Concurrent improvement of strength and ductility in heat-treated C300 maraging steels produced by laser powder bed fusion technique

In this work, C300 maraging steel powder feedstocks at different titanium contents (0.72 and 1.17 wt%) were additively manufactured using the laser powder bed fusion (LPBF) technique to systematically study the mechanical behavior of the material in both as-built and heat-treated conditions. X-ray diffraction techniques along with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were employed to investigate the microstructural characteristics and phase formation in the as-built and heat-treated samples. After heat-treating at 490 °C for 6 h, the HighTi maraging steel showed higher strength and ductility (2057.74 MPa and 4.05%). The microstructural characterization proved that this alloy contains a higher amount of reverted austenite (17.89 wt%), which resulted at higher strength as results of the transformation induced plasticity (TRIP) effect. In terms of ductility improvement, the fiber/copper texture developed in the HighTi sample provided a higher driving force to transform the reverted austenite to martensite. As the TEM analyses revealed, needle-shaped Ni 3 Ti and spherical Ni 3 Mo precipitates were found in both LowTi and HighTi alloys, where the HighTi one showed higher volume fraction of Ni 3 Ti precipitates, and consequently, higher values of tensile strength, which can be explained, based on the Orowan mechanism.