PSI - Issue 7

Theo Persenot et al. / Procedia Structural Integrity 7 (2017) 158–165 Persenot et al. / Structural Integrity Procedia 00 (2017) 000–000

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5. Summary

• EBM fatigue samples were manufactured from both fresh and recycled powder. They were characterised by laboratory X-ray tomography. The pores’ volume fraction and size distribution were reported. The surface state was observed and its roughness measured. The surface defects responsible for the high roughness were analysed and identified as two types of defects : unmelted powder stuck to the surface and “plate-pile” stacking irregularities. • Chemical etching was used to improve the surface state of the EBM as-built samples. Two etching durations were tested and their impact on the surface roughness and defects investigated. A clear improvement of the surface geometry was observed and quantified through a roughness reduction. • The fatigue limit obtained for as-built samples is lower than the one obtained after surface machining and it was also observed that powder recycling tends to further diminish the fatigue resistance. • The study of the fracture surface coupled with the comparison of tomographic scans before and after failure enables us to identify before test the shape and dimensions of the critical defects. For all investigated samples, it is a notch-like defect resulting from a lack of fusion. • Fatigue results obtained for etched samples showed that for both etching duration (30 and 45 minutes), the fatigue strength at 10 7 was increase by 60% to a value of 220 MPa compared to as-built samples. An important scatter at low stress level was observed after 30 minutes of etching. Conner, B.P., Manogharan, G.P., Martof, A.N., Rodomsky, L.M., Rodomsky, C.M., Jordan, D.C., Limperos, J.W., 2014. Making sense of 3-d printing: Creating a map of additive manufacturing products and services. Additive Manufacturing 14, 64 – 76. URL: http://www.sciencedirect.com/science/article/pii/S2214860414000104 , doi:https: // doi.org / 10.1016 / j.addma.2014.08.005. in augural Issue. Facchini, L., Magalini, E., Robotti, P., Molinari, A., 2009. Microstructure and mechanical properties of ti6al4v produced by electron beam melting of prealloyed powders. Rapid Prototyping Journal 15, 171–178. URL: https://doi.org/10.1108/13552540910960262 , doi:10.1108 / 13552540910960262, arXiv:https://doi.org/10.1108/13552540910960262 . Facchini, L., Magalini, E., Robotti, P., Molinari, A., Hges, S., Wissenbach, K., 2010. Ductility of a ti6al4v alloy produced by selective laser melting of prealloyed powders. Rapid Prototyping Journal 16, 450–459. URL: https://doi.org/10.1108/13552541011083371 , doi:10.1108 / 13552541011083371, arXiv:https://doi.org/10.1108/13552541011083371 . Kobryn, P., Semiatin, S., 2003. Microstructure and texture evolution during solidification processing of ti6al4v. Journal of Materi als Processing Technology 135, 330 – 339. URL: http://www.sciencedirect.com/science/article/pii/S0924013602008658 , doi:http: // dx.doi.org / 10.1016 / S0924-0136(02)00865-8. special Issue containing paper from the conference Research and Development in Net shape Manufactureing. Lhuissier, P., de Formanoir, C., Martin, G., Dendievel, R., Godet, S., 2016. Geometrical control of lattice structures produced by ebm through chemical etching: Investigations at the scale of individual struts. Materials and Design 110, 485 – 493. URL: http://www.sciencedirect.com/science/article/pii/S0264127516310929 , doi:http: // dx.doi.org / 10.1016 / j.matdes.2016.08.029. Li, P., Warner, D., Fatemi, A., Phan, N., 2016. Critical assessment of the fatigue performance of additively man ufactured ti6al4v and perspective for future research. International Journal of Fatigue 85, 130 – 143. 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Oh, J., Lee, J.G., Kim, N.J., Lee, S., Lee, E.W., 2004. E ff ects of thickness on fatigue properties of investment cast ti-6al-4v al loy plates. Journal of Materials Science 39, 587–591. URL: http://dx.doi.org/10.1023/B:JMSC.0000011515.84569.ec , doi:10.1023 / B:JMSC.0000011515.84569.ec. Rafi, H.K., Karthik, N.V., Gong, H., Starr, T.L., Stucker, B.E., 2013. Microstructures and mechanical properties of ti6al4v parts fabri cated by selective laser melting and electron beam melting. Journal of Materials Engineering and Performance 22, 3872–3883. URL: http://dx.doi.org/10.1007/s11665-013-0658-0 , doi:10.1007 / s11665-013-0658-0. Suard, M., Martin, G., Lhuissier, P., Dendievel, R., Vignat, F., Blandin, J.J., Villeneuve, F., 2015. Mechanical equivalent diameter of single struts for the sti ff ness prediction of lattice structures produced by electron beam melting. Additive Manufacturing 8, 124 – 131. 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