Tailored Heat-Treatment Strategies for W360 Tool Steel Produced by Directed Energy Deposition

Laser-directed energy deposition (L-DED) was used to manufacture samples of the newly developed W360 hot-work tool steel from voestalpine Böhler Edelstahl. Various heat-treatment processes, including austenitising followed by air or water-quenching and tempering, as well as direct tempering, were applied. The as-built and heat-treated conditions were characterised by optical microscopy (OM), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), while the microstructural evolution during austenitisation was investigated using a high-temperature microscope (HTM). Hardness measurements were performed to determine the material response. The as-built condition exhibited a hardness of 628 ± 12 HV with no manufacturing cracks. The highest hardness (666 ± 13 HV) was obtained after air-quenching, whereas water-quenching produced 651 ± 14 HV. The rapid cooling of water-quenching, however, led to the formation of macroscopic cracks. The lattice distortion differences identified by XRD and the kernel average misorientation values obtained from EBSD indicated differences between the air and water-quenched conditions. High hardness (622–628 HV) was retained after low-temperature direct tempering, whereas high-temperature tempering resulted in significant softening (487 ± 12 HV). These results suggest that low-temperature direct tempering is a promising post-processing treatment for L-DED W360 tool steel, although additional mechanical testing is required to confirm industrial applicability.