Laser Powder Bed Fusion (LPBF) is an additive manufacturing process employed in the aerospace, automotive, and medical industries. In these sectors, nickel-, aluminium-, and titanium-based alloys are mainly used for various applications. Yet, only few of the commonly used steels have been qualified for the LPBF process in the mechanical engineering industry, which normally uses hot work tool steels with less than 0.5 wt.-% carbon content. However, many applications need high wear-resistant steel alloys with high hardness, both of which can be achieved with a higher carbon content, like in high-speed steels. But when processed with LPBF, these steels often form cracks, making the process very challenging. In this feasibility investigation, we demonstrate that LPBF can be used to manufacture dense and crack-free specimens with a hardness of over 62 HRC (as built) from high-speed steel AISI M50 (carbon content of 0.8 wt.-%). Furthermore, we evaluate the influence of typical LPBF process parameters, especially of preheating temperatures up to 500°C, on the microstructure of the specimens.

This roadmap aims to define the guidelines to maximise the impact of the 3D printing revolution on the next generation of devices for the energy transition. It also outlines the current status, challenges and required advances in Science and Technology for a series of power generation technologies (fuel cells, solar cells, thermoelectric generators and turbomachinery) and energy storage technologies (electrolysers, batteries and supercapacitors). Finally, the roadmap discusses the role of 3D printing in improving the mass and heat transfer to improve the energy efficiency of chemical reactors (CO2 conversion) and novel cooling systems. With this document, the authors intend to provide a valuable tool for researchers, technology developers, and policymakers when defining their strategies for the energy sector's future.

While repair is mainly used to restore the original part geometry and properties, hybrid manufacturing aims to exploit the benefits of each respective manufacturing process regarding either processing itself or resulting part characteristics. Especially with the current implementation of additive manufacturing in the production of TiAl, turbine blades for both hybrid manufacturing and repair new opportunities are enabled. One main issue is the compatibility of the two or more material types involved, which either differ regarding composition or microstructure or both. In this study, a TNMTM-alloy (Ti-Nb-Mo) was manufactured by different processes (casting, forging, laser additive manufacturing) and identically heat-treated at 1290 °C. Chemical compositions, especially aluminum and oxygen contents, were measured, and the resulting microstructures were analyzed with Scanning Electron Microscopy (SEM) and High-energy X-ray diffraction (HEXRD). The properties were determined by hardness measurements and high-temperature compression tests. The comparison led to an overall assessment of the theoretical compatibility. Experiments to combine several processes were performed to evaluate the practical feasibility. Despite obvious differences in the final phase distribution caused by deviations in the chemical composition, the measured properties of the samples did not differ significantly. The feasibility of combining direct energy deposition (DED) with either casting or laser powder bed fusion (LPBF) was demonstrated by the successful build of the dense, crack-free hybrid material.

The defect-free processing of TiAl alloy TNM™-B1 by means of Laser Powder Bed Fusion (LPBF) is demonstrated by manufacturing of an automobile turbocharger wheel. Similar precision cast material was used as reference. TNM™-B1 was manufactured crack free with a density > 99.5% using elevated process temperatures above the brittle-to-ductile transient temperature (BDTT). The preheating temperature was provided by an induction preheating system. To minimize oxygen pick up during the LPBF process, the process atmosphere was actively cleaned using a gas-purification system. Produced test samples were analyzed in as-built and heat-treated condition regarding density, micro structure and phases by means of a Light Optical Microscope (LOM) and Scanning Electron Microscopy (SEM). Micro hardness was measured according to Vickers. Oxidation measurements were performed by means of carrier-gas hot extraction. Mechanical properties were determined using room temperature tensile tests. The final automobile turbocharger wheel was analyzed for defects using a Micro-Computer Tomography scanner (MCT). Besides bulk test samples, thin-walled specimens can be manufactured with sufficient density. Depending on the process parameters, an oxygen content < 1000 ppm could be reached. The as-built microstructure consists of lamellar (α2+γ) colonies and nearly globular γ as well as β/β0 at the grain boundaries. High cooling rates in the magnitude of 105 to 106 K/s provide small grain sizes of 1–7 μm. Hardness measurements reveal an increased hardness (515-560HV0.3) compared to cast material (390HV0.3). Samples for tensile tests show tensile strength around 840 MPa and a total elongation of 1.1% for LPBF-manufactured and hot isostatic pressed (HIP) samples. The CT analysis of the turbocharger wheel confirms that complex geometries made of TiAl can be additively manufactured free of cracks.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/srin.202200372.