Selective laser melting is one of the modern methods of manufacturing parts in the production of machine-building equipment, a special place is occupied by complex technological processes used in the manufacture of high-load units of pneumatic-hydraulic system from heat-resistant alloys. The research was carried out on samples made of powder material - stainless steel AISI 316L martensite class. Metallographic studies showed that the density of the sample is 99.83%, the structure of the samples is a martensitic structure of equilibrium constructed tracks. Tests to determine the mechanical properties were performed in accordance with ISO 6892 on an INSTRON test machine. From the tensile diagram it was found that the yield strength was 376.56 MPa, the maximum point of temporary resistance of the sample - 615, 40 MPa 319 seconds after the start of the test. The control of the surface roughness was performed using a BioBase device. The working area of the tensile sample consisted of two areas: a roughness area of 5 μm, which accounted for 80% of the working part of the sample (zones A and Б) and 20% of the working part of the sample (zone Б), the roughness was 17 μm. According to the results of microstructure studies and studies by the method of registration of macrolocalization fields of the working zone of the samples, it was found that the destruction began from the surface of the samples from microconcentrators due to different roughness. It is established that the surface and subsurface layer with increased roughness in comparison with the main body has a smaller elongation by 10.84%. From microstructural studies of the working zone in the area of the gap, it was found that the destruction began from the surface of the samples between zones A and Б. During the research in zone A and Б, one of the concentrators of the gap was detected. As a result of the study, it was found that the destruction began with the surface of the samples and the place of change of its roughness. The mechanism of deformation of the sample from AISI 316L steel is shown, the scheme of extraction of tail sections of tracks and crack propagation in the conditions of tensile testing of the sample is constructed.

Подольський Ростислав Вячеславович Інженер I категорії, відділу проблем деформаційно-термічної обробки конструкційних сталей Інститут чорної металургії ім. З. І. Некрасова НАН України Інженер-матеріалознавець LLC «Additive Laser Technology of Ukraine» УКРАЇНА Селективне лазерне плавленняодин з сучасних методів виготовлення деталей та вузлів складної геометрії, які складно або неможливо відтворити в умовах традиційного виробництва [1, 2].На теперішній час титанові сплави широко використовуються в медичних галузях. З щорічним старінням населення та збільшенням нещасних випадків збільшуються і ортопедичні операції (імплантація). Виготовлення за допомогою 3-D технологій ендопротезу (рис. 1) має безліч переваг перед традиційними методами виробництва: виготовлення ендопротезів з анатомічною точністю, виготовлення пористої поверхні для легшого зростання з натуральними кістковими тканинами (самолікування). Рис. 1. Модель ендопротезу тазостегнового суглобу

The purpose of the work is to study the microstructure and mechanical properties of 316L stainless steel samples made by the SLM method. 316L stainless steel has been extensively studied for the state after fabrication by selective laser melting (SLM). This is due to the wide use of this material in various industries, as it demonstrates sufficient corrosion resistance and excellent plasticity. Thus, its application can be found in the biomedical, aerospace, automotive and marine fields. Some of the studies conducted have shown the ability of SLM to improve the mechanical properties of parts compared to traditional methods. Metallographic analysis, determination of mechanical properties, and chemical analysis were used. The object of the study was austenitic grade 316L stainless steel. The material for making the samples was a 316L alloy powder with a particle size of 45 + 15 μm. Experimental samples for tensile tests were built on the equipment of "Additive Laser Technologies of Ukraine" LLC (Alfa-150) using SLM technology in identical modes: laser power - 290 W, scanning speed - 1100 mm/s, distance between tracks – 0.11 mm, scanning strategy - checkerboard fields, scanning order - Zig-Zag, field size - 5 mm, rotation of the layer relative to the previous one - 67°. From the results of the analysis of mechanical properties, it was established that the samples made on the 3-D printer of Additive Laser Technologies of Ukraine LLC are not inferior in terms of quality to leading global companies, and in some characteristics even exceed them. It should be noted that the results of determining the characteristics of the experimental samples were compared with the properties of the samples manufactured according to the optimal process parameters on the equipment of different manufacturers, but do not include the influence of the thickness of the applied layer. Comprehensive studies of the mechanical properties of the samples made of 316L steel showed full compliance with the samples produced on the equipment presented on the world market for the production of special-purpose products.

To date, means of protection of all types of armored vehicles against damage by small arms are actively being developed, new grades of steel with increased anti-projectile resistance indicators are being developed, which ensure a reduction in the metal content of structures while simultaneously increasing the tactical and technical characteristics of the product. The constant increase in requirements for the protection of armored vehicles, caused by the improvement of highly effective means of attack, dictates the need to find new approaches to increase the dynamic stability of armored steels using modern metallurgical, material science and construction achievements. The development and design of workable materials and structures of armor protection is a complex scientific and technical problem. The purpose of the work is to determine, based on the analysis of literary sources, the main trends in the development and improvement of modern metal materials for the manufacture of armored obstacles, which have high dynamic resistance against modern highly effective small arms weapons. The paper analyzes the most widely used metal materials for the manufacture of armored barriers, presents information about their advantages and disadvantages, and provides an assessment of the prospects for further development of this industry. It is noted that the current concept of weapons development is aimed at the use of high-tech materials and innovative methods that allow improving protective functions without increasing the mass and dimensions of armor protection. Currently, many different materials are used to create armor protection: metal plates based on steel, titanium, aluminum and their alloys, aramid or polyethylene fibers, as well as ceramics based on boron carbides, silicon, and others. In accordance with the existing concept of increasing the effectiveness of armor protection and ensuring a combination of firepower, security and mobility, the use of promising materials for the creation of armor protection provides an additional reserve for increasing the combat and military-economic efficiency of military equipment.

The process of operating vehicles determines the interaction of the wheel and rail. Traffic safety and the main technical and economic indicators of track management and rolling stock largely depend on these parameters. The result of this interaction are changes in the metal, which arise from rolling friction and especially from the friction of the wheel sliding on the rail during braking, due to these changes, the wheels of the rolling stock wear out. The purpose od the work is to research of the microstructure and mechanical properties of steels of promising chemical compositions to meet modern requirements for railway rails. Methods of metallographic analysis, determination of mechanical properties, and chemical analysis were used. Samples made from laboratory melts of steels with a promising chemical composition served as material for detailed microstructure studies. When comparing prospective chemical compositions, it was established that steel 1 meets the requirements of DSTU EN 13674:2018 for basic chemical elements and has differences according to DSTU 4344:2004, namely: increased carbon content. When comparing the experimental chemical composition of steel 2, it was found that this steel does not meet the requirements of DSTU EN 13674:2018 and DSTU 4344:2004, namely: a reduced amount of carbon and an increased content of silicon, chromium and molybdenum. According to the results of the analysis of the values of mechanical properties, it was established that steel 1 and 2 meets the requirements of DSTU EN 13674:2018. Steel 1 does not meet the requirements of DSTU 4344:2004 in terms of yield strength and relative narrowing, and steel 2 does not meet the requirements of DSTU 4344:2004 for the highest category of rails in terms of temporary resistance values. Based on the results of the microstructure studies, it was established that the test steel 1 after heat treatment has a structure of highly dispersed pearlite with a small amount of coarse-plate pearlite. When analyzing the microstructure of steel with a promising chemical composition 2, it was established that the structure consists of carbide-free bainite.