Additive manufacturing of 18Ni300 steels with enhanced performance by introducing intrinsic heat treatment in powder bed fusion

Maraging steels have high strength and good ductility and, therefore, have been widely used in aerospace and tooling sectors for many years. 18Ni300 processed by powder bed fusion (PBF) is highly susceptible to direct aging treatment owing to the rapid cooling rate, and such an aging treatment can significantly change the microstructure and trigger the precipitation of Ni-rich intermetallic phases, thereby enhancing the mechanical properties of the printed parts. To minimize the necessity of postaging treatment, we explored designing innovative PBF processing routes to generate the Ni-rich precipitation phase via intrinsic heat treatment (IHT). The results show that IHT enhances the tensile strength of the 18Ni300 alloy, reaching 1155.1 MPa, a 13.1% improvement over the PBF sample. However, the ductility was reduced, with an elongation at the break of 6.41%. The friction coefficient of the IHT specimens was lower (0.68) compared to the PBF sample, reflecting improved hardness and strength. The wear mechanism in IHT-treated parts was primarily abrasive and adhesive, with some oxidation. The exploration of IHT in powder bed fusion of 18Ni300 alloys provided a new method of improving the mechanical properties for the in situ metallurgically modified AM process.