Metallurgical and Mechanical Assessment of Hybrid Additively-Manufactured Maraging Tool Steels via Selective Laser Melting

Abstract

A complete metallurgical and mechanical assessment of additively manufactured maraging tool steels has been undertaken, beginning with the initial powder and ending at hybrid builds. The effect of powder recycling on powder characteristics is investigated using flowability, size distribution, and density measurements. Virgin and re-used powder have similar characteristics in terms of size distribution and chemical and phase homogeneity, but no flowability. A microstructural characterization of the as-built and heat-treated samples is undertaken, showing the phase evolution, and the formation of porosity between build layers. The age-hardening response of the alloy at 490˚C and 650˚C is demonstrated to be similar to the material in the wrought condition. Finally, hybrid build scenarios are examined – maraging steel powder deposited onto C300 maraging steel, as well as H13 tool steel substrates – using digital image correlation. In both cases, the interface remains coherent without any sign of de-bonding during tensile deformation. In the case of the maraging steel powder / C300 substrate, the deformation is homogeneous throughout until failure localizes away from the interface. In the case of the maraging steel powder / H13 substrate, the deformation is predominantly within the substrate until failure localizes at the interface. A heat treatment strategy for the maraging steel powder / H13 tool steel substrate is proposed.