Abstract
In the present study, compositionally-graded structures of AISI 316L and CoCrMo alloy are manufactured by powder-based laser-beam directed energy deposition (DED-LB). Through a process-integrated adjustment of powder flow, in situ alloying of the two materials becomes feasible. Thus, a sharp and a smooth transition with a mixture of both alloys can be realized. In order to investigate the phase formation during in situ alloying, a simulation approach considering equilibrium calculations is employed. The findings reveal that a precise compositional as well as functional gradation of the two alloys is possible. Thereby, the chemical composition can be directly correlated with the specimen hardness. Moreover, phases, which are identified by equilibrium calculations, can also be observed experimentally using scanning electron microscopy (SEM) and energy-dispersive X-ray-spectroscopy (EDS). Electron backscatter diffraction (EBSD) reveals epitaxial grain growth across the sharp transition region with a pronounced <001>-texture, while the smooth transition acts as nucleus for the growth of new grains with <101>-orientation. In light of envisaged applications in the biomedical sector, the present investigation demonstrates the high potential of an AISI 316L/CoCrMo alloy material combination.
Highlights
Additive manufacturing (AM) is a novel manufacturing method that utilizes the layerwise deposition of material to produce parts from manifold materials, e.g., metals [1]
In comparison to powder bed fusion (PBF), where a heat source such as a laser or electron beam is used to achieve a localized melting of a powder bed, directed energy deposition (DED) is characterized by the direct feed of powder- or wire-based material to the process zone, where it is melted by a focussed heat source, e.g., by a laser beam [1,2]
In order to characterize the microstructural evolution of the two materials upon fabrication by DED-LB, etched cross-sections, which are depicted in Figure 4, were examined
Summary
Additive manufacturing (AM) is a novel manufacturing method that utilizes the layerwise deposition of material to produce parts from manifold materials, e.g., metals [1]. Two prominent AM processes with respect to the fabrication of metals are powder bed fusion (PBF) and directed energy deposition (DED) [2], of which the latter is known as laser-engineered net-shaping (LENS) [1]. The control of process parameters in PBF processes allows for tailored microstructures within a single component and, adapting the mechanical properties to a specific application eventually opening pathways towards funcitonally-graded AM components [3,4,5,6]. DED allows for the use of multiple materials to be fed into the process zone subsquently and simultaneously, such that multi-material additive manufacturing (MMAM) is enabled [7,8]. DED can be used to tailor the components porosity, for example to increase the bond between an implant and its host tissue [10]
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