Effect of Y2O3 dispersoids on microstructure and creep properties of Hastelloy X processed by laser powder-bed fusion

Laser powder bed fusion (LPBF) was used to consolidate powders of a Ni-Cr-Fe-Mo alloy (Hastelloy X) blended with 1 wt% Y2O3 nanometric powders. The nearly-dense, crack-free specimens, and without oxide dispersion strengthening (ODS), exhibit high-aspect ratio grains, aligned in the build direction strong texture: 〈001〉 is along both laser scanning direction. Creep tests performed at 950 °C, compressive stresses elongated grains (and direction), reveal two creep regimes: (i) below ∼50 MPa, diffusional dominates, ODS less resistant than non-ODS alloy, consistent somewhat smaller grain size resulting from grain-boundary pinning by dispersoids; (ii) above dislocation dominates more resistant, as expected dispersoids impeding motion. When tested perpendicular direction, alloys have same resistance, which however much lower when stress reflecting effect texture shape. After ∼10% deformation, structure remain largely unchanged compared pre-creep structure.