Browsing by Keyword "Titanium alloys"
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Item Bone cell adhesion on ion implanted titanium alloys(2005-06-22) Braceras, I.; Onate, J.I.; Goikoetxea, L.; Viviente, J.L.; Alava, J.I.; de Maeztu, M.A.; Tecnalia Research & Innovation; Biomateriales; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSThe authors have previously reported than ion implantation can have a significant effect on osseointegration of an implant, specially when the latter is introduced in areas of poorer bone density. These results indicate that this process is particularly suited for implant devices introduced in elderly patients or in those regions that have a poor quality of bone. The aim of this work is directed to study osteoblast adhesion on Ti alloy surfaces with different ion implantation treatments, so osseoconductive properties of several surfaces can be assessed. Polished discs of Ti–6Al–4V and Ti CP GR1 titanium alloy have been prepared and ion implanted with different species and parameters (dose and energy). Afterwards, the samples have been sterilized by UV light, inoculated with 1.5×105 human bone cells and incubated during 4 h at 37 C and 5% CO2 atmosphere. Then, once fixed and rinsed, image analysis has been used to quantify the number of cells attached to the Ti discs. On a second round of tests, cell proliferation tests have been conducted during 24, 48, 144 and 192 h, respectively. Furthermore, surface analysis techniques (e.g. AFM) have been applied to learn about the qualitative behavior, i.e. morphology, of the attached cells. Cell attachment has shown to be highly sensitive to ion implantation parameters. Although some quantitative differences have been observed, the more significant differences were qualitative. AFM analysis has shown that the star-shaped bone cells attached spread more and occupied larger surfaces like in osseointegration prone surfaces, most probably due to extracellular matrix synthesized around them, while other surfaces showed mainly large and narrow shaped or round shaped bone cells often with great cellular nucleus in the middle of the cells and little extracellular matrix around. So, ion implanted surfaces that facilitate osseointegration have been identified, in terms of initial bone cell attachment quality, where although the number of attached cells were not necessarily always larger, they tended to occupy wider areas with healthier cells.Item Compatibility of materials with hydrogen. Particular case: Hydrogen embrittlement of titanium alloys(2009-07) Madina, V.; Azkarate, I.; MATERIALES PARA CONDICIONES EXTREMAS; Tecnalia Research & InnovationA review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials, hydrogen embrittlement, low temperature effects, material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials, the hydride formation of titanium alloys is considered. Hydrogen absorption and the possible associated problems must be taken into account when considering titanium as a candidate material for high responsibility applications. The sensitivity of three different titanium alloys to the Hydrogen Assisted Stress Cracking phenomena has been studied by means of the Slow Strain Rate Technique (SSRT). The testing media have been sea water and hydrogen has been produced on the specimen surface during the test by cathodic polarization. Tested specimens have been characterized by metallography and scanning electron microscopy. Results obtained show that the microstructure of the materials, particularly the β-phase content, plays an important role on the sensitivity of the studied alloys to the Hydrogen Assisted Stress Cracking Phenomena.Item Development of the ERS process for the fabrication of titanium components(European Powder Metallurgy Association (EPMA), 2020) Lagos, M. A.; Agote, I.; Vicente, A.; Amigó, V.; López, D.; Calero, J. A.; EXTREMATElectric Resistance Sintering (ERS) is a low-cost alternative to Spark Plasma Sintering (SPS). In the developed process the duration of the cycles is very short (seconds) and without protective atmosphere. These features allow an easy industrialization of the process. This paper shows the processing of different titanium alloys by ERS and the effect of the type of powder and composition in the densification of the alloys. The characterization of the products includes the microstructural analysis, EBSD, crystallographic phases by XRD, elastic modulus and bending strength. In addition, oxygen content of the obtained materials was analyzed in detail considering the parameters of the process. It was possible to obtain full densification of the compacts and mechanical properties show interesting results.Item Effect of ERS process parameters on the microstructure and mechanical properties of Ti6Al4V(European Powder Metallurgy Association (EPMA), 2019) Amigó-Mata, A.; Gouvea, Eber; Lagos, M. A.; López, D.; Jesús-Romero, I.; Agote, I.; Vicente-Escuder, A.; Calero, J. A.; EXTREMATThe application of the Electric Resistance Sintering (ERS) process has the advantage of rapid densification and sintering, but it needs to analyse the influence of the parameters on the microstructure and final mechanical properties in a titanium alloy. In an ERS equipment, different current intensities will be applied to atomized powders of Ti-6Al-4V using the commercial pure Ti (CP) with the same parameters as the reference material. Its effect on the microstructure obtained along the thickness of the sample will be analysed. The mechanical characteristics will be determined by tensile and cantilever bending tests, together with maps of microhardness distribution that allows relating the mechanical behaviour with the microstructure applying backscattered electron diffraction techniques (EBSD).Item Growth of carbon layers on Ti-6Al-4V alloy by very high dose carbon implantation(1997-12) García, A.; Viviente, J. L.; Alonso, F.; Loinaz, A.; Oñate, J. I.; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Centros PRE-FUSION TECNALIA - (FORMER); Tecnalia Research & InnovationIon implantation is a useful technique to tailor the surface properties of Ti-6Al-4V alloys. In particular, very high dose C+ implantation (in the range of 1018 ions cm-2) offers the possibility of forming carbon layers without a sharp interface with the substrate material. In this study, ion implantation treatments have been performed on Ti-6Al-4V with C+ doses up to 4 × 1018 ions cm-2. XPS analyses have been carried out to evaluate the chemical states after ion implantation. A change in C 1s binding energies has been observed depending on the carbon concentration in the implanted layer. At relatively low or medium concentrations (about 41 at.% C) mainly carbidic bonds were present, but when the concentration increased up to 88 at.%, the binding peak shifted to values that correspond to C-C bonds. Dynamic microindentation techniques, used to evaluate the hardness of the implanted material, have shown a significant change in relative hardness as a function of C+ dose, owing to the formation of a carbon layer in the titanium alloy surface. A two-fold increase in the hardness ratio and elastic recovery values is observed for the highest implanted dose.Item Influence of the filler metal on the properties of Ti-6Al-4V electron beam weldments. Part I: Welding procedures and microstructural characterization(2009-11-05) Irisarri, A. M.; Barreda, J. L.; Azpiroz, X.; Tecnalia Research & Innovation; EXTREMATThe use of different procedures for electron beam welding of 17 mm thick Ti-6Al-4V plate and the difficulties found in this process are analysed. When this alloy was welded autogeneously the presence of significant amounts of α martensite was observed, recommending looking for another solution. In the early trials a V joint design was used but distortions and defects were detected in the welds when multi-pass procedures were considered. Consequently, for the remaining weldments K or I joint configurations were selected. Initially, Ti-6Al-4V wire was preferred in order to match mechanical properties with base material but no significant improvement was found leading to consideration of using a less alloyed filler metal. Different commercially pure titanium filler metals have been employed to optimise the performance of the fusion zone of electron beam weldments. In a second paper [1] the influence of the welding procedure on the mechanical properties of the various joints will be discussed.Item Materials and hydrogen. Hydrogen assisted stress cracking of titanium alloys(2008-05) Azkarate, I.; Ezponda, E.; Madina, V.; Tecnalia Research & Innovation; MATERIALES PARA CONDICIONES EXTREMASA review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials, hydrogen embrittlement, low temperature effects, material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials, the hydride formation of titanium alloys is considered. Alpha titanium alloys are considered corrosion resistant materials in a wide range of environments. However, hydrogen absorption and the possible associated problems must be taken into account when considering titanium as a candidate material for high responsibility applications. The sensitivity of three different titanium alloys, Ti Gr-2, Ti Gr-5 and Ti Gr-12, to the Hydrogen Assisted Stress Cracking phenomena has been studied by means of the Slow Strain Rate Technique (SSRT). The testing media has been sea water and hydrogen has been produced on the specimen surface during the test by cathodic polarization. Tested specimens have been characterized by metallography and scanning electron microscopy. Results obtained show that the microstructure of the materials, particularly the β phase content, plays an important role on the sensitivity of the studied alloys to the Hydrogen Assisted Stress Cracking Phenomena.Item Tribological study of lubricious DLC biocompatible coatings(2002-12-01) Brizuela, M.; Garcia-Luis, A.; Viviente, J. L.; Braceras, I.; Oñate, J. I.; INGENIERÍA DE SUPERFICIES; TECNOLOGÍAS DE HIDRÓGENO; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Tecnalia Research & InnovationDLC (diamond-like carbon) coatings have remarkable tribological properties due mainly to their good frictional behavior. These coatings can be applied in many industrial and biomedical applications, where sliding can generate wear and frictional forces on the components, such as orthopaedic metal implants. This work reports on the development and tribological characterization of functionally gradient titanium alloyed DLC coatings. A PVD-magnetron sputtering technique has been used as the deposition method. The aim of this work was to study the tribological performance of the DLC coating when metal to metal contact (cobalt chromium or titanium alloys) takes place under dry and lubricated test conditions. Prior work by the authors demonstrates that the DLC coating reduced considerably the wear of the ultra-high-molecular-weight polyethylene (UHMWPE). The DLC coating during mechanical testing exhibited a high elastic recovery (65%) compared to the values obtained from Co-Cr-Mo (15%) and Ti-6AI-4V (23%). The coating exhibited an excellent tribo-performance against the Ti-6AI-4V and Co-Cr-Mo alloys, especially under dry conditions presenting a friction value of 0.12 and almost negligible wear. This coating has passed biocompatibility tests for implant devices on tissue/bone contact according to international standards (ISO 10993).Item Wire arc additive manufacturing Ti6Al4V aeronautical parts using plasma arc welding: Analysis of heat-treatment processes in different atmospheres(2020) Artaza, Teresa; Suárez, Alfredo; Veiga, Fernando; Braceras, Inigo; Tabernero, Iván; Larrañaga, Oihane; Lamikiz, Aitzol; FABRIC_INTEL; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIESPAW (Plasma Arc Welding), a WAAM (Wire Arc Additive Manufacturing) technology with high deposition rates, can produce metallic components, layer by layer, of varied sizes, from different alloys, yielding high mechanical performance. Two Ti6Al4V walls are manufactured in an inert argon atmosphere using WAAM-PAW to analyze the deposition process in terms of growth in height per layer, deposition process temperature, and cooling times. The properties of the walls are compared with the values obtained from a thermomechanical simulation and both the microstructural and mechanical properties of the annealed WAAM-PAW wall are studied. Moreover, the effect of the media on the oxidation layer and on the mechanical properties are also analyzed throughout the heat treatment process, as well as the microstructure of Ti6Al4V. Stable deposition rates were achieved for a high deposition ratio of Ti6Al4V at 2 kg/h, restricting the oxygen levels to under 100 ppm. No significant differences were found in either the microstructural or the mechanical properties following heat treatments in a vacuum, in air or in argon. All the heat-treated samples met the AMS4928 standard for Yield Strength (YS) and Ultimate Tensile Strength (UTS).