EFFECT OF PROCESSING PARAMETERS ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HASTELLOY X MANUFACTURED BY ELECTRON BEAM MELTING

Electron Beam Melting (EBM) is a promising powder-bed fusion (PBF) based additive manufacturing (AM) process that offers the potential to produce highly dense near-net shaped aero-engine components from Ni-based superalloys. Compared to laser based PBF processes, EBM produces parts with comparatively lower residual stresses at a higher build rate. In spite of these merits, the availability of materials for EBM process is very limited due to the highly complex nature of the process. As a result, it is necessary to understand the effect of various processing parameters on final part quality before a new alloy system is added into the fold of EBM. The purpose of this study is to understand the effect of key processing parameters on the microstructure and mechanical properties of Hastelloy X (HX) produced by EBM process. A statistical design of experiments approach was employed to fabricate Hastelloy X specimens using EBM and to investigate the influence of beam speed, beam current, focus offset and line offset on the final part quality. The internal porosity and surface roughness were characterized using Microcomputed tomography (micro-CT) and confocal microscope respectively. Optical and electron microscopy (SEM and EBSD) were used to analyse the microstructure. The mechanical strength of parts produced were characterized using Vickers micro-hardness, tensile and fatigue tests. The as-built specimens demonstrated a strong mechanical anisotropy with lowest values of Young’s modulus measured parallel to the build direction. In addition, the microstructure and mechanical properties of EBM HX are compared with that of their SLM counterparts.