Saint Petersburg Polytechnic University of Peter the Great, Saint Petersburg, Russia:

V. Sh. Sufiyarov, Leading Researcher of the National Technology Initiative Center of Excellence in "Advanced Manufacturing Technologies" (NTI Center), e-mail: Vadim.spbstu@yandex.ru
E. V. Borisov, Researcher of the NTI Center
I. A. Polozov, Researcher of the NTI Center
D. V. Masailo, Researcher of the NTI Center

Additive technologies are of great interest for the manufacture of metal products as they allow the development of complex structures with high mechanical characteristics. At the same time, the question of the possibility of controlling the process of structure formation in products in the process of its production remains topical. Of particular interest is the possibility of simultaneously creating local sections in the product with a given microstructure and properties. A complex study of the influence of technological parameters of the selective laser melting process on the structure and properties of samples from the Inconel 718 alloy is presented. The results of studies of the mechanical properties of compact samples made at different layer thicknesses, both in the initial state and after hot isostatic pressing and heat treatment are presented. The results of a study of the possibility of creating samples with a variable microstructure depending on the parameters of the selective laser melting process are presented. Samples with a variable structure are produced and investigated, in which the regions with finely dispersed equiaxed grains and large columnar grains are programmatically present. At the boundary of these regions, mutual penetration of large and small grains is observed. The EBSD analysis showed that a change in the thickness of the layer and the technological parameters of the selective laser melting process makes it possible to locally change the size and morphology of the grains of the material. When using a large layer thickness, the directional crystallization mode and the formation of columnar grains are possible. It is shown that after the heat treatment and hot isostatic pressing, the differences in the structure and mechanical properties between the regions are preserved.
The work was carried out within the framework of the implementation of the federal target program “Research and development in priority areas of development of Russia's scientific and technological complex for 2014–2020”, the unique identifier of the project RFMEFI57817X0245.

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