Rheological behavior of β-Ti and NiTi powders produced by atomization for SLM production of open porous orthopedic implants

摘要

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied bythe introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion resistance as well as favorablecombination of high mechanical strength, fatigue resistance and relatively low elastic modulus. As part of theSLM process for producing quality β-Ti parts powder flowability is essential to achieve uniform thickness of powderlayers. In this work the flowability of different gas atomized β-Ti, including NiTi, powders has been studied. Theirrheological properties were compared to those of commercially available plasma-atomized Ti–6Al–4V powderusing a newly developed semi-automatic experimental set-up. Not only the particle size, shape and size distributionof the powders display a large influence on the powder flowability but also particle surface properties such asroughness, chemical composition and the presence of liquid on the surface of the particles. It was found that plasmaor gas atomization production techniques for SLM powder have a considerable effect on the particle topography.Among the powders studied regarding SLM applicability only rheological properties of the fine size fraction(25–45 μm) of Ti–45Nb didn't conform to SLM processing requirements. To improve flowability of the Ti–45Nbpowder itwas annealed both in air and argon atmosphere at 600 °C during 1 h, resulting in an improved rheologicalbehavior suitable for SLM processing.