## 1 Introduction  
Aerospace parts are subjected to high mechanical and thermal loads throughout their entire operational lives. Therefore, certified parts must have high density, low surface roughness, and a low level of residual stress, as well as high tensile strength and fatigue strength. In addition, to achieve the desired aerodynamic flows and low fuel consumption, complex geometric shapes and light weight are required [1]. A gas turbine blade is a great example of complex geometry with internal cooling ducts fabricated for maximum possible energy while ensuring proper cooling during operation. However, the fabrication of such geometric shapes and cooling ducts is limited by traditional technologies that prevent us from researching a wider range of designs with new functional capabilities [2, 3].  
Thanks to good oxidation resistance and fatigue strength, high-temperature Ni-based alloys are widely used in rocket engineering and other industries where heat strength and heat resistance are critical requirements [4, 5]. However, the Inconel 718 (IN718) alloy, for example, is a hardly machinable material due to its inability to quench. IN718 has low heat conductivity, which causes a sharp temperature gradient at the tool-shavings boundary, which leads to increased tool wear [2]. Therefore, a more suitable technology should be researched for fabricating parts from IN718.  
Additive manufacturing (AM) technologies, specifically selecting laser melting, offer a flexible solution to the above problems [6, 7]. Selective laser melting (SLM) provides freedom for design necessary for manufacturing parts with complex geometry without using ad-hoc tools, which allows for saving time and materials. The main purpose of SLM is the fabrication of quality parts with predictable mechanical properties, such as density,surface roughness, residual stress, tensile strength, etc. The main process parameters of SLM are the laser power, laser scanning speed, hatch spacing, and scanning strategy, all of which thus create certain microstructures and properties for the fabricated part.  
Despite some advantages, the SLM process has some drawbacks: microstructure inhomogeneity and randomly scattered defects, which lead to the deterioration of mechanical properties [8; 9]. For example, in the course of SLM of IN718, anisotropy, microstructure inhomogeneity, residual stress, undesired phases, and incomplete fusion defects are normally caused by the fast crystallization of molten metal. These factors have complex effects on the mechanical properties of materials, especially compared to their forged and cast counterparts [10]. To optimize mechanical properties, thermal treatment is subsequently used to modify the structure of grains [11; 12], as well as their type, shape, and size as fabricated from IN718 [13; 14]. Therefore, we need to research the correlation between the creeping flow properties and microstructural defects created during AM and thermal treatment. Thus, this work is devoted to the maturing of 3D printing modes for parts fabricated from a high-temperature nickel-based alloy, the research of the mechanical properties of experimental samples, and the comparison of thermal treatment modes.