Microstructure and Mechanical Properties of Additively Manufactured Haynes 230: A Comparative Study of L-PBF vs. LP-DED

This study investigates the microstructure and room temperature mechanical properties of Haynes 230 fabricated via laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED). Both L-PBF and LP-DED specimens underwent similar multiple-step heat treatments (HT): stress-relieving (1066°C for 1.5 hours), followed by hot isostatic pressing (at 1163°C and 103 MPa for 3 hours), and solution annealing (1177°C for 3 hours). Microstructural analysis was conducted employing a scanning electron microscope. Uniaxial tensile tests at room temperature were conducted to evaluate the mechanical properties. The change in microstructures after HT and tensile results for both L-PBF and LP-DED specimens were comparable. Upon HTs, the micro-segregation and dendritic microstructure observed in non-heat treated conditions were almost fully dissolved, and carbide phases (M6C/M23C6) formed within grain interiors and grain boundaries in both L-PBF and LP-DED specimens. Finally, the failure mechanisms under tensile load have been studied and compared by fractography.