Experimental investigation into nano-finishing of β-TNTZ alloy using magnetorheological fluid magnetic abrasive finishing process for orthopedic applications

This study describes the effect of magnetorheological fluid assisted magnetic abrasive finishing (MRAF) process on the surface topography of fine finished high strength biomedical grade β-phase Ti–Nb–Ta–Zr (β-TNTZ) alloy for orthopedic applications. β-type Ti–35Nb–7Ta–5Zr alloy exhibit high strength, better corrosion resistance and excellent bioactivity in comparison with Ti–6Al–4V alloy. The topographic features of finished surfaces (including surface roughness, skewness, and kurtosis), percentage change in surface roughness, and material removal have been studied to understand the influence of MRAF processing parameters, such as carbonyl iron particles proportion, diamond abrasive particles proportion, rotational speed of the abrasive tool, and work gap between workpiece and abrasive tool. Furthermore, MRAF finishing has been conducted using raster and spiral strategies. The topographic characteristics of the finished surfaces have been measured using a noncontact three-dimensional Surface Profilometer and atomic force microscopy. The results of the study showed that all the input process parameters have strongly influenced the surface characteristics in both quantitative (material removal) and qualitative measures (Surface roughness). The β-TNTZ have possed excellent bio-mechanical properties such as high compressive strength (1195 MPa), micro-hardness (515 HV), corrosion resistance, and excellent bioactivity. The best optimal condition to obtain lowest SR (9 nm) and highest MR (65 mg) was obtained in the case of rater path finishing strategy at CIP – 40%vol., Dv – 3.5%vol., Nt – 900 rpm, and Gp – 1 mm. The maximum percentage change in surface roughness (%ΔRa) was measured around 97.68% and 93.27% in raster and spiral path strategy, respectively. The minimum surface finish ranging about 9 nm has been achieved through the MRAF process. Further, the raster path strategy has been found more effective in producing negative skewness (Ssk), kurtosis (Sku) value less than 3, and minimum number of peaks density (Spd). The overall results of the study suggested that MRAF of β-TNTZ alloy is a good solution for obtaining fine-finished orthopedic devices while sustaining their tribological and wear properties.