Additive manufacturing of trabecular tantalum scaffolds by laser powder bed fusion: Mechanical property evaluation and porous structure characterization

Abstract

Porous tantalum scaffolds fabricated by chemical vapor deposition (CVD) have been used commercially for bone tissue reconstruction with excellent treatment efficacy in the past decades. Recently, extensive research has proven that additive manufacturing is a versatile technique for the fabrication of porous materials with well-designed and highly controlled architectures. In this work, we aimed to develop additively manufactured (AM) novel tantalum scaffolds biomimicking trabecular bone by laser powder bed fusion (LPBF) and characterize their mechanical properties and porous structures. Porosity significantly affected the mechanical properties of the AM trabecular tantalum scaffolds. When the porosity decreased from 70% to 60%, the compressive strength, compressive modulus, bending strength, shear modulus, and torque increased to 59.5 ± 0.2 MPa, 3.3 ± 0.3 GPa, 97 ± 4.2 MPa, 6.8 ± 0.3 GPa, 41.2 ± 0.8 MPa, and 91 ± 1.5 N·cm, respectively. At 80% porosity, these values were reduced to 14.2 ± 1 MPa, 1.5 ± 0.4 GPa, 23 ± 0.8 MPa, 1.2 ± 0.2 GPa, 11.2 ± 0.6 MPa, and 27 ± 1.4 N·cm, respectively. The general mechanical properties of AM trabecular tantalum scaffolds were comparable with those of their counterparts fabricated using CVD, which both exhibited excellent ductility and reliability. Industrial computerized tomography analysis showed that open porosity, average pore diameter, largest pore diameter, average strut diameter, largest strut diameter, and pore interconnectivity were 70.1%, 542 μm, 929 μm, 322 μm, 564 μm, and 99.99%, respectively, for AM trabecular tantalum scaffolds (designed porosity of 70%), and 70%, 334 μm, 596 μm, 124 μm, 248 μm, and 99.64%, respectively, for trabecular tantalum scaffolds fabricated using CVD. Their porosity and interconnectivity were identical, whereas the pore diameter and strut diameter exhibited noticeable difference. Scanning electron microscopy (SEM) observations revealed that both methods generated trabecular tantalum scaffolds with a similar porous structure, whereas AM trabecular tantalum scaffolds possessed thicker struts and larger pores. AM and CVD-fabricated trabecular tantalum scaffold struts both demonstrated rough surfaces with nano/microstructures. Our results show that the developed AM trabecular tantalum scaffolds are promising for bone filling and reconstruction applications.