Improvement in the polishing characteristics of titanium-based materials using electrochemical mechanical polishing

Titanium (Ti) and its alloys are widely used in aerospace components and biomaterials. The smoothing of Ti materials is essential for realizing high-quality Ti-based devices and components to enhance their physical and chemical properties, such as fatigue strength and biocompatibility. However, with conventional polishing methods, obtaining sub-nanometer roughness in a large measurement area is difficult because of the generation of crystal grain steps on the polished surface. This paper presents an electrochemical mechanical polishing (ECMP) method that involves electrochemical oxidation and subsequent oxide removal using SiO2 particles to achieve a high material removal rate (MRR) and an ultra-smooth surface of pure Ti and Ti-6Al-4V. Under suitable electrolytic current and mechanical conditions, ECMP provides a higher MRR and smoother pure Ti surface than electroless polishing. X-ray and Raman analyses indicate that the mechanical condition affects the chemical states of polished surfaces; higher mechanical conditions retain less oxide film on the polished surface, resulting in a smoother surface. The highly efficient ECMP provides a defect-free and sub-nanometer roughness for pure Ti and Ti-6Al-4V surfaces without using chemicals. Furthermore, it is an environment-friendly and cost-effective approach to prepare Ti-based components.