Effect of aging temperature on the microstructure and tribological behavior of an 18Ni maraging steel manufactured by laser powder bed fusion (LPBF)

Abstract This study addresses the critical knowledge gap regarding the influence of kinetically controlled austenite reversion on the tribological stability of Laser Powder Bed Fusion (LPBF) 18Ni-300 maraging steel. While conventional aging focuses on peak hardness (450–550 °C), this research investigates the high-temperature aging regime (610 °C and 650 °C) to elucidate the correlation between phase meta-stability and the evolution of protective tribo-layers. Samples were characterized using LOM, SEM, and XRD, with wear performance evaluated via pin-on-disk testing. A significant novelty of this work is the identification of a trevorite-rich oxide layer (Ni 0.86 Fe 2+ 0.12 Co 0.01 )Fe 3+ 2 O 4 whose formation is directly promoted by the presence of reverted austenite. In contrast, hematite was found to form predominantly on the martensitic substrate. Results show that prolonging aging at 610 °C from 10 to 30 min reduced hardness from 540 HV 0.2 to 511 HV 0.2 due to precipitate coarsening and increased austenite reversion. Although high-temperature aging enhances wear resistance compared to the as-built state, the higher austenite content at 610 °C facilitated oxide layer detachment, increasing the coefficient of friction (CoF) to 0.58, compared to 0.44 observed at 650 °C. These findings provide a technical basis for optimizing 3D-printed components, shifting the focus from maximum hardness to the engineering of phase-stabilized tribological surfaces.