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Abstract
Cobalt-Chromium-Molybdenum alloys, a group of materials used in orthopaedic and dental implants, have been recently on the workbench for additive manufacturing due to their exceptional combination of biocompatibility and mechanical features. The current work is focused on a Laser Powder Bed Fusion of Cobalt-Chromium-Molybdenum alloy in which a great percentage of the Cobalt was replaced by Iron. Magnitudes of laser power and scanning speed were changed with constant hatch space and layer thickness values. Density of the specimens were estimated. Evolution of the microstructure and phases, and crystallographic orientation were studied by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Electron Backscattered Diffraction (EBSD) techniques. Microhardness of the alloys were measured. Among the specimens fabricated by the similar volumetric Energy Density (VED) the highest density and hardness belong to the specimen printed by the highest power and speed. TEM investigations suggested the formation of two phases with body centred cubic (bcc) and face centred cubic (fcc) crystal systems. A high density of the dislocations and large number of sub-grains were observed in the bcc matrix which is the primary solidified phase in this material. EBSD studies revealed that the bcc phase was strongly textured compared to that one of the fcc. It was found that the VED induces significant changes in the orientation of the solidified bcc grains. The highest rate of cooling, under the minimum energy density, depressed the intensity of the resultant {001}<100>bcc. Thus, the least intensity of the transformation texture and multiple orientations of the fcc phase were observed.
