Achieving well-balanced strength and ductility in laser powder bed fusion additively manufactured nickel-based superalloys by doping multiple oxides

Abstract

Doping second phase particles tends to improve the strength of additively manufactured nickel-based superalloys fabricated via laser powder bed fusion (LPBF). However, the stress concentration caused by the second phase particles inevitably deteriorates their ductility. In this study, Hastelloy X (HX) composites with single (1 wt% Y2O3) and multiple (0.5 wt% Y2O3 and 0.5 wt% La2O3) oxide particles are successfully prepared via in-situ chemical doping method together with LPBF. The results show that co-doping Y2O3 and La2O3 refines oxide particles from 35 nm to 26 nm in the LPBF fabricated HX. The finer oxide particles can more effectively increase the Zener force and block the grain boundary migration, thus weakening the preferred (001) texture and inhibiting the grain growth. As a result, the Y-HX and Y–La-HX samples possess an ultimate tensile strength of 1091 ± 10 MPa and 975 ± 6 MPa, respectively, representing an increase of 26.8% and 13.3% compared to the HX sample (860 ± 5 MPa). The strengthening mechanisms are mainly attributed to Orowan strengthening, dislocation strengthening and grain refinement. Moreover, the Y–La-HX sample exhibits the highest elongation, increasing by 9% compared to the HX sample. The high elongation is associated with excellent strain hardening behavior caused by finer oxide particles within grains. Our work can provide guidance for the preparation of additively manufactured nickel-based superalloys with superior mechanical properties.