Selective laser melting of 1.2738 mold steel: densification, microstructure and microhardness

Abstract In this study, the effects of laser power and scanning speed on the relative density, microstructure and microhardness of selectively laser melted (SLM) 1.2738 mold steel were systematically investigated. The deposited energy density, which can express the change in these process parameters and the relative density with one curve, were found more reliable than volume energy density (VED) on the design of process parameters. With the same VED value, samples formed by the combination of a high laser power and scanning speed possess a higher densification than that formed by low laser power and scanning speed. High power may lead to keyhole pore formation. In the top of the molten pool, ultrafine cellular structure was formed, causing that the microhardness value of the top section was always higher than that of the side section.