직접용융증착 중 스캔 전략에 따른 18Ni300 마레이징강의 미세조직 및 기계적 특성

Abstract

Although the laser scan strategy does not affect the energy density of laser-based additivemanufacturing, changes in laser scan direction critically influence the residual stress and microstructure ofmetallic components. However, only a limited number of studies have investigated the role of laser scanstrategy on the microstructure and mechanical properties of additively manufactured maraging steels. Therefore, this study examines the effect of laser scan strategy on the mechanical properties of 18Ni300maraging steel. Different laser scan strategies influence the morphologies of the molten pool, where retainedaustenite is concentrated in 18Ni300 maraging steel. The 45o sample exhibits a denser molten pooldistribution compared to the other samples due to reduced layer overlapping. Because of the plastic strainincompatibility between martensite and austenite at the molten pool boundary, this dense molten pooldistribution in the 45o sample resulted in the highest back-stress hardening. Additionally, the minimal layeroverlapping in the 45o sample reduces heat exposure during laser-based additive manufacturing, leading toa finer martensite block and lath size. By combining high back-stress hardening with a fine martensite blockand lath size, the 45o sample achieved the highest tensile property compared to the other samples. Theseresults indicate that the selection of laser scan strategy is crucial for designing a heterogeneous microstructurein additively manufactured parts, which can enhance mechanical properties, even with the same energydensity.