Effect of sandblasting treatment on mechanical and electrochemical corrosion properties of SLM-formed Ti6Al4V radial gradient porous bionic bone scaffold

Abstract

Radial gradient porous structures, which resemble human bone characteristics, are promising for use in implants. Selective laser melting (SLM) of porous biomaterials shows potential, but challenges such as unmelted powder on the surface affect material quality and dimensional accuracy. Considering the complex solution environment in the human body, corrosion resistance is crucial for implanted materials. In this study, a radial gradient porous scaffold is designed using a Gyroid unit cell structure and fabricated by SLM, followed by sandblasting. The forming accuracy, microstructure, mechanical properties, and electrochemical corrosion behavior in simulated body fluid (SBF) are investigated before and after sandblasting. Sandblasting effectively removes adhering powder, improving pore size accuracy and reducing porosity error from 1.41 %-1.69 % to 0.15 %–0.38 %. Grain size decreases, grain density increases, and unmelted voids are eliminated. However, the passivation film is damaged, reducing corrosion resistance, with a tenfold increase in corrosion current density compared to the original samples. After sandblasting, the elastic modulus increases from 7.84–8.83 GPa to 8.08–9.02 GPa, and the yield strength improves from 292.02–328.31 MPa to 300.17–336.73 MPa, enhancing the scaffold's load-bearing capacity. The SB0.8 structure exhibits the highest yield strength. The scaffold transitions from brittle fracture to a mixed fracture mode, with improved toughness and ductility after sandblasting.