This investigation focuses on examining the deformation behavior of the Inconel 718 (IN718) superalloy, manufactured via electron-beam powder bed fusion (E-PBF), under both ambient and high-temperature conditions. Two specific heat treatment routes were applied to the As Printed (AP) material: one aimed at precipitating the delta phase at the grain boundaries (HT1) and the other at keeping the grain boundaries free of the delta phase (HT2), while retaining the gamma' and gamma'' phases in the matrix. The optimized heat treatment resulted in a granular and discontinuous delta phase at the grain boundaries. The HT2 specimens demonstrated higher yield strength and strain hardening rates compared to the HT1 and AP specimens at both room and high temperatures. The stressstrain curves at room temperature were free from serrations, whereas serrations appeared at high temperatures. Although all specimens exhibited temperature-dependent stress drops, this effect was minimal in the HT2 specimens. Post-deformation analysis revealed that the HT1 specimens did not accommodate strain at the grain boundaries, whereas the HT2 specimens showed more homogeneous deformation. In the HT1 specimens, the delta phase exhibited a strong orientation relationship with neighboring grains at the grain boundaries. Additionally, HT1 specimens displayed superior creep resistance compared to HT2, with a two-order magnitude difference in the steady-state creep rate. Electron backscattered diffraction (EBSD) analysis, coupled with Crystal Plasticity Fast Fourier Transform (CPFFT) simulations of the monotonic stress-strain curves, confirmed that HT2 specimens exhibited higher initial resistance to slip and higher hardening rates than HT1 and AP specimens. Creep studies further substantiated that HT1 specimens outperformed HT2 and AP specimens in high-temperature deformation response.

This study investigates the microstructure and mechanical properties of Inconel 718 (IN718) manufactured via electron beam melting (EBM). The EBM‐processed IN718 exhibits a unique grain structure with columnar grains along the build direction (BD) and equiaxed grains perpendicular to it. Contrary to typical solidification textures, the strongest texture intensities are observed for (110) and (111) orientations, attributed to in situ δ phase precipitation during high‐temperature processing. The microstructure notably lacks cellular structures common in additively manufactured materials, instead featuring δ phase formed through in‐situ aging. A tailored heat treatment strategy is developed to control δ phase precipitation at grain boundaries, mitigating grain boundary sliding (GBS). This treatment results in <100> texture and large columnar grains, leading to a twofold increase in yield strength compared to the as‐printed (AP) condition. Interestingly, the AP EBM IN718 shows no signs of dynamic strain aging (DSA), distinguishing it from conventionally processed IN718. This comprehensive analysis of microstructure, texture, and mechanical behavior provides valuable insights for optimizing EBM processing and heat treatment of IN718 for enhanced performance in high‐temperature applications.

The soft magnetic Fe-6.5Si alloy is well known for its excellent soft magnetic properties but its usage is limited due to fabricational constrains by conventional methods. Powder metallurgical processing of Fe-6.5Si is possible by a variety of different methods shown here, sinter-based screen printing (SP), electron beam powder bed fusion (E-PBF) and field-assisted sintering (field-assisted sintering/spark plasma sintering, FAST/SPS). The microstructure of the components varies strongly by process and powder used which is directly influencing their soft magnetic properties. The correlation between powder properties and processing parameters on the structural and magnetic properties is established. Lowest coercivity ( H c = 7 A m −1 ) is achieved by E-PBF due to large grain size minimising hysteresis losses necessary for direct current applications. SP can provide sheets with low coercivity ( H c = 21 A m −1 ) and adjustable thickness reducing eddy current losses especially suitable for alternating current application at higher frequencies. FAST/SPS can be used for a large range of powder particle sizes which is suitable to tune the soft magnetic properties in a wide range between 40 and 210 A m −1 .

TiAl parts fabricated with additive manufacturing have begun to find applications in car and aviation industry. Optimization of their properties concentrates on introduction of new alloying additions improving the TiAl ductility and oxidation resistance. Their effect on the mechanical properties was worked out quite well, but the knowledge how they affect the oxidation processes is still limited. Therefore the present experiment was aimed at investigation of scale grown over mould cast (MC) and electron beam powder bed fusion (EB-PBF) Ti–48Al–2Nb–0.7Cr–0.3Si (at. pct) alloys. It was conducted at 650 °C for 1000 hours both in dry air and steam covering early stages of this process. The scale microstructure, chemical and phase composition was examined with the transmission electron microscopy (TEM). Applied treatment caused development of three-layer scale, i.e. with major portions of R-TiO 2 + α -Al 2 O 3 /R-TiO 2 / α -Al 2 O 3 . The one formed during dry-air oxidation of the EB-PBF alloy was most compact. Steam oxidizing changed morphology of rutile present at its surface from rod/plate-like into whiskers. The Si turned out to be especially active during scale growth diffusing up to its surface. The presence of steam further increased mobility of both Si and Cr rising their presence in the upper part of the scale. The Nb was found to accumulate within the substrate area adjoining to the scale. Refinement of EB-PBF microstructure as compared with the MC alloy resulted in promoting reaction at the scale/substrate front contributing significantly to development of thicker oxide coating and nitrides bearing oxidation affected zone.

The lack of room-temperature ductility of high-strength TiAl-based alloys called for complicated high temperature processing limiting their application areas. Introduction of additive manufacturing (AM) methods allowed to circumvent this disadvantage, but entailed microstructure refinement affecting, among the others, their oxidation resistance. The dry-air high temperature oxidation processing of TiAl-based alloys is relatively well covered for coarse grained materials, but to what extent the TiAl alloys are affected by the changes caused by the AM remains to be found out. Additionally, the role of nitrogen during these processes was to large extent omitted in previous works. Within the present experiment, the mould cast (MC) and the electron beam melted (EBM) Ti-48Al-2Nb-0.7Cr-0.3Si (at. %) RNT650 alloys were dry-air oxidized at 650 degrees C for 1000 h. The TEM/EDS investigations allowed to confirm that the scale formed during such treatment consists of the layers occupied predominantly by TiO2+Al2O3/TiO2/Al2O3 sequence. Additionally, it was shown that N diffuses to the sub-scale and reacts with the substrate forming two distinct discontinuous sub-layers of alpha(2)-Ti3Al(N) and TiN. The scale over EBM was noticeably less porous and nitrogen penetration of the substrate was more extensive, while the MC showed higher susceptibility to local sub-scale oxidation.

The influence of sulphur atmosphere on conventionally cast (CM) and on electron beam melted (EBM) γ - TiAl RNT650 alloy exposed to a 1% (vol.) H2S – air atmosphere at 650 °C for 500 h was investigated. The material produced by CM showed a lower mass gain than the EBM material. XRD and TEM/EDS analyses indicated the formation of rutile-TiO2/(α-Al2O3 + rutile-TiO2)/amorphous-Al2O3 sequence of phases. In EBM a coarse crystalline layer rich in aluminium, oxygen and a small amount of sulphur was found. The higher content of sulphur was in the scale bottom intermixed with amorphous alumina.

Excellent soft magnetic properties of Fe-6.5Si are well known since a very long time. But its usage was hindered by the difficulty of processing by conventional methods. Until now, most innovative fabrication methods are limited to the lab scale. In this study, different powder metallurgical methods are demonstrated for the fabrication of soft magnetic Fe-6.5Si parts. The magnetic properties as well as geometric limitations of the process will be compared for a sinter-based method (screen printing) with an electron beam powder bed-based process (E-PBF) and a more conventional pressing process (FAST/SPS) for manufacturing soft magnetic components from Fe-6.5Si. The magnetic properties will be correlated with the structural properties. Most important aspects like different powder properties as well as fabrication constraints and conditions will be discussed.

Oxidation resistance of gamma - TiAl alloy RNT650 exposed to air and steam at 650 degrees C for 1000 h is reported. The samples were prepared either by conventional casting (CM) or electron beam melting (EBM). The materials were analysed using XPS, XRD, SEM and STEM/EDS techniques. Mass gains in both alloys were comparable and relatively small for air oxidation, but for steam treatment the mass increase in the EBM alloy was up to 50% more than in the CD material. Mass gain showed a faster growth of the scale in the steam treated material. The oxidized materials developed thin nano-crystalline scales predominantly of aluminium and titanium oxides arranged in TiO2+Al2O3/TiO2/Al2O3 sublayers. Whiskers were detected sticking above the scale surfaces, with density much higher in steam treated specimens.

In the present state of the art, highly spherical alloy powders are employed as feedstock in powder bed fusion processes. These powders are characterized by high flowability and apparent density. Their elaborate fabrication process is reflected in high powder price, adding a significant fraction to the cost of additively manufactured parts. Thus, the use of non-spherical powders, such as water atomized material, can lower costs significantly. Here, the electron beam powder bed fusion (PBF-EB) of standard water atomized iron powder used for press-and-sinter is studied. Despite raking problems, using the coating mechanism in standard configuration samples with densities exceeding 99% were fabricated. In a further step, the addition of alloying elements by powder blending is explored. Important powder properties of feedstock blended from irregular and spherical powders are characterized. The PBF-EB processing of two alloys is presented. The first represents a low carbon steel. Samples were characterized by metallographic cross-section, energy dispersive X-ray (EDX) mapping, and mechanical testing. The second alloy system is a FeCrAl. After PBF-EB processing of the powder mixture, chemical homogeneity was achieved. Besides the low cost, this approach of using water atomized powder mixed with master alloy offers the advantage of high flexibility for potential application.

Due to the small variety of materials, the areas of application of additive manufacturing in the toolmaking industry are currently still limited. In order to overcome these material restrictions, AM material development for high carbon-containing iron-based materials, which are characterized by high strength, hardness, and wear resistance, must be intensified. However, these materials are often susceptible to crack formation or lack of fusion defects during processing. Therefore, these materials are preferentially suited for electron beam powder bed fusion (PBF-EB). In this paper, an Fe-Cr-V alloy with 10% vanadium is presented. Investigations were carried out on the PBF-EB system Arcam A2X. Specimens and demonstrators are characterized by a three-phase microstructure with an Fe-rich matrix and VC and M7C3 reinforcements. The resulting microstructures were characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Furthermore, mechanical and physical properties were measured. A final field test was conducted to evaluate durability in use.

Lightweight intermetallic γ-TiAl based alloys are innovative high-temperature structural materials. So far, these alloys are in use as turbine blades or turbocharger turbine wheels in advanced aerospace and automotive engines, where they are produced by means of investment casting as well as wrought processing, e.g. hot-forging. Through the development of powder-based additive manufacturing processes within the last decade, a real paradigm shift for future component production as well as their design and materials properties was created. While so-called proven alloy systems are presently used worldwide for additive manufacturing, the approach of this work is the development of novel process-adapted γ-TiAl based alloys, which on the one hand fulfill the specific requirements of additive manufacturing and on the other hand provide excellent high temperature properties after a suitable heat treatment. Based on the concept of an engineering γ-TiAl based alloy, i.e. the so-called TNM alloy, two alloys are presented. Due to the chemical reactivity of titanium aluminide alloys, electron beam melting processes come into consideration as production methods using optimized manufacturing parameters, providing dense components with only small variations in the Al content between the individual powder layers, which is a decisive factor for the subsequent heat treatment above the γ solvus temperature. The additively produced samples show a fine equiaxed microstructure, whereas the heat-treated samples exhibit a fully lamellar α₂/γ microstructure with an excellent creep resistance. In summary, the adaptation of the additive manufacturing parameters in combination with innovative alloys and subsequent heat treatments are the basis for producing reliable high-performance TiAl components in the near future.

Additive manufacturing (AM) of metals is stimulating the tool making industry. Moreover, besides the production of lost forms, AM processes are now being used to directly generate tools, molds or parts, leading to massive time savings. In the case of material development for AM, the challenge is to operate with carbon-containing iron-based materials distinguished by high strength and hardness, as well as high corrosion resistance and thermal conductivity. Often, those materials are susceptible to crack formation during processing. Using Electron Beam Powder Bed Fusion (PBF-EB), the challenge of crack formation can be overcome by using high process temperatures in the range 800–900 °C. In this paper, results on the processing of a cold-working tool steel (X65MoCrWV3-2) and a hot-working steel (X37CrMoV5-1) will be presented. These include the processing window, processing strategies to minimize the density of cracks and properties with respect to microstructure and hardness.

Tungsten is an outstanding material and due to its properties like highest melting point and tensile strength of all natural metals and its high thermal conductivity it is a prime candidate for being used in very harsh environments and for challenging applications like X-ray tubes or as plasma facing material (PFM) in fusion reactors. Unfortunately, high brittle to ductile transition temperature and hardness represent a great challenge for classic manufacturing processes. Additive manufacturing (AM) of tungsten could overcome these limitations and resulting design restrictions. However, AM of tungsten also poses challenges in particular related to the production of material of high density and mechanical stability. Using a selective electron beam melting and a base temperature of 1000 °C of the powder, we were able to produce tungsten with a theoretical density of 99 % without the need of any post-treatment like a second melting step or a redensification by e.g. hot isostatic pressing (HIP). The surface morphology, microstructure, hardness, thermal conductivity and stability against severe transient heat loads were investigated with respect to the relevant building parameters and compared with recrystallized standard W. Besides simple test geometries also more sophisticated ones like monoblocks were successfully realized illustrating the potential of AM for fusion.

Selective electron beam melting (SEBM) is an additive manufacturing process for the production of complex metallic parts. To optimize their mechanical properties, pores and fusion defects, since not completely avoidable, have to be detected and evaluated. The generated microstructure may contain not only voids, but also weak bonds, sharp interfaces and loose particles causing nonlinear elasticity. This paper reports on Nonlinear Impact Modulation Spectroscopy (NIMS) experiments applied to a set of Ti–6Al–4V samples, each of which contains an internal zone with well-defined porosity ranging from 0.2 to 20%, respectively. Resonance spectra, attenuation and indicators of material nonlinearity were evaluated, which allowed the localization, dimensioning and assessment of porous zones. Properties of used linear and nonlinear methods are discussed.

In addition to the production of lost moulds, additive manufacturing (AM) is increasingly used for the direct manufacture of tools, inserts, or parts thereof. Depending on the material and tool geometry, the combination of additive and conventional technologies (hybrid production) are advantageous. Commercially available AM tool inserts have their limits on the kinds of the materials that can be used. High‐carbon, particle‐reinforced, or crack‐prone materials are indispensable for many areas of tool making but so far can hardly be processed using the common laser‐based AM methods, as rapid solidification in these brittle materials results in high residual stresses, which may lead to crack formation. In contrast, selective electron beam melting (SEBM) is working under elevated temperatures of up to 1100 °C and, thus, minimizes thermal stresses. This study shows how such materials can be processed by SEBM. Results are presented for the first‐time production of high‐carbon iron–chromium alloy. Herein, powder properties and their reusability are focused upon, as well as process parameters and their influence on part quality. Investigations on density, microstructure, and hardness are shown to illustrate the potential of the SEBM process. Final heat treatments reveal that a further increase in hardness is possible in this alloy.

Powder bed fusion of difficult-to-weld-steels such as the 42CrMo4 applied in this study is a challenging task. These materials are often susceptible to crack formation. To minimize thermal gradients and residual stresses, laser beam technologies generally require preheating of the substrates. Selective Electron Beam Melting (SEBM), on the other hand, is based on preheating the powder bed and, thus, enables crack-free printing even at greater heights. The present study demonstrates the processing of 42CrMo4 by SEBM. Besides parameter optimization, powder analysis, microstructural characterization as well as mechanical testing were carried out both for the as built and heat-treated conditions. The results indicate that the mechanical properties are comparable to those of conventional manufacturing technologies. Furthermore, a generic demonstrator with complex structures shows the high potential of SEBM for these particularly challenging steels.

Microstructure and mechanical properties of additively manufactured SS316L has been investigated. The samples produced by selective electron beam melting machine were then subjected to gas tungsten arc welding. Various examinations were performed including metallography and microscopy, hardness testing, and tensile testing coupled with digital image correlation software. Strain distribution was clearly evident on the samples during tensile testing with necking taking place at the heat affected zone on both sides of the weldments. From tensile testing, it was clear that the ductility and strengths of the samples were equal to those of conventionally produced samples such as rolled sheet. Hardness testing indicated the uniform distribution across the base metal and the weldments. Scanning electron microscopy identified the presence of Cr and Mo-rich precipitates on the grain boundaries, while the fracture surface was entirely covered with dimples (microvoid coalescence) indicating a ductile fracture mode.

Additive manufacturing is a powerful tool for rapid prototyping and fabricating metal articles having a complicated geometry. This method is known to be used almost solely for the manufacture of articles consisting of pure metals and alloys. In the present work the possibility of obtaining dense carbide articles by a single-step process of additive manufacturing based on selective electron beam melting was evaluated. A new technology for fabricating cemented carbide granules suitable for selective electron beam melting was developed. It includes conventional granulating WC-Co powders followed by solid-state pre-sintering and preliminary screening of the granules. After that their liquid-phase sintering and final screening are carried out to obtain a desired fraction needed for the additive manufacturing process. Results of experiments on selective electron beam melting at different scan rates and current values indicated that it was possible to obtain non-porous carbide articles of complex geometry from WC-Co granules initially containing 13 wt% Co. The selective electron beam melting process led to the evaporation of some liquid Co and very intense local WC grain growth resulting in peculiar microstructures of the cemented carbide articles comprising layers with medium-coarse and abnormally large WC grains. A near-surface layer of the cemented carbide articles obtained by additive manufacturing is characterized by a high roughness comparable with the mean size of the original WC-Co granules.

The quality of powder used in powder bed-based additive manufacturing plays a key role concerning process performance and end part properties. Even though this is a generally accepted fact, there is still a lack of a comprehensive understanding of the powder property–part property relationship. However, numerous investigations focusing on selected powder properties and their corresponding influence on process aspects or final part properties have been published in recent years. Still, generalized statements on powder requirements for a defined process performance are not available. This can be attributed to the fact that the community has not yet come to an agreement which characterization techniques are most suitable for powder characterization in the additive manufacturing context and in most cases only selected aspects have been investigated for special powder materials. The aim of this review is to assess these building blocks of knowledge and to provide an overview on the current state of the art.