## 3 Results and Discussion
### Microscopic Observation  
Microscopic analysis of surface morphology plays a crucial role in evaluating the effectiveness of surface finishing processes, particularly in components manufactured by additive methods. SEM provides high-resolution insight into topographical and structural surface features, enabling the identification of defects, adhered particles, and changes induced by post-processing. In this study, SEM observations were carried out to assess the surface state of Inconel 939 samples fabricated by LPBF, both in the as-built condition and after subsequent vibratory and MAF machining. The comparative analysis allowed for a detailed evaluation of morphological transformations, offering qualitative evidence of surface refinement mechanisms and the spatial uniformity of the applied processes.  
The first SEM image (Figure 9a,b) presents the surface condition of the sample after manufacturing via LPBF followed by HT in an argon atmosphere. A high concentration of spherical powder particles is visible on the surface, resulting from partially melted or unconsolidated metal particles. The rough texture and micro-inhomogeneity typical of LPBF arise from phenomena inherent to the process, such as spatter adhesion, microcratering, and non-uniform energy distribution of the laser. The surface structure remains notably  
Figure 8: Example of a surface roughness profile (**a**) before MAF, (**b**) after MAF (sample no. 6). The circle indicates the midpoint along the surface roughness profile.  
imperfect, exhibiting characteristic defects in the topmost layer--including discontinuities and potential crack initiation sites.  
The second image (Figure 9c,d) shows the sample after mechanical vibratory finishing. Compared to the as-built state, a significant reduction in adhered powder particles and a flattening of microscopic asperities can be observed. The surface is dominated by subtle marks of micro-cutting and plastic deformation within the top layer. These features indicate effective abrasive action. Despite the general improvement in smoothness, local discontinuities and minor built-up areas are still present, which may negatively affect the surface's contact properties and corrosion resistance.  
The surface condition after the final MAF (Figure 9e,f) demonstrates high uniformity and smoothness. There is an almost complete elimination of micropores and adhered particles, along with the disappearance of the micro-cutting traces present after the vibratory stage. The edges are rounded, and the surface topography is distinctly flattened. The selective removal of surface microgeometry, characteristic of MAF using ferromagnetic  
Figure 9: Microscope images of the sample surface: after 3D printing (**a**)—\(\times 100\), (**b**)—\(\times 500\), after vibratory finishing (**c**)—\(\times 100\), (**d**)—\(\times 500\), and after vibratory finishing and MAF (**e**)—\(\times 100\), (**f**)—\(\times 500\).  
abrasive media, allowed for the formation of a surface with low roughness while preserving material integrity. Such a surface promotes beneficial functional properties, including a reduced friction coefficient, improved fatigue performance, and lower susceptibility to surface crack initiation.