Additive manufacturing of 316L stainless steel by electron beam melting for nuclear fusion applications
2017 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 486, no 1 April, 234-245 p.Article in journal (Refereed) Published
A feasibility study was performed to fabricate ITER In-Vessel components by one of the metal additivemanufacturing methods, Electron Beam Melting®(EBM®). Solid specimens of SS316L with 99.8% relativedensity were prepared from gas atomized precursor powder granules. After the EBM®process the phaseremains as austenite and the composition has practically not been changed. The RCC-MR code used fornuclear pressure vessels provides guidelines for this study and tensile tests and Charpy-V tests werecarried out at 22C (RT) and 250C (ET). This work provides thefirst set of mechanical and micro-structure data of EBM®SS316L for nuclear fusion applications. The mechanical testing shows that theyield strength, ductility and toughness are well above the acceptance criteria and only the ultimatetensile strength of EBM®SS316L is below the RCC-MR code. Microstructure characterizations reveal thepresence of hierarchical structures consisting of solidified melt pools, columnar grains and irregularshaped sub-grains. Lots of precipitates enriched in Cr and Mo are observed at columnar grain boundarieswhile no sign of element segregation is shown at the sub-grain boundaries. Such a unique microstructureforms during a non-equilibrium process, comprising rapid solidification and a gradient‘annealing’process due to anisotropic thermalflow of accumulated heat inside the powder granule matrix. Relationsbetween process parameters, specimen geometry (total building time) and sub-grain structure are dis-cussed. Defects are formed mainly due to the large layer thickness (100mmÞwhich generates insufficientbonding between a few of the adjacently formed melt pools during the process. Further studies shouldfocus on adjusting layer thickness to improve the strength of EBM®SS316L and optimizing total buildingtime.
Place, publisher, year, edition, pages
2017. Vol. 486, no 1 April, 234-245 p.
IdentifiersURN: urn:nbn:se:su:diva-141056DOI: 10.1016/j.jnucmat.2016.12.042OAI: oai:DiVA.org:su-141056DiVA: diva2:1085489