Machining Of Titanium Alloys Research Articles

Machining of titanium alloys for medical application - a review

Titanium alloys for their characteristics have acquired a prominent position in numerous industrial applications. Due to its properties, such as high resistance to corrosion, reduced density, high specific strength, and low Young’s modulus, titanium alloys became indispensable as a biomaterial with high use in medical devices, with special emphasis in the area of orthopedics. Problems associated with its manufacturing by conventional machining processes, such as milling, turning, and drilling are well known and studied. Its low thermal conductivity, high chemical reactivity, high hardness at high temperatures make it classified as difficult to machine material. Despite the already extensive knowledge about machining titanium alloys problems, and the constant technological development to overcome them, it is not yet possible to machine this material like other metals. This work is based on research and review papers from Scopus and Scholar from 2010 to 2020 and addresses the main issues related to the machining of titanium alloys used in medical devices manufacturing and current solutions adopted to solve them. From the research consulted it was possible to conclude that it is consensual that for milling, turning, and helical milling cutting speed can reach up to 100 m/min and up to 40 m/min in drilling. As for feed rate, up to 0.1 mm/tooth for milling and helical milling and up to 0.3 mm/rev for turning and 0.1 mm/rev for drilling. Also, that Minimum Quantity Lubrication is a valid and efficient solution to mitigate titanium alloys machining problems.

Accurate preparation of mesoscopic geometric characteristics of ball end milling cutter and optimization of cutting performance

According to the difficult machinability of titanium alloy, the research shows that the surface micro-textured technology can reduce the friction force and cutting temperature in the cutter-workpiece contact area. Starting with the precise preparation of micro textures by laser processing technology, this paper takes ball-end milling cutter milling titanium alloy as the research object, studies the influence of laser processing parameters on micro-textured size parameters, and optimizes the laser processing parameters as follows: laser power P = 40 W, scanning speed V = 1700 mm/s, scanning times N = 7 times, and spot diameter D = 40 μm. The distribution of temperature field and stress field during laser processing is analyzed, and the accuracy of the influence rule of laser processing parameters on micro-textured size parameters is verified, thus realizing the purpose of accurately preparing micro textures. The interactive influence of mesoscopic geometric features on the cutting performance of ball-end milling cutter is analyzed, and the genetic algorithm is used to optimize the parameters. The results show that the main factor affecting the force-heat characteristics of the tool is the blunt edge radius, and the interaction between the blunt radius of the cutting edge and the distance from blade is obvious. The optimized mesoscopic geometric parameters are as follows: the blunt edge radius is 20 μm, and the distance from blade is 110 μm, the micro-textured diameter is 30 μm, and the micro-textured spacing is 175 μm. The research content of this paper lays a foundation for efficient cutting of titanium alloy materials.

Research on cutting performance in high-speed milling of TC11 titanium alloy using self-propelled rotary milling cutters

Titanium alloys are widely used in many areas, such as aerospace, biomedical, and automotive industries, due to their excellent chemical and physical properties. However, its difficult-to-machine characteristic causes various problems in the machining process, such as serious tool wear and elastic deformation of workpieces. To achieve high efficiency and quality of machining titanium alloy materials, this paper conducted an experimental research on the high-speed milling of TC11 titanium alloy with self-propelled rotary milling cutters. In this paper, the wear mechanism of self-propelled rotary milling cutters was explored; the influence of milling velocity was analyzed on cutting process, and the variation laws with the change in milling length were obtained of milling forces, chip morphology, and machined surface quality. The calculation method of self-propelled rotary velocity was proposed, based on the experimental research. The results showed that in the early and middle stages of milling, the insert coating peeled off evenly under the joint action of abrasive and adhesive wear mechanisms. As the milling length increased, the dense notches occurred on the cutting edge of the cutter, the wear mechanism converted gradually into fatigue wear, and furthermore, coating started peeling off the cutting edge with the occurrence of thermal fatigue cracks on the insert. As the milling length was further extended, the milling forces tended to intensify, the chip deformation worsened, and the obvious cracks occurred at the bottom of chips. The increase in milling velocity intensified the friction between chips and self-propelled rotary milling cutters, and decreased the ratio of self-propelled rotary velocity to milling velocity. This caused the drop in cutting performance of cutters and the growth in tool wear rate.

Chip formation and the interaction of mesoscopic geometric features of cutter

Most of the researches on the properties of micro-textured tools are based on an orthogonal test, while the interaction between micro-textured parameters is ignored. Therefore, this thesis is based on an interaction test to study the cutting performance of cutting tools. According to the chip morphology obtained from the interactive test, the micro texture diameter of 60 μm is obtained when the cutting is stable. It was also found that the synergistic effect of multiple mesoscopic geometric features had a significant influence on cutting performance. By analysis, we found the optimized parameters for the milling tool were D = 60 μm, l = 100 μm, l1 = 150 μm, r = 60 μm. Furthermore, prediction models of the cutting performance were established by univariate linear regression and the validity of these models was verified. Thus, this thesis provides a reference for improving the performance of cutting tools and for achieving efficient and high-quality machining of titanium alloys.

An adaptive neuro-fuzzy and NSGA-II-based hybrid approach for modelling and multi-objective optimization of WEDM quality characteristics during machining titanium alloy

An adaptive neuro-fuzzy and NSGA-II-based hybrid approach for modelling and multi-objective optimization of WEDM quality characteristics during machining titanium alloy

An Experimental and Finite Element Approach for a Better Understanding of Ti-6Al-4V Behavior When Machining under Cryogenic Environment.

Due to increasing demand in manufacturing industries, process optimization has become a major area of focus for researchers. This research optimizes the cryogenic machining of aerospace titanium alloy Ti-6Al-4V for industrial applications by studying the effect of varying the nozzle position using two parameters: the nozzle’s separation distance from the tool–chip interface and its inclination angle with respect to the tool rake face. A finite element model (FEM) and computational fluid dynamics (CFD) model are used to simulate the cryogenic impingement of cryogenic carbon dioxide on the tool–workpiece geometry. Experiments are conducted to evaluate cutting forces, tool wear, and surface roughness of the workpiece, and the results are related to the CFD and FEM analyses. The nozzle location is shown to have a significant impact on the cutting temperatures and forces, reducing them by up to 45% and 46%, respectively, while the dominant parameter affecting the results is shown to be the separation distance. Cryogenic machining is shown to decrease adhesion-diffusion wear as well as macroscopic brittle chipping of the cutting insert compared to dry turning, while the workpiece surface roughness is found to decrease by 44% in the case of cryogenic machining.

Experimental study on surface residual stress of titanium alloy curved thin-walled parts by ultrasonic longitudinal-torsional composite milling

The production of thin-walled titanium alloy curved surfaces is of great significance to aerospace manufacturing industry. The magnitude and distribution of residual stress are one of the important factors affecting the surface integrity of the workpiece. In order to obtain larger surface residual compressive stress, improve the surface integrity of the workpiece, and realize the fatigue-resistant manufacturing, the ultrasonic longitudinal-torsional composite milling method was proposed. Orthogonal and single-factor experiments were carried out on titanium alloy curved thin-walled parts, and the differences of cutting force, cutting temperature, and residual stress between conventional milling and ultrasonic longitudinal-torsional composite milling were compared and analyzed, and the influence of different process parameters on the surface residual stress of titanium alloy thin-walled parts was explored. Compared with conventional milling, the surface residual stress values of ultrasonic longitudinal-torsional composite milling workpiece were negative and significantly increased, with the maximum increase rate of 54.88%.The cutting force was greatly reduced, and Fx and Fy decreased by 31.6% and 45.33%, respectively. The instantaneous cutting temperature was also greatly reduced, the maximum reduction of which is 17.53%. With the increase of ultrasonic amplitude and feed per tooth, the surface residual compressive stress increases gradually but decreases with the increase of spindle speed and curvature. The experimental results show that ultrasonic longitudinal-torsional composite milling is a reliable method for machining titanium alloy curved thin-walled parts, which can obtain larger residual compressive stress and improve the machined surface integrity.

Influence of Additive Manufactured Stainless Steel Tool Electrode on Machinability of Beta Titanium Alloy

Additive manufacturing technology provides a gateway to completely new horizons for producing a wide range of components, such as manufacturing, medicine, aerospace, automotive, and space explorations, especially in non-conventional manufacturing processes. The present study analyzes the influence of the additive manufactured tool in electrochemical micromachining (ECMM) on machining beta titanium alloy. The influence of different machining parameters, such as applied voltage, electrolytic concentration, and duty ratio on material removal rate (MRR), overcut, and circularity was also analyzed. It was inferred that the additive manufactured tool can produce better circularity and overcut than a bare tool due to its higher corrosion resistance and localization effect. The additive manufactured tool can remove more material owing to its strong atomic bond of metals and higher electrical conductivity.

Formulation of Sustainable Water-Based Cutting Fluids with Polyol Esters for Machining Titanium Alloys

The machinability of titanium alloys still represents a demanding challenge and the development of new clean technologies to lubricate and cool is greatly needed. As a sustainable alternative to mineral oil, esters have shown excellent performance during machining. Herein, the aim of this work is to investigate the influence of esters’ molecular structure in oil-in-water emulsions and their interaction with the surface to form a lubricating film, thus improving the efficiency of the cutting fluid. The lubricity performance and tool wear protection are studied through film formation analysis and the tapping process on Ti6Al4V. The results show that the lubricity performance is improved by increasing the formation of the organic film on the metal surface, which depends on the ester’s molecular structure and its ability to adsorb on the surface against other surface-active compounds. Among the cutting fluids, noteworthy results are obtained using trimethylolpropane trioleate, which increases the lubricating film formation (containing 62% ester), thus improving the lubricity by up to 12% and reducing the torque increase due to tool wear by 26.8%. This work could be very useful for fields where often use difficult-to-machine materials—such as Ti6Al4V or γ-TiAl—which require large amounts of cutting fluids, since the formulation developed will allow the processes to be more efficient and sustainable.

Revealing the WEDM Process Parameters for the Machining of Pure and Heat-Treated Titanium (Ti-6Al-4V) Alloy.

Ti-6Al-4V is an alloy that has a high strength-to-weight ratio. It is known as an alpha-beta titanium alloy with excellent corrosion resistance. This alloy has a wide range of applications, e.g., in the aerospace and biomedical industries. Examples of alpha stabilizers are aluminum, oxygen, nitrogen, and carbon, which are added to titanium. Examples of beta stabilizers are titanium–iron, titanium–chromium, and titanium–manganese. Despite the exceptional properties, the processing of this titanium alloy is challenging when using conventional methods as it is quite a hard and tough material. Nonconventional methods are required to create intricate and complex geometries, which are difficult with the traditional methods. The present study focused on machining Ti-6Al-4V using wire electrical discharge machining (WEDM) and conducting numerous experiments to establish the machining parameters. The optimal setting of the machining parameters was predicted using a multiresponse optimization technique. Experiments were planned using the response surface methodology (RSM) technique and analysis of variance (ANOVA) was used to determine the significance and contribution of the input parameters to changes in the output characteristics (cutting speed and surface roughness). The cutting speed obtained during the processing of the annealed titanium alloy using WEDM was quite large as compared to the cutting speed obtained in the case of processing the pure, quenched, and hardened titanium alloys using WEDM. The maximum cutting speed obtained while processing the annealed titanium alloy was 1.75 mm/min.

Machinability of Titanium alloy 6242 by AWJM through Taguchi method

Titanium alloy is difficult to machining in the conventional machining process. Hybrid production technology for abrasive water jet machining (AWJM) allows the machining of all engineering applications. This paper explores the optimization of the process variables of Titanium alloy AWJM (Ti- 6Al- 2Sn- 4Zr- 2Mo). The AWJM process parameters such as water jet strength, traverse speed, and standoff distance were studied against the material removal rate, surface roughness, kerf angle. The contribution of this parameter to responses has been calculated by variance analysis. For material removal rate, surface roughness, kerf angle, regression models were obtained.

A novel method for investigating drilling machinability of titanium alloys using velocity force maps

During the manufacture of critical aerospace components from metastable β titanium alloys, excessive tool wear and machining cost can be significant obstacles. Although tools are highly optimised for drilling the α+β alloy Ti–6Al–4V (Ti-64), insufficient information is available to efficiently improve tools for use on higher strength alloys due to the cost intensive processes required to design and optimise new drills. To reduce this cost, a novel method is presented which enables rapid comparisons of machinability between different alloys, (Ti-64; Ti–6Al–2Sn–4Zr–6Mo (Ti-6246); and Ti–5Al–5Mo–5V–3Cr (Ti-5553)), to quickly assess the performance of specific tool characteristics using industrially relevant drilling parameters. Rapid assessment and comparison of microstructural damage at selected forces was made possible through the development of 3D tool velocity force maps (VFM) for coated TiAlN and uncoated WC/Co tools at different cutting feeds and speeds. Microstructural damage depth has been shown to decrease with increasing alloy strength even for cases where the thrust force between the work piece and the tool was the same ~1600 ​N. In addition, a lower damage depth was measured when using uncoated tools. The machinability evaluation of tool coating and its interaction with force, torque, and material properties showed that TiAlN coated tools responded differently in the case of each alloy, displaying significantly different torque profiles, thus indicating different optimum cutting speeds and feeds. Abrasive and adhesive wear mechanisms were identified in the coated tools, while the majority of wear in uncoated tools was abrasive.

Enhancement of machinability of titanium alloy in the Eductor based PMEDM process

In this study, an attempt has been made in PMEDM process to sustain the homogeneity in the powder-dielectric mixture irrespective of the nature of the powders, their particle size, concentration etc., The traditional way of powder mixing system in Powder Mixing Electric Discharge Machining (PMEDM) has been refurbished with a novel Eductor based system along with a metering devise to ensure uniform mixing of the powers with the dielectric. Additionally sintered crucible filtration test on the sample of powder-dielectric mixture ensured the presence of known quantity of powders in the dielectric. The experiments are conducted on Titanium alloy with Gap current, Duty factor, Delivery pressure, powder types (Alumina, Silica, and copper) and concentration of these powders as variable process parameters. The output responses, namely material removal rate, tool wear index and surface finish obtained during the machining process have been optimized using AHP-TOPSIS method. The confirmation test indicated that the closeness co-efficient value for the TOPSIS analysis improved by 2.37% compared with the predicted value.

Machining simulation of Ti6Al4V using coupled Eulerian-Lagrangian approach and a constitutive model considering the state of stress

The accuracy of a machining model depends on the capability of this model to describe the physical phenomena associated to the real machining system. This includes the material constitutive model and the approach used to describe the field flow of the material in cutting. In this paper, a model of high speed machining (HSM) of Ti6Al4V titanium alloy is developed. This cutting model includes the proposed constitutive model considering the influence of strain hardening, strain-rate, temperature, and state of stress (e.g., stress triaxiality and Lode parameter) in the material plasticity and damage. Finite Element Method (FEM) using Coupled Eulerian-Lagrangian (CEL) approach is used to simulate the cutting model. A sensitivity analysis of the influence of the mesh topography on the chip geometry and cutting force is performed resulting in the determination of the optimal element size and element orientation. Simulation results obtained using the CEL approach are compared with those obtained using the Lagrangian one. Moreover, simulated cutting force and chip geometry obtained using the proposed constitutive model are compared with those obtained using the Johnson-Cook (J-C) model, and experimental data. Both chip geometry and cutting force predicted by the proposed constitutive model is closer to the experimental one than the J-C constitutive model. The CEL approach combined with the proposed constitutive model can simulate material side flow, which results in a larger width of chip compared to the width of cut, and in the formation of lateral burr on the workpiece. It also permits simulating the cyclic variation of the plastic strain and topography of the machined surface along the cutting direction, observed experimentally.

Titanium Ti-6Al-4V Alloy Milling by Applying Industrial Robots

Robotic machining is an alternative to manufacturing processes that combines the technologies of a high-performance machine tool with the flexibility of a 6-axis jointed arm robot. With their large working area, industrial robots are of particular interest for processing large-volume components and large structures, like aircraft components. An influencing variable, which is particularly relevant for milling processes with industrial robots are the cutting force F and the resulting dimensional deviation D. Milling tests of titanium alloys were carried out with an industrial robot and the results compared with a conventional machine tool. Due to the low thermal conductivity and high chemical reactivity of the Ti-6Al-4V alloy, heat is generated and increases the temperature in the contact region of the cutting tool/work piece. That has an impact on the cutting tool wear and increases the cutting force F, and consequently, the dimensional deviation D and the machined surface quality. The aim of the investigations is to find a suitable parameter selection and machining strategy for machining titanium alloys with minimal deviation D and an appropriate surface finish.

A Comprehensive Review on Machining of Titanium Alloys

Titanium (Ti) alloys are produced with the combination of titanium and alloying elements. Titanium and titanium alloys are lightweight materials with high toughness, corrosion resistance and tensile strength at high temperatures. Titanium and its alloys have been widely used in several industrial applications, such as marine, biomedicine, chemical, energy and other industries. However, machining of Ti alloys is extremely difficult due to the high cutting temperature, high tool wear, and built-up edge formation. Therefore, this research aimed to extensively review the impact of machining inputs on the machining force, chip formation, cutting temperature, tool wear, mechanical properties (residual stress, fatigue and hardness) and surface integrity (surface roughness, surface defect and microstructure) during turning and milling of Ti alloys. Moreover, laser-assisted machining, ultrasonically assisted machining and different cooling systems were reviewed and discussed. It was found that these techniques can significantly improve Ti alloys’ machinability. They can improve the surface integrity, tool life and mechanical properties as well as reducing the machining force and cutting temperature. The findings of this research can help manufacturers and researchers who work on machining processes, specially machining of Ti alloys.

Experimental Study on the Influence of Tool Wear on the Cutting Process of Ti6Al4V

The tool wear is a big problem when machining titanium alloy. If the tool wear law is not mastered well, the machining quality will not be guaranteed. In this paper, the theoretical model of the tool is established, which can understand the spatial dimension model of the tool. At the same time, the tool wear experiment of the most commonly used tool for titanium alloy machining in the manufacturing industry is carried out, and the influence of the tool cutting wear on the cutting process is studied. The experimental analysis shows that the tool produces the chip extrusion stripe when it is worn in the initial stage and normal stage, which is perpendicular to the chip in the outflow direction, the fringe protrusions are parallel, and the contact surface of the chips is relatively flat. When the tool reaches the stage of severe wear, the protrusion stripes perpendicular to the outflow direction of the chips are fluffy, and the stripes are twisted. With the continuous cutting wear time of the tool becoming longer, the cutting force, the residual stress of the machined surface layer and the cutting temperature obtained in each stage gradually increase; with the tool reaching the stage of severe wear, the protrusion stripes are fluffy, and the stripes are twisted The tool wear time gradually increases, and the cutting surface roughness obtained by continuous tool wear decreases first and then increases; the surface quality of the tool in the initial wear stage is relatively obvious and the edge burr is large, while in the normal wear stage, the surface quality of the tool is gradually gentle, but when the tool reaches the severe wear stage, the surface quality of the tool begins to be processed Sharp drop and thick edge burr.

Influence of Cutting Parameter and Multi-Objective Optimization on Turning Titanium Alloy

Turning is one of the conventional material removal processes and it is essential in today’s manufacturing industry. Nowadays, titanium alloys are favorable and widely used material due to its superior material properties. However, despite having superior material properties, titanium alloys are hard to machine and will result in shortened tool life. Hence it is important to determine the suitable turning parameter to prolong tool life with best surface roughness. This work focused on investigating the influence of machining parameters in machining titanium alloy under dry cutting condition. The influence of three machining parameters namely feeds rate, cutting speed and depth of cut are investigated using a full factorial design. Surface roughness and tool wear were the responses variables. Analysis of variance was utilized in the analysis to determine their contribution ratio and interaction on each response. The experimental results showed that the feed rate was identified as the most influential factor on surface roughness and tool wear at 54% and 33% contribution ratio respectively. Further multi-response objective optimization was adopted through the desirability function analysis method. For the titanium turning operation, the minimal surface roughness and tool wear were significantly obtained through the specified machining parameters at cutting speed of 44 m/min, feed rate of 0.05 mm/rev and depth of cut of 0.5 mm. The results showed that the single objective response successfully converted into multi-objective optimization through the desirability function analysis method.

Experimental investigation of the electrochemical micromachining process of Ti-6Al-4V titanium alloy under the influence of magnetic field

Abstract An attempt has been made to study the influence of magnetic field on the micro hole machining of Ti-6Al-4V titanium alloy using electrochemical micromachining (ECMM) process. The presence of magneto hydro dynamics (MHD) is accomplished with the aid of external magnetic field (neodymium magnets) in order to improve the machining accuracy and the performance characteristics of ECMM. Close to ideal solution for magnetic and nonmagnetic field ECMM process, the parameters used are as follows: concentration electrolyte of 15 g/l; peak current of 1.35 A; pulse on time of 400 s; and duty factor of 0.5. An improvement of 11.91–52.43% and 23.51–129.68% in material removal rate (MRR) and 6.03–21.47% and 18.32–33.09% in overcut (OC) is observed in ECMM of titanium alloy under the influence of attraction and repulsion magnetic field, respectively, in correlation with nonmagnetic field ECMM process. A 55.34% surface roughness factor reduction is ascertained in the hole profile in magnetic field-ECMM in correlation with electrochemical machined titanium alloy under nonmagnetic field environment. No machining related stress is induced in the titanium alloy, even though environment of electrochemical machining process has been enhanced with the presence of magnetic field. A slight surge in the compressive residual factor, aids in surge of passivation potential of titanium alloy, resulting in higher resistance to outside environment.

Investigation of the Wear Behavior of PVD Coated Carbide Tools during Ti6Al4V Machining with Intensive Built Up Edge Formation

Tool wear phenomena during the machining of titanium alloys are very complex. Severe adhesive interaction at the tool chip interface, especially at low cutting speeds, leads to intensive Built Up Edge (BUE) formation. Additionally, a high cutting temperature causes rapid wear in the carbide inserts due to the low thermal conductivity of titanium alloys. The current research studies the effect of AlTiN and CrN PVD coatings deposited on cutting tools during the rough turning of a Ti6Al4V alloy with severe BUE formation. Tool wear characteristics were evaluated in detail using a Scanning Electron Microscope (SEM) and volumetric wear measurements. Chip morphology analysis was conducted to assess the in situ tribological performance of the coatings. A high temperature–heavy load tribometer that mimics machining conditions was used to analyze the frictional behavior of the coatings. The micromechanical properties of the coatings were also investigated to gain a better understanding of the coating performance. It was demonstrated that the CrN coating possess unique micromechanical properties and tribological adaptive characteristics that minimize BUE formation and significantly improve tool performance during the machining of the Ti6Al4V alloy.