Surface Enhancements from Peening Effect on Inconel 718 Fabricated by Direct Energy Deposition

Direct energy deposition Inconel 718 is increasingly explored and used for various industrial applications due to its near net shape and ability to build complex geometries. For post-processing, hammer peening process is a well-established surface finishing step to enhance the compressive stress of the metal, reducing and preventing cracks. Increasingly, laser has been explored for post-processing additive manufactured metal as an in-situ heat treatment process to relieve tensile stresses formed during the process. In this paper, an investigation into the effects of hammer peening in conjunction with laser is performed. Microstructural analysis, hardness values and tribological properties will be used to observe these effects. It was found that hammer peening increased the hardness of Inconel 718, and when used in tandem with laser, the hardness decreased, albeit higher than the non-post processed sample. Lastly, there is a disconnect between the correlation of higher hardness values with lower wear rate, as the lowest hardness value sample has the lowest wear rate in this study, and that hammer peening itself did not reduce the wear rate of direct energy deposited Inconel 718.