Biographie
Abstract
Despite the great success of the metal additive manufacturing process by Laser Fusion on Powder Bed (L-PBF), this technique still lacks maturity in several areas. Among its major challenges, the low fatigue strength of the L-PBF parts [3] caused, among other things, by two main types of defects. Firstly, a high surface roughness, mainly linked to the phenomenon of partial powder melting on the part surface [1]. Secondly, internal defects are created during the building process and are randomly distributed in the material [2]. The present study aims to investigate the effect of a second lasing [4][5] on the improvements of the characteristics of L-PBF parts. Based on preliminary experiments, two relasing strategies were selected. A high cycle fatigue campaign was subsequently carried out with a stress ratio of R=-1 on samples with or without relasing, in the as-built state or after polishing. Specimens printed in Net-Shape showed even after relasing and polishing, a much lower fatigue strength than those machined in the bulk after additive manufacturing [6]. In addition, preliminary results show that the tested relasing conditions has a slight beneficial effect on the quasi-static and fatigue strength of the 316L obtained by L-PBF.[1] E. Santecchia, S. Spigarelli and M. Cabibbo, Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction, Metals 2020, 10, 341.
[2] B. Zhang, Y. Li, Q. Bai, Defect Formation Mechanisms in Selective Laser Melting: A Review, Chin. J. Mech. Eng. (2017) 30:515–527.
[3] M. Zhang, C.N. Sun, X. Zhang, P.C. Goh, J. Wei, D. Hardacre, H. Li, Fatigue and fracture behaviour of laser powder bed fusion stainless steel 316L: influence of processing parameters, Mater. Sci. Eng. 703 (2017) 251–261.
[4] Liang, A., Hamilton, A., Polcar, T., & Pey, K. S. (2022). Effects of rescanning parameters on densification and microstructural refinement of 316L stainless steel fabricated by laser powder bed fusion. Journal of Materials Processing Technology.
[5] Yasa, E., & Kruth, J. P. (2011). Microstructural investigation of Selective Laser Melting 316L stainless steel parts exposed to laser re-melting. Procedia Engineering, 19, 389-395.
[6] Merot, P., Morel, F., Mayorga, L. G., Pessard, E., Buttin, P., & Baffie, T. (2022). Observations on the influence of process and corrosion related defects on the fatigue strength of 316L stainless steel manufactured by Laser Powder Bed Fusion (L-PBF). IJF, 155, 106552.
