2019, Loginova, I. S., Solonin, A. N., Prosviryakov, A. S., Cheverikin, V. V., Bykovskiy, D. P., Petrovskiy, V. N., Быковский, Дмитрий Петрович, Петровский, Анатолий Николаевич

The direct laser deposition of metal powders is one additive method of producing functional materials. It consists of the melting of metallic powders by a laser beam in inert gas. The main process parameters are the laser-beam power, laser-beam speed and scanning trajectory, and powder consumption. Each parameter is selected depending on the alloy type, which in totality affects the structure and defect formation in products. In this study, experimental rectangular samples of 316L austenitic steel are fabricated by the direct laser deposition of the powder. The microstructure and fractures of samples are investigated using scanning electron microscopy in order to determine the structural features and reveal the defects (pores, holes, crystallization cracks, and oxide inclusions). Uniaxial tension tests and hardness tests are performed. The analysis of the influence of the laser beam scanning trajectory on the microstructure and properties of samples during melting is performed. It is found that a dispersed structure with an average crystallite size of 1.3-1.9 m is formed at a laser power of 250 W and scanning rate of 16 mm/s, which results in a high level of mechanical properties of experimental samples. It is shown that, when using the lengthwise laser-beam trajectory (along the largest sample size), the tensile strength reaches 730 MPa with a relative elongation of 25%, which exceeds the level of mechanical properties of 316L steel by 110 MPa.

2019, Bykovskiy, D. P., Ishkinyaev, E. D., Petrovskiy, V. N., Osintsev, A. V., Dzhumaev, P. S., Polskiy, V. I., Sergeev, K. L., Shchekin, A. S., Быковский, Дмитрий Петрович, Ишкиняев, Эмиль Дамирович, Петровский, Анатолий Николаевич, Осинцев, Андрей Вениаминович, Джумаев, Павел Сергеевич, Польский, Валерий Игоревич, Щекин, Александр Сергеевич

© Published under licence by IOP Publishing Ltd.The microstructure of 316L stainless steel obtained by layer-by-layer direct metal laser deposition is reviewed. Mechanical tests of the samples were performed in accordance with GOST 1497-84. Studies show that changes in power of laser radiation to grow parts lead to changes in their mechanical properties. The research shows dependencies between the strength characteristics of materials and the power of laser radiation. Causes of the forementioned changes are studied through the analysis of the microstructure. Nanosized inclusions of spherical shape were found in the process of studying the microstructure of materials. A study in the nature of the formation of these inclusions and their effect on the properties of the obtained material was performed.

2019, Ishkinyaev, E. D., Petrovskiy, V. N., Polskiy, V. I., Dzhumaev, P. S., Sergeev, K. L., Shchekin, A. S., Panov, D. V., Ushakov, D. V., Ишкиняев, Эмиль Дамирович, Петровский, Анатолий Николаевич, Польский, Валерий Игоревич, Джумаев, Павел Сергеевич, Щекин, Александр Сергеевич

© 2019, Pleiades Publishing, Ltd.The paper presents the results of mechanical tensile tests and microhardness of samples obtained from stainless steel 316L powder by direct laser deposition. The strength characteristics of the deposited samples are better than those of rolled ones obtained in the traditional way. The material strength is reduced and its plasticity is increased with the growth of the laser radiation power during deposition. The obtained regularities are explained by analysis of the microstructure. It is found that the hardness of the cladding is substantially higher than that of the substrate material with the corresponding composition. This is a consequence of hardening of each layer during deposition of the next layer and formation of nanosized spherical inclusions representing oxides of metals that make up the powder in the sample bulk. The density of these particles affects the overall hardness of the material and depends on the radiation power supplied. Individual properties of the material for various applications can be modified by appropriate selection of technological parameters of the printing process.

2019, Panov, D. V., Petrovskiy, V. N., Ushakov, D. V., Osintsev, A. V., Dzhumaev, P. S., Polskiy, V. I., Петровский, Анатолий Николаевич, Осинцев, Андрей Вениаминович, Джумаев, Павел Сергеевич, Польский, Валерий Игоревич

© Published under licence by IOP Publishing Ltd.The paper considers the possibility of using laser milling technology for precision processing of ceramic samples from pre-sintered and sintered ceramics zirconia and lithium disilicate. To find the best radiation source were compared different lasers. To find highest removal rate with acceptable accuracy was studied influence laser and scanning system parameters on ceramics. Accuracy problem of laser milling was considered. Examples of surfaces of prostheses were made.