Evolution of nano/submicro-scale oxide structures on Ti6Al4V achieved by an ultrasonic shot peening-induction heating approach for high-performance surface design of bone implants

Abstract

Modified layers with multiscale structures have been extensively explored and rationally designed on Ti-based orthopedic implants recently, since the remarkable improvement of biomedical properties. In consideration of the inefficiency, costliness and waste products of existing technologies, herein, we proposed the ultrasonic shot peening and induction heating protocol to construct the micro-nano complex oxide structures on Ti6Al4V in term of its advantages of environmental friend, rapid heating, low-cost and easy to process. With the USP pretreatment and induction heating, the nonuniform oxide crystallites firstly appeared on smooth surface and successfully grow up into the well-distributed TiO2 nanocrystallites, and transformed to netlike structures with submicro-sized worms when subjected to high-power of shot peening, which was significantly influenced by the microstructural evolution of alloy matrix. The submicro/nano-structured oxide layers mainly contained rutile/anatase TiO2 and little Al2O3 between grain boundaries, successively enhanced the surface roughness and wettability, and tended to form the hydrophilic surfaces. The adhesion strength of the oxide layers to substrates and hardness were also distinctly increased with increasing the IHT period from 20 to 35 s. In vitro BMSCs culturing proved that the prepared submicro/nano-scale oxide layers possessed favorable cell adhesion and proliferation, and further improved the osteogenic differentiation. The novelty of this work was to explored the evolution law of submicro-and nano-scale structures in osteogenic differentiation, and further better clinical application of Ti-based biomaterials.