Comparative Study on Surface Wettability, Bio-tribology, and Cytotoxicity of Selective Laser Melted 316L SS, CoCrMo, and Ti6Al4V Metallic Biomaterials

The present work deals with fabricating metallic implant surfaces through laser powder bed fusion-based selective laser melting (SLM) technique using the 316L SS, CoCrMo, and Ti6Al4V powders. The topographical, metallographic, and micro-hardness measurements were performed to study the fabricated parts' surface roughness, chemical purity, and mechanical behavior. The results showed that prepared selective laser melted (SLMed) samples have nano-level roughness, high chemical purity, and improved hardness value. Further, the surface functionality was examined through surface wettability and cytotoxicity analysis, and it was found that the Ti6Al4V sample exhibits an improved hydrophilicity with a minimum contact angle (CA) value of 26.25 degrees as compared to the 316L SS (CA: 40.23 degrees) and CoCrMo (CA: 44.54 degrees) samples. The cytotoxicity results for 100% dilution indicate that the CoCrMo sample has the highest cell viability (CV: 170.03 +/- 13.91), followed by 316L SS (CV: 139.47 +/- 2.2) and Ti6Al4V (CV: 101.53 +/- 15.44) specimens. Furthermore, the in-vitro bio-tribology analysis indicated that SLMed samples have improved friction and wear performance, with the lowest COF value of 0.12 for Ti6Al4V at 10N load as compared to the 316L SS and CoCrMo parts. However, the Ti6Al4V surface presented a high volumetric wear loss compared to 316L SS and CoCrMo counterparts at different loads, indicating a brittle behavior. The obtained outcomes dictate that the SLM technique is a promising approach to fabricating implant surfaces using Ti6Al4V metallic biomaterial with improved bulk and surface functionality.