Electron Beam Melting Technology Research Articles

The performance tests of three-dimensional printing titanium alloy craniomaxillofacial bone plate: A preliminary preclinical study

Background/purposeBecause of the complex anatomical structure of the maxillofacial skeleton, bending plates is necessary during surgery. The fast developing three-dimensional printing (3DP) technology has provided a new method for making personalized craniomaxillofacial bone plates. However, the properties of these bone plates remain unknown. This study evaluates the mechanical, fatigue, and morphological properties of these bone plates, which may provide data supporting future clinical applications. Materials and methodsThe 3DP bone plate was fabricated by selective laser melting (SLM) and electron beam melting (EBM) technologies. Mechanical, surface, and defect analyses were performed to compare their properties with a standard machined sample. One-way analysis of variance was applied, with p < 0.05 considered significant. ResultsThe 3DP craniomaxillofacial bone plate had better bending strength than that of the standard machined plate (p < 0.01). Whereas the fatigue resistance of the 3DP bone plate needs to be improved in the future. Surface analysis indicated greater roughness of the 3DP bone plate (p < 0.01). However, the surface roughness could be significantly reduced by polishing the surface, which would meet the needs of clinical application after polishing. Further defect analysis revealed the internal defect inside the plate, which should be avoided to improve the mechanical strength of the printed sample in the future. ConclusionThe 3DP titanium craniomaxillofacial bone plate has good mechanical performance and surface morphology, meeting the requirements of clinical application. However, poorer fatigue resistance and a high number of internal defects should be modified in the future.

Electrochemical deposition of ceramic-like coatings on Ti-6Al-4V parts fabricated by electron beam melting

The problems of micro-arc oxidation of titanium alloy parts Ti-6Al-4V produced by electron beam melting technology were considered. The phase composition, thickness and roughnessof the obtained coating have been evaluated.

Sustained Release of VEGF to Promote Angiogenesis and Osteointegration of Three-Dimensional Printed Biomimetic Titanium Alloy Implants.

Tumor resection and treatment of trauma-related regional large bone defects have major challenges in the field of orthopedics. Scaffolds that treat bone defects are the focus of bone tissue engineering. 3D printing porous titanium alloy scaffolds, prepared via electron beam melting technology, possess customized structure and strength. The addition of a growth factor coating to the scaffold introduces a specific form of biological activation. Vascular endothelial growth factor (VEGF) is key to angiogenesis and osteogenesis in vivo. We designed a porous titanium alloy scaffold/thermosensitive collagen hydrogel system, equipped with VEGF, to promote local osseointegration and angiogenesis. We also verified the VEGF release via thermosensitive collagen and proliferation and induction of the human umbilical vein endothelial cells (HUVECs) via the composite system in vitro. In vivo, using microscopic computed tomography (Micro-CT), histology, and immunohistochemistry analysis, we confirmed that the composite scaffold aids in angiogenesis-mediated bone regeneration, and promotes significantly more bone integration. We also discovered that the composite scaffold has excellent biocompatibility, provides bioactive VEGF for angiogenesis and osteointegration, and provides an important theoretical basis for the restoration of local blood supply and strengthening of bone integration.

Surface functionalization of selective electron beam melting pure tantalum by micro-arc oxidation

Selective electron beam melting (SEBM) technology provides great flexibility for tantalum (Ta) application in the next generation of personalized biomedicine. This article aims to prepare bone-like apatite coatings on the SEBM pure Ta surfaces by Micro-arc oxidation (MAO) and systematically investigate the detailed morphologies, coating thickness and corrosion resistance of as-built samples and MAO coatings. Results show that the hierarchical structures of Ta oxide coatings with thickness of 3–5 μm are successively prepared by MAO with constant current mode on the surfaces of SEBM pure Ta. Bioactive Ca, P-contained amorphous coatings are uniformly dispersed in the hierarchical porous structure and are tightly connected with substrate. The passive current of SEBM pure Ta is decreased significantly by two orders of magnitude after MAO treatment in 3.5 wt% NaCl solution. The MAO coatings can provide positive protective effects for SEBM pure Ta and exhibit great potential for active and further promote biomedical application of SEBM pure Ta.

Additive Manufacturing of Ti-Based Intermetallic Alloys: A Review and Conceptualization of a Next-Generation Machine.

TiAl-based intermetallic alloys have come to the fore as the preferred alloys for high-temperature applications. Conventional methods (casting, forging, sheet forming, extrusion, etc.) have been applied to produce TiAl intermetallic alloys. However, the inherent limitations of conventional methods do not permit the production of the TiAl alloys with intricate geometries. Additive manufacturing technologies such as electron beam melting (EBM) and laser powder bed fusion (LPBF), were used to produce TiAl alloys with complex geometries. EBM technology can produce crack-free TiAl components but lacks geometrical accuracy. LPBF technology has great geometrical precision that could be used to produce TiAl alloys with tailored complex geometries, but cannot produce crack-free TiAl components. To satisfy the current industrial requirement of producing crack-free TiAl alloys with tailored geometries, the paper proposes a new heating model for the LPBF manufacturing process. The model could maintain even temperature between the solidified and subsequent layers, reducing temperature gradients (residual stress), which could eliminate crack formation. The new conceptualized model also opens a window for in situ heat treatment of the built samples to obtain the desired TiAl (γ-phase) and Ti3Al (α2-phase) intermetallic phases for high-temperature operations. In situ heat treatment would also improve the homogeneity of the microstructure of LPBF manufactured samples.

Three-dimensionally printed porous biomimetic composite for sustained release of recombinant human bone morphogenetic protein 9 to promote osteointegration

Three-dimensionally printed porous titanium alloys prepared using the electron beam melting (EBM) technology have customized structures and a low elastic modulus. They can promote the repair of bone defects. Growth factors can enhance the biological activity of plants in vivo, and bone morphogenetic protein 9 (BMP9) is the key factor for osteogenesis. The purpose of this study was to evaluate a porous titanium implant prepared using the EBM technology with temperature-sensitive collagen mixed with recombinant human (rh) BMP9 as a composite scaffold to be continuously provided to enhance osteogenesis in rabbit femoral defects. The in vitro experiments verified cell proliferation, proliferation and application of the composite stent, the degree of release of temperature-sensitive collagen to rhBMP9, and the osteogenesis-inducing effect of the composite stent on bone marrow mesenchymal stem cells. In vivo, the rabbit femoral defect model was used to evaluate the effects of the composite on osteointegration and bone ingrowth. The results showed that the composite scaffold had good biocompatibility and provided bioactive growth factors for bone repair. Further, the release of rhBMP9 significantly enhanced osteogenesis in and around the porous scaffolds. This method helps to study bioactive coating on the titanium alloy surface of patients with bone defects.

Electron Beam Melting of Thermally Sprayed Layers – Overview

Thermal spraying is one of the most common methods enabling the deposition of variously-purposed layers on surfaces of structural elements. However, in certain cases, the process of spraying itself is ineffective in terms of the stability and properties of protective layers. One of the possible solutions making it possible to reduce the porosity and improve the adhesion of surfaced layers involves their melting using the concentrated electron beam. The article contains an overview of reference publications concerning electron beam melting technologies.

Gas discharge combustion with a liquid tetrachloride electrode

Titanium powders are widely used in selective laser melting and electron beam melting technologies to create medical implants. However, powders of a certain fractional composition are suitable for these purposes. A gradual increase in the volume of manufactured products requires the creation of new cheap methods for obtaining metal powders. Plasma-chemical synthesis in titanium tetrachloride solution can be one of the new methods for producing powders. A feature of this method is the use of a gas discharge with liquid electrodes, as a liquid electrode and is a titanium tetrachloride solution. The aim of the work was to study the possibility of obtaining a metal powder and its rapid cooling in a liquid. The question of the influence of the discharge parameters on the formation of metal particles remains open. In this work, a study of a gas discharge with liquid electrodes under the conditions of anode and cathode modes is carried out. A gas discharge between a liquid electrolyte and a metal electrode is experimentally investigated in the voltage range of 300-1000V. The conditions under which a stable discharge column is formed and a metal powder is formed are established. The regularities of the change in the I–V characteristic of the discharge are determined depending on the interelectrode distance.

Spatial and Direction-Based Characterization of Microstructures and Microhardness of TA15 Titanium Alloy Produced by Electron Beam Melting

The extracted position and characterization direction of specimens have an unignorable effect on the microstructural characteristics of materials produced by electron beam melting (EBM). This study focused on the effects of extracted position and characterization direction on the microstructure, defect distribution and Vickers hardness of TA15 titanium alloy fabricated by electron beam melting. Results show that the microstructure at the bottom end of TA15 specimens is coarser and hot cracks are visible at this end. Grain morphology in longitudinal direction is columnar while that in transversal direction is chessboard-like. The results of defect analysis show that gas pores are visible in transversal direction while lack of fusion exists in longitudinal direction. The average relative density of TA15 specimens in transversal direction is higher than that in longitudinal direction. The results of energy spectrum analysis show that there is evaporation of Al during the forming process, but no elements segregation and enrichment are observed. This study provides important insights on the microstructure analysis and defect evaluation of materials made by EBM technology.

Biocompatibility and Osseointegration of Calcium Phosphate-Coated and Non-Coated Titanium Implants with Various Porosities.

The aim of the investigation was to study the influence of pore size and the presence of a biologically active calcium phosphate coating in porous 3D printed titanium implants on the process of integration with the bone tissue.Materials and MethodsSamples of cylindrical implants with three different pore diameters (100, 200, and 400 μm) were fabricated from titanium powder on the Arcam 3D printer (Sweden) using electron beam melting technology. A calcium phosphate coating with a thickness of 20±4 μm was applied to some of the products by microarc oxidation. Cytotoxicity of the implants was determined in vitro on human dermal fibroblast cultures. The samples were implanted in the femoral bones of 36 rabbits in vivo. The animals were divided into 6 groups according to the bone implant samples. The prepared samples and peri-implant tissues were studied on days 90 and 180 after implantation using scanning electron microscopy and histological methods.ResultsAll samples under study were found to be non-toxic and well biocompatible with the bone tissue. There were revealed no differences between coated and non-coated implants of 100 and 200 μm pore diameters in terms of their histological structure, intensity of vascularization in the early stages, and bone formation in the later stages. Samples with pore diameters of 100 and 200 μm were easily removed from the bone tissue, the depth of bone growth into the pores of the implant was lower than in the samples with pore diameter of 400 μm (p<0.001). There were differences between coated and non-coated samples of 400 μm pore diameter, which was expressed in a more intensive osseointegration of samples with calcium phosphate coating (p<0.05).ConclusionThe optimal surface characteristics of the material for repairing bone defects are a pore diameter of 400 μm and the presence of a calcium phosphate coating.

Effects of the Surface Finish on Thin Specimens Made by Electron Beam Melting Technology

AbstractAdditive layer manufacturing (ALM) is increasingly attracting the research and industry community interest due to the several benefits provided by the layer‐by‐layer production approach. With respect to the surface finish, process parameters influence significantly the surface roughness. According to the State of the Art, it is found out that the roughness level may affect the structural performance of ALM products by both quasi‐static and fatigue points of view. In this paper, an experimental investigation is proposed, showing that the roughness level plays a more influent role for thin components, with respect to the quasi‐static response. The investigated ALM process concerns the electron beam melting technology.

Topological, Mechanical and Biological Properties of Ti6Al4V Scaffolds for Bone Tissue Regeneration Fabricated with Reused Powders via Electron Beam Melting.

Cellularized scaffold is emerging as the preferred solution for tissue regeneration and restoration of damaged functionalities. However, the high cost of preclinical studies creates a gap between investigation and the device market for the biomedical industry. In this work, bone-tailored scaffolds based on the Ti6Al4V alloy manufactured by electron beam melting (EBM) technology with reused powder were investigated, aiming to overcome issues connected to the high cost of preclinical studies. Two different elementary unit cell scaffold geometries, namely diamond (DO) and rhombic dodecahedron (RD), were adopted, while surface functionalization was performed by coating scaffolds with single layers of polycaprolactone (PCL) or with mixture of polycaprolactone and 20 wt.% hydroxyapatite (PCL/HA). The mechanical and biological performances of the produced scaffolds were investigated, and the results were compared to software simulation and experimental evidence available in literature. Good mechanical properties and a favorable environment for cell growth were obtained for all combinations of scaffold geometry and surface functionalization. In conclusion, powder recycling provides a viable practice for the biomedical industry to strongly reduce preclinical costs without altering biomechanical performance.

Are powder-technology-built stems safe? A midterm follow-up registry study

BackgroundPowder technology was developed to bring together the mechanical features and high porosity of titanium. However, the high porosity may theoretically compromise mechanical resistance. Literature is deficient about the use and safety profile of cementless femoral implants built using additive manufacturing (in particular electron beam melting technology, EBM). The purpose of this study was to evaluate the survival rates and the reason for revisions (especially implant breakage) of the first two EBM-built stems at a mid-term follow-up, using a joint arthroplasty registry.MethodsThe registry of Prosthetic Orthopedic Implant (RIPO) was investigated about cementless stems implanted from 2010 to 2017. Stems built with EBM technology (Parva and Pulchra stems; Adler Ortho, Milan, Italy) were compared to all the other cementless stems implanted during the same period, acting as control group. The survival rates and reasons for revision were assessed.ResultsNo stem breakage occurred. At 5-year follow-up, the survival rates of the two cohorts were not statistically different (96.8% EBM stems, 98.0% standard cementless stems; p > 0.05). In the EBM stems, aseptic loosening occurred in 1.7% of the cases at the latest follow-up.ConclusionsThis large cohort showed that mechanical resistance is not a concern in EBM stems at mid-term follow-up. However, larger populations and longer follow-ups are needed to further validate these results.

Investigation of support structure parameters and their affects during additive manufacturing of Ti6Al4V alloy via electron beam melting

Electron beam melting technology offers various benefits like the reduced product cycle time, customization, flexibility, high energy density and less material wastage. However, electron beam melting still suffers from redundant usage of support structure material while fabricating overhang structures. The support structures not only consume additional material, but also require additional time for their design and removal. The optimized support structures have to be designed in such a way that they consume minimum material, are easy to remove and are free from defects. The aim of the current study is to study the effect of support design and process parameters on the performance of the support structures (cost and quality) during additive manufacturing of Ti6Al4V alloy via electron beam melting. The results show that the support structures parameters play a significant role in the cost of the applied support and the accuracy of the fabricated object. It was found that with appropriate selection of support design and process parameters, it is possible to reduce the support volume and hence the fabrication cost in metal additive manufacturing (AM). A tooth height of 3 mm, no support offset of 2 mm, and fragmentation separation width of 0.8 mm resulted in lower support volumes without having any effect on the quality of the overhang. This study systematically investigated the support structure design and their outcomes on overhang fabrication. Its conclusions could add value to the researchers working on additive manufacturing of Ti6Al4V alloy by electron beam melting.

A Design for Additive Manufacturing approach based on process energy efficiency: Electron beam melted components

Abstract In the present paper a Design for Additive Manufacturing approach is proposed, with the aim to outline a generalized method and define an energy consumption model that allow, during the development of component design, to evaluate the effects of the different solutions on the energy efficiency of the additive process that will build the component. For this purpose the concept of building energy is introduced, that is the real energy of the heat source during the phases of the building process, and can be directly correlated to key properties of the component (material, geometry and shape, volumetric distribution). For the detailed formulation of the energy consumption model, the Electron Beam Melting technology has been considered. Two parameters are identified to effectively characterize each design solution, combining the geometric and volumetric properties of components in the most significant way, and taking into account also the efficiency in build volume packing. The application of the model to the fabrication of components characterized by different shape classes is detailed, highlighting how a different spatial distribution of the same volume affects the building energy. The outcomes in terms of energy consumption, due to alternative design choices, can be assessed and simulated. The analysis of critical points in the design solutions presents an heuristic potential, as it can guide the designer in effective improvement interventions. The accuracy in the evaluation of the process energy consumption due to the proposed approach, also suggest limiting the use of simplifications, that may not be fully suitable to correlate energy efficiency and component properties in a Design for Additive Manufacturing perspective.

Experimental Investigation on the Mechanical Properties of Thin Beams Built by Electron Beam Melting Technology and Ti6Al4V Material

Electron beam melting (EBM) technology has been popularly used to fabricate flexible devices that performance is directly determined by the elastic deformation of thin beams/flexures. This paper presents the experimental investigation on the effective thickness which determines the mechanical properties of beam-based flexures built by EBM method and Ti6Al4V material. The findings show that the effective thickness of EBM-printed beams is different from the designed value regarding to the building direction. A coefficient factor is proposed to compensate this difference. The experimental results suggest that with EBM-printed flexures having large thickness of ≥ 0.7 mm, the coefficient factors become consistent.

Microstructure and Mechanical Properties of Ti-6Al-4V Fabricated by Electron Beam Melting

Electron beam melting technique is a kind of near-net shaping, environmentally friendly metal additive manufacturing technique, which can form high-performance metal parts with complex shapes. It has been widely applied in the aerospace industry, biomedical application, automobile manufacturing, and other fields. Ti-6Al-4V is the most widely researched and applied alloy in the additive manufacturing field, but its microstructure is diverse, and its mechanical properties vary greatly. In this study, the effect of process parameters on the microstructure and the resulting mechanical properties of Ti-6Al-4V alloy was researched. The results show that the yield strength of Ti-6Al-4V alloy with a bimodal microstructure is higher than those with a basketweave microstructure. Energy dispersion spectrum (EDS) line scan and area scan results show that there is no element enrichment for the specimens with the highest yield strength. A speed factor of less than 40 is a must for obtaining relatively dense Ti-6Al-4V parts built with electron beam melting. We have done basic research for the subsequent manufacturing of complex shape parts, which is helpful to promote the application of electron beam melting technology in the aerospace field.

Effect of Pore Size on the Physicochemical Properties and Osteogenesis of Ti6Al4V Porous Scaffolds with Bionic Structure.

Ti6Al4V is widely used in implants in the fields of orthopedics and dentistry due to its high compressive strength and good biocompatibility. Nevertheless, Ti6Al4V has a certain degree of biological inertness and the elastic modulus of Ti6Al4V is much higher than the cortex and trabecular bone. In this study, we designed and printed a new type of pore size Ti6Al4V with like-trabecular structure scaffold (the pore size is 800/900/1000 μm, named P8/P9/P10, respectively) with electron beam melting (EBM). Its elastic modulus, compressive strength, and other physical and chemical properties, as well as cell adhesion, proliferation, and differentiation ability and in vitro biological properties were studied. The physical and chemical performance test results showed that as the pore size increased, the surface wettability increased and the elastic modulus decreased. As the pore size increased, F-actin and alkaline phosphatase (ALP) increased significantly, and osteogenesis-related genes including BMP2, OCN, RUNX2, and ALP were upregulated significantly. The reason may be that the components on the Ti6Al4V pore size may have an influence on intracellular signal conversion and then change the mode of cell proliferation and diffusion. In summary, the like-trabecular porous structure can effectively reduce the elastic modulus of metal materials, thereby avoiding stress concentration and promoting the adhesion and proliferation of osteoblasts. Porous materials with larger pores are more conducive to the proliferation and differentiation of osteoblasts. The irregular porous Ti6Al4V scaffold prepared by the EBM technology has good mechanical properties and the potential to promote adhesion, proliferation, and differentiation of osteoblasts, and has the possibility of application in the field of implantation.

Thermal characterization of the build chamber in electron beam melting

Abstract Electron beam powder bed fusion, commonly termed electron beam melting (EBM), offers great versatility in multiple-part processes and can produce high quality as-built components due to low residual stresses. The EBM process is complex and requires careful thermal management, including uniform and consistent preheating of the powder bed, in order to ensure quality and consistency of the product. However, most of the simulations in the literature focus on the selective melting stage of the process. As of today, optimal conditions for initial pre-heating temperatures are only available for specific materials. Thus, in order to extend the EBM technology to other desired build materials, a much better understanding of the pre-heating stages is required. In this study, numerical and experimental approaches are combined in order to investigate the effects and sensitivities of heat removal from the build plate during EBM pre-heating stages. For this purpose, a carefully reconstructed numerical model of the build chamber of an ARCAM Q20+ machine is developed. It includes all main parts of the chamber and all relevant heat transfer mechanisms, whereas special attention is paid to radiation heat exchange between various bodies. In order to validate the model, dedicated experiments are performed, in which a system of thermocouples is installed in the build chamber, allowing direct measurement of the local temperatures of the start-plate and heat shields. A good agreement between the simulation and experimental findings is achieved, leading to a better understanding of the thermal processes characteristic to the pre-heating stages. This basic analysis is followed by a representative pre-heating case, where a powder bed is also considered. The energy required to obtain the desired pre-heating temperatures is evaluated, and the role of the powder bed in heat transfer within the chamber is assessed. The pre-heating stage, simulated in the present work, is supposed to create proper conditions for sintering and consequent melting of the powder, which are highly dependent on the local temperatures and heat transfer features. Thus, the findings of the reported work present a step towards a better understanding of the thermal processes that characterize EBM. The reported model can be further used to provide realistic boundary condition inputs for other meso- or macro-scale models as a function of time and geometry. The model can serve also for verification of machine settings, i.e., jump-safe and melt-safe ones which actually provide desired preheat, and for development of settings for new powders.

The Impact of EBM-Manufactured Ti6Al4V ELI Alloy Surface Modifications on Cytotoxicity toward Eukaryotic Cells and Microbial Biofilm Formation.

Electron beam melting (EBM) is an additive manufacturing technique, which allows forming customized implants that perfectly fit the loss of the anatomical structure of bone. Implantation efficiency depends not only on the implant’s functional or mechanical properties but also on its surface properties, which are of great importance with regard to such biological processes as bone regeneration or microbial contamination. This work presents the impact of surface modifications (mechanical polishing, sandblasting, and acid-polishing) of EBM-produced Ti6Al4V ELI implants on essential biological parameters. These include wettability, cytotoxicity toward fibroblast and osteoblast cell line, and ability to form biofilm by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Obtained results indicated that all prepared surfaces exhibited hydrophilic character and the highest changes of wettability were obtained by chemical modification. All implants displayed no cytotoxicity against osteoblast and fibroblast cell lines regardless of the modification type. In turn, the quantitative microbiological tests and visualization of microbial biofilm by means of electron microscopy showed that type of implant’s modification correlated with the species-specific ability of microbes to form biofilm on it. Thus, the results of the presented study confirm the relationship between such technological aspects as surface modification and biological properties. The provided data are useful with regard to applications of the EBM technology and present a significant step towards personalized, customized implantology practice.