WEDMed Surface Research Articles

Evaluating the bio-functionalities of Ti-6Al-7Nb alloy after surface modification using electrical discharge machining

The present work evaluates the influence of surface modification on the bio-functionalities of Ti-6Al-7Nb alloy in terms of apatite formation, metal ion release rate and anti-bacterial activities. The surface modification in the form of change in surface integrity, and increases in the exposed surface area, has been achieved using wire-electrical discharge machining (WEDM) and electrical discharge μ-drilling(EDD). Due to high discharge energies, molten material will deposit on the parent material (recast layer), which increases the surface roughness (parent surface 0.5 μm to 2.34 μm) and hardness (patent material 304VH to 385VH) after subsequent re-solidification and quenching. Surface roughness and hardness near the micro-drilled hole are observed to increase. After surface modification, the apatite formation is increased on Ti-6Al-7Nb alloy with increasing immersion time and the ion released rate was found lowest on the WEDMed surface as compared to micro drilled and polished surface. Field-emission electron scanning microscopy (FESEM) and energy dispersive x-ray spectroscopy (EDAX) observations confirmed the presence of phosphate and calcium ions on the WEDMed surface and nearby the micro-drilled surface. The variation in colour of the simulated body fluid (SBF) after the immersion of WEDMed, EDD, and polished samples indicates the variable effecton pH levels of the SBF solution for three types of samples.The anti-bacterial bioactivity of Ti-6Al-7Nb was found to be better on the WEDMed surface as compared to polished surfaces, which is due to the formation of a rutile-TiO2 layer on WEDMed surface.

Laser polishing and simultaneous hardening of the electrical discharge machined Zr-based metallic glass surface

Wire electrical discharge machining (WEDM) is highly suitable for processing the hard-brittle materials like metallic glasses (MGs). However, the electro-thermal energy conversion involved in the WEDM process inevitably introduces some surface defects including bulges, discharge craters, and recast materials on the WEDMed MG surface, which significantly impedes its practical application. Here, an emerging automated polishing technology, laser polishing (LP), was performed in the nitrogen-rich environment to simultaneously improve the surface quality and hardness of the WEDMed Zr-based MG surface. The detailed effects of LP parameters on the surface roughness and morphology were systematically investigated. The morphology evolution and temperature distribution of the molten pool during LP were analyzed by simulation analysis. The experimental results indicated that after single LP of four representative WEDMed Zr-based MG surfaces using the optimized laser parameters, the surface roughness (Sa) was remarkably reduced from 1.27, 2.10, 3.49, and 4.58 μm to 0.09, 0.14, 0.17, and 0.21 μm, respectively, accompanied by an increase in surface hardness from 6.30 GPa to 7.39, 7.67, 8.51 and 8.99 GPa. This study demonstrated that LP could effectively achieve simultaneous enhancement of the quality and hardness of WEDMed MG surfaces, which would contribute to expanding the application prospects of MGs.

A hybrid approach for machining optimization of the WEDM using grey-fuzzy with Metaphor-Less algorithms for Ti-3Al-2.5V

Purpose This paper aims to investigate the influence of “BroncoCut-X” (copper core-ZnCu50 coating) electrode on the machining of Ti-3Al-2.5V in view of its extensive use in aerospace and medical applications. The machining parameters are selected as Spark-off Time (SToff), Spark-on Time (STon), Wire-speed (Sw), Wire-Tension (WT) and Servo-Voltage (Sv) to explore the machining outcomes. The response characteristics are measured in terms of material removal rate (MRR), average kerf width (KW) and average-surface roughness (SA). Design/methodology/approach Taguchi’s approach is used to design the experiment. The “AC Progress V2 high precision CNC-WEDM” is used to conduct the experiments with ϕ 0.25 mm diameter wire electrode. The machining performance characteristics are examined using main effect plots and analysis of variance. The grey-relation analysis and fuzzy interference system techniques have been developed to combine (called grey-fuzzy reasoning grade) the experimental response while Rao-Algorithm is used to calculate the optimal performance. Findings The hybrid optimization result is obtained as SToff = 50µs, STon = 105µs, Sw = 7 m/min, WT = 12N and Sv=20V. Additionally, the result is compared with the firefly algorithm and improved gray-wolf optimizer to check the efficacy of the intended approach. The confirmatory test has been further conducted to verify optimization results and recorded 8.14% overall machinability enhancement. Moreover, the scanning electron microscopy analysis further demonstrated effectiveness in the WEDMed surface with a maximum 4.32 µm recast layer. Originality/value The adopted methodology helped to attain the highest machinability level. To the best of the authors’ knowledge, this work is the first investigation within the considered parametric range and adopted optimization technique for Ti-3Al-2.5V using the wire-electro discharge machining.

On the WEDM of WNbMoTaZrx (x = 0.5, 1) Refractory High Entropy Alloys.

As a potential candidate for the next generation of high-temperature alloys, refractory high entropy alloys (RHEAs) have excellent mechanical properties and thermal stability, especially for high-temperature applications, where the processing of RHEAs plays a critical role in engineering applications. In this work, the wire electrical discharge machining (WEDM) performance of WNbMoTaZrx (x = 0.5, 1) RHEAs was investigated, as compared with tungsten, cemented carbide and industrial pure Zr. The cutting efficiency (CE) of the five materials was significantly dependent on the melting points, while the surface roughness (Ra) was not. For the RHEAs, the CE was significantly affected by the pulse-on time (ON), pulse-off time (OFF) and peak current (IP), while the surface roughness was mainly dependent on the ON and IP. The statistical analyses have shown that the CE data of RHEAs have relatively-smaller Weibull moduli than those for the Ra data, which suggests that the CE of RHEAs can be tuned by optimizing the processing parameters. However, it is challenging to tune the surface roughness of RHEAs by tailoring the processing parameters. Differing from the comparative materials, the WEDMed surfaces of the RHEAs showed dense spherical re-solidified particles at upper recast layers, resulting in larger Ra values. The proportion of the upper recast layers can be estimated by the specific discharge energy (SDE). Following the WEDM, the RHEAs maintained the main BCC1 phase, enriched with the W and Ta elements, while the second BCC2 phase in the Zr1.0 RHEA disappeared. Strategies for achieving a better WEDMed surface quality of RHEAs were also proposed and discussed.

Examining the surface roughness and kerf quality of micro-slots cut on the surfaces of Ti-B4C nanocomposites by WEDM: a desirability approach

Micro slots and textures are created on Titanium (Ti) composites to improve its surface characteristics. Micro-textured Ti composites are generally recommended for bio implants, automobile, and aerospace components. In the current research, Ti-B4C nanocomposites were prepared by powder metallurgical route. Micro slots were cut on the Ti-B4C surfaces by Wire Electrical Discharge Machining (WEDM) Technology by varying the current, pulse-ON time, and pulse-OFF time. Scanning electron microscopy and XRD analysis validates the uniform distribution and inclusion of B4C nanoparticles in Ti matrix. Response surface methodology was used to plan the experimental runs. Analysis of variance and desirability analysis were employed to identify the most suitable machining factors for obtaining the minimum surface roughness, lower kerf width and higher material removal rate (MRR). Increase in applied current and pulse-ON time, increases the MRR. Increase of pulse-OFF time from 50 μs to 60 μs gradually reduces the MRR and reduce the surface roughness of the cut slots. Contrastingly an increase in pulse-ON time increases the roughness due to an extensive melting and resolidification of Ti nanocomposites. The morphology of the WEDMed surface reveals the recast layer and localized melting zones on the cut surfaces.

Recast layer removal of WEDMed surface by wire electrochemical finishing

To eliminate the recast layer on the surface machined by multi-pass wire electrical discharge machining (WEDM), hence improving the surface integrity, the present paper proposed and investigated a new combined machining process of performing wire electrochemical machining (WECM) after multi-pass WEDM on the same machine tool by utilizing the slight conductivity of the compound working fluid. A theoretical model based on the electric double layer and Faraday’s law of electrolysis was established to calculate the wire feed rate for WECM finishing. Due to the exclusive film protection of the compound working fluid, the theoretical model was modified according to the experimental results under different electrolyte concentrations. Afterward, the optimized model was applied to guide the experiments of the combined process. An electrolyte concentration of 1:5 was used to facilitate the electrochemical reaction. The experimental results showed that the remaining recast layer after multi-pass WEDM could be completely removed at a wire feed rate of 10 µm/s, and a fine surface finish could be obtained. In addition, the surface roughness of the machined part was improved from 1.458 µm Ra to 0.683 µm Ra.

Experimental investigations and prediction of WEDMed surface of nitinol SMA using SinGAN and DenseNet deep learning model

Shape memory alloys (SMA) hold a very promising place in the field of manufacturing, especially in biomedical and aerospace applications. Owing to the unique and favorable properties such as pseudo elasticity, shape memory effect and Superelasticity, Nitinol is the most popular amongst other SMAs. However, a major challenge lies in the final surface features of the machined component. In the current study, Nitinol rods were machined using the wire electrical discharge machining (WEDM) process and subsequently, the surfaces were investigated using the Field emission scanning electron miscroscope (FESEM) technique for the features. In addition to this, Singular Generative Adversarial Network (SinGAN) and DenseNet deep learning models were prepared and applied for the prediction of surface morphology and its correlation with the process parameters. It was concluded from the study that the DenseNet model was highly effective in predicting the surface images with 100% average accuracy both with training and testing whereas the least average accuracy of 99.13% and 98.98% with training and testing respectively are observed with the MNB model. Thus, the proposed methodology can prove to be highly beneficial for prediction, specifically for manufacturing applications where the data is limited.

Examination of Machining Parameters and Prediction of Cutting Velocity and Surface Roughness Using RSM and ANN Using WEDM of Altemp HX

The Altemp HX is a nickel-based superalloy having many applications in chemical, nuclear, aerospace, and marine industries. Machining such superalloys is challenging as it may cause both tool and surface damage. WEDM, a non-contact machining technique, can be employed in the machining of such alloys. In the present study, different input parameters which include pulse on time, wire span, and servo gap voltage were investigated. The cutting velocity, surface roughness, recast layer, and microhardness variations were examined on the WEDMed surface. The genetic algorithm was used to optimize the cutting velocity and surface roughness, thereby improving the overall quality of the product. The highest recast layer values were recorded as 25.8 µm, and the lowest microhardness was 170 HV. Response surface methodology and artificial neural network were employed for the prediction of cutting velocity and surface roughness. Artificial neural network prediction technique was the most efficient method for the prediction of response parameters as it predicted an error percentage lesser than 6%.

EFFECT OF INPUT PARAMETERS ON THE KEY MACHINABILITY ASPECTS OF NITINOL DURING WEDM

Shape memory alloy (SMA), a distinctive class of material, can possess its preceding form when subjected to definite thermo-mechanical energy. Nitinol, an SMA, having an admirable shape memory effect, super elastic, and biomechanical properties, has developed a vast application in the field of biomedical, automobile, robotics, aerospace, etc. Wire electrical discharge machining (WEDM) technique is employed for machining of electrically conductive materials like SMAs, high tech ceramics, smart materials, etc. This paper is focused on analyzing the effect of different significant input parameters on the vital machinability aspects of SMA nitinol during WEDM. Independent input variables like pulse-on time ([Formula: see text], discharge current ([Formula: see text], wire-speed (WS), wire tension (WT) and flushing pressure (FP) were considered to find out their influence on the kerf width (KW), material removal rate (MRR), arithmetic mean roughness ([Formula: see text], and microhardness ([Formula: see text]h). 3D optical profile, X-ray diffraction analysis, and scanning electron microscopy were also executed on the WEDMed surface to inspect the surface, microstructure, and phase changes in the machined surface. It was detected that [Formula: see text], [Formula: see text] and FP were more influential than WT and WS for most of the responses.

Analysis of surface characteristics and electrochemical corrosion behaviour of WEDMed Ti-6Al-7Nb alloy

In present investigation, surface properties of Ti-6Al-7Nb under rough cut and trim cut modes of WEDMed has been analysed in terms of surface roughness, recast layer, micro hardness and wettability. In continuation to this study, the electrochemical corrosion resistance has been studied for polished and WEDMed samples of Ti-6Al-7Nb alloy. WEDM at the rough cut mode resulted into higher surface roughness, micro-cracks and thickness of a recast layer, whereas trim cut mode produces better surface finish and minimum surface damage. In comparison to polished surface and WEDMed at rough cut mode, trim cut mode results into higher corrosion resistance which is due to the formation of a stable protective rutile-TiO2 layer. WEDMed surface possesses higher wettability as compared to a polished surface.

Optimization of WEDM Process Parameters on Surface Roughness and Study of Physical behaviour using SEM for Machining Aluminium Alloy Al 7075 using Brass Coated Copper Wire

Wire Electrical Discharge Machining is one of the most effective Non-Conventional Machining method available to machine intricate shapes which are very difficult to machine with conventional machining methods, on electrically conductive materials havingvarying hardness. In this research work, an attempt hasbeen made to study the effect of process parameters of WEDM on the Surface roughness. Input process parameters considered in this work are Pulse on time (TON), Pulse off time(TOFF), Wire Feed (WF), Wire Tension(WT) and theSurface Roughness as response. Al 7075 Aluminium alloywas taken as work material and Brass coated copper wire as electrode to machine and the values of roughness obtained by varying the input process parameters were analysed using Taguchi method (L 27 orthogonal array). The measured values have been used to develop the mathematical modeland the accuracy of the model wastested using Analysis of Variance (ANOVA) technique. Based on the predicted values the interaction graphs, were drawn betweentheSurface roughnessandthe processparameterstaken for this study. It was construedthatthepulse-on time has the highest impact on the Surface roughness followed by the Wire feed, Wire tension and the Pulse-off time. The surface roughnessgot increasedwith increase in wire feed. Finally optimum parameters have been arrived to achieve better surface roughness. WEDMed surface was also examined by using scanning electron microscope (SEM) and evinced that the physical behaviour of these process parameters on Surface roughness.Copyright © VBRI Press.

An investigation on the effect of different coated electrodes on the surface quality of WEDM by varying discharge energy level

The quality of WEDM surface is still a concern to the researcher. Due to the uneven spark, the energy discharge transferred to the workpiece surface is not accurate for high-quality machining. Such energy is mainly controlled by process variables and electrode parameters. The selection of proper wire electrode and the proper combination of process variables can extend the surface quality into a much higher limit. In the present investigation, machining quality of brass wire, silver-coated brass wire, and zinc-coated brass wire is compared at different discharge energy levels. The quality of machining is measured in terms of average roughness, maximum roughness, kerf width, recast layer thickness, workpiece surface, and elemental inclusions in both wire and workpiece surface. The surface morphologies of the wire have also been investigated. The research material has been carefully chosen as one of the expensive grades of steel named maraging steel 300 due to its wide applicability in the aerospace and automobile industries. From the investigation, it has found that a minor coating of silver over plain brass significantly improves the surface quality. It has also found that, for better quality machining, discharge energy should be kept in a lower limit. Zinc coating over brass improves the strength of the wire as well as machining rate but simultaneously is responsible for the poor quality of surface. Brass wire is neither a good choice for high surface quality machining nor good for high-speed machining. The majority of copper and some zinc elements have been flush out from wire and adhered to the workpiece surface.

Wire Electrochemical Trimming of Wire-EDMed Surface for the Manufacture of Turbine Slots

Turbine slots are categorized as crucial structures in aero engine and have strict demands on surface integrity concerning fatigue strength. In the last decade, low speed wire electrical discharge machining (LS-Wire EDM) with multiple cuttings has been proposed as a method to replace the well-established broaching process, which needs expensive assets investment and lacks flexibility to new designs. However, recast layers and heat-affected zones still remain in doubt from industries. Wire electrochemical machining (Wire ECM) has similar kinematic flexibility with Wire EDM, but possess exclusive advantages like being free of tool wear and recast layers. Unfortunately the state of art of Wire ECM could not afford efficient precision machining of macro structures with a thickness over tens of millimeters.This work proposes an integrated process combining high speed wire electrical discharge machining (HS-Wire EDM) and wire electrochemical trimming (Wire ET) for the manufacture of turbine slots. Here, HS-Wire EDM takes on the low-cost efficient pre-slotting while a single cutting of Wire ET plays the roles of roughing, semi-finishing and finishing. Experimental results indicate that the electrode trimming rate have a significant influence on material removal rate. Under the process conditions as a pulsed voltage of 40% in duty ratio, 16 V in amplitude and 20 kHz in frequency, a trimming depth of 10 μm and an electrode trimming rate of 7.2 mm/min, the material removal depth is 30 μm and recast layers overlapped on WEDM surface could be entirely removed. Finally, a 20 mm-thick fir-tree slot in Inconel 718 free of recast layers was machined in the proposed integrated process. The average machining efficiency is 64 mm2/min and the profile allowance could reach -0.010 to +0.010 mm.

Research on ECM Finishing Process using Wire Electrode

In wire electrical discharge machining (WEDM), discharge craters and heat-affected zone impair the surface roughness and generate micro cracks and residual stress. Hence, this study aimed to finish the WEDMed surface by electrochemical machining (ECM) using the same setup, wire electrode and machining fluid used in WEDM. Ultrashort bipolar pulses were used to improve the finishing speed and surface roughness. To realize electrochemical finishing on a WEDM machine, first the influences of the electrolyte concentration on machining characteristics were investigated, and it was found that machining can be performed even if the electrolyte concentration of NaNO3 aqueous solution is diluted to 0.2 wt%. With lower electrolyte concentration, smaller surface roughness was obtained at smaller machining depth. Next, the material of the wire electrode was changed from platinum to brass which is commonly used for WEDM, and the wear rate of the brass wire was investigated. Although the wear rate was 20 times higher than that of platinum, wire breakage did not occur in most of the experiments conducted in the present work. Then, machining was performed with an equal current density for different thicknesses of workpiece, and influences of the workpiece thickness on the process characteristics were investigated.

Estimation of Crack Length on W-EDMed Surface of Zirconia Ceramics

Estimation of Crack Length on W-EDMed Surface of Zirconia Ceramics

Study of removing the recast layer by electrochemical dissolution with wire low feedrate in WEDM

One characteristic of WEDM surface is that it is covered with numerous craters and re-solidified materials, forming the recast layer which deteriorates the surface quality and other properties such as fatigue strength. In this research, a method combining WEDM and electrochemical dissolution together in a simple process is proposed and studied. The principle of the method is introduced. The recast layer can be dissolved and removed by electrochemical reaction with low wire feedrate in deionized water. The calculation model is established to find the suitable feedrate of the wire electrode, and the experiments are carried out to verify the proposed model. The calculation error of the model coming from the processing instability caused by the vibration of the wire is discussed. The stripes mainly composed of the re-solidified materials can be found on the surface when the high wire feedrate is used to cut the workpiece in WEDM. On the contrary, if the low feedrate is used, these stripes will disappear. If the feedrate further reduces, electrochemical dissolution can play the role to dissolve and remove the recast layer; the surface quality can be improved as a result. The influence of wire feedrate on surface topography and surface roughness is also analyzed.

Corrosion behavior of surface induced by wire EDM on 316L stainless steel: an experimental investigation

Wire electric discharge machining is an efficient technique among the available nonconventional machining process and is mostly used for machining complex shapes and hard materials. This process also acts as a form of surface modification technique. The discharge energy of machining process influences the nature of the machined surface to a very high degree due to high heat generation and deposition of wire electrode material. 316L stainless steel is widely used in engineering, marine and medical applications. Although 316L SS is a corrosion resistant material, there is a lot of research going on to improve its corrosion resistance by different surface modification techniques due to its applications. Investigation on the effect of WEDM parameters on the corrosion behavior of 316L SS material is carried out. Corrosion studies were carried out by Potentiodynamic polarization test and phase analysis was carried out by using XRD. Significant enhancement in the corrosion resistance of WEDMed surface is observed with the variation in pulse on time and peak current. Pulse on time and peak current are the significant parameters influencing the amount of discharge energy. Low level of discharge energy enhanced the corrosion resistance of WEDMed surface.

EFFECT OF ELECTRODE MATERIAL ON CUT QUALITIES OF SHAPE MEMORY ALLOY DURING WEDM: A COMPARATIVE STUDY

This paper compares some of the vigorous machinability characteristics of SMA-Nitinol during WEDM process using uncoated and zinc coated brass wire electrodes. A series of experiments were regulated based on Taguchi’s L[Formula: see text] orthogonal array with an objective of unveiling the benefits of using coated brass wire electrodes in comparison to uncoated counterparts. Five factors, namely pulse-on time ([Formula: see text]), discharge current ([Formula: see text]), wire tension (WT), wire speed (WS) and flushing pressure (FP), were considered, each at three different levels to scrutinize four responses, viz. surface roughness (Ra), kerf width (KW), machining time (MT) and micro-hardness ([Formula: see text]h). It was perceived that zinc-coated brass wire was more preferable to get favorable responses like Ra, KW and [Formula: see text]h when compared with brass wire counterparts. FESEM micrographs also revealed that micro and large cracks, wide craters, recast layer were more prominent on the WEDMed surface of brass wire compared to zinc-coated brass wire. Use of zinc-coated brass wire electrode significantly improves the machinability of the selected work material within the specified range of process variables.

Modelling of surface characteristics of wire-electro discharge machined combustor material specimens

Current research discusses the experimentation on WEDM of combustor material (i.e. nimonic 263) with varying pulse-on time (Ton), pulse-off time (Toff), peak current (Ip) and spark gap voltage (Sv). The influence of parameters is evaluated on the basis of material removal rate (MRR) and surface roughness (SR). Experimental runs are designed according to user-defined RSM. 81 experiments are executed under different parametric conditions. RSM based desirability approach is applied to find out the optimal parameters for maximizing MRR and minimize Sr After that, experimental results are utilized to train the neural network. Furthermore, microstructure changes and composition of WEDMed surface is assessed by FE-SEM. It is observed that WEDMed surfaces contain micro-cracks, craters, spherical droplets and lump of debris. In addition, the mechanism of recast layer formation and microhardness of machined surfaces are critically evaluated to apprehend better understanding of the technique. Furthermore, polishing was considered as a post-processing technique for removing the RLT. The key features of experimental procedure are also highlighted in this paper.

Surface finish analysis of wire electric discharge machined specimens by RSM and ANN modeling

This study discusses the experimental investigation on WEDM of combustor material (i.e. nimonic 263). Experimentation has been executed by varying pulse-on time (Ton), pulse-off time (Toff), peak current (Ip) and spark gap voltage (Sv). The influence of these parameters was studied on the Surface roughness parameters (i.e., average: Ra and ten-point mean: Rz), recast layer thickness (RLT), and changes in the machined surface. Experiments are designed as per Box-Behnken design technique. Parametric optimization has also been performed using response surface methodology. The results of proposed algorithm show that the BPNN is effective tool for the prediction of responses. The BPNN predicted results are 99% in agreement with the experimental results. Furthermore, microstructure and composition of WEDMed surface was assessed by FE-SEM. It was observed that WEDMed surfaces contain micro-cracks, craters, spherical droplets and lump of debris. Longer pulse-on time causes greater discharge energy, hence leading to higher material removal rate, surface roughness, and recast layer thickness. In addition, the mechanism of recast layer formation and microhardness of machined surfaces have been critically evaluated to apprehend better understanding of the technique. Furthermore, polishing was considered as a post-processing technique for removing the RLT. The key features of experimental procedure are also highlighted.