High-speed manufacturing-driven strength-ductility improvement of H13 tool steel fabricated by selective laser melting

ABSTRACT H13 tool steel was additively manufactured by selective laser melting (SLM). The sample printed at a higher laser scan speed exhibited higher strength and ductility than those of the sample printed at a lower speed. The samples were repeatedly exposed to a massive heat input during the SLM. The in-situ tempering effect was applied to the sample; the phase fraction is changed by varying the heat input by controlling the laser scan speed. The microstructure analysis showed that the sample printed at a higher scan speed had a higher fraction of retained austenite than at a lower speed. The former was affected by deformation-induced martensitic transformation with enhanced strain-hardening ability. This study entailed the control of process parameters to improve the mechanical properties and the productivity of SLM-printed H13 tool steel. It investigated the relationship between the laser scan speed and the phase fraction, whose effect on the mechanical properties was confirmed.