Electron beam melted (EBM) 718 superalloys have earned significant attention from the industrial and academic sectors. The attention is primarily owing to the high performance of AM-built critical parts suitable for advanced industrial systems exposed to high thermal or chemical load in combination with mechanical demands by virtue of the design freedom, and with reduced material wastage. However, the very nature of EBM processing can potentially result in surface flaws that can ultimately affect the fatigue life of EBM-built parts [1] and their subsequent functionalization. As a result, the imperfections and extreme roughness on the surface of such parts demand the investigation of potential approaches that can be applied to enhance surface attributes and, thereby, functional performance [2]. 

The present work entails a comprehensive assessment of the near-surface characteristics of EBM Alloy 718 in its original state by using various microscopic techniques and porosity evaluation methods. Further, the as-built surfaces are subjected to three different surface pre-treatment methods, which are grit blasting (GB), electrochemical pickling (PCK), and laser surface texturing (LST). All surfaces were evaluated for their topographical features (2D and 3D) and morphology. In addition, the effect of different surface pre-treatments on the variation of structural defects, pores and surface roughness is contrasted and evaluated in comparison with the as-built state.

Results show variations in the surface characteristics of the as-built condition obtained from various regions of an EBM-built rod structure, particularly with regard to lack of fusion, open and closed porosity in the near-surface region, as well as topographical surface features. Further, it is observed that LST and GB pre-treatments improved the surface quality of the as-built condition by eliminating near-surface imperfections. In contrast, the PCK state does not significantly reduce the average roughness, Ra of the as-built specimens. PCK process etched only a minimal amount of material from the surface of the EBM built substrate. This information provided a comprehensive insight into the effectiveness of various pre-treatments for enhancing the surface functionalities in EBM Alloy 718 and also laid a foundation for deciding on pre-coating surface treatments for EBM-built parts.