The influence of chemical etching on porous structure and mechanical properties of the Ti6AL4V Functionally Graded Porous Scaffolds fabricated by EBM

Abstract

Functionally Graded Porous Scaffolds (FGPS) manufactured from Ti and Ti alloys such as Ti6Al4V is an attractive candidate for mimicking host bone tissue. Porous specimens manufactured by powder-bed fusion additive manufacturing (PBF-AM) methods always contain some amount of powder attached to the surfaces of the outer or the inner parts. Powder removal is an important issue for the porous structures with high relative density designed for biomedical applications. In some cases, traditional powder removal methods such as standard powder recovery systems (PRS) become ineffective. Chemical and electrochemical etching is one of the possible solutions for effective residual powder removal from PBF-AM structures.Traditional single-stage HF/HNO3 chemical etching protocols of the Ti6Al4V often leads to the overetching of the periphery of the porous samples leaving inner parts untouched. The aim of present research was to determine if fractionated chemical etching of porous Ti6Al4V Functionally Graded Porous Scaffolds (FGPS) with multiple immersions could facilitate trapped powder removal and reduction the surface roughness without critical degradation of the mechanical properties. Protocols with different number and time of immersions were studied. Mechanical properties and fracture modes of as manufactured and chemically etched Ti6Al4V FGPS were investigated. Results clearly illustrate that fractionating of the etching times have positive effect. It is possible to achieve more uniform etching of the thin structures at the periphery and inside porous structures, facilitate removal of the powder particles attached to the surfaces, and removal of the powder trapped inside the structures without serious degradation of the mechanical properties.