Surface polishing and modification of Ti-6Al-4V alloy by shear thickening polishing

In this study, a comparison of three newly developed polishing techniques namely, shear thickening polishing (STP), Chemistry enhanced STP (C-STP) and Electrolysis enhanced STP (E-STP) was made to investigate their suitability to Ti-6Al-4V biomaterials polishing and modification, which can produce Beilby layer after polishing and enhance mechanical and biological performance. The surface roughness S_a after STP was about 13.8 nm with a material removal rate of 54.3 nm/min. The C-STP showed the lowest surface roughness of 7.2 nm which was almost half that of STP and the MRR during C-STP was almost 2.1 times that of the conventional STP. The STP did not lead to any change of the surface composition, whereas a 136 nm thick Beilby layer was observed to form during the C-STP which revealed a lower friction coefficient of 0.04 as well as improved osteoblast cell activity. The E-STP showed an intermittent improvement as it provided a surface roughness of 10.2 nm and 1.6 times MRR than that obtained from conventional STP. Due to the dense oxide film of about 60 nm, the E-STP processed surface showed the best wettability and corrosion resistance. Overall, we reveal an important pathway for achieving scalable finishing on Ti-6Al-4V with desirable surface characteristics.