Titanium Alloy Grade Research Articles

Tuning nanofluids for improved lubrication performance in turning biomedical grade titanium alloy

In this paper, two nanofluids suitable for minimum quantity cooling and lubrication (MQCL) assisted turning of Ti6Al4V ELI are reported after a comprehensive study of 18 nanofluids. The nanofluids were prepared by adding three different nanoparticles (Al2O3, MoS2, and rutile-TiO2) to vegetable oils (canola and extra virgin olive oils) respectively, at three different concentrations (0.5, 2, and 4% vol). The use of canola nanofluid containing 0.5 vol% Al2O3 provided a superior surface finish; on the other hand, canola nanofluid enriched with 0.5 vol % MoS2 was found to be conducive to lowering T and increasing rc. Moreover, the nanofluids rendered an auspicious tool wear behavior and impeded attrition wear. Traces of tribofilm formation and the effect of nano-polishing were identified after examining the finished surface using scanning electron microscopy and energy dispersive x-ray spectroscopy. This analysis also reports on the kinematic and dynamic viscosity, contact angle, contact area and thermal conductivity of the nanofluids, the machined surface morphology, and the improvements concerning surface defects provided by the engineered nanofluids. Finally, the results were compared with those found for dry machining and mineral oil based MQCL turning.

Characterisation of laser metal deposited titanium and molybdenum composite

Laser Metal Deposition (LMD) is a unique way of building components by adding the material(s) layer by layer until the components are built. This process is based on the geometry path defined by the CAD model data form the component development. This paper reports on the characterization of Laser Metal Deposited Titanium alloy and Molybdenum Powder on Titanium alloy grade 5 substrate. The depositions are the process of delivering of the Titanium and Molybdenum powder from a powder feeder of two different hoppers containing each powder. The deposited samples were achieved through the combination of different ratios of Titanium and Molybdenum, i.e. 95%, 90% and 85% of Titanium and 5%, 10%, 15% Mo respectively. Three sets of experiments were conducted with multiple tracks at a constant laser power of 1.2kW, Scan speed of 0.5m/min and gas flow rate at 2 l/min. While the powder flow rate for both Ti6Al4V and Mo were varied. The deposits were sectioned through the thickness, metallographically prepared and characterized through microstructural evaluation and microhardness. The results from the microstructure revealed that columnar grains describe the layers, which gives an excellent interfacial bonding between the layers. The Micro Vickers hardness values were observed to decrease as the percentage of Mo increases. Through the EDS, the un-melted powders and pores were identified. Also, the grain sizes were found to reduce as the percentage of Molybdenum increases.

Investigation of pulsed electrochemical micro-drilling on titanium alloy in the presence of complexing agent in electrolyte

Titanium and its alloys have excellent mechanical and chemical properties; however, these properties make the processing of titanium alloys more challenging compared with other engineering materials. Electrochemical micromachining (ECMM) is a non-conventional machining process, which removes material through anodic dissolution regardless of the material’s hardness. However, during the electrochemical machining of titanium, the formation of a passive oxide layer inhibits further material removal and deteriorates the machined surface quality. In addition, the accuracy of micromachining of titanium alloys is especially affected by the formation of electrolysis precipitates such as TiO2 and stray current dissolution. In this study, the effect of the addition of the complexing agent to different electrolytic solutions on the radial overcut during micro-drilling of titanium alloy grade 5 (Ti6Al4V) has been experimentally studied using the in-house developed ECMM set-up. The influence of parameters such as applied voltage and different electrolytic concentration with and without the complexing agent on overcut during ECMM on Ti6Al4V of micro-holes has been studied. It has been safely concluded that the quality of micro-holes fabricated in the presence of EDTA in the electrolyte while machining is responsible for better dimensional characteristics.

Anodised TiO2 nanotubes as a scaffold for antibacterial silver nanoparticles on titanium implants

Medical grade titanium alloy is widely used for bone/dental implants, but the material alone has no innate antimicrobial properties that would reduce infection risk following surgery. However, silver nanoparticles (Ag NPs) are known to be antibacterial. This study investigated the growth of Ag NPs on titanium dioxide nanotubes (TiO2 NTs) on Ti-6Al-4V discs. The TiO2 NTs were grown on the Ti alloy using an electrochemical method, and then decorated with Ag NPs. The Ag NPs were synthesised by chemical reduction using δ-gluconolactone. A silver ammonia solution (silver nitrate + liquid ammonia) was used as the source of silver. Two separate approaches were used: (1) The δ-gluconolactone was mixed with the silver ammonia and then exposed to the TiO2 NTs (the ‘mixing method’), which produced micron-sized clusters of the Ag NPs. (2) The TiO2 NTs were exposed to the silver ammonia first and then to δ-gluconolactone (the ‘sequential addition method’), which resulted in the formation of nano-sized clusters of the nanoparticles. The Ag-TiO2 composites were confirmed by scanning electron microscopy and the elements analysed using energy dispersive X-ray spectroscopy (EDS). The composite coatings were exposed to a simulated body fluid for 24 h in order to determine the total Ag released. The release from the micron-sized clusters from the mixing method (14.6 ± 0.67 ppm) was higher than that from the nano-sized clusters (4.05 ± 0.36 ppm) when 0.015 M of silver ammonia was used. Additionally, Staphylococcus aureus, was cultured on the composite coatings for 24 h. Both the micron- and nano-sized clusters of the Ag NPs were found to be antibacterial using the Live/Dead assay. Overall, δ-gluconolactone was successfully used to reduce silver to Ag NPs on the surface of TiO2 NTs. The sequential addition method was the preferred method of synthesis because of its slower silver release, better coverage of the Ag-NPs on the TiO2 NTs and strong antibacterial properties.

The Influence of Ultrasonic Vibration Frequency on the Properties of TiN Coated Biomedical Ti–13Zr–13Nb

Bare biomedical grade titanium alloys are prone to degradation when in a body fluid environment. Surface coatings such as Physical Vapor Deposition (PVD) can serve as one of the options to minimize this issue. Past reports showed that the PVD coated layer consists of pores, pinholes, and columnar growths which act as channels through which the aggressive medium attacks the substrate. Duplex and multilayer coatings seem able to address this issue to varying extents but at the expense of manufacturing time and cost. In this paper, the effect of an ultrasonic vibration frequency on PVD TiN coated Ti–13Zr–13Nb biomedical alloy was studied. Disk type samples were prepared and coated with TiN at fixed conditions: bias voltage (−125 V), substrate temperature (300 °C), and nitrogen gas flow rate (300 standard cubic centimeters per minute (SCCM)). An ultrasonic vibration was then subsequently applied to the TiN coated samples at frequencies of 8 kHz and 16 kHz for 5 min. All TiN coated samples treated with ultrasonic vibrations exhibited a higher corrosion resistance than the untreated ones. Microstructure analysis under Field Emission Scanning Electron Microscopy (FESEM) confirmed that the coated sample at frequencies of 16 kHz produced the most compact coating. It is believed that the hammering effect of the ultrasonic vibration reduced the micro channels’ size in the coating and thus decelerated the corrosion’s attack.

Investigation of tool wear and surface roughness on machining of titanium alloy with MT-CVD cutting tool

In this study, machining of titanium alloy (grade 5) is carried out using MT-CVD coated cutting tool. Titanium alloys possess superior strength-to-weight ratio with good corrosion resistance. Most of the industries used titanium alloy for the manufacturing of various types of lightweight components. The parts made from Ti-6Al-4V largely used in aerospace, biomedical, automotive and marine sectors. The conventional machining of this material is very difficult, due to low thermal conductivity and high chemical reactivity properties. To achieve a good surface finish with minimum tool wear of cutting tool, the machining is carried out using MT-CVD coated cutting tool. The experiment is carried out using of Taguchi L27 array layout with three cutting variables and levels. To find out the optimum parametric setting desirability function analysis (DFA) approach is used. The analysis of variance is studied to know the percentage contribution of each cutting variables. The optimum parametric setting results calculated from DFA were validated through the confirmation test.

Experimental and Numerical Analysis of Titanium Alloy Microtube Tube-End Nosing Forming

This study is mainly based on five sets of mold cone angle and friction coefficient of micro-tube tube end necking forming analysis, and the tool cone angle of 60° experimental verification is carried out to analyze the titanium alloy (Grade 1) micro-tube for different mold cone angle and the different friction coefficient caused by the difference between the shrinkage forming. In this paper, Prandtl-Reuss's plastic flow rule, combined with finite element deformation theory and updated Lagrangian formulation (ULF) concept, establish an incremental elasto-plastic finite element analysis program for simulating the miniature tube end necking. The forming process also uses the generalized rmin algorithm to deal with elasto-plastic state and contact problems. From the simulation data of necking process, deformation history, punch load and punch stroke, stress and strain distribution is obtained. The analysis results show that by increasing the mold cone angle and friction coefficient, the thickness tends to be thicker in the certain area.

Fem and Von Mises Analysis of OSSTEM ® Dental Implant Structural Components: Evaluation of Different Direction Dynamic Loads.

Purpose:The objective of this investigation is to study prosthodontics and internal components resistance to the masticatory stress and considering different force directions by using Finite Element Method analysis (FEM). The structural materials of the components are usually Titanium alloy grade 4 or 5 and thus, guarantee the integration of the fixture in the bone due to the osteointegration phenomena. Even if the long-term dental implant survival rate is easy to be obtained and confirmed by numerous researches, the related clinical success, due to the alteration of the mechanical and prosthodontics components is still controversial.Methods:By applying engineering systems of investigations like FEM and Von Mises analyses, it has been investigated how dental implant material was held against the masticatory strength during the dynamic masticatory cycles. A three-dimensional system involved fixture, abutment and the connection screws, which were created and analyzed. The elastic features of the materials used in the study were taken from recent literature data.Results:Data revealed a different response for both types of devices, although implant neck and dental abutment showed better results for all conditions of loading while the abutment screw represented aweak point of the system.Conclusion:The data of this virtual model showed all the features of different prosthetic retention systems under the masticatory load. Clinicians should find better prosthetic balance in order to better distribute the stress over the component and to guarantee patients’ clinical long-term results.

Corrosion and biocompatibility examination of multi-element modified calcium phosphate bioceramic layers

Multi-ions doped bioactive calcium phosphate (dCaP) layers were developed by pulse current deposition onto surgical grade titanium alloy material (Ti6Al4V). The coatings were electrodeposited from base electrolyte containing adequate amounts of calcium nitrate and ammonium dihydrogen phosphate at 70 °C. After electrodeposition, the pure CaP layers were doped with different ions that possess bioactive and antimicrobial properties, such as Zn2+, Mg2+, Sr2+ and Ag+ ions. The morphology and structure of coatings were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray Spectroscopy (EDX) as well as XRD and FT-IR measurements. The results revealed the pulse current deposited and surface post-treated CaP layer to be mainly in hydroxyapatite phase. The corrosion properties of bioceramic coatings were assessed in conventional simulated body fluid (SBF) in a three electrode open cell by using potentiodynamic polarization measurements over two weeks period. The electrochemical results revealed that the pure calcium phosphate (CaP) coated implant material and the bare implant possess the highest resistivity to corrosion, while the modified calcium phosphate coating showed lower corrosion resistance by at least one order of magnitude. The cell viability measurements showed that the electrochemically deposited CaP layer was biocompatible.

High Strain Rate and High Temperature Behavior of Ti–6Al–4V Alloy Under Compressive Loading

The titanium alloy (grade 5) is a two-phase material, which finds significant applications in aerospace, medical, marine fields, owing to its superior characteristics like high strength-to-weight ratio, excellent corrosion resistance, and good formability. Hence, the dynamic characteristics of the Ti-6Al-4V alloy are an important area to study. A compressive split Hopkinson pressure bar (SHPB) was used to evaluate the dynamic properties of Ti-6Al-4V alloy under various strain rates between 997 and 1898s−1, and at temperatures between −10 °C and 320 °C. It was evident that the material strength is sensitive to both strain rate and temperature; however, the latter is more predominant than the former. The microstructure of the deformed samples was examined using electron back-scattered diffraction (EBSD). The microscopic observations show that the dynamic impact characteristics of the alloy are higher at higher strain rates than at quasi-static strain rates. The SHPB tests show that the force on the transmitter bar is lower than the force on the incident bar. This indicates that the dynamic equilibrium cannot be achieved during high rate of damage evolution. Various constants in Johnson–Cook (JC) model were evaluated to validate the results. An uncertainty analysis for the experimental results has also been presented.

Weakly Stable Structural-Phase States of a Submicrocrystalline Alloy Grade 2 in the Weld Zone Obtained Using Electron-Beam Welding

The structural-phase state of weld joints of the samples of Grade 2 alloys with micro- and submicrocrystalline structure is studied using methods of X-ray diffraction analysis. The weld joint was obtained by joining plates with a thickness of 2 mm using the electron-beam welding method. It is established that the transfer of the titanium alloy Grade 2 from the microcrystalline state into the submicrocrystalline state during the process of gradual grinding of grains in the samples by the abc-pressing method at a parallel stepwise decrease of the temperature in the range of 750-500 °C leads to an intensive introduction of oxygen atoms into the crystalline lattice of the solid solution a-Ti. The presence of an increased content of oxygen atoms in the crystalline lattice of the solid solution a-Ti in the submicrocrystalline state in the Grade 2 alloy in the weld zone and in the heat-affected zone promotes the formation of metastable phases w-Ti and α''-Ti. The obtained results made it possible to assume that in the process of electron-beam welding in the Grade 2 alloy in the submicrocrystalline state, an increased concentration of interstitial oxygen atoms in the crystalline lattice of the solid solution based on a–Ti plays a significant role in the formation of a wide range of structural-phase states in the weld zone and in the heat-affected zone.

Heat affected zone Relationship with processing parameter in Additive Manufacturing Process

The microstructural development in additive manufacturing process is characterized by columnar grains that are produced as a result of globular grains that are formed in the heat affected zone during solidification of melt pool. This microstructure development also account for the evolving property disparity obtained using additive manufacturing process that is largely dependent on the processing parameters. In this study, heat affected zone produced during laser metal deposition process of laser metal deposition of titanium alloy grade five was studied. Laser metal deposition process is an additive manufacturing technology. The laser power was varied from 0.8 to 3.0 kW while other processing parameters were kept at constant values. The influence of laser power on the length of heat affected zone into the substrate was studied. The study showed that the length of heat affected zone increases with increasing laser power. The importance of this study is know the length of this heat affected zone as it relates to the laser power, the knowledge will help to know the highest power to employ for application where this heat affected zone needs to be minimized.

Experimental determination of the temperature in the cutting zone during turning of titanium alloy grade 2

Czasopismo Techniczne » 2018 » Volume 8 » Experimental determination of the temperature in the cutting zone during turning of titanium alloy grade 2 A A A

Taguchi-Grey Relational Based Multi-Response Optimization on the Performance of Tool Coating Thickness in Pocket Milling

In this paper, the Taguchi method and Grey relational analysis is used to evaluate the effect of tool coating thickness by machining Titanium Alloy Grade 5 (Ti6Al4V) with Titanium Aluminium Nitrate (TiAlN) Nano coated tools by varying their coating thickness. The pocket milling operation is carried out using the L9 orthogonal array with three levels and four factors design on the CNC vertical machining center. The tool coating thickness, spindle speed, feed rate and depth of cut was selected as machining input parameters for the experiment. The various output parameters such as cycle time, tool wear, surface roughness, material removal rate, micro hardness were found out after machining process. After obtaining all the output parameters the optimization was done by finding out the S/N ratio and grey relation analysis method. According to grey relational grading it was found out that tool coating thickness is the most affected factor for the machining. The confirmation test was done using the optimized value and the results obtained were close to each other.

The Analysis of Causes of the Damage of a Turbine Blade Made of Ti-6Al-4V Alloy

The main causes of the damage of a compressor’s turbine blade are documented and described in the article. The turbine blade was made from titanium alloy grade 5 (VT6, Ti-6Al-4V). The analysed segments of the turbine blade were damaged by corrosion and erosion. The sample from the damaged blade was compared with an undamaged reference sample. The observed substantial distinctions between microstructure of the damaged and the reference sample were found using of light and scanning electron microscopy. The observed distinctions of the microstructure were caused by the differences in the heat treatment process.

Development and characterization of multi-element doped hydroxyapatite bioceramic coatings on metallic implants for orthopedic applications

Multi-element modified bioactive hydroxyapatite bioceramic (mHAp) coatings were successfully developed onto surgical grade titanium alloy material (Ti6Al4V). The coatings were prepared by pulse current deposition from electrolyte containing adequate amounts of calcium nitrate and ammonium dihydrogen phosphate at 70C. The pure HAp layer was doped and co-deposited with Ag, Zn, Mg, Sr ions. The biocompatible properties of layers were investigated by seeding osteoblast-like MG-63 cells onto the samples’ surface. The biocompatible measurements revealed enhanced bioactivity of modified HAp compared to uncoated implant materials and pure bioceramic coating. The morphology and structure of coatings and cells were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) as well as FT-IR and XRD measurements. The biodegradable properties of samples were investigated by electrochemical potentiodynamic measurements.

Corrosion Behavior of Titanium Oxynitrided by Diffusion and Magnetron Sputtering Methods in Physiological Solution

Abstract This work presents the study of the corrosion-electrochemical behavior of titanium alloy Grade 2 treated with combined coatings—presaturation with nitrogen diffusion layer by thermal-chemical treatment, oxygen diffusion layer by thermal-chemical treatment, and a titanium oxynitride (TiNxOy) coating deposited by magnetron sputtering—in physiological solution. Structural analysis has shown that TiNxOy can be represented as a face-centered cubic (fcc) structure in which nitrogen atoms are replaced by oxygen atoms, or oxygen atoms are replaced by nitrogen atoms. Presaturation of titanium Grade 2 with oxygen and nitrogen leads to the formation of TiNxOy with near equiatomic composition at subsequent oxynitriding by magnetron sputtering. Rutherford backscattering spectrometry (RBS) measurements show the homogeneity of the coating composition. The surface of titanium Grade 2 with a nitrogen diffusion layer presents the highest lightness factor and reflectivity in the range of the visible spectrum. Diffusion presaturation of titanium Grade 2 with either oxygen or nitrogen provides better adhesion of TiNxOy film to substrate. The presence of an oxygen diffusion layer leads to a stronger bond. It was found that a TiNxOy coating increases the corrosion resistance (isotonic solution of 0.9 % sodium chloride (NaCl)) 1.2 times as compared to a nontreated alloy. When the titanium alloy was presaturated with oxygen or nitrogen, the combination of the Physical Vapor Deposition (PVD) oxynitride coating and the diffusion layer, 50µm thick, assists in additional enhancement of corrosion properties 1.5 to 3 times.

Oxygen and nitrogen concentrations in the Ti-6Al-4V alloy manufactured by direct metal laser sintering (DMLS) process

Two machines from two scientific centers (Russia and South Africa) were used for the manufacturing of the Ti6Al4V alloys by the direct metal laser sintering. The chemical composition of powders complies with the ASTM F-136 (grade 5), ASTM B348 (grade 23) standard for medical applications. Analysis of the oxygen and nitrogen contamination in DMLS alloys was done with Van de Graaff accelerator with two Mega Volts. It is found that structures of the samples manufactured with two different machines used the same regimes are close to each other. TEM studies found the metastable martensitic structure and silicon nitride Si3N4. It was found that the oxygen and nitrogen contents in both samples are within the normal range for medical grade titanium alloys.

Laser-induced coloring of titanium alloy using ultraviolet nanosecond pulses scanning technology

This paper presents the laser-induced coloring of commercial titanium alloy (Grade 5) sheets using nanosecond-duration pulsed ultraviolet laser (355 nm) scanning technology in an atmospheric environment. This study evaluated the effect of different scanning speeds and pitches of cross-hatch scanning paths parameters on optical properties and chemical composition of the titanium alloy sheets. The optical properties, surface morphology, and surface chemical composition characteristics of the titanium alloy (Grade 5) sheets depended on the laser irradiation conditions. The characteristics of the samples were systematically analyzed using an ultraviolet–visible/near-infrared spectrophotometer, an X-ray photoelectron spectroscope, and an optical microscope. The experimental results indicated that the reflectance spectra decreased as the laser scanning speed decreased from 100 to 25 mm/s. From the CIE 1931 diagram, the color changes in the optical microscopy images were consistent. The atomic content of oxygen increased with decreases in the scanning speed. When the scanning speed was decreased, the binding energy decreased from 530.4 eV to 529.5 eV and was attributed to the TiO bond in TiO2. In the oxidation layer thickness analysis that decreased greatly with increasing the hatching distances and scan speeds. When the scan speed and hatching distance of 25 mm/s and 5 μm that cause the thermal accumulation; therefore, the largest oxidation thickness approximately 1000 nm. The titanium alloy sheet main ingredient (i.e. titanium (Ti), aluminum (Al), and vanadium (V)) proportion was decreased that depending on different laser-induced coloring parameters. Moreover, the carbon (C) and oxygen (O) concentration that depended on the scan speeds and hatching distance. While the oxygen concentration increased with the scan speed decreasing.

Effect of microstructure and cutting speed on machining behavior of Ti6Al4V alloy

Machining of aerospace and biomedical grade titanium alloys has always been a challenge because of their low conductivity and elastic modulus. Different machining methods and parameters have been adopted for high precision machining of titanium alloys. Machining of titanium alloys can be improved by microstructure optimization. The present study focuses on the effect of microstructure on machinability of Ti6Al4V alloys at different cutting speeds. Samples were subjected to different annealing conditions resulting in different grain sizes and local micro-strains (misorientation). Cutting forces were significantly reduced after annealing; consequently, sub-surface residual stresses were reduced. Deformation twinning was also observed on samples annealed at a higher temperature due to larger grain size. Initial strain free grains and deformation twinning during machining reduces the cutting force at higher cutting speed.