Electron Beam Melting Samples Research Articles

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 The ultimate tensile strength was only determined for BJ (495 ± 6 MPa) and EBM (726 ± 50 MPa) as the strength of SLM superseded the strength of the holder of the universal testing machine.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.

Directionally-Dependent Mechanical Properties of Ti6Al4V Manufactured by Electron Beam Melting (EBM) and Selective Laser Melting (SLM).

An investigation of mechanical properties of Ti6Al4V produced by additive manufacturing (AM) in the as-printed condition have been conducted and compared with wrought alloys. The AM samples were built by Selective Laser Melting (SLM) and Electron Beam Melting (EBM) in 0°, 45° and 90°—relative to horizontal direction. Similarly, the wrought samples were also cut and tested in the same directions relative to the plate rolling direction. The microstructures of the samples were significantly different on all samples. α′ martensite was observed on the SLM, acicular α on EBM and combination of both on the wrought alloy. EBM samples had higher surface roughness (Ra) compared with both SLM and wrought alloy. SLM samples were comparatively harder than wrought alloy and EBM. Tensile strength of the wrought alloy was higher in all directions except for 45°, where SLM samples showed higher strength than both EBM and wrought alloy on that direction. The ductility of the wrought alloy was consistently higher than both SLM and EBM indicated by clear necking feature on the wrought alloy samples. Dimples were observed on all fracture surfaces.

Morphological effects on the electrochemical dissolution behavior of forged and additive manufactured Ti-6Al-4V alloys in runway deicing fluid

The particular microstructure of Ti-6Al-4V fabricated by additive manufacturing (AM) makes it exhibit a different corrosion resistance compared with that of the conventional forged Ti-6Al-4V. Here we utilize the electrochemical impedance (EIS) and potentiodynamic polarization (Tafel) to evaluate the electrochemical dissolution behavior in runway deicing fluids (RDF) of three kinds of Ti-6Al-4V alloy, which are respectively fabricated by forging, electron beam melting (EBM), and selective laser melting (SLM). The microstructure and electrochemical results suggest that EBM samples have a better corrosion resistance than others', which is attributed to an appropriate proportion of α-lath width and the volume fraction of β phase. A higher relative proportion of TiO2 is formed on surface, resulting in the fine-lamellar structure with a higher density of grain boundaries. Besides, the corrosion resistance anisotropy of AMed Ti-6Al-4V samples is ascribed to the existence of β columnar gains. In addition, the acicular martensite α′ phase with metastable structure leads to the worst corrosion resistance of SLMed Ti-6Al-4V samples. This work enriches the corrosion resistance of Ti-6Al-4V alloy in strong electrolyte solutions, which helps to promote the service performance of aviation titanium alloys in harsh environments.

Role of Superficial Defects and Machining Depth in Tensile Properties of Electron Beam Melting (EBM) Made Inconel 718

Since there is no report on the influence of machining depth on electron beam melting (EBM) parts, this paper investigated the role of superficial defects and machining depth in the performance of EBM made Inconel 718 (IN718) samples. Therefore, as-built EBM samples were analyzed against the shallow-machined (i.e., only removal of outer surfaces) and deep-machined (i.e., deep surface removal into the material) parts. It was shown that both as-built and shallow-machined samples had a drastically lower yield strength (970 ± 50 MPa), ultimate tensile stress (1200 ± 40 MPa), and ductility (28 ± 2%) compared to the deep-machined samples. This was since premature failure occurred due to various superficial defects. The superficial defects appeared in two levels, as (1) notches and pores on the surface and (2) irregular pores and cracks within the subsurface. Since the latter occurred down to 2 mm underneath the surface, shallow machining only exposed the subsurface defects to outer surfaces. Thus, the shallow-machined parts achieved only 68% and 8% of UTS and elongation of the deep-machined parts, respectively. This low performance occurred to be comparable to the as-built parts, which failed prematurely due to the high fraction surface voids and notches as well as the subsurface defects.

Effects of Process-Induced Supersaturation on the Oxidationbehavior of Alloy718 Fabricated By Additive Manufacturing Technologies

Alloy718 is widely used in gas turbines and related aerospace applications due to its excellent mechanical properties and structural stability at elevated temperatures. Alloy718 is a precipitation-strengthened superalloy which is generally manufactured through casting, forging, and heat treatment. Over the past decade a variety of additive manufacturing (AM) technologies involving laser and electron beam have become increasingly attractive fabrication methods due to their several advantages over conventional manufacturing methods, such as a large degree of design flexibility, and reductions in the lead time and investment cost. However, the selective laser melting process (rapid heating and cooling) will make matrix gets supersaturated in alloying elements, in particular Nb, Ti and Al, which have significant effects on the formation of the strengthening phases in austenite matrix, e.g., γ′′ (Ni3Nb,), γ′ (Ni3Al,Ti) phases.Up to now, the specific influences of supersaturation on the oxidation behavior of the scales in a Cr-forming Ni-based alloy have not been dealt with in depth.In this study, the oxidation behavior of Alloy718 specimens produced by selective laser melting (SLM) and electron beam melting (EBM) process were comparatively examined. A slower cooling rate and a preheating process in the EBM process contribute relatively lower degree of saturation in \U0001d6fe matrix. On the other hand, the high thermal gradient and rapid solidification rate in SLM process lead to supersaturation in \U0001d6fe matrix. All alloys were studied in two versions to compare the order of supersaturation: “As-received” and heat treated (HT). The heat treatment procedure was carried out at 980 °C for 1 h/air cooling to room temperature and a two-step aging treatment consisting of 718 °C for 8 h/furnace cooling to 621 °C and holding at 621 °C for 10 h before AC to room temperature. The oxidation kinetics as well as the surface morphology of the oxide scales were characterized by means of weight gain measurements, scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), electron probe microanalysis (EPMA), X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis techniques.The experimental results indicated that the oxidation performance of as-received SLM samples were better than those of as-received EBM samples due to the formation of thinner Cr2O3 scale without spallation. In addition, the morphology of their chromia scale was different. Coarse and columnar chromia grains developed on SLM samples, whereas the chromia scale of EBM samples consisted of extremely fine grains. After heat treatment process, the oxidation kinetics of heat-treated samples were increased compare to as-received samples. Moreover, the fine-grained chromia scale which is similar to that formed on EBM samples was formed on heat-treated SLM samples. The mentioned results indicate that the degree of supersaturation in the matrix did affect the morphology of chromia scale resulting in the oxidation kinetics.

Abrasive fluidized bed finishing to improve the fatigue behaviour of Ti6Al4V parts fabricated by electron beam melting

A study of the abrasive fluidized bed (AFB) finishing process was conducted to quantify the obtainable improvement of the fatigue behaviour of Ti6Al4V parts produced by electron beam melting (EBM). Axial-symmetric EBM samples were rotated at high speed inside a fluidized bed of stainless-steel media. The effects of the treatment time and the rotational speed on morphological features and fatigue life of the EBM samples were investigated. Outcomes showed that the improvement in surface properties induced by the AFB finishing process determined an increase up to 50% in fatigue life and a shift of the S-N curve.

Hot deformation behavior and flow stress modeling of Ti–6Al–4V alloy produced via electron beam melting additive manufacturing technology in single β-phase field

The hot working behaviour of additively manufactured Ti–6Al–4V pre-forms by Electron Beam Melting (EBM) has been studied at temperatures of 1000–1200 °C and strain rates of 0.001–1 s−1. As a reference, a wrought Ti–6Al–4V alloy was also analyzed as same as the EBM one. In order to investigate the hot working behaviour of these samples, all the data evaluations were carried out step by step, and the stepwise procedure was discussed. No localized strain as a consequence of shear band formation was found in the samples after the hot compression. The flow stress curves of all the samples showed peak stress at low strains, followed by a regime of flow softening with a near-steady-state flow at large strains. Interestingly, it is found that the initial microstructure and porosity content as well as the chemistry of material (e.g. oxygen content) as being possible contributors to the lower level of flow stress that could be beneficial from the industrial point of view. The flow softening mechanism(s) were discussed in detail using the microstructure of the specimens before and after the hot deformation. Dynamic Recrystalization (DRX) could also explain the gentle oscillation in the appearance of the flow softening curves of the EBM samples. Moreover, the hot working analysis indicated that the activation energy for hot deformation of as-built EBM Ti–6Al–4V alloy was calculated as ~193.25 kJ/mol, which was much lower than the wrought alloy (229.34 kJ/mol). These findings can shed lights on a new integration of metal Additive Manufacturing (AM) and thermomechanical processing. It is very interesting to highlight that through this new integration, it would be possible to reduce the forging steps and save more energy and materials with respect to the conventional routes.

Effects of laser shock peening on microstructure and fatigue behavior of Ti–6Al–4V alloy fabricated via electron beam melting

Laser shock peening (LSP) is a post-treatment process that is widely used to modify the surface microstructure and mechanical properties of parts constructed by additive manufacturing (AM). In this study, the influence of LSP on the microstructure and fatigue behavior of Ti–6Al–4V alloy manufactured via electron beam melting (EBM), a popular method of AM, was investigated. The microstructure of the EBM sample consisted of the β phase (~6 vol%) and α lamellar phase. Grain refinement of the α phase occurred via both dislocation evolution and deformation twinning during LSP. A theoretical description of the microstructural evolution, particularly the distribution of deformation twins, was developed. The fatigue strength and micro-hardness of the EBM samples increased by approximately 17% and 11% after LSP treatment, respectively. The fatigue fracture morphologies at three defined damage stages (crack initiation, crack propagation, and instantaneous rupture) were examined for EBM samples before and after LSP. The dominant mechanism of fatigue strength enhancement by LSP was discussed. The effects of residual compressive stress assistant with adiabatic temperature increase and grain refinement of the α phase produced by LSP reduced the pre-existing crack size, suppressed crack initiation, and increased the required work for fatigue fracture.

SLM 및 EBM 적층제조로 제작된 두개골 임플란트의 기계 물리적 특성 분석

Metal lamination manufacturing equipment and patient-specific implants that design and directly output implants suitable for patients by utilizing the medical image data of patients have been produced and used. The purpose of this study is to identify the mechanical characteristics of selective laser melting (SLM) and electron beam melting (EBM) 3D printer output methods of skull implants and to suggest a suitable output method for patient-specific skull implants. SLM and EBM samples were prepared in the hemispherical form with reference to commercial implants. Thereafter, the compressive strength and flange cantilever of the plates of the samples were examined; surface roughness and hardness were further evaluated. The EBM sample was found to have excellent strength and elasticity characteristics. As a result, it was judged that the sample prepared via EBM was suitable for skull implant preparation.

Corrosion Behaviour of Electron Beam Melted Ti6Al4V: Effects of Microstructural Variation

Microstructural analysis and electrochemical measurements were carried out on longitudinal and transverse planes of an additively manufactured (AM) Ti–6Al–4V rod printed in the horizontal direction by electron beam melting (EBM), and compared with those performed on a commercially available alloy. Microstructural differences in the planes parallel and perpendicular to the build direction were characterized using optical and scanning electron microscopy, X-ray diffraction, and transmission electron microscopy coupled with energy dispersive spectroscopy. The microstructures of three different locations along the transverse axis on the EBM samples were also studied. The starting point, the middle, and the end of the sample in the build direction consisted primarily of α-phase and a small amount of β-phase. On progressing from the starting point towards the end of the build, the size of both phases increased and the elemental distribution of alloying elements showed more segregation of vanadium and iron into the β-phase. The electrochemical behaviour was studied as a function of time using electrochemical impedance spectroscopy and potentiodynamic polarization. The film resistance of the wrought sample was slightly better than those of the EBM samples. The film resistance of the EBM-transverse sample improved slightly more with exposure time than that of the longitudinal sample.

Production of net-shape Mn-Al permanent magnets by electron beam melting

The main goal of this work is the adoption of additive manufacturing for the production of inexpensive rare-earth free MnAl-based permanent magnets. The use of more advanced binder-free additive manufacturing technique such as Electron Beam Melting (EBM) allows obtaining fully-dense magnetic materials with advanced topology and complex shapes. We focus on the feasibility of controlling the phase formation in additively manufactured Mn-Al alloys by employing post-manufacturing heat treatment. The as-manufactured EBM samples contain 8% of the desired ferromagnetic τ-MnAl phase. After the optimized annealing treatment, the content of the τ-phase was increased to 90%. This sample has a coercivity value of 0.15 T, which is also the maximum achieved in conventionally produced binary MnAl magnets. Moreover, the EBM samples are fully dense and have the same density as the samples produced by conventional melting density.

Friction welding of electron beam melted Ti-6Al-4V

Ti-6Al-4V samples produced by electron beam melting (EBM) are welded using solid-state friction welding (FW) process. The microstructure of the weld sample shows the presence of fine equiaxed α grains with irregular β phase. Microstructural investigations reveal a pronounced change in the shape and size of the α phase in the weld metal as-compared to the base material along with the disappearance of columnar prior β grains. Such variations in the microstructure significantly change the mechanical properties of the FW material. The hardness in the weld zone increases and a decrease of hardness is observed along the heat affected zone (HAZ) with respect to the base metal as expected. Similarly, the room temperature tensile tests show an improvement of ductility in the welded EBM samples. However, the yield and the ultimate strength show a marginal drop in the welded samples compared to the as-prepared EBM specimens. The present work demonstrates that solid-state FW process not only permits successful joining of additively manufactured materials, but also helps in improving their ductility.

Superior Wear Resistance in EBM-Processed TC4 Alloy Compared with SLM and Forged Samples.

The wear properties of Ti-6Al-4V alloy have drawn great attention in both aerospace and biomedical fields. The present study examines the wear properties of Ti-6Al-4V alloy as prepared by selective laser melting (SLM), electron beam melting (EBM) and conventional forging processes. The SLM and EBM samples show better wear resistance than the forged sample, which correlates to their higher hardness values and weak delamination tendencies. The EBM sample shows a lower wear rate than the SLM sample because of the formation of multiple horizontal cracks in the SLM sample, which results in heavier delamination. The results suggest that additive manufacturing processes offer significantly wear-resistant Ti-6Al-4V specimens in comparison to their counterparts produced by forging.

Surface Treatment of Powder-Bed Fusion Additive Manufactured Metals for Improved Fatigue Life

High-cycle fatigue (HCF) tests were conducted on samples fabricated by two powder-bed additive manufacturing techniques. Samples were tested with as-produced surfaces and after various non-contact surface improvement treatments. Ti-6Al-4V samples were made using both electron beam melting (EBM) and selective laser melting (SLM), while Inconel 625 was fabricated using SLM. Ti-6Al-4V was treated with a commercial chemically accelerated vibratory polishing process, with target material removal of approximately 200 µm from each surface for EBM samples and 100 µm for SLM samples. This technique led to increases in both the number of cycles before failure at a given loading condition and endurance limit (at 107 cycles) compared to samples with as-produced surfaces. The results are interpreted as the reduction in elastic stress concentration factor associated with surface defects where fatigue cracks initiate. SLM 625 was treated with both an abrasive polishing method and laser surface remelting. Both methods led to improvements in surface roughness, but these did not lead to improvements in fatigue properties of SLM 625. For abrasive polished samples, the combination of improved measured surface roughness without fatigue property enhancement suggests that surface material is removed, but the roots of surface defects, where fatigue cracks initiate, were left intact. For laser treatment, the remelted surface layer retained a rapidly solidified microstructure that did not increase the number of cycles before crack initiation even though the surface was smoother compared to the surface prior to polishing.

Influence of Inherent Surface and Internal Defects on Mechanical Properties of Additively Manufactured Ti6Al4V Alloy: Comparison between Selective Laser Melting and Electron Beam Melting.

Additive manufacture (AM) appears to be the most suitable technology to produce sophisticated, high quality, lightweight parts from Ti6Al4V alloy. However, the fatigue life of AM parts is of concern. In our study, we focused on a comparison of two techniques of additive manufacture—selective laser melting (SLM) and electron beam melting (EBM)—in terms of the mechanical properties during both static and dynamic loading. All of the samples were untreated to focus on the influence of surface condition inherent to SLM and EBM. The EBM samples were studied in the as-built state, while SLM was followed by heat treatment. The resulting similarity of microstructures led to comparable mechanical properties in tension, but, due to differences in surface roughness and specific internal defects, the fatigue strength of the EBM samples reached only half the value of the SLM samples. Higher surface roughness that is inherent to EBM contributed to multiple initiations of fatigue cracks, while only one crack initiated on the SLM surface. Also, facets that were formed by an intergranular cleavage fracture were observed in the EBM samples.

Microstructure and fracture properties of open-cell porous Ti-6Al-4V with high porosity fabricated by electron beam melting

The open-cell porous Ti-6Al-4V structure with high porosity, intended to be applied as replacement for human cancellous bone, were fabricated by electron beam melting (EBM). Computer aided design (CAD) was applied to design porous structures using the same unit cell with different unit cell sizes from 2.5 to 4 mm, different ligament widths from 600 to 900 μm, and different pore sizes from 1200 to 1800 μm, in order to achieve high porosity of 80% in avoiding the stress shielding effect. In comparison with the CAD designs and the EBM samples, there were minor discrepancies in terms of pore size and ligament width, mainly a result of melting pool. The measured data on the Young's modulus and yield strength of the EBM porous samples can be predicted by the Gibson and Ashby model. All samples with high porosity were found to match well with cancellous bone, with Young's modulus of 2 GPa and yield stress of 31 MPa, effective to diminish the risk of stress shielding effect. For porous EBM sample with high 80% porosity, the work of fracture can increase from 15.9 to 47.6 kJ/m2 with increasing ligament width from 600 to 900 μm.

Enhancing the tensile properties of EBM as-built thin parts: Effect of HIP and chemical etching

As-built Ti-6Al-4 V thin parts were manufactured using Electron Beam Melting (EBM) and characterized by optical microscopy and laboratory X-ray tomography in order to observe their microstructure, pore distribution and surface aspect. Chemical etching and HIP post-treatments were applied to as-built samples and their effect on the material and static mechanical properties were studied. Tensile tests were performed on both as-built and post-treated samples and their results compared to the ones reported in the literature for machined EBM samples. Because of the significant variations of the cross section observed along the gauge length, the calculation of the tensile stresses is not straightforward. Three simple sections were measured from the tomography scans. The average section along the gauge length was considered as the most suitable. The tensile mechanical properties of the as-built samples were studied and a detrimental effect of the surface state on the yield strength, ultimate tensile strength and elongation to failure was observed. Smoothing of the surface irregularities induced by chemical etching provoked an increase of those mechanical properties whereas the change of the microstructure generated by the HIP treatment leads to a decrease of the material strength that goes along with an increase of the ductility. Down scaling factors were proposed in order to take into account the sample state, as-built or post-treated.

A Comparison of Biocompatibility of a Titanium Alloy Fabricated by Electron Beam Melting and Selective Laser Melting.

Electron beam melting (EBM) and selective laser melting (SLM) are two advanced rapid prototyping manufacturing technologies capable of fabricating complex structures and geometric shapes from metallic materials using computer tomography (CT) and Computer-aided Design (CAD) data. Compared to traditional technologies used for metallic products, EBM and SLM alter the mechanical, physical and chemical properties, which are closely related to the biocompatibility of metallic products. In this study, we evaluate and compare the biocompatibility, including cytocompatibility, haemocompatibility, skin irritation and skin sensitivity of Ti6Al4V fabricated by EBM and SLM. The results were analysed using one-way ANOVA and Tukey’s multiple comparison test. Both the EBM and SLM Ti6Al4V exhibited good cytobiocompatibility. The haemolytic ratios of the SLM and EBM were 2.24% and 2.46%, respectively, which demonstrated good haemocompatibility. The EBM and SLM Ti6Al4V samples showed no dermal irritation when exposed to rabbits. In a delayed hypersensitivity test, no skin allergic reaction from the EBM or the SLM Ti6Al4V was observed in guinea pigs. Based on these results, Ti6Al4V fabricated by EBM and SLM were good cytobiocompatible, haemocompatible, non-irritant and non-sensitizing materials. Although the data for cell adhesion, proliferation, ALP activity and the haemolytic ratio was higher for the SLM group, there were no significant differences between the different manufacturing methods.

Microstructure, defects and mechanical behavior of beta-type titanium porous structures manufactured by electron beam melting and selective laser melting

This study investigates the differences in the microstructure, defects and mechanical behavior of porous structures from a β-type Ti24Nb4Zr8Sn manufactured by electron beam melting (EBM) and selective laser melting (SLM). The phases, size and shape of melt pool, volume and distribution of defects are analyzed and correlated to the compressive mechanical and fatigue properties. Due to different powder bed temperatures, the microstructure of EBM and SLM samples consists of α+β phases and a single β phase, respectively. The faster cooling rate during SLM promotes the formation of fine β dendrites, which leads to a higher compressive strength (50 ± 0.9 MPa) and lower Young's Modulus (0.95 ± 0.05 GPa) in comparison to the EBM parts (45 ± 1.1 MPa and 1.34 ± 0.04 GPa respectively). The large defects present within solid strut are likely a result of tin vaporization. The tin vapor is more easily trapped during the SLM process due to a smaller laser spot size and a faster cooling rate. This results in a 10 times increase in the number of defects. These defects have a limited influence on both the static properties and low stresses level fatigue strength, but it causes a reduced and variable fatigue life at high stresses level.

Corrosion evaluation of Ti-6Al-4V parts produced with electron beam melting machine

Purpose This paper aims to evaluate the corrosion behavior of Ti-6Al-4V parts produced with electron beam melting (EBM) machine and compare it with wrought Ti-6Al-4V alloy. Design/methodology/approach Potentiodynamic and potentiostatic tests were applied on EBM Ti-6Al-4V in 3.5 per cent mass NaCl solution to determine the pitting potential and critical pitting temperature (CPT). A relation between pitting potential and temperature was established for EBM Ti-6Al-4V alloy by conducting potentiodynamic testing under different temperatures. CPT was also measured for EBM Ti-6Al-4V alloy in 3.5 per cent mass NaCl solution at a standard potential of 800 mV vs saturated calomel electrode (SCE). The same tests were performed on wrought Ti-6Al-4V for comparison purposes. Moreover, CPT for EBM Ti-6Al-4V alloy was measured in 3.5 per cent mass NaCl solution of different pH of 2.0, 5.7 and 10.0 to examine the effect of aggressive conditions on the pitting corrosion of EBM alloy. Findings Potentiodynamic test resulted in a relatively high pitting potential of EBM alloy, which was close to the pitting potential of wrought alloy even at higher temperatures. In addition, EBM samples did not pit when potentiostatic test was performed at 800 mV vs SCE, even at high and low values of pH. Originality/value EBM Ti-6Al-4V alloy has been increasingly playing an important role in aerospace, automobile and industrial fields. The technique and conditions of manufacturing form voids and increase roughness of the exterior surface of EBM objects, which might increase the tendency to initiate pitting corrosion within its holes and surface folds. This article shows that, despite surface variations and porosity in EBM Ti-6Al-4V alloy, the material maintained its corrosion resistance. It was found that the corrosion behavior of EBM alloy was close to that of the conventionally made wrought Ti-6Al-4V alloy.