Influence of various metal powder mixed dielectric on micro-EDM characteristics of Ti-6Al-4V

Ti-6Al-4V, an advanced engineering material is difficult-to-machine using conventional machining process due to its high strength. It has properties like low weight ratio, outstanding corrosion resistance along with high level of reliable performance in micro components. Micro-electro-discharge machining (Micro-EDM), a popular nontraditional machining process has been identified as the most appropriate machining process for such material. In this paper, the effect of various conducting powders such as copper, nickel and cobalt with different concentrations are mixed with deionized water dielectric, on various responses such as material removal rate (MRR), tool wear rate (TWR), overcut (OC) and taper has been presented. Also, principal component analysis (PCA) has been applied to select the optimal parametric combination of micro-EDM process to achieve optimal values of MRR, TWR, OC and taper during micro-through hole machining. The optimal process parametric setting obtained from the proposed approach is peak current (I_p) of 1.5 A and cobalt (Co) powder concentration of 4 g/L so as to obtain the desired responses. It is also observed from the SEM image that the machined profile and surface topography obtained through the multi-objective optimal parametric combination based on PCA is quite satisfactory and can be applied to achieve geometrically more accurate micro-through holes on Ti-6Al-4V.     

EDM of Ti-6Al-4V: Electrode and polarity selection for minimum tool wear rate and overcut

Titanium and its alloys especially Ti-6Al-4V are being widely used numerous application areas. In addition to have iconic properties, Ti-6Al-4V is considered as challenging material in machining perspective that is why it has captured global research focus. In this research, electric discharge machining of Ti-6Al-4V has been carried out by employing four different types of electrode materials (graphite, aluminum, copper, and brass) assigned with two alternate polarities (positive and negative). Selection of the most appropriate tool material and electrode polarity is the important aspect needed to be explored for this alloy. In addition to polarity, discharge current, and pulse time ratio have been considered as process variables owing to have their direct influence in electric discharge machining. Taguchi L9 array has been employed for each of the four electrodes with positive polarity and similarly L9 with negative polarity. Thus, a total number of 72 experiments have been conducted. Tool wear rate and overcut (OC) around the machined surfaces are the response characteristics to be investigated in order to achieve minimum amounts of both of these two responses. Selection of the most suitable tool with common tool polarity has been carried out meeting the decision criteria of minimum tool wear and minimum OC.     

Effect of Powder Mixed Dielectric on Material Removal and Surface Modification in Microelectric Discharge Machining of Ti-6Al-4V

Microelectric discharge milling is one of the variants of microelectric discharge machining process which acquire the attention of researchers due to its unique ability to produce microchannels and three-dimensional structures in difficult-to-machine materials like titanium. In the present work, an experimental investigation has been performed in order to study the effect of SiC microparticle suspended dielectric on machining Ti-6Al-4V with tungsten carbide electrode. The effects of major electric discharge milling process parameters—voltage, capacitance, and powder concentration in dielectric—on responses—viz., material removal rate (MRR) and tool wear rate (TWR)—were studied. Experiments were designed and performed based on response surface methodology (RSM)-Box–Behnken statistical design and the significance of in put parameters were identified with the help of analysis of variance. From the results, it is recommended to use powder concentration of 5 g/L, capacitance of 0.1 µF, and voltage of 115 V for achieving high material removal and low tool wear rate. Finally, the studies were conducted to analyze the surface modification and the quality of machined surface.     

Machinability of titanium alloy through electric discharge machining

Titanium alloy (Ti-6Al-4V), being considered as hard-to-machine material, offers many challenges especially during conventional machining. Electric discharge machining could be a good option if it offers a good match between material removal rate and surface finish of the machined feature. The issue of appropriate selection of electrode material for good machining of Ti-6Al-4V is not yet comprehensively explored which is the core focus of this study. Moreover, the effect of pulse time ratio is thoroughly examined which is not specifically studied before. Discharge current and pulse time ratio are considered as the input variables, whereas the material removal rate and surface roughness are selected as performance measures of machinability. Copper, aluminum, brass and graphite are employed to evaluate the machining behavior. Experimental results revealed that aluminum electrode provides the lowest surface roughness, whereas the maximum material removal rate is achieved using graphite electrode. However, graphite electrode can offer high material removal rate with low surface roughness by initially employing negative tool polarity for rough machining and then positive tool polarity for fine machining.     

Fuzzy Modeling and Analysis of Machining Parameters in Machining Titanium Alloy

Titanium alloys are utilized in many engineering fields such as chemical, industrial, marine, and aerospace due to their unique properties. Machining of these materials causes severe problems. At high temperatures, they become chemically active and tend to react with tool materials. In the present study, fuzzy logic (a tool in artificial intelligence) is used for the prediction of cutting parameters in turning titanium alloy (Ti-6Al-4V). The parameters considered in this study are cutting speed, feed, and the depth of cut. Fuzzy rule-based modeling is employed for prediction of tool flank wear, surface roughness, and specific cutting pressure in machining of titanium alloy. These models can be effectively used to predict the tool flank wear, surface roughness, and specific cutting pressure in machining of titanium alloys. Analysis of the influences of the individual important machining parameters on the responses have been carried out and presented in this study.     

Nano-second UV laser processed micro-grooves on Ti6Al4V for biomedical applications

Laser surface texturing can be used to produce well defined micro-grooves on biomedical materials such as Ti-6Al-4V. Such micro-grooves can be optimized to improve the integration with surrounding tissue. This paper examines the effects of Gaussian shaped beam profiles for nano-second laser processing on the laser micro-groove geometry, topography, and micro-structure of Ti-6Al-4V under atmospheric conditions. Laser and machining parameters such as pulse rate, scan speed, wavelength, groove width and pitch are shown to affect the resulting micro-groove geometries. In contrast to prior micro-groove studies using top-hat beam profiles with ultra-violet (UV) Excimer lasers or large area masking techniques, grooves produced with Nd:YVO₄ exhibit improved roughness parameters and reduced heat-affected zones. Initial processing parameters are established for the fabrication of micro-groove geometries on flat geometries that are relevant to biomedical implants and devices.     

Thermal aspects, material considerations and cooling strategies in cryogenic machining

 Conventional machining prolongs tool life by using cutting oils to cool the metal cutting process. Unfortunately, the cutting fluid contaminates the environment, and endangers the health of humans. Cryogenic machining offers an environmentally safe alternative to conventional machining by using liquid nitrogen, which can be naturally recycled. However, for the cryogenic machining process to be effective and economical, manufacturers must select the correct cooling approach. This paper describes our experimental study to investigate the cryogenic properties of some common cutting tool materials and five workpiece materials of industrial interest: low carbon steel, AISI 1010, high carbon steel AISI 1070, bearing steel AISI 52100, titanium alloy Ti-6Al-4V, and cast aluminum alloy A390. The paper addresses the major aspects of heat generated in metal cutting in terms of its effects on chip formation, tool wear, and on the functional integrity of the machined component. The paper then discusses the cooling strategies for cryogenic machining each material based on the thermal effects and material properties. The investigators conclude that the cooling approach must be finely adjusted for different materials to obtain the optimum effectiveness in cryogenic machining. The goal of our study is to provide a basis for designing the cryogenic machining system. Received: 25 November 1998 / Accepted: 12 February 1999     

A Hybrid Machining Process Combining Micro-EDM and Laser Beam Machining of Nickel–Titanium-Based Shape Memory Alloy

Micro-electrical discharge machining (EDM) is a slow process as compared to laser machining, on the contrary laser machining lacks good surface quality. To overcome the drawbacks of both these processes, this paper suggests a hybrid machining process which combines laser and micro-EDM processes for drilling microholes in advanced engineering materials such as Nickel–Titanium (Ni–Ti)-based shape memory alloy. To achieve the objective of the suggested hybrid process, pilot holes are drilled with laser machine and rimmed out by micro-EDM drilling. The suggested process requires investigation of various combinations of micro-EDM drilling process conditions to obtain optimum machining parameters for the hybrid process. It has been found that the proposed hybrid machining process resulted in 50–65% reduction in machining time without affecting the quality of microholes as compared to the standard micro-EDM process.     

CFRP复合材料/钛合金叠层螺旋铣孔工艺

利用螺旋铣变偏心距加工的特点,提出了在刀具回程过程中进行二次精加工的工艺策略。通过正交试验研究了回程各工艺参数对CFRP/Ti-6Al-4V叠层孔加工质量和加工精度的影响规律,并依此优化工艺参数。试验结果显示:采用优化参数的回程精加工工艺提高了叠层孔的制孔精度,避免了复合材料孔壁加工损伤,复合材料孔粗糙度均值从Ra3.52降低到Ra1.31,入口撕裂明显改善,钛合金孔出口无毛刺。     

Optimal machining conditions for turning Ti-6Al-4V using response surface methodology

Machining titanium is one of ever-increasing magnitude problems due to its characteristics such as low thermal conductivity, modulus of elasticity and work
hardening. The efficient titanium alloy machining involves a proper selection of process parameters to minimize the tangential force (F_z) and surface roughness (R_a). In the present work, the performance of PVD/TiAlN coated carbide inserts was investigated using response surface methodology (RSM) for turning Ti-6Al-4V. The effects of process parameters such as speed (v), feed (f), depth of cut (d) and back rake angle (γ_y) on F_z and R_a were investigated.
The experimental plan used for four factors and three levels was designed based on face centered, central composite design (CCD). The experimental results indicated that F_z increased with the increase in d, f and decreased with the increase in v and γ_y, whereas Ra decreased with the increase in v and γ_y, and increased with d and v. The goodness of fit of the regression equations and model fits (R ²) for F_z and R_a were found to be 0.968 and 0.970, which demonstrated that it was an effective model. A confirmation test was also conducted in order to verify the correctness of the model.     

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.     

Prediction of cutting force based on machining parameters on AL7075-T6 aluminum alloy by response surface methodology in end milling

Cutting forces modeling is the basic to understand the cutting process, which should be kept in minimum to reduce tool deflection, vibration, tool wear and optimize the process parameters in order to obtain a high quality product within minimum machining time. In this paper a statistical model has been developed to predict cutting force in terms of geometrical parameters such as rake angle, nose radius of cutting tool and machining parameters such as cutting speed, cutting feed and axial depth of cut. Response surface methodology experimental design was employed for conducting experiments. The work piece material is Aluminum (Al 7075-T6) and the tool used is high speed steel end mill cutter with different tool geometry. The cutting forces are measured using three axis milling tool dynamometer. The second order mathematical model in terms of machining parameters is developed for predicting cutting forces. The adequacy of the model is checked by employing ANOVA. The direct effect of the process parameter with cutting forces are analyzed, which helps to select process parameter in order to keep cutting forces minimum, which ensures the stability of end milling process. The study observed that feed rate has the highest statistical and physical influence on cutting force.     

Multiobjective optimization and analysis of copper–titanium diboride electrode in EDM of monel 400™ alloy

Electrical discharge machining (EDM) is one of the most accepted machining processes in the precision manufacturing industry. In EDM process, finding an alternative tool material is the demand in modern manufacturing industry. Therefore, an attempt had been made to fabricate copper–titanium diboride powder metallurgy electrode to test in EDM on monel 400? material. The experiments are planned using center composite second-order rotatable design and the model is developed by response surface methodology. The machining characteristics have analyzed using the developed model. In this study, four input parameters such as titanium diboride percentage, pulse current, pulse on time, and flushing pressure are selected to evaluate the material removal rate (MRR) and tool wear rate (TWR). The adequacy of the developed regression model has tested through analysis of variance test. The desirability-based multiobjective optimization is used to find the optimal process parameter which has given maximum MRR and minimum TWR. The optimum process parameters obtained were titanium diboride of 16%, pulse current of 6 A, flushing pressure of 1 Mpa, and pulse on time of 35?µs. The validity of the response surface model is further verified by conducting confirmation experiments.     

Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V – PART 1: Material characterisation

Ti-6Al-4V is one of the most frequently used titanium alloy in aerospace applications such as for load carrying engine structures, due to their high strength to weight ratio in combination with favourable creep resistance at moderate operating temperatures. In the virtual development process of designing suitable thermo-mechanical forming processes for titanium sheet metal components in aero engine applications numerical finite element (FE) simulations are desirable to perform. The benefit is related to the ability of securing forming concepts with respect to shape deviation, thinning and strain localisation. The reliability of the numerical simulations depends on both models and methods used as well as on the accuracy and applicability of the material input data. The material model and related property data need to be consistent with the conditions of the material in the studied thermo-mechanical forming process. In the present work a set of material tests are performed on Ti-6Al-4V at temperatures ranging from room temperature up to 560°C. The purpose is to study the mechanical properties of the specific batch of alloy but foremost to identify necessary material model requirements and generate experimental reference data for model calibration in order to perform FE-analyses of sheet metal forming at elevated temperatures in Ti-6Al-4V.     

Process parameter optimization and experimental evaluation for nanofluid MQL in grinding Ti-6Al-4V based on grey relational analysis

Nanofluid minimum quantity lubrication is an environmental-friendly, resource-saving, and sustainable process compared with traditional flood lubrication. Especially, it is widely applied in difficult-to-cutting material, such as Ti-6Al-4V. However, optimized process parameters have not been obtained with considering grinding temperature, tangential grinding force, specific grinding energy, and surface roughness (R_a). And it is important for reaching the best surface quality and highest grinding efficiency. Henceforth, grinding parameters were set reasonably through an orthogonal experiment in this study and they were optimized preliminarily through a signal-to-noise analysis, getting four optimal groups of single grinding parameter. Next, a grey relational analysis was implemented based on the optimal signal-to-noise analysis of signal objective, getting two optimal combinations of multiple objectives. Finally, surface qualities in several groups of optimized experiments were characterized and analyzed by the profile supporting length ratio, surface morphology, and energy spectra. Furthermore, the grinding efficiency experiment was evaluated by material removal rate and specific grinding energy based on satisfying workpiece surface quality, and the optimal parameter combinations of surface quality and processing efficiency were gained. Research results provide theoretical basis for industrial production.     

Characteristics of wire-electro discharge machined Ti6Al4V surface

Titanium and titanium alloys (e.g., Ti6Al4V) are increasingly used in aerospace and automotive industries, and also used as medical implant material in wide variety of applications. Wire-electro discharge machining (WEDM) is an important non-traditional machining process, widely used for machining a variety of difficult-to-machine materials including titanium alloys with intricate shapes. The process is essentially a thermal process and the nature of surface produced is studied in this paper. It is observed that more uniform surface characteristics are obtained with coated wire electrode. Among the parameters such as time between two pulses, pulse duration, injection pressure, wire speed and wire tension that have more influence on the surface characteristics, the time between two pulses is the most sensitive parameter.     

退火热处理对等径角挤压回收Ti-6Al-4V合金微观结构和显微硬度的影响

采用等径角挤压法回收Ti-6Al-4V合金切屑,并研究了回收样品和退火处理样品的微观结构和显微硬度。结果表明:在回收样品中,切屑之间的边界依然存在,而由于剧烈塑性变形,超细晶结构和较强的纤维织构得以形成。退火处理后,切屑边界部分消失,超细晶组织部分再结晶;而与此同时,退火处理样品展现出更宽泛的织构,再结晶晶粒并不存在择优取向。值得注意的是,退火处理样品的显微硬度较回收样品略有升高。     

Adhesive B-doped DLC films on biomedical alloys used for bone fixation

The long-term failure of the total hip and knee prostheses is attributed to the production of wear particles at the articulating interface between the metals, ceramics and polymers used for surgical implants and bone-fixtures. Therefore, finding an adhesive and inert coating material that has low frictional coefficient should dramatically reduce the production of wear particles and hence, prolong the life time of the surgical implants. The novel properties of the non-toxic diamond-like carbon (DLC) coatings have proven to be excellent candidates for biomedical applications. However, they have poor adhesion strength to the alloys and biomaterials. The addition of a thin interfacial layer such as Si, Ti, TiN, Mo and Cu/Cr and/or adding additives such as Si, F, N, O, W, V, Co, Mo, Ti or their combinations to the DLC films has been found to increase the adhesion strength substantially. In our study, grade 316L stainless steel and grade 5 titanium alloy (Ti-6Al-4V) were used as biomaterial substrates. They were coated with DLC films containing boron additives at various levels using various Si interfacial layer thicknesses. The best film adhesion was achieved at 8% and 20% on DLC coated Ti-6Al-4V and grade 316L substrates, respectively. It has been demonstrated that doping the DLC with boron increases their adhesion strength to both substrates even without silicon interfacial layer and increases it substantially with optimum silicon layer thickness. The adhesion strength is also correlated with the hydrogen contents in the B-DLC films. It is found to reach its maximum value of 700 kg/cm² and 390 kg/cm² at 2/7 and 3/6 for CH₄/Ar partial pressures (in mTorr ratio) for Ti-6Al-4V and 316L substrates, respectively.     

Optimization of photochemical machining process parameters for manufacturing microfluidic channel

In the present study, the investigation on photochemical machining (PCM) of stainless steel (SS-304) by ferric chloride as etchant is reported. SS-304 is machined by PCM process to obtain accurate dimensions and better geometrical features. Weighted grey relational analysis (WGRA) technique is used in optimization of PCM process parameters. DoE (L₂₇) orthogonal array is applied to evaluate machining parameters, such as concentration of etchant, etching time, and temperature of etchant. The multiobjective optimization technique is used to optimize material removal rate (MRR), surface roughness (R_a), undercut (U_c) and etch factor (EF). Weighted grey relational grade is calculated to minimize U_c and surface roughness and to maximize MRR and EF. The quality characteristics MRR, EF, U_c, and R_a are reporting the improvement after the confirmatory test. The optimum machining parameters are processed to manufacture the microfluidic channel used in biomedical applications. The microfluidic channels and its assembly with Y-type for mixing of fluid with a size of 100 µm, 200 µm, and 300 µm are developed and investigated.     

Material characterization and corrosion behavior of hybrid coating Ti−Al−Si−Cu/Ti−6Al-4V composite

Titanium alloy grade 5 is a grade of the titanium material that is in-demand in the marine, aerospace, biomedical and turbo machinery industries. It offers great properties such as being light weight, good corrosion performance and great strength. However, some of the other properties, namely: its low hardness and poor tribological performance, has limited its various industrial application. Developments have focused on the enhancement of the surface properties without altering the bulk of the material. This has led to the laser metal deposition technique categorized under the additive manufacturing processes. It is a feasible technique that operates on layer-by-layer additive processing to manufactures whole parts or repair local damages in components. This study aims to ascertain the optimum processing conditions of the process by varying the laser intensity and scanning speed between 0.9 kW–1 kW and 1.0 m/min–1.2 m/min, respectively, while maintaining all the other process parameters. The specimens were produced by utilizing the ytterbium laser system to conduct laser surface alloying of Ti−Al−Si−Cu/Ti-6Al-4 V. Metallographic preparations, characterizations to conduct laser metal deposition (LMD), microhardness and corrosion test were conducted. It was deduced that Ti-9Si-3Cu alloy had the best optimum performance at 1 kW and 1.0 m/min. The hardness and corrosion were optimum improved at reduced scan speeds and increased laser power.