Evolution of material removal in the magnetorheological polishing of Ti6Al4V by laser power bed fusion

Abstract

This study aimed to obtain super smooth surface medical implant laser power bed fusion Ti6Al4V samples. A self-modified magnetorheological polishing device and polishing fluid were used to polish the laser power bed fusion additive shaped Ti6Al4V samples to study the effect of the main factors such as abrasive grain size, polishing pressure, and polishing time on the surface roughness and material-removal efficiency of the samples. With continuously decreased Al2O3 abrasive-particle size, the surface roughness initially increased and then decreased, and the material-removal rate decreased. The polishing result of 5 µm Al2O3 was better, no new scratch damage was found after 3 µm Al2O3 polishing; With increased polishing pressure from 5 N to 25 N, the deeper the abrasive particles were pressed, the greater the cutting effect and the more obvious the scratches. Surface roughness initially decreased and then increased, and the material-removal rate increased from 1.19 nm/min to 8.68 nm/min. With continuously extended polishing time, the grinding and polishing effect continued to accumulate, and the surface quality significantly improved, decreasing from 366.33 nm to 19.77 nm. These results showed that magnetorheological polishing technology was very effective in removing LPBF forming defects; the surface roughness was reduced by 96.27% and the additive defects can be completely removed.