## 3 Results and Discussion
Treatment with 3 M HF increased the Ra value to 0.23 \(\pm\) 0.02 \(\upmu\)m, while 12 M HF treatment further elevated it to 0.32 \(\pm\) 0.03 \(\upmu\)m. This increased roughness may be beneficial for cell adhesion, although it is noteworthy that surface hardness slightly decreased from 79.8 \(\pm\) 0.4 to 78.5 \(\pm\) 0.9. Sandblasting treatment led to a substantial increase in surface roughness while also enhancing surface hardness. Treatment with 80-grit sand resulted in an Ra value of 2.25 \(\pm\) 0.41 \(\upmu\)m, whereas 120-grit sand produced an Ra value of 1.20 \(\pm\) 0.13 \(\upmu\)m. This difference likely stems from the varied impact effects due to different sand particle sizes. Notably, sandblasting also increased surface hardness to 84.3 \(\pm\) 0.4 and 83.1 \(\pm\) 0.2, respectively. The sandblasting and acid-etching (SLA) process further altered surface characteristics. For samples treated with 80-grit sand, the subsequent 3 M HF treatment slightly reduced roughness (Ra = 2.23 \(\pm\) 0.36 \(\upmu\)m), while the 12 M HF treatment significantly decreased roughness (Ra = 1.43 \(\pm\) 0.27 \(\upmu\)m). This phenomenon may be attributed to the selective corrosion and smoothing effects of high-concentration HF on the surface. For samples treated with 120-grit sand, the subsequent acid etching reduced surface roughness in both cases, particularly with the 12 M HF treatment (Ra = 0.85 \(\pm\) 0.19 \(\upmu\)m). These composite treatments also decreased surface hardness to levels approaching that of the original Ti-64. Shot peening treatment produced a moderate increase in surface roughness, with Ra values ranging from 0.72 to 0.85 \(\upmu\)m. Interestingly, as treatment pressure decreased and duration increased, surface roughness slightly decreased, but surface hardness remained relatively high (82.5-83.8). This suggests that shot peening may provide sufficient surface roughness to promote biological responses while maintaining the bulk properties of the material. Acid etching following shot peening further increased surface roughness, with Ra values reaching 0.87-0.97 \(\upmu\)m, while reducing surface hardness to levels similar to the original Ti64. This composite treatment may offer additional possibilities for optimizing surface characteristics, increasing surface roughness while avoiding excessive surface hardening. These results demonstrate that through the selection of appropriate surface treatment methods and parameters, precise control over the roughness and hardness of Ti-64 surfaces can be achieved. Different treatment methods produce a wide range of roughness scales, from submicron to micron levels, offering diverse options to meet the requirements of various biomedical applications. Raman spectroscopy analysis plays a crucial role in this study, providing essential information about the chemical composition and structure of Ti-64 alloy surfaces, particularly in assessing the impact of various surface treatments on oxide layer formation. This non-destructive characterization technique offers deep insights into phase changes during the surface modification process, providing a scientific basis for optimizing the surface characteristics of biomedical implants. Figure 6 presents the Raman spectra of the original polished Ti-64 surface and those subjected to different treatments. The original polished surface exhibits relatively flat spectral features with only a weak broad peak around 300 cm\({}^{-1}\) (Figure 6a), possibly associated with an extremely thin natural oxide layer. In contrast, the sample treated with 3 M HF immersion corrosion shows a significant peak at 520 cm\({}^{-1}\), corresponding to the Eg mode of anatase phase TiO\({}_{2}\). This indicates that HF corrosion effectively promotes the formation of an oxide layer, primarily generating anatase phase structures. The spectrum of the shot-peened (Zr SP) sample displays an enhanced broad peak near 300 cm\({}^{-1}\), reflecting increased surface roughness, but no distinct TiO\({}_{2}\) characteristic peaks are observed.