Open Access

Inconel 718 (IN718) is the most commonly used nickel-based superalloy for high-temperature structural applications due to its remarkable strength, as well as its resistance to creep, fatigue, and corrosion up to 650 °C. This study investigated the room- and high-temperature (650 °C) tensile and low-cycle-fatigue (LCF) behavior of IN718 produced by laser powder bed fusion (PBF-LB/M). A bidirectional scanning strategy with 90° rotation after each layer and a four-step heat treatment was applied, and the results were compared to the conventional wrought material. The hierarchical microstructure after heat treatment was characterized on different length scales using microscopic methods. Distinct microstructural characteristics generated during the PBF-LB/M process, such as grain size and morphology, and the periodically graded arrangement of stacked columnar grains interspersed with regions of elongated grains aligned with the build direction, are largely preserved following the applied heat treatment. Additionally, the heat treatment reduces microsegregation and dislocation density associated with the cellular structure, promoting a more uniform precipitation of γ’/γ’’ strengthening phases. At both room and elevated temperatures, the elastic and yield properties of the PBF-LB/M material are comparable to those of the wrought variant. However, the additively manufactured material shows slightly reduced tensile strength, ductility, and strain hardening capability. As a result, it exhibits slightly lower inelastic strain under LCF conditions at both temperatures. While the fatigue life of the PBF-LB/M material is slightly lower than that of the wrought alloy at room temperature, it is vice versa at 650 °C. Both materials demonstrate cyclic softening behavior, which becomes more pronounced at the higher test temperature. Crack propagation is primarily influenced by grain orientation, morphology, and the presence of δ phase at grain boundaries. Under LCF loading at both room and elevated temperatures, multiple crack initiation sites are observed on the surfaces of PBF-LB/M specimens. In microstructurally heterogeneous regions, pronounced crack branching and deflection occur, suggesting that crack paths are shaped by sharp micromechanical gradients and localized clusters of grains with ⟨001⟩ orientation, which are favored for crack growth. The tendency of the PBF-LB/M material to exhibit systematic crack branching and deflection results in irregular crack fronts and mixed-mode propagation behavior. This crack path complexity contributes to additional energy dissipation during fatigue loading. Consequently, despite the relatively large average grain size and a pronounced formation of slip bands, the fatigue life at room temperature approaches that of the wrought material.

Representing experimental procedures in an unambiguous way that can be understood and reproduced by other scientists is at the heart of scientific progress. For centuries, these descriptions were made by humans and for humans, often assuming implicit or tacit knowledge. However, when Materials Acceleration Platforms (MAPs) and Self-Driving Labs (SDLs) are used for the autonomous discovery and optimization of materials, sharing knowledge, and workflows that were designed and executed by machines becomes increasingly important. These machines require an explicit, precise and accurate description and modeling of all process parameters and steps that need to be executed. To address these needs, especially in the domain of materials science and nano and advanced materials synthesis, we developed the Wet Chemical Synthesis Ontology (WCSO), which is based on the Platform MaterialDigital core ontology (PMDco) and the Basic Formal Ontology (BFO). The ontology contains recurring concepts from millions of wet chemical synthesis procedures in the scientific literature. We discuss the design considerations, concepts, and architecture of our ontology in detail, and demonstrate how it can be applied to the construction and querying of semantically annotated knowledge graphs from wet chemical nano- and advanced materials synthesis workflows that were previously designed for and then executed on an SDL. Using such formal representations and semantic annotations for describing synthesis procedures and workflows facilitates the reproducibility, sharing, and execution of synthesis procedures across different labs around the world that use different orchestrators for their robotic hardware.

The goal of this work is to provide a deeper understanding of the high-temperature fatigue properties of this alloy. For that purpose, a comparison of the mechanical properties, fatigue lives, and fatigue crack initiation mechanisms at room temperature, 300°C, 650°C, and 750°C has been conducted. This approach enabled the determination of the fatigue behavior of VDM 780 at elevated temperature.

Ni-Superalloy ATI 718Plus samples were produced by PBF‑LB using a range of island scanning strategies to investigate microstructural control and its influence on creep behaviour. Distinct microstructural differences were retained even after full heat treatment and recrystallisation. Creep testing at 700 °C and 650 MPa revealed significant variations in creep life and ductility as a function of scanning strategy and build orientation, with vertically built specimens outperforming horizontally built ones. All additively manufactured conditions showed inferior creep performance compared to cast and wrought 718Plus.

High-and medium entropy alloys have been investigated for more than two decades and their potential keeps being evaluated. Their “baseless” character distinguishes them from classic alloys that are characterized by one main element, such as steel – Fe based. The question has arisen whether our analysis methods are suited for alloys without a base element and is has been found that they are within the limitations of the methods. This dataset shows the compatibility between inductively coupled plasma optical emission spectrometry, combustion analysis, x-ray fluorescence analysis and energy dispersive x-ray spectroscope, measured in the scanning electron microscope. Four alloys from the well-studied Co-Cr-Fe-Ni medium entropy family have been used as testing materials.