Influence of Rotational Magnetorheological Abrasive Flow Finishing Process on Biocompatibility of Stainless Steel 316L

Surface morphology plays a significant part in the longevity of the bio-implants. In this regard, the surface finishing of biomedical implants such as 316L stainless steel (SS 316L) requires intensive focus. A rotational magnetorheological abrasive flow finishing process (R-MRAFF) was engineered to ensure SS 316L surface uniformity within the nanometer range. Various process parameters such as pressure, revolution of the magnet, number of cycles, and distance between permanent magnet in rotating die and workpiece fixture have been taken into account. In this study, three different surface morphology samples A, B, and C with the surface roughness of 167, 173, and 184 nm, respectively, were compared to sample D which is pristine SS 316L with SR of 319 nm. The effect of biocompatibility achieved by using the R-MRAFF process was measured by comparing the finished sample with the pristine sample. Scanning electron microscopy images reveal the level of finishing obtained using the R-MRAFF process. From the surface wettability analysis, the finished surface exhibits hydrophilic nature (θ < 90°). X-ray photon spectroscopy study concludes that R-MRAFF promotes stable oxide formation in surface layers. Corrosion studies were carried out using potentiodynamic polarization (PDP) study and electron impedance spectroscopy (EIS) in artificial blood plasma (ABP). The corrosion rate was reduced from 4.3064 to 0.09236 µm/year in the finished samples with an improved protection efficiency of 97.85%.