PSI - Issue 53

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Author name / Structural Integrity Procedia 00 (2019) 000 – 000

Stefania Franchitti et al. / Procedia Structural Integrity 53 (2024) 397–406

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3. Qualification Procedure 3.1. AM Definition phase

Within the AM definition phase, the Electron Beam Melting (EBM) technology was chosen as AM process. In the EBM, three dimensional parts are produced layer by layer, by using a high-energy electron beam as a moving heat source to melt metal powder. EBM technology has been designed to process titanium alloys as well as materials that require elevated process temperatures. The material most used by EBM-users is the Ti6Al4V Titanium alloy. Due to the relatively low oxygen level, the fine-grain size and the in situ age hardening, the mechanical properties of the EBMed Ti6Al4V are similar to those of normally processed titanium as confirmed by Pirozzi et al. (2017). All those aspects make EBM technology suitable for application in critical fields, such as the aerospace one. Further detail about EBM technology can be found in Koerner (2016) and Borrelli et al. (2020). For the qualification of the Space Rider flap supports, an ARCAM A2X EBM system was used. The main check in the AM definition phase was on the dimensions and consisted in verifying the possibility to manufacture the two components in the building envelope volume of the ARCAM A2X which is equal to 210 x 210 x 380 mm. As regards the inner flap support is concerned, it was chosen to position it vertically (Fig. 3a), while for the outer flap support, which is longer, it was necessary to tilt the part in order to fit it into the build envelope volume (Fig. 3b). a b

Fig. 3. (a) Inner Flap Support; (b) Outer Flap Support.

3.2. Verification phase at powder level One of the most typical issues when dealing with PBF technique is the powder recyclability that results in metallurgical and cost-effective matters. It is worth considering that Ti6Al4V powder feedstock for PBF is more expensive than billet, bar or sheet types; as a consequence, the cost of built parts would be prohibitive if the powder cannot be reused in several build jobs making the process less competitive due to the cost involved, although the design freedom granted by AM. Nonetheless, the recycling process affects the chemical and morphological features of the reused particles consequently altering the properties of the final workpieces as stated by Seifi et al. (2016). Hence, an important step within the qualification of a PBF based AM process is to determine acceptable powder properties. For the qualification of the Space Rider flap supports, ARCAM powder specification for Ti6Al4V grade 5 were used as acceptable powder properties. They were determined by performing the following powder