A novel medium-carbon steel adapted to laser powder bed fusion: Microstructure, mechanical and wear properties

• New medium-carbon steel for laser powder bed fusion was developed. • Process parameters for crack-free fabrication of components were identified. • As-built steel possesses hierarchical microstructure. • Deformation-induced martensitic transformation occurred during compressive testing. • Friction-induced martensitic transformation occurred during abrasive wear testing. Laser powder bed fusion (PBF-LB/M) is designed for the near-net-shape fabrication of complex tool steel parts. In high-carbon steels, however, its broader application is limited by crack formation arising from severe thermal gradients and from stresses induced by austenite-to-martensite transformation. In this work, a materials design-driven strategy is presented to overcome these limitations through the development of a lean medium-carbon tool steel (Fe94.1Cr0.8Mo0.5Mn1.1Ni3.0C0.5) adapted to PBF-LB/M processing. By reducing the carbon content, transformation-induced stresses are mitigated, enabling the fabrication of crack-free components with a relative density of 99.7% without substrate preheating. The as-built microstructure consists predominantly of α ′-martensite containing MnS precipitates, ε -martensite, and retained austenite, which undergoes deformation-induced transformation to martensite during mechanical loading and friction. The transformation-induced plasticity (TRIP) effect promotes work hardening and contributes to a favorable combination of strength and wear resistance. The additively manufactured steel exhibits a yield strength of 1317 MPa and an ultimate compressive strength of 2061 MPa. Benchmarked against commercial H11 tool steel, superior abrasive wear resistance is achieved despite lower macrohardness, which is attributed to a friction-induced austenite-to-martensite transformation at the worn surface. This work demonstrates the effectiveness of alloy design for enhanced processability and performance in additively manufactured tool steels.