OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 4 2024 surface of the TiNi alloy and the development of a granulated structure in steel contribute to an increase in the surface roughness Ra of the specimens, as indicated by the measurements of surface roughness of metallic materials before and after laser treatment. Initially, the Ra of the TiNi specimens is 40.9 ± 5.3 nm, while for the steel specimens, Ra is 27.7 ± 5.3 nm. Long-term UV laser treatment (600 s) results in a more than twofold increase in roughness: Ra increases to 82.3 ± 5.3 nm for TiNi and to 64.3 ± 6.2 nm for steel. Changes in surface topography (roughness) do not signifi cantly aff ect the wettability of the TiNi alloy surface, while for steel specimens, a slight tendency to decrease the contact angle with increasing roughness is noted. These results are consistent with the results presented in [20, 27], which emphasize the complex relationship between roughness and surface chemistry in changing hydrophilicity and biocompatibility. The formation of an oxide fi lm on the surface of TiNi specimens after UV laser treatment is further substantiated by data obtained through XRD. Figs. 6 and 7 illustrate the XRD patterns of TiNi and steel specimens both before and after laser treatment. The XRD pattern of the initial TiNi specimens (Fig. 6, a) and the XRD patterns of the specimens after UV laser treatment for 10, 120, and 300 s (Fig. 6, a) contain only the peaks corresponding to the B2 phase of TiNi (Ti49.5-Ni50.5) and the phase TiC, which was formed during the material manufacturing process, with a volume fraction of 5–7 %. The XRD pattern obtained from TiNi specimens after 600 s of UV laser treatment (Fig. 6, a) indicates a change in phase composition. In addition to the primary B2 (TiNi) phase and TiC precipitates, peaks relating to the oxides TiO2 and Ti4Ni2Ox are also observed in the XRD pattern (Fig. 6, b). The oxide phases identifi ed on the surface of TiNi specimens after long-term laser treatment are most likely present on the surface of both the initial specimens and the specimens with a short duration of laser exposure, as evidenced by the data on the oxygen content on the surface obtained using EDS. Apparently, Fig. 5. SEM images of stainless steel specimens with the results of EDS analysis: initial surface (a), surface after UV laser treatment for 60 s (b), 420 s (c), 600 s (d) а b c d
RkJQdWJsaXNoZXIy MTk0ODM1