Electron Beam Melting Technique Research Articles

A Prediction Model of Evaporation Behavior of Nickel-Based Superalloy in Electron Beam Melting

The electron beam melting technique has emerged as a novel refining technology extensively employed for alloy purification due to its advantages of effectively eliminating volatile impurities and non-metallic inclusions. However, a drawback associated with the melting process is the evaporation of alloy elements, which results in an uncontrollable alloy composition. In this paper, Wagner model is used to calculate and study the evaporation behavior. of nickel-based superalloy, and the database of infinite dilution activity coefficient and interaction coefficient of nickelbased superalloy has been established. The results show that the model can well predict the composition of electron beam melting superalloy, establish the relationship between electron beam melting power and temperature, and predict the composition of several groups of DZ125 alloys after melting with different power, which is in consistent with the experimental results. This model is of guiding significance for electron beam melting of nickel-based superalloy.

Anodic Oxidation of 3D Printed Ti6Al4V Scaffold Surfaces: In Vitro Studies

This study focuses on the surface modification of Ti6Al4V scaffolds produced through additive manufacturing using the Powder-Bed Fusion Electron-Beam Melting (PBF-EB) technique. From our perspective, this technique has the potential to enhance implant osseointegration, involving the growth of a layer of titanium dioxide nanotubes (TiO2) on surfaces through anodic oxidation. Scaffolds with anodized surfaces were characterized, and the formation of a nanoporous and crystalline TiO2 layer was confirmed. The analysis of cell morphology revealed that cells adhered to the anodized surfaces through their filopodia, which led to proliferation during the initial hours. However, it was observed that the adhesion of Saos-2 cells was lower on anodized scaffolds compared to both built and chemically polished scaffolds throughout the cell culture period. The results obtained here suggest that while anodic oxidation is effective in achieving a nanoporous surface, cell adhesion and interaction were affected by the weak adhesion of cell filopodia to the surface. Thus, combining surface treatment techniques to create micro- and nanopores may be an effective alternative for achieving a favorable cellular response when the objective is to enhance the performance of porous titanium scaffolds in the short term.

Inelastic mechanical behaviour of an additively manufactured titanium alloy: a statistical continuum mechanics theory perspective

Statistical continuum mechanics theory was used to simulate the inelastic stress of polycrystalline materials using two-point statistics. For the experimental part, the Electron beam melting (EBM) technique (Arcam EBM Q10 additive machine) was used to fabricate cylindrical rods of Ti-6Al-4V both in horizontal and vertical directions. Electron backscatter diffraction (EBSD) technique was employed to achieve statistically reliable orientation maps of vertically and horizontally printed samples. In this study, high strain rate compression tests at six different strain rates were performed, and the stress–strain curves were generated. This work is amongst the first attempts to model the microstructure of additively manufactured hexagonal alloys under compressive loadings using the statistical continuum mechanics theory. The model is capable of simulating reasonably large microstructures (statistically representative) with a practical computational cost and accuracy, unlike numerical models that require a high computational cost. It should be noted that in additive manufacturing, due to large grains and high anisotropy, microstructures used in the simulations should be large enough to include sufficient information from the material’s structure. Therefore, using finite element models would be very challenging here. On the other hand, the statistical continuum mechanics theory uses the statistical representation of the material’s characteristics for solving the governing equations with Green’s function that enables this methodology to use more microstructure characteristic information without having a noticeable change to the computational cost. The proposed model in this study uses different microstructure characteristics such as crystal grain orientation, total slip systems, active slip systems, gain morphology, and chemical phases that are obtained from EBSD images for simulating the inelastic mechanical behavior of polycrystalline materials. Although this model simulates polycrystalline materials by considering various crystal and grain information, unlike numerical methods, it doesn’t simulate the grain interactions well and we cannot study local deformation and crack nucleation sites. This model works very well for simulating the overall behavior of material instead of each individual grain and failure analysis. This model has shown a good combination of computational cost and accuracy in which the error between the simulated and experimental strength for vertical and horizontal samples was 6.21% and 8.07%, respectively.

Microstructure evolution, corrosion behavior, and biocompatibility of Ti-6Al-4V alloy manufactured by electron beam melting (EBM) technique

It is the purpose of this study to investigate the effects of heat treatment on the microstructure, corrosion, and biological behavior of Ti-6Al-4V alloy manufactured using electron beam melting (EBM). The EBM parts were exposed to different heat treatments at 1000 °C and various cooling rates (HT-1, HT-2, and HT-3) to obtain a combination of α and β phases. Electrochemical analyses indicate that the non-heat treated alloy (Ref) exhibits superior corrosion resistance during early immersion, while all samples display similar corrosion performance after one month of immersion. The higher corrosion performance was associated with the content of β phases in the manufactured alloy. The Ref, HT-1, HT-2, and HT-3 EBMed alloys had corrosion current densities of 0.46, 0.66, 0.67, and 0.92 µA cm−2, respectively, after one month of immersion. Cell adhesion and durability were shown to be excellent on HT-3 samples. In conclusion, a suitable heat treatment can improve the biological performance of the EBMed alloy, despite resulting in lower corrosion performance in the early stages of corrosion.

Recent advances of metallic bio-materials in additive manufacturing in biomedical implants–A review

During the last three decades, metal additive manufacturing (metal-AM) has evolved significantly. It has become possible to produce prototypes of products using metal-AM in combination with various manufacturing processes since the technology has matured enough to be used for complex geometries. Recent advancements in biomedical implants have attracted increasing attention to additive manufacturing (AM). The use of titanium and its alloys in biomedical implants, cobalt alloys, stainless steel 316L, nickel-titanium, and others is explored. A number of metal additive manufacturing processes are available, including Selective Laser Melting (SLM), Selective Laser Sintering (SLS), and Electron Beam Melting (EBM). Moreover, the paper discusses the latest developments in metal-AM via direct metal laser sintering and the fabrication and characterization of a three-dimensional scaffold. There is increasing use of laser or electron beam melting techniques in the manufacture of metal implants, among all methods of additive manufacturing (AM). In the future, metal-AM is expected to provide various benefits to the biomedical industry.

Parametric optimization of multi-pass electron beam melting for molybdenum alloy containing 47.5 wt% rhenium

In this study, the effects of multi-pass electron beam melting (EBM) processes under vacuum condition on microstructure and mechanical behavior of a molybdenum alloy containing 47.5 wt% rhenium were systematically investigated. Nine experimental designs were performed to improve the surface quality and minimize the defects. Results showed that beam power, scan speed, processing step and penetration depth played a critical role in the specific energy density function, which would further influence the porosity and microhardness. Meanwhile, specific energy density was significantly influenced by beam power at higher scan speed (e.g. 15 mm/s) whereas it was mainly related to scan speed under lower beam power (e.g. 2 kW). With a processing step of 0.5 mm (half of the beam diameter), a continuous melt morphology and less porosity were obtained, indicating that a significant overlap between the scan tracks was beneficial for the optimization of microstructure. Microhardness results showed that mechanical performance can be improved with the reduction of porosity together with the increased specific energy density. Thus, a combination of 10 kW beam power, 2 mm/s scan rate and 0.5 mm processing step can realize surface optimization in melted plates through multi-pass EBM technique.

Enhancement of grain refinement and heat resistance in TiB2-reinforced Al-Cu-Mg-Fe-Ni matrix composite additive manufactured by electron beam melting

Additive manufacturing (AM) by electron beam melting (EBM) has many advantages over the laser-based AM techniques, but is subjected to a lower cooling rate and a long time thermal exposure with a much higher temperature. Therefore, the EBMed aluminum alloys commonly have coarser solidification structures such that lower mechanical properties compared to their SLMed counterparts. In this work, we proposed a strategy of introducing TiB2 particles into heat-resistant Al-Cu-Mg-Fe-Ni alloy to enhance the grain refinement and heat resistance for EBM fabrication. Applying a “presintering-densification” scanning strategy, near fully dense samples were build up with precise contours and good surface quality. The as-built EBMed TiB2/Al-Cu-Mg-Fe-Ni composite possessed a highly homogeneous microstructure with uniformly distributed TiB2 and Fe/Ni rich intermetallic particles. A fully equiaxed grain structure was achieved in the composite with a profoundly refined grain size of ~9 µm. The improved grain refinement effect was attributed to the sufficient activation of TiB2 particles as heterogeneous nuclei under a high cooling rate. Additionally, the solidified microstructure has shown an excellent thermal stability under ~500 °C during EBM process. The coexistence of thermal stable TiB2 and Fe, Ni-rich intermetallics at grain boundaries restricted the grain growth effectively. The as-built composite exhibited a high tensile strength of 253.4 MPa with an outstanding elongation of 13.5 %. After a T6-like heat treatment, the tensile strength was increased to 322 MPa with an elongation of 9.8 %. This study might shed a new light on designing high performance aluminum alloys/composites suitable for EBM technique.

Influence of printing procedure and printing axis of dental alloys on dimensional accuracy, surface roughness, and porosity

Objectives: This study aimed to evaluate the printing procedure and printing axis and its influence on the dimensional accuracy, surface roughness, porosity, and strength of 3D-printed dental alloys used in orthodontics prepared using binder jetting (BJ), electron beam melting (EBM), or selective laser melting (SLM). Material and Methods: Specimens with a dimension of 50 mm × 12 mm were produced using BJ, EBM, and SLM techniques of dental alloys and were printed either along the X-, Y-, or Z-axis (n = 8 per group). Specimen dimension was chosen according to the ISO standard 6892-1 for tensile strength test specimens. Surface roughness parameters Sa, Sz, Sq, and Ssk were obtained using a 3D laser microscope and porosities were visualized with scanning electron microscopy (SEM). The specimen surfaces were optically scanned and volumetric deviations from the original stereolithography files were calculated. Afterward, tensile strength was measured. Results: The printing method and printing axis significantly affected surface roughness parameters (P < 0.05). Overall, the lowest surface roughness Sa values were found for BJ (9.1 ± 3.4 µm) followed by SLM (39.8 ± 24.2 µm) and EBM (50.4 ± 6.4 µm). BJ showed the smallest dimensional deviation followed by EBM and SLM. SEM analysis revealed a porous structure of BJ while fewer pores were observed on EBM and SLM samples. The ultimate tensile strength was only determined for BJ (495 ± 6 MPa) and EBM (726 ± 50 MPa) as the strength of SLM superseded the strength of the holder of the universal testing machine. Conclusion: BJ printing provides the highest dimensional accuracy with the smoothest surfaces irrespective of the printing axis. However, the remaining porosities owed to this printing procedure may have decreased the strength of the material.

Effect of Temperature on Sliding Wear Behavior of Ti-6Al-4V Alloy Processed by Powder Bed Fusion Additive Manufacturing Techniques

Ti-6Al-4V is suitable for powder bed fusion additive manufacturing processes; however, until now, limited studies are conducted to investigate the high temperature tribological performance of Ti-6Al-4V samples made by selective laser melting (SLM) and electron beam melting (EBM) techniques. This paper investigated dry sliding wear resistance of Ti-6Al-4V alloy manufactured by SLM, EBM and conventional processes at elevated temperatures up to 600 °C in contact with WC-Co. Linear reciprocating sliding wear tests were carried out under different applied loads and temperatures, and different wear mechanisms were identified and related to the manufacturing technique. Deviations of wear track width measurements indicated shape irregularly, which has been presented and discussed by SEM images of the wear tracks. Energy-dispersive x-ray analysis of surface layer showed how increasing temperature affects the surface oxide layer and debris. The results showed that for all three types of samples, the oxygen richer oxide debris layer at higher temperatures provided a protective layer with higher wear resistance, although strength and hardness of Ti-6Al-4V are lower at a higher temperatures. So, the combination of these two effects results in no significant effect of temperature on wear rate.

Characterization and statistical modeling of texture and microstructure evolution in dynamically fractured electron beam melted Ti-6Al-4V

Two different Ti-6Al-4V cylindrical rods, horizontally and vertically built, fabricated through the electron beam melting technique, were underwent compression loadings to failure at the strain rates of 2350s−1 and 1750s−1, respectively. Low-angle grain boundary formation, dislocation array, and dislocation pinning were observed and attributed to the stress-induced dislocation formation in the as-built microstructure. Superior strength at each strain rate in vertically built samples was concluded to be a consequence of its finer microstructure and the presence of martensite α˙. Hardness measurements revealed higher values at the areas close to the fracture surface. Electron microscopic characterization revealed parallel-twin formation resulting from adiabatic temperature rise, increasing short-ranged clustering, and the high stacking fault energy. Dynamic compressive deformation led to the appearance of dislocation structure, cell blocks, and extended dislocation walls formation. Texture analysis showed <c+a> type pyramidal slip systems and contraction twins as the most favorable slip systems. Texture evolution interpretations from the region far from the area close to the fractured surface indicated that mean grain size decreased, and higher dislocation densities were obtained. The more preferred texture tended to rotate by approaching the fracture surface so that the basal plane became parallel to the fracture surface, which is directly related to the facilitation of crack propagation. Moreover, the generalized spherical harmonics were used to apply 2-point statistics on the texture and then statistically compare the texture changes. The results were in good agreement statistically, where principal components (PC) were utilized to explain variances in the database.

The comparison of properties of Ti-6Aluminum-4Vanadium porous scaffolds fabricated through low-power selective laser Melting and electron beam melting

Background and Purpose: Three-dimensional printing (3DP) selective laser melting (SLM) and electron beam melting (EBM) technique can construct porous Ti-6Aluminum-4Vanadium (Ti-6Al-4V) scaffolds with special microstructural and biomechanical properties. However, it is still needed to be tested for bone tissue engineering. Materials and Methods: To investigate the microstructure and surface modification of a porous titanium scaffold, 3DP-SLM technique was used, and the mechanical and biological performance of the scaffolds was compared with that fabricated by EBM technique. Ti-6Al-4V scaffolds were computer-designed and fabricated using low-power SLM (L-SLM). The microstructure morphologies of L-SLM Ti-6Al-4V (L-SLM-Ti) scaffolds were determined and compared with EBM-fabricated Ti-6Al-4V (EBM-Ti) scaffolds. Each scaffold was immersed with marrow clot for 1 h until fully combined with bone mesenchymal stem cells in clots. The biomechanical and cellular response of these two kinds of Ti-6Al-4V scaffolds were compared. Results: The L-SLM-Ti scaffolds showed a microstructure closer to the designed parameters than that of the EBM-Ti scaffolds. The L-SLM-Ti scaffold fibers had a rougher surface than the EBM-Ti scaffolds. Meanwhile, L-SLM-Ti scaffolds had a lower elasticity modulus and lower bearing force than EBM-Ti scaffold. Cell proliferation and the relative expression levels of OPN, COL1, and RUNX2 in L-SLM-Ti scaffolds was apparently higher than in the EBM-Ti scaffolds, with no significant difference found between the percentage of live cells found in L-SLM-Ti and EBM-Ti scaffolds. Conclusion: 3DP-Ti-6Al-4V scaffolds fabricated by L-SLM and designed with rougher surfaces and larger pore sizes may have more reasonable biomechanical properties and increased biological performance than traditional EBM-Ti scaffolds. These L-SLM-Ti scaffolds might be suitable candidates for bone defect repair.

Direct tuning of the microstructural and mechanical properties of high-alloy austenitic steel by electron beam melting

In the present work austenitic stainless steel X2CrMnNi16-7-9 was additively manufactured using electron beam melting (EBM) technique. In order to reach the highest work of deformation processing parameters such as scan speed, beam current and volume energy were varied. Different properties of manufactured samples, including chemical composition, density, roughness, yield and tensile strength, ductility, grain morphology, texture, and phase composition were thoroughly examined by means of SEM, EDX, EBSD, tensile testing, Archimedes and other methods. The correlation between the parameters was analysed and optimal processing settings allowed to reach work of deformation up to 39 GPa with remarkable elongation up to 110%. It was also found that tuning of the Mn evaporation during EBM by varying the beam energy resulted in the change of stacking fault energy and martensitic transformation temperatures of the steel. This led to the change of the austenite stability and plasticity mechanisms, such as the occurrence of deformation induced martensite in the initially TWIP steel. Comparison of phase diagrams of the studied X2CrMnNi16–7–9 steel and similar X5CrMnNi16-6-6 steel has proven that the reason for in situ EBM grain refinement in the latter one is the presence of primary bcc phase field. • Manipulation of Mn content via EBM can be used to change CrMnNi steel properties. • Grain refinement during EBM of CrMnNi steel is due to bcc to fcc transition. • CrMnNi steel with 39 GPa·% work of deformation and 110% strain is produced by EBM. • Optimal processing window for EBM production of X2CrMnNi16-7–9 steel is revealed.

Enhanced cytocompatibility and mechanical properties of electron beam melted Ti-6Al-4V by friction stir processing

Electron Beam Melting (EBM) is an emerging additive manufacturing technique for the fabrication of titanium alloy Ti-6Al-4V for orthopedic applications. Here, a hybrid manufacturing technique viz. EBM with Friction Stir Processing (FSP) has been proposed to enhance implant surface properties. The surface modification using FSP reduces the roughness generated by the EBM technique from ~44.77 μm to ~15.82 μm. Simultaneously, FSP improves the biological and mechanical properties of the Ti-6Al-4V substrates. The roughness, wettability, amounts of ions released, and surface microhardness were measured to analyze the stability of the substrates. The effect of the hybrid processing strategy on cell viability was tested against mouse fibroblast cells NIH3T3 through MTT assay, and we found that the friction stir processed substrate (EBM-F) showed the highest cell viability. The EBM-F surface displays a two-fold increase in the cell-viability as compared to the unprocessed EBM surface after 24 h of cell-seeding. The FSP substrate allows human cervical cells HeLa to adhere onto its surface while selectively preventing the attachment of E.coli bacterial cells. These observations towards cells signify biocompatible surface characteristics of the FSP EBM substrate.

Mitigating Corrosion Effects of Ti-48Al-2Cr-2Nb Alloy Fabricated via Electron Beam Melting (EBM) Technique by Regulating the Immersion Conditions

The corrosion behavior of newly fabricated γ-TiAl alloy was studied using electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization (CPP) techniques. The γ-TiAl alloy was produced from powder with compositions of Ti-48Al-2Cr-2Nb processed using electron beam melting (EBM) technique. The corrosion behavior of the bulk alloy was investigated in 1 M HCl solution for different immersion times and temperatures. The experimental results suggest that the fabricated alloy exhibits good resistance to corrosion in acid solution at room temperature. The results also indicate that with an increase in immersion time and solution temperature, the corrosion potential (Ecorr) shifts to a higher positive value, resulting in an increase in corrosion current (jcorr) and consequently a decrease in the corrosion resistance (Rp) of the alloy.

Microstructural and Mechanical Evaluation of a Cr-Mo-V Cold-Work Tool Steel Produced via Electron Beam Melting (EBM).

In this work, a highly alloyed cold work tool steel, Uddeholm Vanadis 4 Extra, was manufactured via the electron beam melting (EBM) technique. The corresponding material microstructure and carbide precipitation behavior as well as the microstructural changes after heat treatment were characterized, and key mechanical properties were investigated. In the as-built condition, the microstructure consists of a discontinuous network of very fine primary Mo- and V-rich carbides dispersed in an auto-tempered martensite matrix together with ≈15% of retained austenite. Adjusted heat treatment procedures allowed optimizing the microstructure by the elimination of Mo-rich carbides and the precipitation of fine and different sized V-rich carbides, along with a decrease in the retained austenite content below 2%. Hardness response, compressive strength, and abrasive wear properties of the EBM-manufactured material are similar or superior to its as-HIP forged counterparts manufactured using traditional powder metallurgy route. In the material as built by EBM, an impact toughness of 16–17 J was achieved. Hot isostatic pressing (HIP) was applied in order to further increase ductility and to investigate its impact upon the microstructure and properties of the material. After HIPing with optimized protocols, the ductility increased over 20 J.

A review on post processing techniques of additively manufactured metal parts for improving the material properties

Metal additive manufacturing (AM) processes are used to produce metal parts with greater design freedom and no material wastage from a CAD model, using powder or wire as feedstock with a layer by layer joining of materials by a high intensity energy source such as laser or electron beam. These processes include selective laser melting (SLM), electron beam melting (EBM) and wire arc additive manufacturing (WAAM) techniques which has wide usage in fabricating metal alloys such as aluminum and titanium for the aerospace and automotive applications. However, these AM parts show many limitations in the as built state like poor surface finish and high tensile residual stress, which will affect the mechanical properties and surface integrity because of the usage of high intensity energy-based melting for the fabrication of parts. This give rise to the need for post processing techniques such as heat treatment and additional machining and polishing operations such as shot peening (SP), laser shock peening (LSP), abrasive flow machining(AFM), friction stir processing (FSP) and hot isostatic pressing (HIP) to improve its surface finish, fatigue life and other material properties. This review paper aims to understand the defects of as built AM parts and focus on the post processing techniques employed by the researchers and its effects on the improvement of AM components.

Osseointegration of additive manufacturing Ti–6Al–4V and Co–Cr–Mo alloys, with and without surface functionalization with hydroxyapatite and type I collagen

The introduction of additive manufacturing (AM) technologies has profoundly revolutionized the implant manufacturing industry, with a particularly significant impact on the field of orthopedics. Electron Beam Melting (EBM) and Direct Metal Laser Sintering (DMLS) represents AM fabrication techniques with a pivotal role in the realization of complex and innovative structure starting from virtual 3D model data. In this study, Ti–6Al–4V and Co–Cr–Mo materials, developed by EBM (Ti-POR) and DMLS (Co-POR) techniques, respectively, with hydroxyapatite (Ti-POR + HA; Co-POR + HA) and type I collagen (Ti-POR-COLL; Co-POR-COLL) coatings, were implanted into lateral femoral condyles of rabbits. Osseointegration process was investigated by histological, histomorphometrical and microhardness evaluations at 4 and 12 weeks after implantation. Both Ti–6Al–4V and Co–Cr–Mo implants, with or without HA and COLL coatings, demonstrated good biocompatibility. As expected, HA coating hastened bone-to-implant contact (BIC) process, while collagen did not significantly improved the osseointegration process in comparison to controls. Regarding newly trabecular bone formation (B.Ar/T.Ar), Co-POR presented the highest values, significantly different from those of Co-POR-COLL. Over time, an increase of BIC parameter and a decrease of B.Ar/T.Ar were detected. Higher mineral apposition rate was observed for Ti-POR and Co-POR in comparison to Ti-POR-COLL and Co-POR-COLL, respectively, at 12 weeks. The same behavior was found for bone formation rate between Co-POR and Co-POR-COLL at 12 weeks. In conclusion, the AM materials guarantee a good osseointegration and provide a suitable environment for bone regeneration with the peculiarity of allowing personalized and patient-specific needs customization to further improve the long-term clinical outcomes.

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.

Additive manufacturing of ZrB2–ZrSi2 ultra-high temperature ceramic composites using an electron beam melting process

Owing to their high melting points and ability to resist extreme thermal stresses, ultra-high temperature ceramics (UHTCs) are important materials for critical applications such as hypersonic flights, space re-entry vehicles, and rocket engines. Traditional manufacturing processes restrict the freedom to manufacture UHTCs with complex geometries due to the limitations of die and mold designs. Electron beam melting (EBM) is an established powder-bed layer-by-layer additive manufacturing (AM) process for metal parts. In this research, an effort was made to evaluate the feasibility of EBM for the AM fabrication of UHTC-based materials, and to investigate the microstructures of the fabricated materials under different processing conditions. A mathematical model was developed to simulate and optimize the processing parameters for the fabrication of ZrB2-30 vol% ZrSi2 UHTC using EBM. The simulation results were compared with experimental observations. For EBM fabrication of ZrB2-30 vol% ZrSi2 composites, the optimal processing parameters are beam power of 500 W with scanning speeds of 500, 750, and 1000 mm/s, and beam power of 1000 W with scanning speed of 1000 mm/s. This study demonstrates the potential for additive manufacturing of UHTCs with complex geometries by the EBM technique.

Improved osseointegration of 3D printed Ti-6Al-4V implant with a hierarchical micro/nano surface topography: An in vitro and in vivo study

Three-dimensional (3D) printing technology is serving as a promising approach of fabricating titanium (Ti) and its alloys used for bone tissue engineering. However, the biological inertness nature of Ti material limits its capability to bind directly with the bone tissue. This paper aims to enhance the bioactivity and osteogenesis of 3D printed Ti-6Al-4V implants by constructing a hierarchical micro/nano-topography on the surface. Ti-6Al-4V implants were prepared by the electron beam melting (EBM) technique. A method combining ultrasonic acid etching with anodic oxidation is proposed for surface modification of EBM Ti-6Al-4V implants in this study. The acid etching step was to remove any existent residual powders on the implant's surface and construct micro-pits and -grooves on the EBM microrough surface. Nanotube arrays with a diameter of 40–50 nm were superimposed on the micro-structured substrate via anodic oxidation. The results of in vitro experiments showed that the hierarchical micro/nano-structured surface on Ti-6Al-4V after acid etching and anodic oxidation (AN) promoted the proliferation and osteogenic differentiation of pre-osteoblast cells (MC3T3-E1) via enhancing the surface hydrophilicity and bioactivity compared with the polished Ti surface (P). Micro-CT and histological analysis were used to assess the in vivo osteogenic properties enhancement. The results 8 weeks after the surgery showed the ratio of bone volume to total volume (BV/TV) of AN implant was 43.4%, which represented 1.5 times that of as-printed implants (AM) without any post-treatment. Considerable increment of bone-to-implant contact area was also detected from the micro-CT reconstructed 3D models in comparison with AM implants and acid etched (AE) EBM implants. In conclusion, the hierarchical micro/nano topography generated on the EBM native surface showed an improvement of bioactivity and osteogenic properties, which is expected to accelerate the application of 3D printed orthopedic and dental implants in clinics. Statement of significanceTraditional titanium implants have the nature of biological inertness, which limits their capability to bind directly with the bone tissue. The failure of implants after couple of years of implantation will cause huge pain to the patients. In this work, a surface modification method for 3D printed implants was developed to construct a hierarchical micro/nano-structure. Through the in vitro and in vivo experiments, we proved that this hierarchical micro/nano-structure induced a better promotion effect on osteoblast proliferation and differentiation comparing with untreated surface or polished surface, and was also capable of bolstering the new bone formation, suggesting a potent strategy to improve the biological properties of 3D printed titanium implants. The work is expected to accelerate the application of 3D printed orthopedic and dental implants in clinics.