Electrophoretic Deposition of Nanocrystalline Calcium Phosphate Coating for Augmenting Bioactivity of Additively Manufactured Ti-6Al-4V

Additive manufacturing(AM) is being widely explored for engineeringbiomedical implants. The microstructure and surface finish of additivelymanufactured parts are typically different from wrought parts andexhibit limited bioactivity despite the other advantages of usingAM for fabrication. The aim of this study was to enhance the bioactivityof selective laser melted Ti-6Al-4V alloy by electrophoretic depositionof nanohydroxyapatite (nanoHAp) coatings. The deposition parameterswere systematically investigated after the coatings were depositedon the as-manufactured surface or after polishing the surface of theadditively-manufactured sample. The surfaces were coated with nanoHApsuspended in either ethanol or butanol using different voltages (10,30, or 50 V) for varied deposition times. The formation of the nanoHApcoating was confirmed by Fourier-transform infrared spectroscopy andX-ray diffraction. Microstructural analysis revealed that severalconditions of the coating led to crack formation. The coated sampleswere subsequently heat-treated to improve the integrity of the coating.Heat treatment led to crack formation in several conditions due tothermal shrinkages. Coatings prepared using butanol were more uniformand had minimal cracks compared with the use of ethanol. Nanoindentationconfirmed good stability and integrity of the nanoHAP coatings onthe as-manufactured and polished surfaces. The coating on the as-manufacturedsample exhibited higher hardness and lower elastic modulus as comparedwith the coating on the polished sample. In vitro study revealed that the nanoHAp coating markedly enhanced the attachment,proliferation, and differentiation of preosteoblasts on the alloy.These results provide a viable route to enhancing the bioactivitythrough deposition of nanoHAp with important implications for engineeringadditively manufactured orthopedic and dental implants suitable forbetter clinical performance.