Using a differential aerosol spectrometer (DSA), a study was made of the homogeneous formation of solid phase nuclei in the process of laser-plasmochemical deposition of SiCN from hexamethyldisilazane vapor in a flow of plasma-forming argon gas. It was found that the characteristic size of SiCN nanoparticles in the gas phase is in the range of 20–120 nm and depends on the HMDS vapor concentration and the total argon flow rate. The studies performed have shown that the formation of a layer of silicon carbonitride in laser plasma-chemical deposition proceeds with the formation of nuclei in the gas phase, and upon their collision with the substrate and activation by laser plasma, it leads to the formation of a solid nanostructured coating.

Experimental studies of the NiCr powder interaction with the CO2-laser radiation in the conditions of free jets of a coaxial nozzle for laser cladding are carried out. Optical diagnostics is used with the video recording of moving particles and registration of the radiation spectrum. The influence of the type of working gas, i.e., air and argon, as well as laser operation modes - the continuous CW and pulse-periodic PP on plasma ignition - is studied. An increase in the average particle velocity from 3 m/s in a cold flow to 10 m/s, when exposed to a laser, was found and the maximum velocity values at the level of 50-60 m/s were registered. The phenomena of particle break-up and plasma plume formation on their surface are described. It is shown that particles rotating with a frequency of 30-40 kHz are present in the powder flow. The continuous thermal radiation of particles and the spectral lines of plasma radiation in the range of 400-900 nm are analyzed.

A new laser-plasma deposition method has been developed for the plasma chemical deposition of hard silicon carbonitride coatings on stainless steel substrates from the hexamethyldisilazane (HMDS) Si2NH(CH3)6 vapor in a high-speed Ar and Ar + 10 vol.% He gas stream at the HMDS gas flow activation after the laser beam focus. The method allows depositing silicon carbonitride coatings at the rate of 0.4 - 1.2 μm·min-1, i.e. ~2 times higher than that at introducing HMDS in the laser beam focus zone. The properties of the prepared coatings have been studied by the methods of IR and Raman spectroscopy, atomic force microscopy, nanoindentation and X-ray diffraction (XRD) analysis. Studying the film structure with the use of XRD showed that the prepared silicon carbonitride coatings are X-ray amorphous. It has been found that the coating deposition rate and the structure of coatings depend on the process parameters: HMDS flow rate and plasma-generating gas (argon or (Ar + He). The method allows depositing SiCN films at a high speed and a hardness of 20 - 22 GPa.

Hard silicon carbonitride coatings are prepared using Ar and Ar (10 vol.% He) laser plasma from hexamethyldisilazane (HMDS) [(CH 3 ) 3 Si] 2 NH and HMDS+benzene vapors. The coatings are characterized by infrared (IR), Raman, and X-ray photoelectron spectroscopies, transmission electron microscopy, and atomic force microscopy. The obtained coatings are amorphous and uniform in composition and over the film thickness. The microhardness of coatings synthesized on steel from a HMDS+ benzene mixture increases from 12 GPa to 18 GPa provided that other parameters remain constant.

The paper presents a case study of powder jet interaction with laser radiation under the conditions imitating laser cladding process with a lateral material feed. Optical diagnostics was used to study the motion and heating of TiC particles sized 20-40 mu m. It was established that the pulsed-periodic CO2-laser radiation of power 1 kW not only leads to the heating of particles up to 3600 K and higher, but also to the acceleration of particles in the laser beam direction, and to a substantial change in their trajectories, which results in the powder plume expansion. It is shown that laser radiation can increase the maximal velocities of particles by approximately 50% (similar to 20 m/s). An ignition of laser plasma is observed in the focusing area with the primary radiation of argon atoms lines (transport gas). The break-up process of powder particles after laser heating is observed. The effect of transport gas flow rate on the motion of powder jets is investigated including their reflection from the flat substrate. The analysis of particle heating dynamics in the laser radiation field is carried out.

The effect of an electric field on the plasma of an optical discharge in an air stream is experimentally studied. At a constant electric field strength of more than 3 kV/cm, the existence of an optical discharge plasma contributed to the electrical breakdown. In this case, the shape and limiting characteristics of electrical breakdown depended on the shape of the electrodes, the polarity of the applied voltage, and the speed of the air flow. For the configuration of the field symmetrically relative to the flow axis, an electrical breakdown was observed from the nozzle exit (positively charged electrode) to the laser beam focus point; there were no streamers in the optical discharge trace.

The purpose of this work is to study the effect of laser radiation on powder particles transported by gas during laser cladding. The temperature and velocity of particles entering the light field of a CO2 laser were determined by measuring particle radiation as well as the scattered radiation of the diode laser, two independent methods. It is shown that under the action of laser radiation, the particles acquire additional acceleration due to the vapor pressure from the irradiated part of the particle surface. This sonic recoil vapor pressure can significantly affect the in-flight characteristics of powder particles in a gas jet. Particle velocities due to laser acceleration exceeded 100 m/s in a carrier gas with a flow rate less than 30 m/s. Particle temperature depends on several factors and was found to vary from ambient temperature to the boiling point of the powder.

This paper presents the results of experimental research concerning the laser-plasma coating of steel substrate with the following powder grades: AP-FeCr4MnSiB (Fe71.75C4.81Cr3.33Si3.54B14.10Mn1.74V0.73), AP-FeCr11Mn4SiB (Fe66.8Mn2.84C2.85Si5.3B11.42Cr10.79), AP-FeNi19Mn10SiB (Fe56.12Ni15.82C1.65Si4.92B12.82Mn8.66) and AP-G14 (Fe29.4Ni32.24C5.32Cr14.78Si4.06B10.22Mo2.8W1.16). As a focusing head was used self-made lateral nozzle for feeding powder. The nozzle was used in conjunction with scanning the laser radiation in the direction perpendicular to the movement of the focusing head. Coated tracks with various nozzle head movement speed (7-20 mm/s) was obtained. The elemental compositions of the resulting coatings were studied. Alloying elements are uniform distributed throughout the coating. During surfacing the powder particles are completely melted and partially mixed with the base material. This leads to increased iron content in the resulting coatings compared with the original powder. The hardness and thickness of the deposited layers were measured depending on the speed of the process. The hardness of the coatings is in the range of 7-12 GPa, the thickness is 0.15-0.7 mm. The wear resistance of the resulting coatings is up to 10 times higher than that of a steel substrate.

This paper presents the results of experimental research concerning the laser-plasma processing (hardening) of the following steel grades: 65Mn, 40Cr, GCr15, 30CrMnSiA, grade "2" steel used in accordance with GOST 398-2010 in production of wheel tyres for railway locomotives; as well as alloys Fe71.75C4.81Cr3.33Si3.54B14.10Mn1.74V0.73 and Fe66.8Mn2.84C2.85Si5.3B11.42Cr10.79 in addition to the aforementioned. It is shown that the thickness of the hardened layer of processed steels is dependent on the processing mode and varies between 0.3-1 mm, while its hardness reaches values of 10-14 GPa, 2-4 times higher than the base material. The sample studies of the grade "2" steel after the processing have demonstrated the substantial increase (by approx. 10 times) in wear resistance. The laser-plasma processing of alloys leads to the formation of a fine-crystalline layer with a characteristic crystallite size of 0.5-1 mu m and a thickness of 3-5 mu m. The hardness of said layer is increased by approx. 1.2 times.

Самым тугоплавким из известных на сегодняшний день материалов является карбид гафния. Были проведены исследования возможности получения изделий из расплавленного карбида гафния методом разогрева механокомпозита гафний/углерод высокоинтенсивным лазерным излучением.

The proportion of products manufactured by additive methods is constantly growing in modern technology. The use of radiation technologies makes it possible to obtain materials that combine the best characteristics of metals, oxides, carbides, borides, and so on. It attracts the interest of developers of new technology. Tungsten boride is a promising material for enhancing the protective properties of containers in which radioactive materials are stored. The possibility of synthesizing borides by electron beam processing is studied.

A comparative analysis is presented for the particle velocity and temperature in the light field of a continuous wave (CW) or pulsed CO2-laser in a coaxial jet gas flow. The problems of measuring the particle velocity and temperature in the light field are solved using noncontact registration methods based on a spectrometer and a combination of laser and optical devices. Alumina, molybdenum, nickel and aluminum powders are used with standard size distributions of the particles. It is shown that, in the field of laser radiation, powder particles get an extra acceleration due to the reactive force resulting from the recoil pressure in evaporation from particles. Laser radiation essentially influences the in-flight velocity of particle velocity and temperature.

A study is performed on the possibility of obtaining products from molten hafnium carbide, the most refractory material known so far, by heating a hafnium/carbon mechanocomposite with high-intensity laser radiation.

The results of experiments on influence of laser-plasma influence on structure and microhardness of surfaces of structural steels with various structures, wheel steel grade "2" for the production of railway wheels and grey cast iron are presented. As a result, it was revealed that laser-plasma treatment allows to make hardening of a surface of constructional steels up to 9.0-12.0 GPa of hardness, on depth about 0.8 mm. The application of laser-plasma treatment for surface hardening is possible at different stages of the technological process of manufacturing or repair of machine parts. It is important that for laser-plasma treatment technology is characterized by a small time of thermal impact on the surface, which does not lead to the change of the phase structure of the main volume of metal and increase cold brittleness. The offered technologies are directed on multiple increase of a resource of the most responsible details defining basic characteristics and service life of the final product, its consumer qualities and competitiveness. The efficiency and prospects of introduction of laser-plasma technologies in shipbuilding and ship-repairing production for increase of a resource of transport means, equipment and constructions are considered.

Introduction. In recent years, the fundamentals of the laser-plasma methods for surface modification and micropowder coating application have been developed in the Institute of Laser Physics. The methods are based on the use of optical pulsed discharge plasma. The discharge is ignited by the repetitive laser pulses focused on the surface of the workpiece in a gas or a gas-powder stream. The high pulse repetition frequency of 10-120 kHz is achieved using the generator-amplifier CO2-laser system with the half-height pulse duration set tau = 150-200 ns. The search for other timely applications of these methods is currently ongoing. An interest in the obtaining of amorphous metallic coatings on the surface of structural materials is yet to wane after the decades of intense research done by scientists all over the world due to the outstanding physical, chemical and mechanical properties of such coatings. The purpose of this work is to obtain the hardening coatings based on theFe-Cr-Si-B-C alloys with high glass-forming ability and to investigate the possibility of obtaining a coating with an amorphous structure using laser-plasma methods. Theory. As the surface of the metallic alloys was under the intense thermal influence of the pulsed laser plasma, the numerical modeling was applied to determine the dependence of amorphized layer's thickness on the material properties, as well as in relation to the parameters of the laser irradiation and the laser plasma. Experimental methods. The experiments are carried out in two stages using the installation designed at the Institute: (1) at first, the uniform coatings were prepared on the surface of steel substrates using the laser-plasma application method incorporating the powders of the AP-FeCr4Mn2Si2B4V1 (Fe71.75Cr3.33Si3.54B14.10C4.81Mn1.7 V-4(0.73)) and AP-FeCr11Mn4SiB (Fe66.8Cr10.79Si5.3B11.42C2.85Mn2.84) grades; (2) then, the surface coatings underwent the rapid laser-plasma modification to ensure the remelting of the thin surface layer. Results and discussion. The numerical methods applied have proven the theoretical possibility of obtaining an amorphous layer of about 3-5 mu m thick, based on the Fe-Si-B alloys. As a result, the parameter range required for the successful laser-plasma modification is determined. The hardness of the obtained coatings is measured and its thickness has been determined in dependence on the application parameters. The hardness is measured using the nanoindentation method and equals 12 +/- 1 GPa in regards to the coating incorporating the powder AP-FeCr4Mn2Si2B4V1 and 8.5 +/- 0.7 GPa in case of the powder AP-FeCr11Mn4SiB; the thickness of the coatings is up to 0.1-0.4 mm. Using optical microscopy, SEM and X-ray diffraction the structure of the coatings is investigated. It is demonstrated that the laser-plasma modification of the coatings on the surface leads to the structure refinement of the surface layer. The characteristic size of the crystallites is 0.5-1 mu m. In addition, the hardness of the remelted layer is increased up to 13.8 +/- 0.7 GPa for the AP-FeCr4Mn2Si2B4V1 alloy and up to 10.5 +/- 0.5 GPa for the AP-FeCr11Mn4SiB alloy. Using SEM and X-ray diffraction the structure of the coatings is investigated. The amorphous phase in the remelted coating layer is not detected, which might be due to an increase in the critical cooling rate during the laser amorphization as compared to the traditional methods of melt quenching.

Mechanochemical preparation of nanoscale hafnium (IV) carbide was explored. It was demonstrated that the Hf/C mechanocomposite with a wide particle-size distribution was formed in the first step. Fused hafnium (IV) carbide was produced from nanoscale hafnium (IV) carbide and the hafnium/carbon mechanocomposite by treatment with high-intensity photon flux. According to research results, the mechanocomposite is more preferable and may be used as a precursor to make products of fused hafnium (IV) carbide using additive technologies.

The mechanocomposites hafnium/carbon was performed in a water-cooled high-energy planetary ball mill during 2 min. Molten hafnium carbide from the mechanocomposite hafnium/carbon was obtained under the action of high-intensity laser radiation. High-resolution XRD studies of the samples were carried out using "hard" (quantum energy of 33.7 keV) synchrotron radiation. The study of morphological characteristics of the samples was carried out using scanning electron microscope.

A new method has been developed for the plasmochemical deposition of hard protective silicon carbonitride coatings from a hexamethyldisilazane (HMDS) Si2NH(CH3)6 vapor and HMDS+ benzene activated by a powerful optic pulse discharge (POPD) in a high-velocity gas flow of argon. The method allows depositing silicon carbonitride coatings with a rate of 0.5−1.2 μm·min−1 that is (1−5)·102 times higher than in conventional CVD processes. It has been found that coating deposition rate and structure of coatings depend on the process parameters: flow rates of HMDS and HMDS+benzene and plasma generating gas (argon). The method allows depositing SiCN coatings containing Si–C, Si–N and Csp3–N bonds with high velocity and microhardness 24 GPa.