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

Laser powder bed fusion (PBF-LB/M), one widely used metal additive manufacturing (AM) technology, enables the layer-by-layer fabrication of components with complex geometries. Therefore, this versatile manufacturing method is particularly well-suited for tooling applications with their intricate shape, such as cooling channels. However, the PBF-LB/M fabrication of medium and high carbon steels used for tooling is challenging, due to evolving residual stresses eventually leading to pronounced cracking. Residual stresses primarily arise from the thermal contraction inherent to the PBF-LB/M process (repeated heating–cooling cycles) and for tool steels additionally from the austenite-to-martensite transformation. In this study, we present a novel high-strength medium-carbon tool steel adapted to PBF-LB/M, which can be processed into crack-free and highly dense parts (99.7%) without pre-heating the substrate plate. The as-built microstructure of the steel consists mainly of martensite and residual austenite, whereby residual austenite is transformed to martensite during loading. The resulting transformation induced plasticity (TRIP) effect causes strong work-hardening behavior. This is one reason why the PBF-LB/M fabricated steel shows good mechanical properties with a yield strength of 1317 ± 69 MPa and an ultimate compressive strength of 2061 ± 13 MPa. Despite the lower macrohardness, the PBF-LB/M fabricated steel shows a significantly higher wear resistance than the H11 reference steel in dry abrasive wear testing.