Crack elimination and mechanical properties enhancement in additive manufactured Hastelloy X via in-situ chemical doping of Y2O3

Nowadays, applying the SLM technology to produce crack-free high-performance solution strengthened superalloys or refractory metal is still a big challenge. In this work, an innovative method via in-situ chemical doping of Y₂O₃ was used to solve the above problem. The results show that the Y₂O₃ introduced by this method forms a smooth and uniform coating on the surface of Hastelloy X spherical powders. Using this powder as the precursor, cracks in the SLM manufactured Hastelloy X can be completely eliminated. More heterogeneous nucleation sites provided by doped Y₂O₃ significantly reduce the grain and cell size of SLMed Hastelloy X, thereby inhibiting crack initiation and propagation. Based on the microstructural optimization, the ultimate tensile strength of Y₂O₃-doped Hastelloy X alloy increases significantly from 982 ± 66 MPa to 1405 ± 26 MPa, along with its yield strength increasing from 820 ± 46 MPa to 1130 ± 25 MPa. Besides, its total elongation also increases from 22.7 ± 1.7% to 27.7 ± 0.5%. The increase of strength is attributed to the strengthening effect of Y₂O₃ nanoparticles and the refinement of cells and grains, while the increase of total elongation is attributed to the elimination of internal cracks. The strategy of introducing uniform rare earth oxide coating on the surface of metal powders by in-situ chemical method proposed in our work provides a new perspective for SLM manufacturing high-performance solution strengthened superalloys or refractory metal prone to crack.