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Despite the variety of different methods of metal 3D printing on Earth, only a few of them can be realized in space. Processes that employ electron beam as a heat source and wire as a consumable material is among the most promising methods for these applications. But to date, such processes still have not been implemented in actual space operation, mainly due to the low accuracy and resolution of these 3D printed products that require significant post-processing for their intended use. Large and heavy hardware employed in these processes is another significant problem. xBeam 3D Metal Printing is the electron beam DED-wire additive manufacturing technology that has already demonstrated the capability to produce high-quality parts with high productivity on terrestrial relatively lightweight and compact hardware. xBeam process employs a profile electron beam generated by low-voltage gas-discharge electron beam guns combined with the coaxial wire feed to provide excellent control of metallurgy processes in the melt pool and around it during deposition. Realized metallurgy conditions are the crucial factor in providing the combination of high accuracy and resolution with good metal structure and properties. Moreover, maintaining such metallurgy conditions does not require gravity—only cohesion/adhesion forces and surface tension forces are involved. This fact suggests good prospects for using the xBeam 3D Metal Printing in space applications. In addition, the method opens several unique technological opportunities that are important in space exploration, including the nonstick deposition technique allowing the production of "ready-to-use" parts, surface glazing able to substitute machining, recycling of the metal waste directly into wire for 3D printing, and others. The article presents technical solutions for implementing 3D printing and related processes in space conditions and analyzes the metallurgical aspects of the technology using titanium alloy Ti-6Al-4V as an example. [ABSTRACT FROM AUTHOR]

A novel coaxial electron beam wire feeding additive manufacturing technology (CAEBWAM) was proposed in our previous work to refine the microstructure and improve the mechanical properties of titanium alloys. In the present work, different post-heat treatments were performed to understand the microstructure evolution and the resultant mechanical properties of CAEBWAMed Ti-6Al-4V alloy. The as-built sample was dominated by equiaxed prior β microstructure, with the first several deposited layers containing columnar prior β grain morphology. The as-built alloy showed a mixed microstructure composed of large α′ martensite and fine α + β lamella. As the annealing temperature was increased, α′ martensite decomposed into α + β phase, while the width of the α lamellae increased, causeing an increase in the ductility and a decrease in the strength. [ABSTRACT FROM AUTHOR]

Advanced additive manufacturing technology of direct energy deposition type called x Beam 3D Metal Printing was employed for manufacturing of articles of various size and shape using titanium Ti-6Al-4V alloy wire as a feedstock material. The key distinctive feature of this process is applying of the hollow conical electron beam generated by low-voltage (< 20 kV) gas-discharge electron beam gun for heating and melting of the substrate and wire, which ensures precisely controllable liquid metal transfer from the wire end to the substrate, specific temperature gradients at the fusion area and heat flow from liquid metal pool. Such conditions of heating, melting and cooling during deposition of molten additive material provide controllable microstructure formation, including grain size and material texture. Influence of processing parameters and cooling conditions on fusion, crystallization, grain growth and intragrain structure of manufactured "chunky" Ti-6Al-4V blocks was discussed. The post-processing heat treatment was used to relieve residual stresses formed during article manufacturing. Tensile and fatigue testing has been performed for samples cut in various directions of produced articles to investigate the material uniformity. Optimization of processing parameters allowed production of 3D printed articles from Ti-6Al-4V with isotropic microstructure and mechanical characteristics which met standard requirements for Ti-6Al-4V material. [ABSTRACT FROM AUTHOR]

The electron beam additive manufacturing technology named xBeam 3D Metal Printing was presented at EBT-2016 Conference in Varna in summer of 2016. It was announced an expectation that this new technology can solve the most critical problems of numerous existing metal additive manufacturing processes and systems, including conflicts between accuracy and productivity, high quality and production cost, availability and price of raw materials and equipment, numerous after-processing operations as well. Authors will present the technical and technological progress in development of the xBeam 3D Metal Printing achieved on the base of the pilot xBeam 3D Metal Printer in near production environment since that time. Results of numerous experiments with the most important materials for metal additive manufacturing like titanium alloys which have proved possibility to produce defect-free material with good metal structure and high mechanical properties will be demonstrated. Numerous exclusive technological opportunities provided by xBeam 3D Metal Printing will be presented. Economic efficiency of the xBeam 3D Metal Printing will be also analyzed on the base of testing manufacture of real industrial parts from titanium alloys. [ABSTRACT FROM AUTHOR]

Long-term experience of application of gas-discharge electron beam guns in different technological processes such as melting, refining, coating, welding and others has proved their technical and economic efficiency both in industrial operation and R&D works. Wide range of permissible operating conditions, simple design and easy maintenance procedure, reasonable price of complete systems equipped by gas-discharge electron beam guns have been attracted more and more attention of customers worldwide. In addition to above mentioned features gas-discharge electron beam guns provide a number of another distinctive characteristics which could be interesting in additive manufacturing systems - for example they are capable to generate rather fine and accurate beam under low accelerating voltage down to 10 kV and even less, they have very light weight, their cathodes have extremely long life time as well. Application of gas-discharge electron beam guns of special configurations can make additive manufacturing technology more obtainable for customers and can provide new interesting opportunities to get new properties of produced materials. Pilot electron beam installation of new generation based on special gas-discharge electron beam guns will be presented. [ABSTRACT FROM AUTHOR]

Coaxial Electron Beam Wire-feed Additive Manufacturing (CAEBWAM), which is a novel additive manufacturing process, can produce fully dense alloy components with equiaxed β grains (EGβ) and isotropical mechanical properties and is considered as a potential manufacturing method for large-scale complex components. However, actual complex components inevitably include bonding regions, which are similar to welded joints, in the wire-feed deposition process, and limited knowledge is available on the microstructures and mechanical properties for this kind of regions. This work thoroughly studied the microstructures and mechanical properties of the Ti-6Al-4V alloy cruciform structure fabricated by CAEBWAM. It was found that the microstructure at the Bonding Zone (BZ) was composed of coarse columnar β grains (CGβ), continuous grain boundary α (α GB) phase, and coarse α laths due to a higher temperature and poor heat dissipation condition. The average width of α lath in the BZ region was larger and the hardness was lower compared with those in the EGβ region. Tensile properties and fracture behaviours of the tensile samples extracted at cruciform structure were examined. The fracture tended to occur at the BZ region and exhibited a mixed fracture mode with trans- and inter-granular fractures. This work will improve the understanding of microstructures and mechanical properties for representative cruciform structure in wire-feed AMed components, which would be conducive to further progress of the actual complex components. [Display omitted] • The microstructure and mechanical properties of the Ti-6Al-4V cruciform structure were investigated. • The formation of inhomogeneous microstructure and the tensile behaviour were elucidated. • Coarse columnar β grains, continuous grain boundary α phase, and coarser α-lath were formed in the Bonding Zone (BZ). • The fracture tends to occur at the BZ region and exhibits a mixed fracture mode with trans- and inter-granular fractures. [ABSTRACT FROM AUTHOR]