A high-alloy (Cr-Mo-V) cold-work tool steel was manufactured by laser powder-bed fusion (PBF-LB) without preheating and by electron-beam powder-bed fusion (PBF-EB) with the build temperature set at 850 °C. The solidification rates, cooling, and thermal cycles that the material was subjected to during manufacturing were different in the laser powder-bed fusion than electron-beam powder-bed fusion, which resulted in very different microstructures and properties. During the solidification of the PBF-LB steel, a cellular–dendritic structure was formed. The primary cell size was 0.28–0.32 µm, corresponding to a solidification rate of 2.0–2.5 × 10⁶ °C/s. No coarse primary carbides were observed in the microstructure. Further rapid cooling resulted in the formation of a martensitic microstructure with high amounts of retained austenite. The high-retained austenite explained the low hardness of 597 ± 38 HV. Upon solidification of the PBF-EB tool steel, dendrites with well-developed secondary arms and a carbide network in the interdendritic space were formed. Secondary dendrite arm spacing was in the range of 1.49–3.10 µm, which corresponds to solidification rates of 0.5–3.8 × 10⁴ °C/s. Cooling after manufacturing resulted in the formation of a bainite needle-like microstructure within the dendrites with a final hardness of 701 ± 17 HV. These findings provide a background for the selection of a manufacturing method and the development of the post-treatment of a steel to obtain a desirable final microstructure, which ensures that the final tool’s performance is up to specification.

The process of an unstable plastic flow associated with the strain rate sensitivity of mechanical properties was studied in porous 316L austenitic steel samples manufactured by laser powder bed fusion (L-PBF). Different micromechanisms of deformation and fracture of porous samples dependent on strain rate were found. It was found that despite the porosity, the specimens showed high strength, which increased with the loading rate. Porosity led to lower ductility of the studied specimens, in comparison with literature data for low porous 316L L-PBF samples and resulted in de-localization of plastic deformation. With an increase in strain rate, nucleation of new pores was less pronounced, so that at the highest strain rate of 8 × 10⁻³ s⁻¹, only pore coalescence was observed as the dominating microscopic mechanism of ductile fracture.

Powders consisting of 60 at% Fe and 40 at% Al were mechanically alloyed in a planetary ball mill. The high energy milling process resulted in small powder particles composed of an extended solid solution, Fe(Al). After up to four hours of milling, laminae of different composition were observed which decreased to a size below detection limit in the SEM after heat treatment or further milling. The heat treatment resulted also in a non-stoichiometric ordered FeAl. A decrease in milling ball size resulted in a decrease of the width of the lamellae.

This study experimentally and numerically investigates fatigue damage in additively manufactured 316L stainless steel produced by selective laser melting using the powder bed fusion–laser beam process. More than 100 specimens were tested under tensile and strain‐controlled fatigue loading to evaluate the effects of surface condition, hot isostatic pressing (HIP), and build orientation. Machining provides the greatest improvement in fatigue performance by removing sub‐surface defects, while HIP provides additional benefits through reduced porosity. Vertically built specimens exhibit approximately 40% longer fatigue life than diagonal and horizontal specimens because elongated grains aligned with the build direction enhance ductility and stabilize crack propagation. A unified continuum damage mechanics‐based constitutive model predicts cyclic softening and fatigue life across low‐ and high‐cycle regimes. Fatigue anisotropy is represented by an orientation‐dependent fatigue ductility coefficient, while remaining parameters are orientation‐independent. The model accurately reproduces cyclic hysteresis loops and fatigue life to failure.