Effects of annealing powder on microstructures and tensile properties of LPBF-processed Haynes230 superalloy

This study reveals a novel understanding of the influence of annealing the feed powder, which alters the precipitate characteristics in the powder particles on the microstructure and mechanical properties of Haynes230 superalloy fabricated by laser powder bed fusion (LPBF) plus hot isostatic pressing (HIP) and solution treatment. Specifically, annealing Haynes230 superalloy powder at 1000°C for 1 h under vacuum resulted in the precipitation of M6C carbide instead of the typical M23C6 found in unannealed powder. The alloy fabricated by LPBF of the annealed powder plus HIP and heat treatment exhibited an increased number density of the carbide precipitates at grain boundaries, but a reduced number density of the intragranular carbide precipitates. Consequently, its ambient temperature tensile properties decreased clearly in terms of yield strength (406–383 MPa), ultimate tensile strength (936–841 MPa) and elongation to fracture (38.6% to 25%) compared to the alloy fabricated by LPBF of the as-received powder plus same post-print processing. However, the annealing of the feed powder had little effect on the tensile properties of the samples at 900°C. These findings underscore the significant impacts of feed powder microstructure on the mechanical properties of LPBF-processed superalloys.