Reduction of hot cracking by magnetofluiddynamic modification of the laser-induced melt pool convection during powder-based generative laser cladding
Final Report Abstract
Within the funded project, a novel approach for modifying the solidifcation morphology during direct energy deposition (DED) of nickel-based superalloys for hot-crack mitigation was investigated. This approach is based on the combination of the DED process with temporally constant or rotating magnetic fields. Firstly, a system was developed, which enables DED under the influence of a magnetic field with a magnetic flux density of up to 1 T and a rotational speed of up to 20 Hz. Within elaborate experimental investigations, the hot-crack reduction as well as the change in microstructure caused by magnetofluiddynamic phenomena were examinded for the three alloys Ni-SA 247LC, Udimet 710 and Inconel 100, which are considered to be difficult to weld. However, the metallographic and mechanical analyses show no significant changes between sample fabrication without and with the application of a strong magnetic field (B = 1 T). For the alloys Ni-SA 247LC and Inconel 100, numerous hot cracks continue to appear and the microstructure was not significanty modified. In the case of the alloy Udimet 710, cracks did not appear in any of the specimens, both with and without an applied magnetic field. The microhardness testing also showed no significant effect of a magnetofluiddynamic interaction. As the major reason for the absence of a microstructural modification, too small melt pool dimensions were identified. On the one hand, this results in too low Hartmann numbers, which are considered a measure of the influence on the Hartmann flow. On the other hand, due to high cooling rates caused by the small melt pool, the interaction time is too low for a stirring effect to be generated by the rotating magnetic field.
Publications
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Novel Approach for Suppressing of Hot Cracking Via Magneto-fluid Dynamic Modification of the Laser-Induced Marangoni Convection. The Minerals, Metals & Materials Series, 972-981. Springer International Publishing.
Seidel, A.; Degener, L.; Schneider, J.; Brueckner, F.; Beyer, E. & Leyens, C.
