High-temperature mechanical properties of laser powder bed fusion 304L stainless steel with in-situ oxide inclusions

• Compared to traditional mechanical alloying (MA), LPBF achieves more uniform oxide dispersion and enables in-situ fabrication of ODS 304L stainless steel by tailoring chamber O 2 (50–1500 ppm). • The 500-ppm sample showed superior properties at 600 °C(YS of ∼294 MPa, UTS of ∼351 MPa, EL of 26%, outperforming reported LPBFed 304L. • The 500-ppm sample shows the longest endurance life (194 h), surpassing the 50-ppm sample by ∼63 h (131 h), while the 1500-ppm one performs poorest (99 h), a 49% drop from 500 ppm. • Stable in-situ SiO 2 nano-oxides (∼22 nm at 500 ppm) key to enhancement: pin dislocations, suppress grain coarsening, synergize with ultrafine cells (∼400 nm) and twins for high-temperature stability. • The unique microstructure induced by LPBF incorporates multiple strengthening mechanisms, 500 ppm’s superior YS over 1500 ppm due to stable cells and high-density dislocations. Laser powder bed fusion (LPBF) provides an innovative strategy for in-situ generation of nanoscale oxide dispersoids, benefiting matrix compatibility and mechanical performance. This study systematically investigates the microstructure and high-temperature mechanical behavior of LPBFed 304L stainless steel (SS) by tailoring chamber oxygen content (50, 500, 1500 ppm), observing that the 500-ppm sample exhibited superior properties at 600 °C, with a yield strength (YS) of ∼294 MPa, an ultimate tensile strength (UTS) of ∼351 MPa, an elongation (EL) of 26%, and a durability of 194 h (600 °C, 225 MPa). These improvements are attributed to the stable oxide particles that effectively pin dislocations and suppress grain coarsening during deformation. Compared to traditional mechanical alloying (MA), LPBF achieves uniform oxide dispersion, outperforming methods in both mechanical strength and microstructural stability. This work demonstrated that LPBF as a robust technique for fabricating high-reliability ODS alloys, offering promising applications in nuclear core structural components.