Titanium Alloy Ti6Al4V Research Articles

Microstructures and properties of FeCrAlMoSix high entropy alloy coatings prepared by laser cladding on a titanium alloy substrate

By laser cladding, a FeCrAlMoSix high entropy alloy (HEA) coating (x = 0, 0.05, and 0.10) was produced on Ti6Al4V titanium alloy surface to improve its resistance to the influence of high-temperature fretting wear on Ti6Al4V. The mechanical characteristics, phase composition, and fretting wear resistance of the coating were examined at RT and 400 °C. The findings show that the FeCrAlMoSix coating is made up of a B2 phase and an intermetallic compound μ phase. At RT and 400 °C, increasing the Si concentration significantly enhanced the coating's microhardness. At x = 0.10, the average microhardness of the coated surface was 805 HV, and grain refinement and increase in μ phase were the reasons for the improvement of microhardness. The fretting wear experiment shows that the coating system can reduce wear loss and COF. In addition, at RT and high temperature, increasing the Si element can considerably improve the coating's resistance to fretting wear. However, due to stress concentration, too much μ phase may increase the risk of microcracking in the coating. This work provides a potential method for improving the protection against fretting wear damage on the titanium alloys' surface.

Laser melting deposition of Inconel625 to Ti6Al4V bimetallic structure via vanadium interlayer

Inconel 625 (IN625) nickel-based high-temperature alloy and Ti6Al4V (TC4) titanium alloy are widely used in the aerospace industry due to their respective excellent properties. Developing the IN625/TC4 bimetallic structure (BS) has more apparent benefits and broader application prospects. Still, it has been challenging for industry research to connect these two materials successfully. In this study, IN625/TC4 BS without metallurgical defects such as cracks was successfully fabricated by adding the V interlayer using laser melting deposition (LMD) technique, and its microstructure and mechanical properties were investigated. The results indicate that IN625/TC4 BS can be divided into five regions from the IN625 side to the TC4 side, namely IN625 region, IN625/V transition region, rich V region, V/TC4 transition region, and TC4 region. The phase evolution of the five regions is as follows: γ-Ni + laves → γ-Ni + (Ni2Cr)V + TiNi3 + (V, Cr, Ni) solid solution → (V, Cr, Mo) solid solution + TiNi → β-Ti + TiNi + Ti2Ni → α-Ti + β-Ti. The Vickers hardness in the transition region is not uniformly distributed, with the highest value reaching 955 HV. The tensile strength of IN625/TC4 BS via V interlayer is approximately 267.6 MPa. The fracture location is located at the interface between rich V region and V/TC4 transition region, and its fracture morphology displays features of a quasi-cleavage fracture.

Improving the Surface Quality and Tribological Characteristics of 3D-Printed Titanium Parts through Reactive Electro-Spark Deposition.

This work presents the results of research conducted with an aim to improve the surface quality, hardness and wear resistance of titanium alloy Ti6Al4V, obtained via the laser powder bed fusion of metals (PBF-LB/M) process of additive manufacturing (AM) known as the 3D printing of metals. The 3D surfaces were coated via reactive electrospark deposition (RESD) with low-pulse energy and electrode materials of low-melting metals and multi-component hard alloys. The relationship between the electrical parameters of the RESD process and the quality, composition, structure, microhardness and wear resistance of the treated surfaces were investigated and analysed. It was found that the roughness and thickness of the resulting surface layers could be changed by changing the RESD modes within the limits of 2.5-5 µm and 8-20 µm, respectively. RESD processing allowed us to achieve two to five times lower roughness than that of titanium AM surfaces. The microhardness and wear resistance of the RESD surfaces are two to four times higher than those of the titanium substrate. Possibilities for the purposeful synthesis of new wear-resistant phases and compounds and for obtaining surface layers with predetermined thickness and roughness were established. It was shown that the subsequent reaction's electrospark processing helped to simultaneously reduce the roughness and increase the hardness and wear resistance of the modified surfaces, and can be successfully used instead of the material-energy-labour and machine-intensive finishing treatments of the titanium surfaces obtained after 3D printing.

Microstructure and Wear Resistance of Ti6Al4V Titanium Alloy Laser-Clad Ni60/WC Composite Coating.

In this paper, Ni60/WC wear-resistant coatings have been created on the Ti6Al4V substrate surface using a pre-layered powder laser cladding method by deploying various scanning speeds of 8, 10, 12, and 14 mm/s. The coatings are characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), and a high-speed reciprocating fatigue wear tester. It is found that the phase composition of the coating comprises the synthesized, hard phase TiC and TiB2, the silicides WSi2 and W5Si3, and NiTi and γ-Ni solid solutions. At different scanning speeds, there is a metallurgical fusion line in the bonding area of the fused cladding layer, indicating a good metallurgical bonding between the substrate and the powder. At a low scanning speed, the coating develops into coarse dendrites, which shows significant improvement with scanning speed. The microhardness first increases and then decreases with the scanning speed, and the coating's average microhardness was 2.75-3.13 times higher than that of the substrate. The amount of mass wear has been reduced by 60.1-79.7% compared to the substrate. The wear behavior of the coatings was studied through detailed analysis of wear surfaces' microstructures and the amount of wear to identify the optimum scanning speed.

Study of structure and properties of titanium alloy manufactured by selective electron beam melting using "thin walls" mode

The results of research on the powder from the titanium alloy Ti—6Al—4V, used for selective electron beam melting, are presented. The study reveals the structure and mechanical properties of standard thin samples made from the titanium alloy Ti—6Al—4V using the developed ‘thin walls’ mode. It has been established that the alloy structure obtained through the "thin walls" mode exhibits a Widmansttten structure with low dispersion of α-phase plates. The manufactured samples demonstrate higher strength compared to samples produced using traditional technology.

Characterization of stress drop and strain localization for titanium alloy subjected to electrically-assisted tension

The stress drop and strain localization behaviors of Ti–6Al–4V titanium alloy under the action of single pulse were investigated using electrically-assisted (EA) tension tests in this study. It is found that the flow stress drop gradually increases with the increase of current density and pulse width during EA tension. The digital image correlation (DIC) technology was adopted to analyze the strain distribution evolution and fracture regulation in EA micro-tension process. It turn out that the EA tensile sample will suddenly form two new intersecting high-strain bands at the moment of applying a pulse. With the increase of strain, the two high-strain bands converge toward the center and gradually evolve into a crossed localized flow zone, which makes the EA tensile sample exhibit a high local plastic deformation compared with room temperature tension. Furthermore, with the increase of current density, the temperature gradient in the tensile direction of the sample increases gradually, resulting in the narrowing of localized flow zone. The transformation of the localized flow zone eventually leads to the increase of fracture angle and the formation of a sawtooth shape fracture morphology. Finally, a material flow model for the single-pulse EA tension process was established. The calculation results show that about 11 % of the stress drop comes from the contribution of non-thermal electroplastic, the main mechanism of stress drop is thermal softening and thermal expansion induced by Joule heat during EA tension.

Improving corrosion resistance of additively manufactured Ti6Al4V titanium alloy by post heat treatment

Additive manufacturing (AM) is a developing manufacturing method and has become an advanced one for producing unique and complex shaped parts. This method is promising for manufacturing of titanium alloys, as it allows to significantly reduce the costs of titanium parts compared to conventional manufactured methods. In this work, the effect of post heat treatment on the microstructure evolution and corrosion resistance of AM titanium alloy in a hydrochloric acid solution was studied by comparing it with a conventional manufactured one (wrought). As AM was chosen selective laser melting method which performed by 3D Metal Tech company (Ukraine). The corrosion resistance was studied by electrochemical and immersion test according to ASTM G 31-72 standard. The results obtained via corrosion tests show that the anti-corrosion properties of AM titanium alloy was worse than for the wrought one, which was explained by the presence of a non-equilibrium metastable martensitic phase and residual stresses in AM titanium alloy. Microstructural results showed that post heat treatment led to the reduction of the non-equilibrium phase martensitic α′, relief of residual stresses, and formation of the β phase, which has higher corrosion resistance. These changes lead to an improvement of the corrosion resistance of AM titanium alloy and result in the performance comparable to that of conventional wrought titanium alloy. These results indicate that the selective laser melting method of AM accompanied by the post heat treatment processes can be used to produce AM Ti6Al4V parts in comparison to wrought ones.

Profiling interfacial reaction features and mechanical properties of B4C ceramic and Ti6Al4V titanium alloy brazed with Ag-based brazing filler

B4C ceramic can be used for the surface protection of Ti6Al4V titanium alloy because of its high hardness and excellent wear resistance. However, the joining of these two materials remains relatively unexplored in current research. In this study, two kinds of active brazing fillers (AgCuTi and AgCuInTi) are applied to braze B4C and Ti6Al4V. The microstructures of the ceramic interface are detailly characterized using TEM, revealing that the reaction layers adjacent to B4C are composed of nano-TiC and TiB whiskers. When AgCuTi is used as the brazing filler, the brazed joints exhibit low shear strength (16.6 MPa) and consistently fail at the ceramic side after the shear test due to the presence of large residual stress. To mitigate the residual stress in the joints, B4C and Ti6Al4V are brazed using the AgCuInTi filler with a lower melting point. The effects of the brazing temperature and the holding time on the microstructure and the mechanical property of the joints are thoroughly investigated. The results demonstrate that reducing the brazing temperature effectively alleviate residual stress in the joint and enhance its shear strength. The maximum shear strength achieved is 90.6 MPa when the joints are brazed at 720 ℃ for 10 min. The study presents a new idea for conducting dependable surface protection on the metal.

Microstructure and tribological properties of cold sprayed WCp/Ti composite coatings on Ti6Al4V titanium alloy

In this study, WCp/Ti composite coatings with the WC proportions of 30.1–44.1 vol% were cold sprayed using powders with WC proportions of 40–80 vol%. Coatings are well bonded to Ti6Al4V substrates, with a thickness of more than 3.8 mm, and have dense microstructure with a porosity of lower than 1.0% despite the high proportion of ceramics. The wear testing shows that coatings exhibit excellent tribological behavior with wear rates reduced by an order of magnitude compared with Ti6Al4V substrate. WC particles help develop more stable mechanically-mixed layers, obtaining a stable coefficient of friction and lower wear. The significance of crack extension resistance and plastic deformation resistance of Ti matrix reflected by H/E and H3/E2, respectively, in determining tribological behavior is also discussed.

Influence of Tools and Cutting Strategy on Milling Conditions and Quality of Horizontal Thin-Wall Structures of Titanium Alloy Ti6Al4V.

Titanium and nickel alloys are used in the creation of components exposed to harsh and variable operating conditions. Such components include thin-walled structures with a variety of shapes created using milling. The driving factors behind the use of thin-walled components include the desire to reduce the weight of the structures and reduce the costs, which can sometimes be achieved by reducing the machining time. This situation necessitates, among other things, the use of new machining methods and/or better machining parameters. The available tools, geometrically designed for different strategies, allow working with similar and improved cutting parameters (increased cutting speeds or higher feed rates) without jeopardizing the necessary quality of finished products. This approach causes undesirable phenomena, such as the appearance of vibrations during machining, which adversely affect the surface quality including the surface roughness. A search is underway for cutting parameters that will minimize the vibration while meeting the quality requirements. Therefore, researching and evaluating the impact of cutting conditions are justified and common in scientific studies. In our work, we have focused on the quality characteristics of horizontal thin-walled structures from Ti6Al4V titanium alloys obtained in the milling process. Our experiments were conducted under controlled cutting conditions at a constant value of the material removal rate (2.03 cm3⁄min), while an increased value of the cut layer was used and tested for use in finishing machining. We used three different cutting tools, namely, one for general purpose machining, one for high-performance machining, and one for high-speed machining. Two strategies were adopted: adaptive face milling and adaptive cylindrical milling. The output quantities included the results of acceleration vibration amplitudes, and selected surface topography parameters of waviness (Wa and Wz) and roughness (Ra and Rz). The lowest values of the pertinent quantities were found for a sample machined with a high-performance tool using adaptive face milling. Surfaces typical of chatter vibrations were seen for all samples.

Surface Characteristics, Properties and Wear Resistance OF TIB2 BASED Hard-Alloy Coatings Obtained by Electrospark Deposition at Negative Polarity on Ti6Al4V Alloy

In the present work, the possibilities of improving the surface properties of titanium alloy Ti6Al4V by electrospark deposition (ESD) at negative polarity were investigated. The coatings were deposited with a TiB2-TiAl-based hard-alloy electrode with nano-sized additives of NbC and ZrO2. The effect of polarity in ESD at low pulse energy (0.01-0.07 J) on the surface roughness, thickness, composition and structure of coatings was studied by profilometric, metallographic, XRD, SEM and EDS methods. In both polarities, dense and uniform coatings were obtained with roughness and thickness, which could be varied by changing the ESD modes within the range Ra=1.5÷4.5 µm, d= 6÷20 µm and microhardness from 9 to 12 GPa, respectively. It was found that the negative polarity coatings obtained are denser and uniform with higher thickness, lower roughness, finer structure, and lower coefficient of friction, and can be successfully used to reduce the surface roughness and defects of 3D printed titanium alloy. Abrasion and erosion wear tests showed that the wear resistance of coated titanium surfaces at both polarities was 2.2 to 3.5 times higher than that of the substrate. Coatings deposited in positive polarity demonstrated higher resistance to abrasive wear, while those in negative polarity are more resistant to erosive wear.

Моделирование эрозионного износа титанового сплава высокоскоростным потоком частиц

Introduction. Predicting solid particle erosion (SPE) in gaseous flow and managing its intensity is still a relevant problem in mechanical engineering. It requires the development of a general modeling methodology, which also depends upon many special cases studying various physical processes. Such studies should also include verification analysis, process parameters and model sensitivity studies. Mainly computational fluid dynamics and finite element analysis (and mesh-free methods such as smooth particle hydrodynamics or similar) are used to simulate the erosion process. Papers focused on CFD simulation of solid particle erosion of metal alloys are widely presented, but most of it is associated with relatively low or medium particle velocities (< 100–150 m/s) and is close to uniform diameter distribution. This paper presents a CFD study of Ti6Al4V titanium alloy SPE at relatively high particle velocities and sufficiently non-uniform unimodal particle diameter distribution. The paper also studies the turbulence model influence and particle shape effect which appears as a “shape factor” coefficient in the particle drag model. Methods. The heterogenous flow simulation was based on the Reynolds-averaged Navier-Stokes formulation, where the particles, according to Euler-Lagrange formulation, were simulated as mathematical points with corresponding properties. The influence of turbulence models, such as k-epsilon standard, RNG k-epsilon, and a relatively new Generalized equation k-omega (GEKO) model and its coefficients were also studied. Oka and DNV erosion models were also compared based on the general sample mass loss and more specific erosion intensity profile criterions. The simulation results were compared to the lab-scale experimental results. Results and discussion. It is shown that neither erosion intensity profile or sample mass loss do not depend upon the turbulence model choice or GEKO parameters variation. As expected, erosion is dependent on the erosion model and its coefficients. A notable influence of the shape factor is shown. As the drag coefficient increased due to the particle shape, the erosion intensity decreased and the erosive profile on the surface also changed due to the changing velocity and diameter distribution of the heterogenous flow. It is expected that such results would be useful not only for erosion prediction in all areas of mechanical engineering, but also for wear management in mechanical assemblies and shot peening / shot peen forming management and simulation.

Effect of passivation and surface treatment of a laser powder bed fusion biomedical titanium alloy on corrosion resistance and protein adsorption

The biomedical titanium alloy Ti6Al4V has excellent corrosion resistance and biocompatibility and is, therefore, widely used in orthopedic and orthodontic implants. Biomedical implants are increasingly fabricated by additive manufacturing, such as laser powder bed fusion (LPBF). These manufacturing protocols often include sandblasting, surface finish, and passivation. This study aims to investigate the effect of different surface finishes and the commonly used ASTM F86–13 nitric acid passivation for LPBF Ti6Al4V on its corrosion resistance, metal release, and surface changes in benign (bovine serum albumin in a pH 7.4 buffer) and harsh (hydrochloric acid at pH 1.5) solutions using various electrochemical and spectroscopic techniques. Electrochemical, solution and surface analysis showed an insignificant effect of passivation. Smooth surfaces exhibited a slightly better corrosion resistance than rough surfaces due to a 10–20 % smaller true surface area and lower protein adsorption. Implanted ceramic beads from the sandblasting procedure remained on the surface even after the mirror-polishing and passivation procedures.

Evaluation of the Depth and Width of Cuts after Controlled-Depth Abrasive Water Jet Machining Using Low Pressure.

The presented paper is focused on the evaluation of material removal during machining via an abrasive water jet with a controlled depth of cut. In the introductory parts of the work, a theoretical analysis of water jet technology and an analysis of the current state of the problem are presented. The experimental part of the work is devoted to testing the effects of technological parameters on material removal from the point of view of the maximum erosion depth and volume loss of material during machining with a low water pressure of 50 MPa. The tested material was a Ti 6Al 4V titanium alloy. The experiments were carried out by changing the traverse speed of the cutting head, the mass flow of the abrasive and the angle of inclination of the cutting head, according to the DoE 33 experiment plan. The obtained values were evaluated using the method of variance (ANOVA) and regression analysis. Furthermore, the values of the width of the erosion track and the maximum and minimum erosion effects for both tested materials were evaluated.

New Approach for Manufacturing Ti–6Al–4V+40%TiC Metal-Matrix Composites by 3D Printing Using Conic Electron Beam and Cored Wire. Pt. 1: Main Features of the Process, Microstructure Formation and Basic Characteristics of 3D Printed Material

In this paper, a new approach for additive manufacturing metal-matrix composites based on Ti–6Al–4V titanium alloy reinforced with titanium carbide particles, as well as layered structures consisted of such composite and Ti–6Al–4V alloy layers is considered. The approach is based on 3D printing with a conical electron beam using a special cored wire, whose composition corresponds to metal-matrix composite. The issues of production such a wire, the features of the 3D printing process, when using it, as well as the features of formation of the microstructure and phase composition of the printed composite material are described. The issues of titanium-carbide particles’ wetting with Ti–6Al–4V melt during process of 3D printing, as well as possible thermogravitational effects (floating or drowning) for solid TiC particles within the melt are considered in detail with additional experiments. The influence of individual components of the wire composition on the formation of the microstructure and its uniformity over the cross section of the printed layer is shown. The possibility of controlling the formation of homogeneous structural state and obtaining sufficiently high values of the hardness (of above 600 HV) of the metal-matrix composite layer printed on the Ti–6Al–4V baseplate is shown.

Analysis of Power Grid Parameters Depending on the Variable Concentration and Size of Copper Nanoparticles and Aerosol Formation Parameters in the Minimum Quantity Lubrication Method During Turning of Ti6Al4V Titanium Alloy

Analysis of Power Grid Parameters Depending on the Variable Concentration and Size of Copper Nanoparticles and Aerosol Formation Parameters in the Minimum Quantity Lubrication Method During Turning of Ti6Al4V Titanium Alloy

Development of Multicomponent Nanostructured Nitride Coatings to Protect against Corrosion Products from Titanium Alloy

Phase-structural characteristics and the corrosion resistance of coatings ZrN, (Zr,Ti)N, (Zr,Hf)N, (Zr,Nb)N, (Ti,Zr,Hf)N and (Ti,Zr,Nb)N, which were deposited on a Ti6Al-4V titanium alloy substrate, were investigated. It was found that the titanium substrate has a crystalline structure, including grains with high (up to 24 at.%) and low (less than 2 at.%) vanadium content. Thus, during the deposition process, the coating can form adhesive bonds with local areas of the substrate that have quite different compositions. The diffusion of the coating elements into the substrate takes place up to a depth of 200 nm. The diffusion of titanium alloy elements (primarily titanium and vanadium) into the adhesive sublayer of the coating to a depth of 100 nm is also observed. Corrosion studies were carried out in 1M solutions with acidic (H2SO4), alkaline (NaOH) and neutral (NaCl) media at a constant temperature of 50 °C. The actual change in the mass of the samples during corrosion tests is extremely small. The protective coatings under study have very high anti-corrosion characteristics and practically do not react with solutions that imitate the liquid environments of the human body.

Investigation of Gas Turbine Blade Materials for Efficient Energy System

The present study aims to determine the best and most economical material for a gas turbine blade, which operates under high-temperature conditions and experiences high static structural and thermal loads. To achieve this objective, three different types of material alloys, namely Titanium alloy Ti6AL4V, Magnesium alloy AZ80, and Aluminum alloy 7075-T6, were selected for comparison. A turbine blade model was designed using Solid Works software, and structural and thermal analyses were performed using ANYAS 15.0 under steady-state conditions. The structural analysis aimed to determine the stress, strain, and deformation results on turbine blades by applying high pressure, while the thermal analysis aimed to determine the temperature distribution influences and heat flux generation by applying high temperatures. Based on the results obtained from both analyses of the three different materials, Titanium alloy Ti6AL4V is the best and most economical material. This material showed low stress, strain, and little deformation and the best material properties at high temperatures when compared to Magnesium alloy AZ80 and Aluminum alloy 7075-T6.

Dimensional Deviations of Horizontal Thin Wall of Titanium Alloy Ti6Al4V Determined by Optical and Contact Methods

Thin-walled structures are used in many industries. The need to use such elements is dictated by the desire to reduce the weight of the finished product, as well as to reduce its cost. The most common method of machining such elements is the use of milling, which makes it possible to make a product of almost any shape. However, several undesirable phenomena occur during the milling of thin-walled structures. The main phenomenon is a deformation of the thin wall resulting from its reduced stiffness. Therefore, it is necessary to control the dimensional and shape accuracy of finished products, which is carried out using various measuring instruments. The development of newer measuring methods such as optical methods is being observed. One of the newer measuring machines is the 3D optical scanner. In the present experiment, thin-walled samples in horizontal orientation of Ti6Al4V titanium alloy were machined under controlled cutting conditions. During machining, the cutting speed and feed rate were assumed constant, while the input factors were the tool and cutting strategy. This paper presents graphs of deviations in the determined cross-section planes of thin-walled structures using a 3D optical scanner and a coordinate measuring machine. A correlation was made between the results obtained from the measurement by the optical method and those determined by the contact method. A maximum discrepancy of about 8% was observed between the methods used.

Effect of femtosecond laser processing atmosphere on micro-nano structures and wetting properties of Ti6Al4V surface

Femtosecond laser processing was carried out to build the hydrophobic micro-nano structure on Ti6Al4V titanium alloy, and the effect of processing atmosphere, i.e., air and nitrogen, on the geometric dimension feature, distribution, element content, and the hydrophobic property was investigated. Results showed that the disordered micro-hump structure was induced in air, while micro-spindle structure with regular geometrical morphology formed in nitrogen. The size of micro-nano structure induced in air is larger than that in nitrogen, and both of them increased with the laser energy density. The micro-hump structure surface induced in air exhibited better hydrophobicity (water contact angle of 144.6°) than that in nitrogen. Processing in nitrogen could effectively inhibit the oxidation of the micro-nano structure, providing a breakthrough to improve the surface hydrophobic stability by reducing the micro-nano structure size and the surface polar metal oxides.