High-Temperature Properties and Microstructural Stability of the AISI H13 Hot-Work Tool Steel Processed by Selective Laser Melting

The microstructural stabilities, softening resistance, and high-temperature tensile properties of the H13 hot-work tool steel by selective laser melting (SLM) were systematically studied. A series of tempering procedures were performed on the as-SLMed specimens. Afterwards, the mechanism of softening resistance behavior was discussed based on the XRD, SEM, EBSD observations, hardness measurements, and high-temperature tensile tests. It was found that the as-SLMed H13 consisted of α-iron and γ-iron. The carbide-stabilizing elements aggregated as the cell-like substructures for the rapid solidification of the SLM process. After the softening resistance treatment, the retained austenite transformed to ferrite and carbide mixtures. The cell-like substructures dissolved slowly into the matrix when the temperature was below 550 °C. These factors increased the hardness and retarded the softening of the material. When the temperature was 600 °C, the microstructural constituents transformed to soft ferrite and globular carbides, which lead to a considerable decrease of the hardness. Due to the grain refinement, solid solution strengthening, and residual stress, the as-SLMed H13 exhibited better mechanical properties than that of the wrought counterparts.