Comprehensive pore defect analysis for electron beam-powder bed fusion of Ti48Al2Cr2Nb

The process-microstructure relationship of gamma-titanium aluminide (Ti-48Al-2Cr-2Nb) parts fabricated via electron beam-powder bed fusion (PBF-EB) process was investigated. A set of 107 records of process parameter combinations were deployed to analyze and classify relative density, lack-of-fusion (LoF) and Gas porosity defects. The bulk density ranges spanned 88 %–99.99 %, with Gas porosity spanning 0.01 %–0.30 %, and lack-of-fusion defects spanning 0.001 %–12 %. Based on literature pertaining to defects addressable via hot isostatic pressing, four classes of density performance were identified: excellent (>99.8 %), good (99.6–99.8 %), poor (98.0–99.6 %), and failed (<98.0 %). For the purpose of this study, a high density outcome (excellent class) is identified to be ideal in terms of expected mechanical properties, specifically strength, fatigue, and ductility. Pore properties were mapped against different energy representations, for example, volumetric energy density (VED) and normalized enthalpy (NE). The results showed the importance of utilizing NE to visualize data and identify zones in the process parameter space where best performance is expected. A region of NE > 15 is expected to have an excellent performance, whereas NE < 10 is expected to result in unacceptable porosity outcomes.