1,720,984 research outputs found
Electropolishing in ecofriendly solution of Ti6Al4V parts produced by electron beam melting
No full textThe additive manufacturing process is gaining increasing interest due to the possibility of producing components with a complex shape, very close to the final geometry. On the other hand, however, it involves a very high final roughness, such as to compromise the mechanical performance and resistance to corrosion. Therefore, post-processing treatments are required. Electropolishing could be the ideal treatment to reduce the roughness of these components. It is known that various parameters, such as the type of electrolyte solution, the voltage or current applied, the treatment time, agitation, etc. They could affect the effectiveness of the electropolishing treatment. The most used electrolyte solutions are dangerous to handle and difficult and expensive to dispose of. The aim of this work was to study a possible electropolishing treatment on Ti6Al4V samples made by Electron Beam Melting (EBM) using an “eco-friendly” electrolytic solution
Evaluation of roughness and electrochemical behavior of titanium in biological environment
No full textThe increasing use of titanium in the biomedical field arises from the excellent biocompatibility due to the ability to spontaneously become covered with a passive layer. Several studies have shown that some surface treatments can enhance the biological response and corrosion resistance of the implants. The aim of this work is to study the effect of surface treatments of sandblasting and etching with HF on the electrochemical behavior in biological environment and on the roughness of two types of commercially pure titanium, Ti grade 2 and Ti grade 4, used for prostheses and dental implants. The electrochemical characterization has allowed showing that the passive current density increases with the duration of the sandblasting treatment for both alloys. A smaller increase was found in samples subjected to blasting and subsequent etching. It follows that the variation of specific surface induced by blasting is partially canceled by the chemical treatment. The value of passive current density was used to assess the extent of the increase of the real surface of the samples. The roughness analysis showed that the blasting process produces a surface with a large number of peaks, and that the etching with HF tends to level the surface attenuating peaks. The sandblasting and etching treatments, alone or combined, significantly modify the surface of the samples and the magnitude of this change differs depending on the alloy used. Finally, it is proposed to use four roughness parameters to characterize the treated surfaces
The Electropolishing of Additively Manufactured Parts in Titanium: State of the Art
No full textRecently, additive manufacturing technologies have begun to play a significant role in the industrial field due to the possibility to build complex, near-net-shape, and porous parts, optimizing costs, and time processing. Simultaneously, the high roughness of additively manufactured parts remains a critical drawback, limiting their use like an as-built component. Therefore, postprocessing treatments are needed. The electropolishing (EP) treatment could be ideal for simple, complex, or porous parts characterized by low surface quality. Herein, it is aimed to provide the state of the EP treatment's art carried out, to date, on additively manufactured parts made of titanium and Ti6Al4V alloy. A scientific literature research on EP of additively manufactured titanium and Ti6Al4V alloy is conducted using the Scopus database. The evaluation of recent research, still very few to date, reveals that a significant reduction of the roughness can also be achieved in complex shape additively manufactured parts. Although the EP is a versatile technique to reduce the roughness of additively manufactured parts, further studies are needed to improve its effectiveness, especially for complex and porous structures, to reduce the environmental impact of the materials used
Metallic Biomaterials Surface Engineering
No full textMetals are widely used as biomaterials due to their good thermal conductivity and mechanical and surface properties [...
Designing the Surface of Medical Devices
No full textThe most important properties of metal medical devices are i) biocompatibility, ii) mechanical strength and, in some cases, iii) reliable osseointegration. The surface of biodevices can be designed and then modified to improve these properties. After a brief review of the technologies used to modify the surface of metallic biodevices, some examples of surface treatments used to improve their properties are given. The effect of acid etching on the surface shape of the metal material to improve implant osseointegration, to produce a surface with more ‘valleys’ than ‘peaks’, a requirement for improved osseointegration, is shown. It is demonstrated that the “shape” of the surface can be easily and quantitatively measured by using appropriate roughness parameters. In addition, to reduce the risk of implant rejection, nanoscale reservoirs for controlled drug delivery can be formed on the previously acid-etched implant surface. To this end, the methods used to grow titania nanotube dental screws from commercially pure titania are presented. The shape and length of the nanotubes can be varied to increase or decrease the duration of drug delivery as required
As-Built EBM and DMLS Ti-6Al-4V Parts: Topography–Corrosion Resistance Relationship in a Simulated Body Fluid
No full textMachined devices made of titanium or titanium alloys are widely used in biomedical applications. Recently, additive manufacturing technologies (AM) were proposed to reduce the cost of parts and customise their shape. While several researchers have studied the characterisation of the machined surfaces of AM products, less attention has been focused on the study of the surfaces of as-produced parts. The aim of this study was to compare the surface and bulk properties of Ti-6Al-4V alloy products obtained using two types of AM—i.e., electron beam melting and direct metal laser sintering—in comparison to the wrought material and analyse their metallographic, crystallographic, topographic, and electrochemical properties. The metallographic and crystallographic, as well as topographic, analysis showed different microstructures and surface area extensions between the tested specimens. Potentiodynamic polarisation tests highlighted the complex electrochemical behaviour of additively manufactured parts if compared to that of the traditionally fabricated ones. The tests performed on mechanically polished parts underlined similar electrochemical performance between them, even if the additive manufactured ones exhibited a certain instability. Although the as-produced additive manufactured parts present exciting surface shapes, useful in the biomedical field, significant drawbacks remain. A more in-depth study of the device surface modifications, to improve their electrochemical behaviour, is needed
Corrosion resistance of additive manufactured titanium alloy parts: The effect of recycled powders
No full textThe possibility to reduce costs of the additive manufacturing (AM) technologies by using recycled powders is still an open question. The present paper aims to investigate the effect of using virgin and recycled powders on the corrosion resistance of Ti6Al4V titanium alloy additive manufactured parts. Although the study of the electrochemical behaviour of titanium parts produced by using AM is present in the literature, the corrosion resistance of samples manufactured using recycled powders is less investigated. This work would like to contribute to the deepening of this aspect. The experimental investigations have been carried out on as-built samples as well as on samples after mechanical polishing. The metallographic observations of additive manufactured samples showed a martensitic microstructure inside the prior β grain grew up as columnar structure. X-ray diffraction analysis revealed the presence of titanium oxide in rutile crystallographic phase. The electrochemical characterisation unveiled the lower corrosion resistance of the as-built additive manufactured components compared to the traditional counterpart. It also highlighted the effect due to the use of recycled powders when the bulk of the samples has been investigated
Surface Engineering of Magnesium Alloys for the Next Generation of Biodegradable Device
No full textAlthough the biocompatibility and good mechanical properties make the magnesium and its alloys excellent candidates for biomedical applications, the high corrosion rate, involving hydrogen release and the alkalization of the physiological environment, limit their clinical use. However, this constrain could be exploited for the realization of biodegradable devices. In this regard, it is necessary to ensure a degradation rate comparable to the rate of growth of the hosting tissues, avoiding side effects, premature failures, and adverse reactions. The surface engineering approaches which involve the use of a coating made of single or multiple layers represent a possible method to tailor the deterioration rate. The poor adhesion strength between layers could be an important drawback of this approach. In the present research, a multilayer coating composed of an oxide layer, a bio-inspired polydopamine (PDA)-based one and a biodegradable polymer film, made of polylactic acid (PLA) has been realized on magnesium alloys substrates. The first layer was obtained by a plasma electrolytic oxidation (PEO) treatment to increase the corrosion resistance. Then, the polydopamine layer has been applied by the dip-coating method to improve the adhesion between the oxide layer and the polylactic acid film. Each layer and their combinations were characterized by using morphological examinations, and electrochemical test by means of potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS) methods. The use of a multilayer coating has demonstrated to be a promising strategy to control the degradation rate of the magnesium alloys to produce biodegradable device
Durability of AZ31 magnesium biodegradable alloys polydopamine aided. Part 2: Ageing in Hank's solution
Full text linkMagnesium alloys are candidates as biodegradable medical materials due to their biocompatibility and favorable mechanical properties. Unfortunately, the high corrosion rate in physiological media and the release of hydrogen, limit their widespread use in biomedical applications. In this work, an intermediate coating based on polydopamine (PDOPA), between Mg substrate and an organic coating, was used to decreasing the degradation rate of AZ31 magnesium alloy, during the long-term exposure in simulated body fluid. Electrochemical Impedance Spectroscopy measurements were carried out to study the corrosion resistance of samples. Results demonstrated that the PDOPA interlayer determined the reduction of the substrate degradation rate. The results were interpreted supposing a synergistic effect which occurred when PDOPA and the organic coating were used together
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