Machining Of Titanium Alloys Research Articles

Effect of Wire Electric Discharge Machining Parameters on Material Removal Rate in Machining of Titanium Grade 7 Alloy

Titanium alloys are widely used in various fields, including the medical field, the automotive and manufacturing sectors. Traditional machining processes are only useful for a limited number of tasks due to the detrimental effects they have on the strength and stiffness of the machined alloys. However, one of the most favoured post-processing equipment used to obtain a high-quality surface is the wire electrical discharge machining (WEDM) technology. The most crucial aspects of WEDM are the rates of the electrical current and voltage, in addition to the pulse-on and pulse-off durations. As a form of wire, WEDM makes use of brass wire that has been zinc-coated. The WEDM method is utilised in the machining of titanium alloy of grade 7 for this project. The surface of titanium grade 7 that had been processed using WEDM was analysed with a scanning electron microscope. The pictures revealed that the material exhibits homogenous solidification and a columnar grain structure along the build direction. As the pulse-on time gets longer, the Material Removal Rate (MRR) also gets higher. When the pulse-on time is set to 60 µs, the greatest MRR that can be achieved is 7.357 mm3/min. As the pulse-off duration gets longer, the MRR is getting lower. At a pulse-off time of 20 µs, the minimal MRR is reached, and it is equivalent to 5.935 mm3/min. At a peak current 6A, the highest MRR is measured is equivalent to 7.795 mm3/min.

Advanced Optimization of Surface Characteristics and Material Removal Rate for Biocompatible Ti6Al4V Using WEDM Process with BBD and NSGA II.

Machining titanium alloy (Ti6Al4V) used in orthopedic implants via conventional metal cutting processes is challenging due to excessive cutting forces, low surface integrity, and tool wear. To overcome these difficulties and ensure high-quality products, various industries employ wire electrical discharge machining (WEDM) for precise machining of intricate shapes in titanium alloy. The objective is to make WEDM machining parameters as efficient as possible for machining the biocompatible alloy Ti6Al4Vusing Box-Behnken design (BBD) and nondominated sorting genetic algorithm II (NSGA II). A quadratic mathematical model is created to represent the productivity and the quality factor (MRR and surface roughness) in terms of varying input parameters, such as pulse active (Ton) time, pulse inactive (Toff) time, peak amplitude (A) current, and applied servo (V) voltage. The established regression models and related prediction plots provide a reliable approach for predicting how the process variables affect the two responses, namely, MRR and SR. The effects of four process variables on both the responses were examined, and the findings revealed that the pulse duration and voltage have a major influence on the rate at which material is removed (MRR), whereas the pulse duration influences quality (SR). The tradeoff between MRR and SR, when significant process factors are included, emphasizes the need for a reliable multi-objective optimization method. The intelligent metaheuristic optimization method named nondominated sorting genetic algorithm II (NSGA II) was utilized to provide pareto optimum solutions in order to achieve high material removal rate (MRR) and low surface roughness (SR).

An experimental and FEM study on ultrasonic-assisted turning of titanium alloy

The increase in demand for aerospace parts leads to a need for effective and efficient machining methods to enhance the machinability of titanium alloys. This research investigates the effect of ultrasonic-assisted turning (UAT) on aerospace titanium alloy Ti-6Al-4V by varying cutting parameters. Ultrasonic turning experiments were conducted to investigate the reduction in cutting forces and tool wear at different cutting parameters with wear and surface roughness analysis. Consequently, a finite element model is used to simulate the ultrasonic turning of titanium to have a better understanding of the effect of UAT on stresses and temperature profiles in the process and help explain the results found experimentally. Separation time between the tool and chip was found to be inversely proportional to the cutting speed and the depth of cut with a reduction in cutting forces and surface roughness of up to 42.5% and 61.4%, respectively, for low cutting speed and depth of cut. Tool wear is also shown to decrease in the ultrasonic machining where adhesion-diffusion wear is reduced on the rake face due to separation in the tool-chip interface. The chip temperature was found to increase while the tool temperature is found to decrease with the motion of the tool.

Effect of Copper Percentage in Copper Tungsten Electrode on Ti6Al4V by Electrical Discharge Machining

The aim of this study was to identify the optimal parameters for electrical discharge machining of Ti6Al4V titanium alloy using copper tungsten electrodes with tungsten compositions of 70% and 80%, respectively. The experiment involved varying current, pulse on time, and duty factor were determined using the Taguchi experimental method L-18 orthogonal arrays. The level of importance of each machining parameter on material removal rate (MRR) was determined using analysis of variance (ANOVA), and the optimal machining parameter combination was obtained using the analysis of signal-to-noise (S/N) ratio. The results showed that a Cu30/W70% electrode performed the best in terms of MRR, electrode wear, and surface roughness. The optimal machining conditions for achieving maximum MRR were found to be a current of 30 A, a pulse on time of 50 μs, and a duty factor of 40%.

Electrical discharge machining of titanium alloy using diatomite powder-mixed dielectric fluid based on response surface methodology

In this investigation, variables such as diatomite powder concentration, spark duration and discharge current are varied to study the impact on material removal rate (MRR) on titanium alloy and tool wear rate (TWR). Totally 20 run of different parameter combinations are formulated using central composite design. It is found from the obtained results that there is a linear increasing pattern for MRR with variation in I, spark duration and powder concentration. Moreover, TWR exhibited inverse effect with addition of diatomite powder and linear uptrend with change in pulse energy and sparking period. In sequence, desirability function method is used to satisfy two conflicting metrics (Maximum MRR and Minimum TWR) and the obtained combination of variables are I = 24 amps, Ton = 8 μs and powder concentration = 8 gm/litre. Desirability value of 0.680 obtained for the conflicting performance characteristics.

Measuring Surface Characteristics in Sustainable Machining of Titanium Alloys Using Deep Learning-Based Image Processing

Measuring Surface Characteristics in Sustainable Machining of Titanium Alloys Using Deep Learning-Based Image Processing

Numerical Investigation on the Effect of Cutting-Edge Shape Factor on the Cutting Performance of Titanium Alloy

Titanium alloys are extensively utilized in the aerospace industry due to their exceptional properties, encompassing high specific strength and corrosion resistance. Nevertheless, these alloys present inherent challenges as difficult-to-machine materials characterized by low thermal conductivity and high chemical reactivity. The machining of titanium alloys often gives rise to elevated cutting forces and temperatures, thereby resulting in compromised machining quality and substantial tool wear. This study explores the influence of the cutting-edge shape factor on tool performance and optimizes the cutting-edge structure through finite element simulation. Remarkably, the cutting performance of the tool demonstrates significant enhancement following cutting-edge passivation. Alterations in the geometric shape of the cutting-edge after passivation exert a notable impact on the tool’s cutting performance, with a superior performance observed for shape factor K > 1 compared to alternative edge structures. Additionally, numerical simulation is employed to analyze the influence of passivation values Sγ and Sα on cutting force and temperature, which are crucial factors affecting cutting performance. The results underscore the significant impact of Sγ on cutting force and temperature. Furthermore, within the confines of maintaining an identical shape factor K, the blade segment group featuring Sγ = 40 μm and Sα = 25 μm exhibits the lowest maximum cutting temperature, thereby indicating the optimal tool design attainable through this study.

Analysis and Optimization of Milling Deformations of TC4 Alloy Thin-Walled Parts Based on Finite Element Simulations

TC4 (DIN3.7164/5) alloy thin-walled parts are widely used in aviation and aerospace industries. However, due to their special structure, shape and poor machinability, large milling forces and milling deformation often occur in the milling process, which cannot guarantee the machining quality and accuracy. The milling processing parameters and milling geometric parameters have a significant impact on the milling force and the deformation, and optimization of the influence factors of milling deformations is important for milling quality. Considering that performing milling experiments under multiple conditions is often costly and time-consuming, this paper provides a finite-element-simulation-based method to study effects of the factors on the forces and deformations during milling thin-walled parts. Firstly, using ABAQUS, a finite element simulation model of the milling process of thin-walled parts is established. Additionally, an orthogonal experimental scheme is designed for optimization of the milling parameters, so as to determine the optimized experimental scheme, and then the optimized experimental scheme is verified to reduce the milling force and deformation by finite element simulations. The optimal parameters for a minimal milling force are a spindle speed of 2000 r/min, a feed rate per tooth of 0.04 mm/z, a milling depth of 1.6 mm, a milling width of 1 mm, a diameter of 6 mm, a rake angle of 20°, a tilt angle of 45°, and two teeth. Similarly, the optimal parameters for minimal node deformations are a spindle speed of 4800 r/min, a feed rate per tooth of 0.18 mm/z, a milling depth of 1 mm, a milling width of 1 mm, a diameter of 16 mm, a rake angle of 20°, a tilt angle of 40°, and four teeth. In addition, this paper uses an optimization algorithm to fit the empirical function with a certain practical value, which can provide a reference for the machining of TC4 titanium alloy. By doing so, we can optimize the milling parameters to obtain the desired machining quality and accuracy, while also saving on time and resources.

Enhancing MRR in face milling by varying cutting speed

The goal of the research is to use grey relational analysis to increase the material removal rate during high-speed machining of titanium alloy. By utilizing the best materials and processes, contemporary industries aim to increase the quality of their products. Achieving the desired product quality at a reasonable cost is ensured by choosing materials that are challenging to cut, like titanium, and by setting the best machining parameters. Depending on the process conditions, industries strive for increased productivity and improved surface finish in machining operations. In order to maximize the rate of material removal during high-speed machining of Ti-6Al-4 V, the process parameters of feed rate, cutting speed, stepover, and depth of cut are chosen in this research work. During the experiments, a L9 orthogonal array was used. The study reveals that the cutting speed, stepover have a direct impact on the rate of material removal. The rate of material removal was found to rise with respect to stepover, speed, and frequency for all depths of cut. A confirmation test was run, and the results were compared to what was anticipated. Inferring that it is in strong agreement with the experimental results.

Optimizing Processing Parameters and Surface Quality of TC18 via Ultrasonic-Assisted Milling (UAM): An Experimental Study.

This study conducted longitudinal ultrasonic-assisted milling (UAM) tests and optimized a combination of milling technological parameters to achieve high-quality machining of TC18 titanium alloy. The motion paths of the cutter under the coupled superposition states of longitudinal ultrasonic vibration and end milling were analyzed. Based on the orthogonal test, the cutting forces, cutting temperatures, residual stresses, and surface topographical patterns of TC18 specimens under different UAM conditions (cutting speeds, feeds per tooth, cutting depths, and ultrasonic vibration amplitudes) were examined. The differences between ordinary milling and UAM in terms of machining performance were compared. Using UAM, numerous characteristics (including variable cutting thickness in the cutting area, variable cutting front angles of the tool, and the lifting of the cuttings by the tool) were optimized, reducing the average cutting force in all directions, lowering the cutting temperature, increasing the surface residual compressive stress, and significantly improving the surface morphology. Finally, fish scale bionic microtextures with clear, uniform, and regular patterns were formed on the machined surface. High-frequency vibration can improve material removal convenience, thus reducing surface roughness. The introduction of longitudinal ultrasonic vibration to the end milling process can overcome the limitations of traditional processing. The optimal combination of UAM parameters for titanium alloy machining was determined through the end milling orthogonal test with compound ultrasonic vibration, which significantly improved the surface quality of TC18 workpieces. This study provides insightful reference data for subsequent machining process optimization.

State-of-the-art and perspectives of cutting edge preparation and its effect on the cutting performance of titanium alloy

Titanium alloys are commonly used in industrial applications due to their exceptional mechanical and chemical properties. However, their low thermal conductivity and high chemical reactivity pose significant challenges in machining, leading to increased cutting forces, rapid tool wear, and poor surface quality. To overcome these issues, advanced cutting edge preparation techniques have been developed to enhance the machining performance of titanium alloys. This paper provides an overview of state-of-the-art cutting edge preparation techniques for titanium alloy machining and examines their effects on machining performance. It first presents a characterization method for cutting edge geometry and explores how it affects machining performance, demonstrating that strategic cutting edge preparation can significantly enhance performance by reducing cutting forces and improving surface finish. The paper also emphasizes the underlying mechanisms of cutting edge preparation and its impact on machining performance and subsequent cutting edge erosion. Finally, it concludes by discussing future research directions in this field, highlighting the need to develop new cutting edge preparation techniques and optimize existing ones. Overall, this paper serves as a valuable resource for researchers and engineers seeking to improve the cutting performance of titanium alloys in various applications.

Hole processing in parts made of titanium alloys

The features of machining of titanium alloys by cutting are considered. Measures are developed to improve the machinability of these alloys. It is shown that a decrease in the vibration amplitudes of the machine—fixture—tool—part (MFTP) technological system during cutting can significantly increase the machinability of such materials. Methods are given to increase the vibration resistance of the MFTP system, the accuracy of processing and tool life when threading with taps and drilling, namely: reducing the contact area of the tool with the workpiece in the cutting zone; increasing the strength and stiffness of the tool itself. It is indicated that the first method is the main one for increasing the tool life and the quality of hole processing. Taking this into account, patented high-performance designs of taps and attachments, drills are developed. The results of their tests are presented. Keywords: titanium alloys, machinability of titanium alloys, processing of holes, taps, drills for titanium machining. ragus05@mail.ru

Numerical and experimental investigations on the laser assisted machining of the TC6 titanium alloy

In order to improve the machinability of difficult-to-machine materials in aviation, laser-assisted cutting technology has received extensive attention. This method of machining allows the workpiece to obtain a localized high temperature prior to cutting in order to benefit from thermal softening. A 3D transient laser heating model was developed for the finite element method to predict the preheating temperature of the cutting layer. The effect of cutting parameters (cutting speed, feed rates, depth of cut) on the magnitude, frequency and amplitude of the cyclic cutting forces was investigated both in conventional machining and in laser assisted machining. It is founded that the laser assistance decreases the flow stress of the material, magnitude of cutting forces and the amplitude of cutting forces. But the frequency of circulating cutting forces increase comparing with the CM (conventional machining). In addition, this paper considers the effect of the LAM (laser-assisted machining) technique on reducing the magnitude of cutting force fluctuations, which results in a flatter machined surface profile and reduces the number of surface defects. A chip morphology different from that of CM is created due to the influence of the cutting force by the temperature field in LAM. Furthermore, a “transitional chip” is discovered, which is a transition from a continuous chip to a segmented chip. The completely thermal-mechanical coupled orthogonal cutting model was established to reveal the evolution mechanism of shear band formation with laser assistance. The results show that shear bands can be formed faster and with less stress in LAM compared to CM. The model can effectively predict the shear angle and keep the prediction error within 10 %. The shear band formation processes in both machining methods were uncovered according to the models. The developed model is very useful for understanding the chip formation process and the cutting force variation in laser assisted machining.

Machinability investigation of Ti-6Al-4V titanium alloy under dry, flood, MQL and nanofluid-MQL techniques using textured tools

ABSTRACT While machining titanium alloys, using metalworking fluids (MWFs) helps improve the tribological properties. However, its usage is restricted considering the harmful effects on health and the environment under sustainable machining. Using minimum quantity lubrication (MQL) to improve machining performance without utilising an excessive amount of cutting fluid is becoming more prevalent. Pure-MQL, however, might not be adequate for machining titanium alloys. Due to their improved heat transfer capabilities, nanofluid-based lubricants are extremely popular for use in the machining of superalloys. In this direction, the efficacy of the MQL mixture can be improved by using vegetable-oil-based cutting fluid reinforced with nanoparticles. Therefore, this study compares dry, flood, MQL and nanofluid-MQL techniques while machining Ti-6Al-4V titanium alloy with textured tools. The Hexagonal Boron Nitride (hBN) nanoparticles are added to the base fluid to develop a nanofluid-MQL mixture. Machinability indicators are analysed, namely tool wear, surface roughness, power consumption, and specific cutting energy. The outcomes showcased the efficacy of nanofluid-MQL with lower surface roughness, tool wear, and specific energy requirements compared to other conditions. It is observed that combining vegetable oil and hBN nanoparticles in nanofluid-MQL reduced friction and improved cooling in the machining interfaces.

Study and Optimization Defect Layer in Powder Mixed Electrical Discharge Machining of Titanium Alloy

Electrical discharge machining (EDM) has recently become very popular for processing titanium alloys, but surface quality is a major problem. During machining, a defect layer inevitably forms on the surface, which can have a negative impact on surface quality. One of the ways to reduce the defect layer is to add powder to the dielectric. However, it is not yet completely clear which powder and in what quantity it should be added to reduce the defect layer. In this sense, the present study aims to investigate the effects of machining parameters on the defect layer in powder-mixed electrical discharge machining of titanium alloys. The main goal is to achieve the minimum thickness of the defect layer by optimally adjusting the input parameters. Experimental studies were performed using the Taguchi orthogonal array L9, considering discharge current, pulse duration, duty cycle, and graphite powder concentration as input parameters. Based on the Taguchi and ANOVA analyses, the discharge current was found to have the greatest effect on the defect layer. In addition, analysis of variance revealed that pulse duration was the second influential parameter, followed by graphite powder and duty cycle. The minimum thickness of the defect layer is obtained at a discharge current of 1.5 A, a pulse duration of 30 µs, a duty cycle of 50%, and a graphite powder concentration of 12 g/L. The results obtained in this study provided answers to some of the unresolved research questions and confirmed the findings that the proposed method can be applied in the industry.

Novel texture pattern on WC inserts fabricated using reverse-μEDM for enhanced cutting of Ti6Al4V

Textured rake and flank surfaces of a cutting tool exhibit promising results in machining performances. This work proposes a novel texture pattern to mitigate the disadvantages of the existing textures. Experiments are performed to check the fabrication feasibility of the proposed pattern on the rake face of Tungsten Carbide (WC) inserts using Reverse-micro Electrical Discharge Machining (R-μEDM) process. In order to investigate the advantage of the proposed pattern, orthogonal machining of Titanium alloy is conducted. A significant reduction of 25.77% is obtained in the measured temperature and 11.1% in the friction coefficient compared to the plain insert.

티타늄 합금의 평엔드밀 가공 시 공구 방향에 따른 가공성 평가

Titanium alloys are classified as difficult-to-cut materials with poor machinability, leading to a continuous demand for the development of machining methods. For machining titanium alloys, various tool orientations can be employed based on the shape of the workpiece, such as the presence of an inclination angle. In this study, machining tests considering tool orientation were performed using a solid carbide end mill tool. The tool orientation was classified into three categories with inclination angles of 90° (Reference), 45° (Upward), and 135° (Downward). The machining tests indicated that the Reference orientation exhibits the longest tool life and best surface roughness. Conversely, the Upward orientation exhibited the shortest tool life, while the Downward orientation exhibited the poorest surface roughness. When considering the Upward and Downward cases, the contact length between the cutting edge and the material becomes longer due to the inclination angle during machining, which in turn affects cutting performance.

Machinability Study in Turning of Ti-6Al-4V under CO2-based Vortex Tube Cooling System

The study on the machinability of titanium alloys provides new ways to minimize the difficulty levels of machining the alloys due to substantial heat accumulation. To improve machinability, pivotal factors such as heat accumulation and cutting temperature must be regulated. In this study, a turning operation was performed on Ti-6Al-4V and the cutting temperature was reduced by supplying cooled CO2 gas through a vortex tube connected with two nozzles. Variations in cutting force, cutting temperature, and surface roughness with cutting speed, feed, and depth of cut were recorded. Subsequently, responses were compared for single nozzle vortex tube, dry, and compressed air environments at different cutting speeds. Cutting force and surface roughness followed a similar trend which increased with decreasing speed, and increasing feed and depth of cut. The cutting temperature increased with all three variables. The proposed cooling system provided better results in terms of cutting temperature and surface roughness, while a marginally higher cutting force was observed compared to dry cutting

Multi-response optimization of machining parameters of Ti-6Al-2Sn-4Zr-2Mo alloy using EDM process through grey relational analysis

Due to its high corrosion resistance and low density, it is tedious to machine high strength materials such as titanium alloy for the manufacture of engineering products related to aerospace, automobiles, and medical applications. In this study, an attempt was made to consider the impact of tool electrodes in the electrical discharge machining method for successful machinability of titanium alloy. High temperatures are used during electrical discharge machining to melt and vaporise the hard titanium alloy. In the current work, an EDM machining method was used to machine a Ti-6Al-2Sn-4Zr-2Mo alloy while using the input parameters of pulse on time, voltage, and current as process parameters. The experiments were carried out based on the workpiece, and surface morphology was performed on the workpiece surface. The process parameters were optimised using the Multi-Response Grey Relation Analysis method, and a major effects plot was created to see how the factors affected the MRR and surface roughness. Surface finish and MRR have been discovered to be directly correlated with discharge current. These are the best process parameters for machining pulse on time (150 s), voltage (60 V), and discharge current (16 A).

Effect of high-speed ultrasonic vibration cutting on the microstructure, surface integrity, and wear behavior of titanium alloy

Titanium alloys are widely used in aviation, marine, automotive, offshore, and medical fields. However, their poor wear resistance reduces the safety and reliability of components during service. Few study has been previously conducted on the wear resistance enhancement of titanium alloys (including Ti–6Al–4V alloy) processed by mechanical cutting. High-speed ultrasonic vibration cutting (HUVC) is an effective approach for improving the machinability of titanium alloys. In this study, we attempted to utilize HUVC improving the wear resistance of titanium alloys. After conducting high-speed turning (cutting speed within the range of 200–300 m/min), the surface integrities (surface roughness, microstructure, in-depth micro-hardness, and residual stress) of conventional cutting (CC)- and HUVC-machined samples were characterized. Experimental results demonstrated that, compared with CC, HUVC achieved a thicker plastic deformation layer (greater than 46.93 μm), lower surface roughness, higher surface micro-hardness (greater than 433 HV0.05), and higher compressive residual stress (up to −840 MPa). Moreover, surface nanocrystallization and gradient nanostructured layer were observed in HUVC-machined Ti–6Al–4V samples. In addition, compared with CC, HUVC effectively further reduced the friction coefficient and worn volume loss (decreased by 20.98%–25.59%) and ultimately improved the wear resistance. The hardness has a higher influence on the wear resistance of the machined Ti–6Al–4V alloy than the other surface integrity factors. Therefore, the proposed mechanical cutting operation was confirmed to improve the wear resistance of titanium alloys.