X-ray Tomography Characterisation of Lattice Structures Processed by Selective Electron Beam Melting

Abstract

Metallic lattice structures intentionally contain open porosity; however, they can also contain unwanted closed porosity within the structural members. The entrained porosity and defects within three different geometries of Ti-6Al-4V lattices, fabricated by Selective Electron Beam Melting (SEBM), is assessed from X-ray computed tomography (CT) scans. The results suggest that horizontal struts that are built upon loose powder show particularly high (~20 × 10 −3 vol %) levels of pores, as do nodes at which many (in our case 24) struts meet. On the other hand, for struts more closely aligned (0 • to 54 • ) to the build direction, the fraction of porosity appears to be much lower (~0.17 × 10 −3 %) arising mainly from pores contained within the original atomised powder particles.

The manufacturability and compression properties of the Schwarz Diamond type Ti6Al4V cellular lattice fabricated by selective laser melting

“…Observed internal porosity on one hand results from the nature of the SLM process and machining parameters, while on the other, it might be also influenced by the specific geometry of the built structures. In case of self-supporting structures, which are these structures, it has been shown that the tendency to the formation of defects during the SLM process is almost negligible [52,53]. Microtomography allowed fast detection of structure defects.…”

The effects of powder reuse on the mechanical response of electron beam additively manufactured Ti6Al4V parts

“…A defocused electron beam is used at high scanning speed so that the energy input is low enough to sinter the powder particles. This is performed to avoid charging of the powder by electrons, commonly referred to as 'powder smoke' [6], and to reduce residual stress development in the part caused by rapid cooling [7]. Following preheating, selective melting is performed using a focused electron beam at relatively low scanning speed.…”

Additive manufacturing of WC-Co hardmetals: a review

“…These internal, contouradapted cooling channels allow higher cutting speeds and, consequently, a remarkable increase in the productivity of the machining process. The main additive manufacturing technologies suitable for metals are selective laser melting (SLM), selective electron beam melting (SEBM), laser powder deposition, binder jet additive manufacturing (BJAM), and wire arc additive manufacturing (WAAM) [39][40][41][42][43][44][45][46][47][48][49]. So far, AM technologies have been successfully applied to stainless steels [50][51][52][53][54], Ni alloys [55,56], Ti alloys [57,58], refractory metals [59,60], Al alloys [61,62], etc.…”