Surface engineering of Ti-Ta alloys via laser powder bed fusion for orthopaedic applications

Titanium-tantalum (Ti-Ta) alloys are promising materials for orthopaedic implants because of their excellent biocompatibility, corrosion resistance, and favourable mechanical properties. Surface characteristics play a critical role in regulating osseointegration; however, conventional surface modification methods are often difficult to apply to complex implant geometries. In this study, laser powder bed fusion of metals (PBF-LB/M) using prealloyed Ti-40Ta (wt.%) powder was employed as both a manufacturing technique and surface-engineering strategy for Ti-40Ta implant materials. By varying the volumetric energy density during PBF-LB/M, Ti-40Ta alloy surfaces with different surface roughness values (areal arithmetic mean height, S a ) were fabricated. Reducing the energy density from 156.8 J/mm 3 to 54.2 J/mm 3 increased the mean S a from 13.5 μm to 17.6 μm. An as-polished surface with an S a of 0.009 μm was included as the control. The results showed that the rougher as-built surface with greater surface area supported increased protein adsorption, promoted osteoblast proliferation after 14 days, and enhanced osteogenic differentiation, as evidenced by alkaline phosphatase activity and calcium mineralisation after 28 days. Surface wettability exhibited no direct correlation with surface roughness, osteoblast proliferation, and differentiation in this study. Scratch testing showed that the rougher as-built Ti-40Ta surface exhibited lower friction and a narrower scratch track than the smoother as-built surface, while surface-adhered particles remained attached to all as-built surfaces after scratching at a constant load of 20 N. Overall, the results demonstrate that PBF-LB/M can simultaneously fabricate Ti-40Ta implants and tailor their surface characteristics to enhance in vitro biological performance.