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Ti-48Al-2Nb-2Cr is a challenging and difficult-to-cut titanium aluminide (TiAl) alloy with several manufacturing issues because of the high sensitivity to crack formation and oxygen picking up. Electron beam powder bed fusion (EB-PBF) made feasible TiAl near net shape components, but the surfaces are particularly rough and present complex surface topographies. In this present investigation, experimental analysis and optimization are proposed for electro-chemical machining (ECM) on as-built Ti-48Al-2Nb-2Cr surfaces manufactured using EB-PBF. Experimental runs are performed under pulsed machining conditions and varying specific process metrics to understand the machining effects on the process efficiency and removal phenomena. In particular, the morphology and isotropy of the surface are studied before and after the machining by scanning electron and confocal microscopies. The results establish the optimal machining conditions and a range for the active machining time that produce, compared to the as-built surface, an extremely smooth and isotropy surface without any detrimental effect on the surface integrity and microstructure.

Electro-chemical machining (ECM) is a nonconventional machining process based on the anodic dissolution of the workpiece. The peculiar features of this process make it suitable for application in the aerospace, automotive, or medical fields where laser-based powder bed fusion (L-PBF) is consolidating as a manufacturing solution for high-performance components. The roughness of as-built L-PBF parts often requires surface finishing before usage in order to enable a correct operation as well as to prevent early fatigue failure. The viability of ECM on L-PBF components is still scarcely investigated in the literature. In this article, the process was applied to AlSi10Mg parts produced by L-PBF. An experimental plan was designed to select the process parameters and to study their effect on the surface roughness and morphology. Process variables including feed rate, time, voltage, and water pressure were investigated. As a result, it was observed that the ECM performance was different for parts produced by traditional processes or by L-PBF, even for comparable composition. Owing to the presence of satellite particles on L-PBF surfaces, ECM was only effective in the pulsed mode.

Multi Jet Fusion (MJF) is an emerging additive manufacturing (AM) technique that enables the production of prototypes and functional parts starting from a thermoplastic-based powder, mainly polyamide 12 (PA12). Layer upon layer, the polymeric particles are selectively impregnated with two different inks and then fused and consolidated by an infrared (IR) lamp. Much faster than other AM techniques for polymers, MJF has shown exciting potentialities. However, little is known about the consolidation mechanisms acting in MJF and about the effect on the properties of the finished parts of the quality of the materials, powder and inks, and of the printing conditions. The present contribution investigates these issues. The study also compares virgin PA12 powder with pure PA12, recycled PA12 for MJF and PA12 for in selective laser sintering (SLS). The powders showed slight differences. The two inks have the same composition, except for the presence of graphitic carbon. Tensile tests showed that the printed parts are isotropic. However, the deformation at break is affected by building direction of the sample. Occasionally, poor inter-layer adhesion is observed and the tensile strength and the deformation at break collapse. Printed tensile specimens are found to be representative of the material behaviour of a printed component, apart from the deformation at break which is systematically overestimated.

Powder bed fusion (PBF) is an additive manufacturing technique, which allows to build complex functional mechanical parts layer-by-layer, starting from a computer-aided design (CAD) model. PBF is particularly attractive for biomedical applications, where a high degree of individualization is required. In this work, the microstructure of two biomedical alloys, namely Co-Cr-Mo and Ti-6Al-4V, were studied by X-ray diffraction and electron microscopy techniques. Hardness and tensile tests were performed on the sintered parts.