RT Journal Article SR Electronic A1 Knast, Paweł A1 Petrů, Jana A1 Legutko, Stanislaw A1 Soos, Lubomir A1 Pokusova, Marcela T1 SEM Analysis of Surface Layers with Variable Ra Parameters for Tribological Optimization in Design Engineering JF Manufacturing Technology Journal YR 2025 VO 25 IS 2 SP 185 OP 201 DO 10.21062/mft.2025.022 UL https://journalmt.com/artkey/mft-202502-0007.php AB In this study, the microstructure of surface layers with varying roughness (Ra parameters) was analyzed using scanning electron microscopy (SEM) to optimize tribological properties in engineering design. SEM revealed key microstructural features - sharp and mild protrusions, pitting, microcracks and contaminants - that were not available in traditional profilometry. Reducing the Ra value improved surface uniformity by reducing irregularities and defect lengths, which had a positive effect on tribological properties and surface durability. However, defects were still present even at Ra < 1.25 μm, indicating the "Law of Microstructural Roughness," which emphasizes the inevitability of surface irregularities despite minimizing roughness. The integration of SEM results with profilometric methods enabled comprehensive identification and assessment of defects, combining microstructure with tribological properties. Results suggest that controlled roughness is key in combining materials and optimizing functional surfaces, particularly in the aerospace, biomedical and automotive industries, where reliability under demanding operating conditions is a priority.