## 5 Conclusions  
1. It was established that additive microplasma deposition of powder of Fe-Cr-Ni-B-Si system (40-60 \(\upmu\)m particle size) results in the formation of a layered metal structure with the deposited layer height of the order of 650 \(\upmu\)m and wall thickness of 3.0-3.5 mm. Metal distribution by the sample height is uniform. Additive formation of a sample by powder deposition results in the appearance of colonies of coarse and fine dendrites, the size and orientation of which change along the wall height. The deposited metal has a presumably austenitic structure with (40-100) \(\times\) (200-600) \(\upmu\)m grain size and 15-30 \(\upmu\)m substrain size (lower and middle part) with its refinement in the upper part and reduction of grain shape coefficient \(\sigma\) by 1.3 times on average. The subgrain structure of the deposited metal is of a cellular type, and it provides a certain effect of metal strengthening. Deposited metal ensures a high ultimate strength (more than 600 MPa). Susceptibility to porosity or cracking is absent;
2. The finite element method was used to derive a solution to the thermomechanical problem of additive deposition with HYF-103 powder of the Fe-Cr-Ni-B-Si system for five selected hollow spatial prototypes (<<cylinder>>, <<triangular prism>>, <<square prism>>, <<reverse cone>>, and <<straight cone>>). It was found that in all the cases in the first bead of the modeled samples, there was a high level of residual equivalent stresses (\(\sim\)500 MPa) due to the substrate rigidity. In each subsequent deposited bead, the residual equivalent stresses decreased by 7-20%, which corresponds to the level of 390 MPa in the third pass. Equivalent stresses of the greatest magnitude (565 MPa) are predicted in the model sample of the <<reverse cone>> type, and the smallest ones (552 MPa) in the sample of the <<straight cone>> type. The maximal values of radial movements corresponded to the range of 0.22-0.28 mm for all the models. Experimental studies of residual deformations of the deposited products showed an up to 20% deviation from the modeled values, which is acceptable;
3. To minimize the stress-strain state of the manufactured 3D objects, basic techniques of the process of additive microplasma deposition were developed, including the process starting at a higher current (\(\sim\)35 A) with a rapid transition (\(\sim\)1 s) to a stable mode (\(\sim\)25 A); reduction in the filler powder flow rate (to 6 g/min); lowering of the plasma-forming gas flow rate from 0.4 to 0.2 L/min; stabilization of the process energy input at the level of 85-90 J/mm; and minimization of the arc length (to 5 mm). The application of a system of automatic regulation of arc voltage was proposed for the stabilization of the energy input and the arc length.  
[PERSON]. ([PERSON]) and [PERSON]--created the hypothesis and planned the experiments; [PERSON]. ([PERSON]), [PERSON] and [PERSON]--conducted the technological experiments and metallographic investigations; [PERSON]. ([PERSON]) and [PERSON]--conducted finite-element modeling and performed the calculations. All authors have read and agreed to the published version of the manuscript. Funding was provided within the following programs. 1. Strategic project of the Academy of Sciences of Guangdong Province, (GDASProject of Science and Technology Development, 2020 GDASYL-20200301001), China. 2. The National Key Research and Development Program of China--in the framework of the strategy <<One Belt--One Road>> (grant number 2020 YFE0205300), China. Data Availability Statement: The data presented in this study are available on request from the corresponding author due to the authors' preference to exchange data directly upon request. Conflicts of Interest: The authors declare no conflicts of interest.