Microstructures and Mechanical Properties of H13 Tool Steel Processed by Selective Laser Melting

Abstract

The correlation between microstructure and mechanical properties of H13 tool steel processed by selective laser melting was investigated under as-SLMed condition. The microstructures were predominantly featured by cellular structures and columnar grains, which composed of lath martensite and retained austenite with numerous nanoscale carbides distributing at and within sub-grain boundaries. The average size of cellular structure was ~500 nm and Cr and Mo element were enriched toward the cell wall of each cellular structure. The as-SLMed H13 steel offered the yield strength of 1468 MPa, the ultimate tensile strength of 1837 MPa and the fracture strain of 8.48%. The excellent strength-ductility synergy can be attributed to the refined hierarchical microstructures with fine grains at a level of 1.67 μm, the unique cellular structures and the presence of dislocations. In addition, the enrichment of solute elements along cellular walls and carbides at sub-grain boundaries can enhance grain boundary pinning for strengthening.

Keywords: H13 tool steel, Selective laser melting, Microstructure, mechanical properties