mixture based on a nickel–chromium heat-resistant alloy with an additive reinforcing ceramic WC particles was used. The cladding parameters such as radiation power, scanning speed, laser beam diameter were optimized. The possibility of forming a multilayer ceramic–metal coating without pores and cracks and with ceramic concentration of 40 wt.

This paper proposes a method for manufacturing a metallic composite material made of Ti64 titanium alloy reinforced with SiC ceramic fibers using surface laser cladding technology. The influence of the laser action parameters on the shape of a single track is studied. The stability of the formed composite material under a high-velocity impact is considered. It is shown that, for a sample reinforced with ceramic fibers, the depth of a crater in a substrate is 37% smaller than for a sample made of Ti64 alloy.

For the first time, experimental investigations of the resistance of a cermet coating formed by a combined method (cold gas-dynamical spraying with subsequent laser treatment) to high-speed impact was carried out. It is shown that as a result of laser interaction of TiAl–B 4 C with cold gas-dynamically deposited coating, boron carbide particles dissolve in the metal matrix, and secondary phase compounds of TiC and TiB 2 are formed. Measurement of microhardness showed that created cold gas-dynamically deposited coating, involving B 4 C, Ti, and Al, has a microhardness of 466.3 HV0.3, while the microhardness of a coating after laser treatment is equal to 1331.3 HV0.1. Investigation of highspeed impact has shown the influence of formed coatings on the size of the crater in the substrate. It is also shown that the created cermet coating (cold gas-dynamical deposition + laser radiation) decreases the crater depth in the substrate by more than twice, with the crater width decreasing by 1.4 times compared with a sample without coating.