Additively Manufactured Hastelloy-X: Effect of Post-Process Heat Treatment on Microstructure and Mechanical Properties

In this study, the effect of post-process heat treatment on the microstructure and mechanical properties of Hastelloy-X superalloy fabricated via two different additive manufacturing technologies, namely, laser beam powder bed fusion (LB-PBF) and laser powder directed energy deposition (LP-DED), is investigated. Microstructure was examined using scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) analysis, while mechanical properties were evaluated by macro-hardness testing using the Rockwell B method. Microstructure of the alloys was studied thoroughly after several heat treatments that involve stress-relieving (at 1066°C for 1.5 hours), hot isostatic pressing (HIP at 1163°C for 3 hours under 103 MPa pressure), and/or solution treatment (at 1177°C for 3 hours). The results revealed that, for both LB-PBF and LP-DED Hastelloy-X, the post-process heat treatments resulted in uniform grain structure as well as partial dissolution of carbides, although they have different grain sizes.