Influence of travel speed on microstructure and mechanical behavior of Inconel 625 fabricated using wire fed laser directed energy deposition

Abstract

The printing of Inconel 625 via wire-fed laser directed energy deposition is required for the near net shape fabrication of large scale components. In this study, an array of processing parameters was tested to identify a defect-free low-travel-speed and high-travel speed parameter for wire-fed laser directed energy deposition of Inconel 625. Samples printed using these parameters were subject to characterization in terms of grain morphology and tensile properties. Results showed that the high-travel-speed parameter had a refined columnar+equiaxed grain structure, whereas the low-travel-speed parameter had a columnar grain structure. The experimentally observed microstructure is correlated to the processing parameters by calculation of the solidification rate and thermal gradient. When tested perpendicular to the build direction, both parameters exhibited a similar yield strength. When tested parallel to the build direction, the high-travel-speed parameter exhibited a higher yield strength than the low-travel-speed parameter. For both parameters, samples pulled parallel to the build-direction showed a lower yield strength than samples pulled perpendicular to the build direction. The differences in yield strength for differing parameters and orientation are attributed primarily to dislocation strengthening.