Industrialization of Selective Laser Melting for the Production of Porous Titanium and Tantalum Implants
Industrialisatie van selectief laser smelten voor de productie van poreuze titanium en tantalum implantaten
Wauthle, Ruben; S0160201
As the number of orthopedic surgeries is increasing, so is the need for implants that not only can reconstruct a mechanical stable joint, but also serve as bone replacement material since the availability of transplant bone is rather limited. Already more than two decades porous metal implants have been a solution to address this need since they can exhibit mechanical properties close to human bone and thus provide sufficient implant strength and stability while at the same time they allow for bone to grow inside the pores, ensuring a long-term implant fixation. Only now, with the introduction of additive manufacturing or 3D printing techniques like selective laser melting it has become possible to manufacture on an industrial scale porous metallic structures in a controlled and reproducible manner. In this dissertation three types of porous metallic implants made by selective laser melting have been evaluated: porous implants made from Ti6Al4V, tantalum and pure titanium. Today, Ti6Al4V is still the material of choice since it is a mechanically strong material with a proven clinical track record. But in order to select the right implant design and processing steps, it is important to identify all the variables that influence the final result. This dissertation presents and discusses probably the largest experimental data set on the influence of geometrical variables (structure relative density and unit cell geometry) and processing variables (build orientation, heat treatment, bio-functionalizing surface treatments) on the mechanical and biological implant performance. Tantalum, on the other hand, is an interesting metal since it has a very good biocompatibility, but because of its high price and difficulty to process, the use of tantalum for porous implants is not that obvious. In this dissertation it is shown for the first time that selective laser melting can be successfully used to manufacture porous tantalum implants with interesting mechanical properties and promising in vivo performance. Since porous pure titanium implants showed very similar mechanical behavior, this could potentially lead to a revival of the use of pure titanium for dynamically loaded porous implants. But in the end, the manufacturing cost is also important for the acceptance of this new technology to produce porous metallic implants on a commercially suitable level. Therefore significant productivity improvements have been achieved to lower the production costs of porous implants made by selective laser melting.