Search

The use of additive manufacturing in metals by powder bed fusion via electron beam (PBF-EB) is increasing for fabricating high-quality parts meeting industrial standards. However, high surface roughness poses a consistent challenge in PBF-EB. This study investigates two novel approaches to optimise surface roughness for a given machine and powder combination. Using machine control software’s recently introduced research mode functionality, we develop customised beam control code to effectively explore a vast parameter space. Additionally, we explored the impact of beam travel direction and spot morphology on surface roughness. Line-melt-based contours were explored by specimen manufacturing with layer-wise parameter change, whilst spot-melting-based samples were built using a full factorial design of experiments with four factors at three levels. Initial sample characterisation was done using a stylus-based contact profilometer, followed by detailed evaluation using focus variation microscopy. Results reveal that increasing beam power and spot energy exacerbate surface roughness. We also find that a well-defined energy distribution at the spot's edge contributes to smoother surfaces. Whilst the influence of beam travel direction on surface roughness remains uncertain, our findings underscore the importance of parameter selection in achieving optimal results. By adjusting contouring parameters, we achieve a vertical roughness of Ra17.7 ± 0.9 (Sa 21.6), significantly lower than in the current literature. These findings advance our understanding of surface roughness optimisation in PBF-EB and offer practical insights for improving part quality in industrial applications. By harnessing tailored beam control strategies, manufacturers can enhance the capabilities of additive manufacturing technologies in producing metal components.

Electron-Beam Powder Bed Fusion (EB-PBF) is one of the most important metal additive manufacturing (AM) technologies. In EB-PBF, a focused electron beam is used to melt metal powders in a layer by layer approach. In this investigation two pre-alloyed steel-based powders, stainless steel 316L and V4E, a tool steel developed by Uddeholm, were used to manufacture functionally graded materials. In the proposed approach two powders are loaded into the feeding container, V4E powder on top of 316L one, preventing their mixing. Such type of feeding yields components with two distinct materials separated by a zone with gradual transition from 316L to V4E. Microstructure and local mechanical properties were evaluated in the manufactured samples. Optical Microscopy, Scanning Electron Microscopy and EDX on the polished cross-sections show a gradual microstructural and compositional transition from characteristic 316L at the bottom of the specimens to the tool steel towards the top. Nanoindentation experiments confirmed a consequent gradient in hardness and elastic modulus, which gradually increase towards the top surface of the samples. The achieved results provide great possibilities to tailor the composition, microstructure, mechanical properties, and wear resistance by combining different powders in the powder bed AM technology. Potential applications include the tooling industry, where hard and wear-resistant materials are demanded on the surface with tougher and more ductile materials in the core of the tool.

This study investigates the use of Electron Beam Powder Bed Fusion (PBF-EB) spot melting on SDSS 2507, a material known for its high tensile strength, corrosion resistance, and welding properties. Spot melting, a localized melting technique, utilize a stationary beam to create melt pools before rapidly repositioning to form new ones, offering precise control over material properties in additive manufacturing. We conducted a design of experiments with 32 samples and analysed them using SEM, XRD, EBSD, optical microscopy, nanoindentation and statistical modelling.

This study focuses on adapting the Electron Beam Powder Bed Fusion (E-PBF) process for the manufacturing of parts from 2507 super duplex stainless steel, combining high strength and corrosion resistance, therefore presenting an interesting choice for E-PBF implementation. Samples manufactured using four sets of process parameters were characterized by scanning electron microscopy, tensile testing, X-ray diffraction analysis, energy dispersive X-ray spectroscopy and nanoindentation. The different E-PBF process temperatures investigated had the strongest influence on the phase characteristics and the resulting microstructure. The processability of the material was good, and high productivity rates were achieved, indicating good suitability for industrial transfer.

Electron beam melting (EBM) is one of the constantly developing powder bed fusion (PBF) additive manufacturing technologies (AM) offering advanced control over the manufacturing process. Development of the additive manufacturing today is targeting both widening of the available materials classes, and introducing new manufacturing modalities. Present research is related to the new possibilities in tailoring different properties within additively manufactured components effectively adding “fourth dimension to the 3D-printing”. Through manipulating beam energy deposition (scanning strategy) it is possible to tailor quite different material properties selectively within each manufactured component, including crystalline and amorphous state, effective material density, as well as mechanical, thermal, electrical and acoustic properties. With the blends of precursor powder, it is also possible to acquire by choice both metal-metal composite and completely alloyed material. Specific examples are given in relation to the EBM, but majority of the conclusions are valid for the other PBF techniques as well.

One of the serious obstacles preventing wide industrial use of additive manufacturing (AM) in metals and alloys is a lack of materials available for this technology. It is particularly true for the Electron Beam Melting (EBM®) process, where only a few materials are commercially available, which significantly limits the use of the method. One of the dominant trends in AM today is developing processes for technological materials already widely used by other methods and developed for other industrial applications, gaining further advantages through the unique value added by additive manufacturing. Developing new materials specifically for additive manufacturing that can utilize the properties and specifics of the method in full is still a research and development subject, and such materials are yet far from full scale industrial usage. Stainless steels are widely used in industry due to good mechanical properties, corrosion resistance and low cost of material. Hence, there is potentially a market for this material and one possible business driver compared with casting for example is that lead times could be cut drastically by utilizing an additive approach for one-off or small series production. This paper presents results from the additive manufacturing of components from the known alloy 316L using EBM®. Previously the samples of 316L were made by laser-based AM technology. This work was performed as a part of the large project with the long term aim to use additively manufactured components in a nuclear fusion reactor. Components and test samples successfully made from 316L stainless steel using EBM®process show promising mechanical properties, density and hardness compared to its counterpart made by powder metallurgy (hot isostatic pressing, HIP). As with the other materials made by EBM®process, 316L samples show rather low porosity. Present paper also reports on the hierarchical microstructure features of the 316L material processed by EBM®characterized by optical and electron microscopy.

Additive manufacturing (AM) is becoming one of the most discussed modern technologies. Significant achievements of the AM in metals today are mainly connected to the unprecedented freedom of component shapes this technology allows. But full potential of these methods lies in the development of new materials designed to be used specifically with AM. Proper understanding of the AM process will open up new possibilities, where material and component properties can be specifically tailored by controlling the parameters throughout the whole manufacturing process. Present paper discusses the issues related to the beam melting technologies AM and electron beam welding (EBW). We are speaking of new direction in material science that can be termed “non-stationary metallurgy”, using the examples from material and process development for EBW, electron beam melting (EBM®) and other additive manufacturing methods.

This paper presents some results achieved in the biomedical applications of the EBM® technology, and describes the resolved and unresolved challenges presented by modern medical implant manufacturing. In particular it outlines the issues related to the cellular structure design and metal surface modification. Moving to precision control of the metal surface at a micro-and sub-micrometer scale is a serious challenge to the EBM® processing, because it uses the powder with average grain size of about 0.04 to 0.1 mm. Though manufacturing of components with solid-mesh geometry and porous surfaces using EBM® is quite possible, post-processing (for example chemical or electrochemical) is needed to achieve desired control of the surface at smaller scales to realize full potential of the technology for biomedical applications.