Micro/nanoscale bioactive oxide coatings on Ti6Al4V fabricated by SLA and induction heating

Abstract

Titanium (Ti)-based implants with micro/nano multiscale structures have been highlighted in dental and orthopedic fields due to the enhanced osteogenic abilities and mechanical interlocking. In this study, induction heating treatment (IHT) was developed to superimpose nano structure on microrough sandblasted and acid-etched (SLA) Ti6Al4V surface. The influences of SLA and IHT on the phase compositions, microstructures, properties, and formation mechanism of the coatings were explored. IHT for 12, 18 and 24 s realize the transformation of initially generated nanodot-like crystallites into a relatively uniform and high density of nanoscale protuberances. The oxide coating obtained by SLA + IHT has larger grains compared with that obtained by IHT separately. The nanoscale protuberances comprise crystalline rutile TiO2 and a small amount of α-Al2O3. IHT results in a successive increase of roughness on smooth surface with extension of IHT period, while samples induction heated for 18 and 24 s following SLA retain the initial microscale roughness of SLA surface. Since the larger porosity inside the oxide and local plastic deformation from SLA enhance adsorption and interaction ability of Ti6Al4V with oxygen, the thickness of oxide coating obtained by SLA + IHT increases to 861 nm compared with the 408 nm formed by IHT for 24 s. The micro/nano-structured oxide coating is in favor of improving the hydrophilicity of SLA surface in terms of the decreased contact angle from 129.4° to 69.1°, and shows good capability to induce hydroxyapatite deposition in simulated body fluid.