| AVS 54th International Symposium | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuP |
| Session: | Aspects of Applied Surface Science Poster Session |
| Presenter: | S.T. Downey II, FAMU-FSU College of Engineering |
| Authors: | H.M. Meyer III, Oak Ridge National Laboratory R.M. Trejo, Oak Ridge National Laboratory S.T. Downey II, FAMU-FSU College of Engineering P.N. Kalu, FAMU-FSU College of Engineering K. Han, FAMU-FSU College of Engineering |
| Correspondent: | Click to Email |
This poster presents the characterization of chemically modified 316LN used as a conduit alloy in Superconducting Outsert of the 45T Hybrid Magnet System housed at the NHMFL. The conduit material acts as a protective jacket and carrier of the Nb3Sn superconductors formed within the magnet coil. This alloy was developed to withstand the deteriorative effects of the Nb3Sn reaction heat treatment while maintaining high strength, toughness and ductility at liquid helium temperatures. This heat treatment, necessary for forming the Nb3Sn superconductors within the magnet coil, is known to cause sensitization in most unmodified austenitic steel grades. Sensitization is the formation of brittle, chromium rich phases which degrade the mechanical behavior of this structural material. Cryogenic mechanical testing of M316LN upon exposure to the high temperature, long duration heat treatment (700C for 100 hours) was used to validate its current use. Mechanical tests show a significant loss in fracture toughness (~45%), although little microstructural characterization has been performed to support these findings. This poster describes our effort to provide microstructural and chemical characterization of the M316LN alloy exposed to the prescribed environments. In particular, we present scanning Auger microanalysis of the changes in chemical composition at the grain boundaries of M316LN caused by the heat treatment and resultant precipitate formation. Correlation of the Auger results with nanohardness tests at the grain boundaries will be presented. Research sponsored in part by the NSF through the Partnership for Research and Education in Materials Science under Grant No. DMR-0351770 and in part by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of FreedomCAR and Vehicle Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract number DE-AC05-00OR22725.