Design of porous architectures in laser powder bed fusion: effect of hatch spacing and rotation angle on density and pore morphology

Abstract

Bone is a complex and hierarchical structure with the ability to provide extensive structural support to the body while also being lightweight for ease of motion. Bone can be damaged due to injury or illness, requiring the need for an orthopedic implant to enhance function, to provide structure and to encourage the growth of new bone. A challenge with current metal orthopedic implants is stress shielding, where there is a mismatch of mechanical moduli between the implant and human bone. When designing implants, it is important to tailor the mechanical response of the implant to natural bone to avoid stress shielding. This research explores a new method for implant design, incorporating pores stochastically using laser powder bed fusion (PBF-LB). This type of porosity is introduced into a solid metal part during printing by altering process parameters in PBF-LB. The density and pore morphology are dictated by the hatch spacing (100 – 500 µm) and rotation angle (60° and 67°). These structures were printed in Ti-6Al-4V. The effects of the hatch spacing and rotation angle on melt pool morphology and porosity were investigated, resulting in densities of 50.20 - 99.98% and columnar and stochastic pore morphologies.