Electron Beam Melting Technology Research Articles

Research on Additive Manufacturing Technology in the Field of Mold Repair

With the rapid development of modern industry, mold as a basic hardware facility has become one of the important factors affecting the development of modern industry. The surface quality and working reliability of the mold have a direct impact on the quality of the part. Faced with a large number of failed molds in industrial production, fast and reliable mold repair technology can realize mold reuse under the premise of ensuring mold performance. It effectively shortens the construction period, saves costs and reduces mold waste. The article outlines the characteristics of wire and arc additive manufacturing technology, selective electron beam melting technology and laser cladding technology in additive manufacturing technology. The application characteristics of three additive manufacturing technologies in mold repair are analyzed. The application prospect of laser cladding technology in mold repair is pointed out. In view of the improved work reliability, the direction of laser cladding technology in the field of mold repair can be prospected.

Fatigue properties of titanium alloy custom short stems fabricated by electron beam melting

The fatigue properties of titanium alloy short-stems with four different lengths, manufactured by electron beam melting (EBM) technology, were investigated by in vitro test and finite element (FE) analysis. FE simulation results indicate that the maximum tensile stress concentrates at the lateral side of the stem body. The magnitude of the concentrated tensile stress increases and the corresponding area of the axial section decreases with increasing of stem length. Results from fatigue tests demonstrate that fatigue cracks mainly initiate from the rough surface of the stem where the maximum tensile stress concentrates. The fatigue strength decreases with the increase of stem length, which is attributed to the higher stress concentration on the longer stem surface. In addition, it is found that post EBM treatment via hot isostatic processing (HIP) is able to enhance the fatigue properties of the stems, since the pores generated during EBM are mostly closed during HIP. Our work also demonstrates that the stress concentration on the stem surface can be effectively mitigated and the corresponding fatigue properties of the EBM-fabricated titanium alloy short stem can be considerably improved by optimizing the design in the stem length.

Correlation between real geometry and tensile mechanical behaviour for Ti6Al4V electron beam melted thin specimens

The Electron Beam Melting (EBM) is an Additive Layer Manufacturing (ALM) technique used to directly manufacture 3D functional parts from metal powder, selectively melted, layer by layer, by an electron beam according to a geometry defined by a CAD model. The EBM technology allows benefitting from countless advantages: material waste reduction, easy manufacturing of complex shapes, lead time reduction, etc; on the other hand the EBM process is typically associated with lower resolutions and higher surface roughness (Ra = 25–30 μm) compared to similar laser based powder bed metal processes.Therefore the surface morphology may be a critical issue for the structural integrity of components made in EBM and used in-service in their “as built” condition, i.e. with the characteristic surface released by the process.This study evaluates surface morphology and tensile properties of Ti6Al4V specimens of varying nominal thickness (1–5.0 mm), made by using EBM process with a layer thickness of 50 μm. The aim is therefore to investigate how the surface morphology and the tensile properties are affected by the nominal thickness of the component.

Potentiality of hybrid structures in CFRP and additive manufactured metal octet-truss lattice

Lattice structures are very light and strong, but they need to be wrapped with skin to evenly distribute the loads over the entire surface of the structure. Considering additive manufacturing as a process to produce lattice structures, the easiest way to add the skin is its building together with the lattice core. However, if the core is made of metal, this solution leads to weight increase, since the skin should be made of the same material as the core. Therefore, in this work, the flexural behaviour of two kinds of structures, with titanium alloy skin or carbon fibre skin and a titanium alloy lattice core produced by Electron Beam Melting technology, was investigated. The experimental tests found that the structure with carbon fibre composite skins, even if it was not so performing as the other ones, had great potential due to its lightness.

Additive manufacturing of TiAl-based alloys

The ever-increasing demand for developing lightweight, high-temperature materials that can operate at elevated temperatures is still a subject of worldwide research and TiAl-based alloys have come to the fore. The conventional methods of manufacturing have been used successfully to manufacture the TiAl-based alloy. However, due to the inherent limitations of the conventional methods to produce large TiAl components with intricate near-net shapes has limit the widespread application and efficiency of the TiAl components produced using conventional methods. Metal additive manufacturing such as Electron Beam Melting technology could manufacture the TiAl alloys with intricate shapes but lack geometrical accuracy. Laser powder bed fusion (LPBF) technology could manufacture the TiAl-based alloys with intricate shapes with geometrical accuracy. However, the inherent high rate of heating and cooling mechanisms of the LPBF process failed to produce crack-free TiAl components. Various preheating techniques have been experimented, to reduce the high thermal gradient and residual stress during the LPBF process that causes the cracking of the TiAl components. Although these techniques have not reached industrial readiness up to now, encouraging results have been achieved.

Microstructure refinement for superior ductility of Al–Si alloy by electron beam melting

Refining the microstructure to improve the ductility of an Al‒Si alloy is challenging. In this paper, we report for the first time a novel microstructure refinement approach for AlSi10Mg (wt%) alloys using electron beam melting (EBM) technology, without the addition of any modification elements. The synergetic effect of superheating, fast cooling, and preheating contributes to a refined Si phase with a fine granular structure (0.5–2 μm) within bimodal Al grains (40 μm grains and 0.5–2 μm sub-grains). The results provide good evidence for the proposed refinement mechanism. A maximum ductility of approximately 32.7 % with a tensile strength of approximately 136 MPa was achieved for the as-built AlSi10Mg EBM alloy. After solution heat treatment and T6-like aging, nano-Si precipitates formed which strengthened the alloys. The pathway developed in this study for refining the Al–Si alloy microstructure to improve the tensile ductility will provide a feasible and fast manufacturing method for improving the microstructure and mechanical properties of other low-melting temperature alloys in the near future using EBM technology.

Reconstruction of Complex Zygomatic Bone Defects Using Mirroring Coupled with EBM Fabrication of Titanium Implant

Reconstruction of zygomatic complex defects is a surgical challenge, owing to the accurate restoration of structural symmetry as well as facial projection. Generally, there are many available techniques for zygomatic reconstruction, but they hardly achieve aesthetic and functional properties. To our knowledge, there is no such study on zygomatic titanium bone reconstruction, which involves the complete steps from patient computed tomography scan to the fabrication of titanium zygomatic implant and evaluation of implant accuracy. The objective of this study is to propose an integrated system methodology for the reconstruction of complex zygomatic bony defects using titanium comprising several steps, right from the patient scan to implant fabrication while maintaining proper aesthetic and facial symmetry. The integrated system methodology involves computer-assisted implant design based on the patient computed tomography data, the implant fitting accuracy using three-dimensional comparison techniques, finite element analysis to investigate the biomechanical behavior under loading conditions, and finally titanium fabrication of the zygomatic implant using state-of-the-art electron beam melting technology. The resulting titanium implant has a superior aesthetic appearance and preferable biocompatibility. The customized mirrored implant accurately fit on the defective area and restored the tumor region with inconsequential inconsistency. Moreover, the outcome from the two-dimensional analysis provided a good accuracy within 2 mm as established through physical prototyping. Thus, the designed implant produced faultless fitting, favorable symmetry, and satisfying aesthetics. The simulation results also demonstrated the load resistant ability of the implant with max stress within 1.76 MPa. Certainly, the mirrored and electron beam melted titanium implant can be considered as the practical alternative for a bone substitute of complex zygomatic reconstruction.

Modeling the Effect of Different Support Structures in Electron Beam Melting of Titanium Alloy Using Finite Element Models

Electron beam melting (EBM) technology is a novel additive manufacturing (AM) technique, which uses computer controlled electron beams to create fully dense three-dimensional objects from metal powder. It gives the ability to produce any complex parts directly from a computer aided design (CAD) model without tools and dies, and with variety of materials. However, it is reported that EBM has limitations in building overhang structures, due to the poor thermal conductivity for the sintered powder particles under overhang surfaces. In the current study, 2D thermo-mechanical finite element models (FEM) are developed to predict the stresses and deformation associated with fabrication of overhang structures by EBM for Ti-6Al-4V alloy. Different support structure geometries are modeled and evaluated. Finally, the numerical results are validated by experimental work.

Energy efficiency improvement in electron beam purification of silicon by using graphite lining

Electron beam melting technology can remove volatile impurities from silicon very effectively. However, the strong cooling capacity of water-cooled copper crucible brings high energy consumption, which confines the wide application of this technology. As far as energy utilization is concerned one can see in this paper, the refining process of silicon is improved based on numerical simulation and experimental results. The energy efficiency is increased through using a graphite lining between silicon and the bottom of water-cooled copper crucible. The results show the addition of graphite lining is resulting in increased thermal resistance and the heat loss is reduced. Compared with traditional electron beam melting technology, the temperature of the melt pool is increased at the same power accelerating purification process. The experiment results show that refining cycle time for same amount of material can be reduced while keeping same purification efficiency. As a consequence, the energy consumption is reduced by 33%.

Modeling three-dimensional-printed trabecular metal structures with a homogenization approach: Application to hemipelvis reconstruction.

The application of three-dimensional printing technologies to metal materials allows us to design innovative, low-weight, patient-specific implants for orthopedic prosthesis. This is particularly true when the reconstruction of extensive metastatic bone defect is planned. Modeling complex three-dimensional-printed highly repetitive trabecular-like structures based on finite elements is computationally demanding, while homogenization algorithms offer the advantage of reduced simulation cost and time, allowing an effective evaluation of new personalized design suitable for clinical needs. This article describes and discusses the implementation of a reliable method for the multiscale modeling of trabecular structures by means of asymptotic expansion homogenization. Following the material characterization of the Ti6Al4V alloy obtained by electron beam melting technology, the asymptotic expansion homogenization was applied to two alternative low-density cell-unit designs. Model predictions demonstrated satisfactory agreement with compressive experimental tests and cantilever bending tests performed on both designs (differences lower than 5.5%). The method was extended to a real patient-specific hemipelvis reconstruction, exploiting the capability of the asymptotic expansion homogenization approach in quantitatively describing the effect of cell-unit designs and three-dimensional-printing stack direction (i.e. cell-unit orientation) both on the overall mechanical response of the implant and on the stress distribution. The hemipelvis implant filled with the higher density cell unit demonstrated to be 14% stiffer than using the lower density one, while changing the cell-unit orientation affected the stiffness up to 10%. The maximum stress values reached at the anchors were affected in a minor extent by the investigated design parameters.

Highly Porous Titanium Cups versus Hydroxyapatite-Coated Sockets: Midterm Results in Metachronous Bilateral Total Hip Arthroplasty

Objective: Highly porous titanium cups have been recently introduced, with contradictory outcomes. A retrospective consecutive case series involving bilateral metachronous total hip arthroplasties (THA) performed with 2 different cups, i.e., Fixa (F) and Fixa Ti-Por (T) (Adler Ortho, Milan, Italy), and the same stem, was evaluated. T sockets, manufactured using electron beam melting, were supposed to prove superior in terms of clinical results, survival rates, and radiographic parameters in comparison to hydroxyapatite-coated F cups with conventional porosity. Subjects and Methods: Twenty-four bilateral metachronous THAs with an F cup on one side and a T socket on the other side were evaluated. Preoperative and postoperative Harris hip scores (HHS) were collected for every patient. Radiographic signs of loosening were assessed. The radiographic signs of osseointegration (radiolucent lines, superolateral buttress, inferomedial buttress, radial trabeculae, and stress shielding) were evaluated. Results: No intraoperative complications occurred. The mean HHS score was excellent and comparable in both groups. At the mean follow-up of 134 months (F) and 79 months (T), no cup or liner revisions were performed. No radiographic signs of loosening were reported. All of the patients revealed 3 parameters of good bony ingrowth at least. Both groups showed similar radiographic parameters regarding osseointegration, which were stable over the time. Stress shielding was more evident in the T cohort (p =0.07). Conclusion: Highly porous titanium cups produced using an additive manufacturing and electron beam melting technology achieved reliable midterm clinical and radiographic results not inferior to those of second-generation cups.

Adhesion, proliferation, and osteogenic differentiation of human mesenchymal stem cells on additively manufactured Ti6Al4V alloy scaffolds modified with calcium phosphate nanoparticles.

In the present study, biocomposites based on 3D porous additively manufactured Ti6Al4V (Ti64) scaffolds modified with biocompatible calcium phosphate nanoparticles (CaPNPs) were investigated. Ti64 scaffolds were manufactured via electron beam melting technology using an Arcam machine. Electrophoretic deposition was used to modify the scaffolds with CaPNPs, which were synthesized by precipitation in the presence of polyethyleneimine (PEI). Dynamic light scattering revealed that the CaP/PEI nanoparticles had an average size of 46 ± 18 nm and a zeta potential of +22 ± 9 mV. Scanning electron microscopy (SEM) revealed that the obtained spherical CaPNPs had an average diameter of approximately 90 nm. The titanium-based scaffolds coated with CaPNPs exhibited improved hydrophilic surface properties, with a water contact angle below 5°. Cultivation of human mesenchymal stem cells (hMSCs) on the CaPNPs-coated Ti64 scaffolds indicated that the improved hydrophilicity was beneficial for the attachment and growth of cells in vitro. The Ti6Al4V/CaPNPs scaffold supported an increase in the alkaline phosphatase (ALP) activity of cells. In addition to the favourable cell proliferation and differentiation, Ti6Al4V/CaPNPs scaffolds displayed increased mineralization compared to non-coated Ti6Al4V scaffolds. Thus, the developed composite 3D scaffolds of Ti6Al4V functionalized with CaPNPs are promising materials for different applications related to bone repair.

Novel 3D Printed Modular Hemipelvic Prosthesis for Successful Hemipelvic Arthroplasty: A Case Study

In this study, in order to prevent the failure of hemipelvic arthroplasty using a patient-specific Computer-Aided Design (CAD) and Additive Manufacturing (AM) approach, a new design for modular hemipelvic prosthesis was developed. Moreover, the biomechanical properties of the new design were determined. The 3D printed pelvic prosthesis with a sacrum portion that completely matches the back surface of the patient’s sacrum offers more potential for bone ingrowth between the host bone and prosthesis. The new approach integrated the capabilities of digital medical imaging techniques, CAD and metal AM to realize a modular hemipelvic prosthesis. The patient’s pelvic Digital Imaging and Communication in Medicine (DICOM) data were imported into Mimics software to construct a digital representative patient model for design of the prosthesis. A physical model was obtained using a Stereolithography (SLA) 3D printer for preoperative planning. The final customized implant was designed by using UG NX 10.0 software. Then a surgically modular hemipelvic prosthesis was fabricated from the Ti6Al4V titanium alloy by electron beam melting technology. The operation was performed according to the preoperative planning. The outcome of the operation was good at the 6-month follow-up. Also, the stress distribution and the relative micromotion revealed positive results based on a finite element model built to detect prosthesis stability. The 3D printed modular hemipelvic prosthesis provided good resolution for the failure of hemipelvic arthroplasty. Personal customization will be important in future surgeries aiming at improving the anatomy and function of the implant.

Fracture behaviour of notched as-built EBM parts: Characterization and interplay between defects and notch strengthening behaviour

Additive manufacturing (AM) offers the potential to economically produce customized components with complex geometries. However, the introduction of complex geometry goes hand in hand with the presence of notches. Thus, the basic understanding of the tensile behaviour of AM fabricated notched components must be substantially improved so that the unique features of this rapidly developing technology can be utilized in critical load bearing applications. This work aims to assess the tensile behaviour of different notched specimens manufactured by means of the Electron Beam Melting (EBM) technology and tested in their as-built conditions in order to reveal the interplay between notch geometry and AM specific processing. Scanning Electron Microscopy (SEM) was used to investigate the fracture surface of the broken samples, revealing the presence of process-induced defects, harmfully affecting tensile strength with a reduction of 10% and elongation to failure with 40% with respect to values reported in literature for heat treated AM parts, respectively. Interestingly, the authors have discovered an increase in the tensile strength with the severity of the stress concentrators, quite contrary to what is commonly observed for wrought Ti-6Al-4V. This notch strengthening behaviour particular to AM specimens is related to the influence of defects on the failure driving force. The authors provide a qualitative explanation for this phenomenon using 3D FE analyses together with a theoretical description via the ellipse criterion.

Effect of overlap distance on the microstructure and mechanical properties of in situ welded parts built by electron beam melting process

Electron Beam Melting (EBM), one of the powder bed-based additive manufacturing processes that is able to produce complex geometrical metal parts directly, has many application possibilities in various fields. However, an issue has been raised when we apply the EBM technology to fabricate medium volume components. Lack of energy when the scanning line is longer than 100 mm results in the lack-of-fusion pores, which degrades the mechanical properties of the printed part dramatically. Therefore, we propose an in situ welding process to overcome the issue. In order to further understand the microstructure and mechanical properties resulting from the in situ welded process with various overlap distances, we evaluate a series of overlap distances and successfully fabricate a big plate with dimensions of 200 × 200 × 4 mm3. It is suggested that the defects and microstructure vary according to the overlap distance. Optimized overlap distances are 0.25–0.75 mm for Ti-6Al-4V. Within this range, no microstructural variation is observed which results in constant microhardness and superior mechanical properties of the EBM-built component. An overlap distance ≥1.5 mm results in microstructure coarsening and mechanical property degradation in the overlap zone. Furthermore, the localized deformation mechanism is discussed based on the findings of the tensile properties and digital image correlation analysis.

Investigation on Electron Beam Melting: Dimensional accuracy and process repeatability

Electron Beam Melting (EBM) is one of a few Additive Manufacturing (AM) technologies capable of making full-density functional metallic parts. In particular, the ability of direct fabrications of metallic parts can accelerate product designs and developments in a wide range of metallic-part applications, especially for complex components, e.g., fine network structures, internal cavities and channels, which are difficult to make by conventional manufacturing means. In the field of aerospace industry it is crucial for quality certification purpose that components are produced through qualified and robust manufacturing processes ensuring high product repeatability. The work presented describes the results of an experimental study on the variability in the dimensional accuracy of rectangular parallelepiped samples manufactured in Ti6Al4V by EBM technology. The dimensional accuracy of obtained samples was put into relationship with EBM process parameters, such as orientation, location and height of the sample in the build chamber.

Discrepancy of complete-arch titanium frameworks manufactured using selective laser melting and electron beam melting additive manufacturing technologies

Statement of problemTitanium frameworks for implant-supported prostheses can be additively manufactured using different powder-based fusion technologies, including selective laser melting (SLM) and electron beam melting (EBM). Some manufacturers have developed a technique that combines the printing of the framework with the subsequent machining of the implant interface. Whether these technologies produce frameworks with acceptable accuracies is unclear. PurposeThe purpose of this in vitro study was to evaluate the discrepancy obtained from the digitizing procedures of the definitive cast, the implant-prosthesis discrepancy, and the distortion of the manufacturing processes in the fabrication of titanium frameworks for implant-supported complete-arch prostheses manufactured using SLM and EBM additive manufacturing technologies. Material and methodsA completely edentulous mandibular definitive cast with 4 implant analogs and a replica of a screw-retained interim restoration was obtained. A standard tessellation language (STL) file of the framework design was prepared using dental software (Exocad). Six frameworks were manufactured using either SLM (3D Systems) or EBM (Arcam) technologies. Discrepancy (μm) was measured at the x- (mesiodistal), y- (buccolingual), and z- (occlusogingival) axes by using the formula 3D=x2+y2+z2 three times by best-fit superimposure of the definitive cast STL file, the definitive cast titanium framework, and the framework STL file by using a coordinate measuring machine (CMM) controlled by software (Geomagic). The Kruskal-Wallis and Mann–Whitney U statistical tests were used (α=.05). ResultsThe digitizing procedures of the definitive cast showed a mean accuracy of 3 ±3 μm. Except for the z-axis (P<.05), no significant differences were observed between the SLM and EBM technologies for implant prosthesis discrepancy for the x- or y-axis (P>.05). The most favorable results were obtained in the z-axis, representing the occlusogingival direction. Three-dimensional discrepancy measurements in all comparisons ranged between (60 ±18 μm and 69 ±30 μm) and were not statistically significant (P>.05). The highest discrepancy was observed in the y-axis (37 to 56 μm), followed by the x- (16 to 44 μm) and z- (6 to 11 μm) axes (P<.05). ConclusionsThe titanium frameworks analyzed for a complete-arch implant-supported prosthesis fabricated using either the SLM or EBM additive technologies showed a clinically acceptable implant-prosthesis discrepancy, where similar discrepancies on the x-, y-, and z-axes were found between the additive manufacturing technologies. Both technologies showed comparable abilities to manufacture the STL file additively on the x-, y-, and z-axes.

A new 3D printed titanium metal trabecular bone reconstruction system for early osteonecrosis of the femoral head.

Presently, biomechanical support therapy for the femoral head has become an important approach in the treatment of early osteonecrosis of the femoral head (ONFH). Previous studies have reported that the titanium metal trabecular bone reconstruction systems (TMTBRS) achieved satisfactory clinical results for the treatment of early femoral head necrosis. Electron beam melting technology (EBMT) is an important branch of 3D printing technology, which enables the construction of an interface that is required for support of bone in-growth. However, the effect of TMTBRS created using EBMT for clinical applications for early ONFH is still unknown. At present, there are no reports on this topic worldwide. The purpose of this study was to assess the safety of a new 3D printed TMTBRS implant and to evaluate its clinical efficacy in early ONFH.Thirty patients who underwent surgery for ONFH were selected. The stages of ONFH were classified according to the Association Research Circulation Osseus (ARCO) classification. They were followed-up and radiological examination was performed at 6, 12, and 24 months post-surgery to assess TMTBRS stability and bone growth in the bone trabecular holder portion surface. To evaluate hip function, postoperative Harris and Visual Analogue Scale (VAS) scores were used.The postoperative Harris score increased significantly and VAS score decreased significantly at the 12-month follow-up compared to the 24-month follow-up, wherein the Harris score declined slightly and the VAS score was slightly elevated with the aggravation of ONFH. With the passage of time, postoperative improvement rates were 100% for IIA, 70% for IIB, and 0% for IIC. Hip-preserving rates were 100% for IIA, 100% for IIB, and 50% for IIC.The effect of TMTBRS treatment for early ONFH in ARCO IIA and ARCO IIB is satisfactory. However, it is not recommended for a relatively large area of necrosis such as in ARCO IIC.

Possibilities of Electron Beam Melting Technology: Titanium Processing

Nowadays, 3D printing of metallic materials is a hot topic in many industrial spheres as it provides a one-step production of very complex parts. The additive principle based on processing of powders or wires in many successive layers minimizes material losses and so production costs. It also ensures great control over built shapes exactly according to computer-designed models. The most available technology is Selective Laser Melting (SLM) that uses a laser beam to selectively melt a metallic powder into the form of a desired product. The Electron Beam Melting (EBM) technology, that is based on a similar principle, is not so widespread, especially in the Czech Republic. Instead of a laser beam, it uses an electron beam. Related to that, EBM is far more energy-efficient and has different process characteristics. In this contribution, on the example of titanium alloy, we show marginal possibilities of this technology in the processing of bulk materials, from porous to highly dense.

Realizing a full volume component by in-situ welding during electron beam melting process

As one of the powder-bed-fusion additive manufacturing processes, electron beam melting (EBM) is able to produce metal parts directly. Many small volume components with high quality have been fabricated using the EBM technology. However, there are only few reports on the EBM fabrication of medium-sized components. One of the reasons is the lack of energy issue when the scan length is too long, which results in the generation of lack of fusion pores. This, in turn, drastically degrades the mechanical properties of the EBM printed parts. Here, we firstly report an in-situ welding process to overcome the lack of energy issue caused by the long scan length during EBM process. After the investigation of the corresponding microstructure, microhardness and tensile properties, it is revealed that the in-situ welding zone is fully joined and the mechanical properties of the in-situ welded part are comparable to that of the wrought counterpart. This implies that medium-sized components can be successfully fabricated using the EBM, with no compromise on the mechanical properties.