Additive Manufacturing of Compositionally-Graded AISI 316L to CoCrMo Structures by Directed Energy Deposition

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 -texture, while the smooth transition acts as nucleus for the growth of new grains with -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.

Automated summary

This study fabricated compositionally-graded structures of AISI 316L and CoCrMo alloy using powder-based laser-beam directed energy deposition (DED-LB), achieving sharp and smooth transitions with a mixture of both alloys. The research demonstrated the potential of a precise compositional and functional gradation of the two alloys, directly correlating chemical composition with specimen hardness. Phase formation during in situ alloying was investigated using simulation approach considering equilibrium calculations, with experimental observations confirming the findings.