Observation of keyhole-mode laser melting in laser powder-bed fusion additive manufacturing |
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Authors: | Wayne E. King Holly D. Barth Victor M. Castillo Gilbert F. Gallegos John W. Gibbs Douglas E. Hahn Chandrika Kamath Alexander M. Rubenchik |
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Affiliation: | 1. Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA;2. Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA;3. Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA;4. Computations Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA;5. NIF and Photon Science Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA |
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Abstract: | Laser powder-bed fusion additive manufacturing of metals employs high-power focused laser beams. Typically, the depth of the molten pool is controlled by conduction of heat in the underlying solid material. But, under certain conditions, the mechanism of melting can change from conduction to so-called “keyhole-mode” laser melting. In this mode, the depth of the molten pool is controlled by evaporation of the metal. Keyhole-mode laser melting results in melt pool depths that can be much deeper than observed in conduction mode. In addition, the collapse of the vapor cavity that is formed by the evaporation of the metal can result in a trail of voids in the wake of the laser beam. In this paper, the experimental observation of keyhole-mode laser melting in a laser powder-bed fusion additive manufacturing setting for 316L stainless steel is presented. The conditions required to transition from conduction controlled melting to keyhole-mode melting are identified. |
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Keywords: | Keyhole-mode laser melting Additive manufacturing Powder-bed fusion Selective laser sintering Selective laser melting Direct metal laser sintering |
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