The doctoral thesis deals with the optimization of the shape of the axial powder-feed nozzle and the characterization of the influence of the laser-beam intensity distribution (LBID) on the performance of the process of annular laser-beam directed energy deposition (DED) with axial powder feed. It has been shown that the diameter of the powder stream can be reduced by a suitable adjustment of the nozzle shape. The most suitable nozzle shape proved to be a divergent conical shape at the exit of the nozzle, which improved the powder-catchment efficiency by more than 10%. It was also important to consider the roughness of the inner surface of the nozzle, as too high roughness eliminates the positive effect of the divergent exit shape. For the experimental characterization of the LBID influence, three LBID shapes were compared: Gaussian-like (G-LBID), top-hat (TH-LBID), and ring (R-LBID). It was found that LBID affects the DED process stability, powder-catchment efficiency, and clad properties. When using G-LBID and TH-LBID, the highest powder-catchment efficiency and the lowest dilution ratio are achieved, but at the same time there is an uneven shape of the dilution area, incomplete metallurgical bonding, and porosity in the interface area between the clad and substrate. Conversely, R-LBID achieves a more uniform shape of the dilution area, less porosity, and better metallurgical bonding, but at the same time a higher dilution ratio and lower powder-catchment efficiency. At the same time, the R-LBID provides better process stability at both high and low mean surface-energy densities. From the perspective of using the annular laser-beam DED process to produce single-layer cladding, the use of R-LBID proved to be the most suitable.
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