Minimum Recast Layer Research Articles

Optimization of Machining Parameters in Wire Electric Discharge Machining Inconel 600 Using Regression analysis

In this investigation, Inconel 600 is used as the workpiece material, which is typically applied in aerospace products, chemical processing equipment, furnace parts etc., due to its good resistance to stress and wear resistance. In this work, the effect of machining parameters of Wire Electric Discharge Machining (WEDM) process is investigated. Molybdenum wire electrode of 0.1mm diameter and de-ionized water dielectric medium are used for machining. Voltage, Pulse on-time, Pulse Off-time, Peak Current and Bed speed are considered as the machining parameters. Recast layer thickness is considered as the response parameter. The type of design of experiments considered for this work is Taguchi’s L18 orthogonal array. Analysis of variance is indicating the percentage contribution of each machining parameters on response parameters. The optimum combination of machining parameters yielded minimum Recast layer thickness 4.11μm.

Performance evaluation of electrical discharge turning of inconel-825 under influence of different magnetic field intensities

ABSTRACT Electrical discharge turning (EDT), an unconventional machining method that utilises electrical discharges generated between an electrode and a rotating workpiece to remove material. However, it faces some challenges with numerous advantages, particularly in the effective removal of debris from the machining zone. In this context, magnetic field assistance is an emerging technique in facilitating the efficient removal of debris during the EDT process. This comparative study compares the effects of various magnetic field intensities on the electrical discharge turning (EDT) process of the Inconel-825 material, a nickel-based superalloy. The experiments were carried out on a self-developed magnetic field assisted electrical discharge turning setup. The experimental results show that increasing magnet intensity enhances the material removal rate (MRR) and improves the overcut (OC) surface finish (Ra) of the machined parts. Additionally, at higher magnetic fields intensity tool wear rate (TWR) has been reported higher. The machined surface has also been observed using SEM and found that the minimum recast layer and debris are formed on the surface at higher magnetic intensity. EDX result also confirmed that the formation of oxide and carbide on the machined surface was minimum at higher magnetic field intensity.

Effect of graphene dispersed coconut biodiesel on the Micro ED milling characteristics of Inconel 718 alloy

Micro Electrical discharge milling is a familiar micromachining process for machining of complex microstructures using a cylindrical tool. In this research work, the influence of process parameters namely capacitance, voltage, threshold on response indicators during machining of Inconel 718 with coconut biodiesel and graphene nano powder dispersed coconut biodiesel is investigated in detail. Further, surface-topography of the machined surface was critically examined using scanning electron microscopy and three-dimensional non-contact roughness tester. Graphene nano powder concentration (0.3 g l−1) increased the MRR around 68% compared to coconut biodiesel (BD). A medium order of capacitance (10 nF) offered a maximum MRR irrespective of dielectric used. With higher order capacitance, the minimum TWR is obtained due to longer pulse off duration. High surface finish is achieved with graphene nano powder dispersed coconut BD due to uniformly distributed of craters on the machined surface. Recast layer thickness is 3.08 μm, 1.62 μm and 2.34 μm with coconut biodiesel, 0.3 g l−1 and 0.6 g l−1 graphene particles mixed coconut biodiesel, respectively. Minimum recast layer is observed with graphene particles mixed coconut biodiesel under considered parametric conditions due to lesser eroded particle deposition. EDS results confirm that the sedimentation of graphene nano powder (increase in carbon %) on work surface results in increase in hardness. Crater size, voids and cracks were reduced with graphene nano powder dispersed coconut BD due to uniform distribution of heat energy over machining region. Results showed that the graphene nano powder mixed coconut biodiesel can be the substitute for mineral oil.

Alumina Nano Powder Impact on Electrical Discharge Machining of Titanium Alloy Wire

WEDM is an unconventional method of thermal machining that produces products with irregular shapes. The results of milling titanium (TI-6242) under various machining conditions that affect the WEDM process are provided. Pulse on time (Ton), pulse off time (Toff), peak current (Ip), voltage (V), wire tension (Wt), and wire feed are all considered machining parameters (Wf). They are established using an experimental design and the Box–Behnken approach to optimize the machining factors. The optimization goal is to attain the highest Material Removal Rate (MRR) and the least amount of recast layer (RL). ANOVA determines the most important factor. Moreover, a regression analysis is used to predict MRR and RL based on defined machining parameters. Ton = 120s, Toff = 50s, Ip = 11 A, Wt = 1kg, and V = 50 volt are the optimal regulatory factors for obtaining the highest MRR, depending on the consequences. Ton = 130s, Toff = 60s, Ip = 12 A, Wt = 3 kilogram, and V= 30 volt are the best control variables for achieving the lowest RL. Ton = 120s, Toff = 50s, Ip=10 A, and Wt=1kg are thought to be the ideal control parameters for achieving minimum RL and greatest MRR. In ideal machining circumstances, the microstructure of the machined surface exhibits a recast layer on the machined surface.

Measurement of WEDM performance characteristics of aero-engine alloy using RSM-based TLBO algorithm

Alloy-706 is a newly introduced exceptional class of turbine wheel alloy for high-performance aero-engine. To precisely measure the WEDM performance of complex aero-engine parts, the RSM-based TLBO algorithm is proposed in the current study. Morphology, topography, recast layer thickness, and roughness parameters of machined surface are studied to examine the surface integrity of aero-engine components. Better surface morphology, smoother topography, low roughness value, and minimum recast layer are observed at low pulse duration, high pulse-off period, and high servo voltage. RSM is used for statistical modeling of removal rate and average roughness. Then, these models are used in TLBO algorithm for individual and multiple performance optimizations. The Pareto optimal solutions are obtained for lower roughness value and highest removal rate. The microscopic investigation represents a considerable number of melted droplets, micro-holes, and craters on the WEDM-cut surface due to high energy discharge pulses followed by improper flushing of molten material.

Influence of Process Parameters on the Microstructural Characteristics and Mechanical Properties of Recast Layer Thickness Coating on Die Steel Machined Surface after Electrical Discharge Machining

The surface layer machined after electrical discharge machining (EDM) is different from it after traditional methods, and studying the surface layer structure machined by this method will contribute significantly to the selection of finishing methods. In this study, the surface layer of SKD61 steel after EDM using copper (Cu) electrode was analyzed. Technological parameters including discharge current (Ie), pulse on time (Ton), pulse off time (Tof), and voltage (Ue) were used in the study. The minimum recast layer thickness (RLT) was determined using the Taguchi method. The results showed that Ie, Ton, and Tof were significant influences on RLT, and Ue was insignificant. Minimum, value of RLT = 3.72 µm at process parameters Ie = 1 A, Ton = 50 µs, Tof = 12 µs, and Ue = 30 V. The machined surface layer after EDM is inconsistent with the workability of the product, and it should be removed from the machined surface.

Assessment on surface integrity of AISI 304 steel during powder mixed electrical discharge machining

The effect of mixing molybdenum-di-sulphide (MoS2) powder particle into the dielectric medium of electrical discharge machining is analysed. The duty factor and MoS2 powder particle size were taken as input parameters. Duty factor is varied at 2, 6, 10 and two different size of MoS2 powder particles 40 µm, 90 nm were used. The significance of input parameters on crater, globules, and recast layer thickness were analysed. Peak current 6 A, discharge duration 300 µs, gap voltage 80 V, powder concentration 1 g/l, and a continuous ultrasonic vibration to dielectric fluid were maintained constant throughout the experiments. For both sizes of MoS2 powder particle, small size crater and minimum global appendages generated on the surface machined at duty factor 2. Compared to 40 μm size powder, more MoS2 powder particles gets deposit on the machined surface and minimum recast layer thickness is achieved while using 90 nm size powder into dielectric medium.

Experimental investigation and parametric optimisation of the hole-circularity and recast layer during the laser trepan drilling

ABSTRACT Re-solidified layer of molten metal during laser trepan drilling of Inconel-718 is a serious concern. Re-solidification affects the dimensional stability and geometrical features. Many scientific efforts have been reported for understanding and minimising the re-solidification layer (recast layer) thickness in laser cutting and percussion drilling operations. However till date, limited scientific work has been reported concerning recast layer formation during the laser trepanning of Inconel-718. In the present work, a methodology has been proposed for reducing the recast layer formation during the laser trepanning of Inconel-718. For understanding and achieving minimum recast layer thickness with better circularity, series of laser trepanning experiments have been performed on a thin sheet of Inconel-718. Recast layer thickness and hole- circularity are measured for each laser trepan drilled hole followed by the development of mathematical models using response surface methodology. The developed mathematical models are optimised with the help of multi-objective genetic algorithm to ascertain the optimum trepan drilling parameters. The obtained values of optimum parameters are validated by conducting more experiments. From validation experiments, it has been found that the obtained range of input parameters is significant, and the heat affected zone can be controlled using the proposed methodology.

Study of material characteristics in laser trepan drilling of ZTA

Zirconia Toughened Alumina (ZTA) ceramic is used to make distinct components of aerospace, military and biomedical industries which require suitable machining method free of mechanical forces. Recent researchers reveal that Laser Beam Machining has diverse potential to overcome machining difficulty of structural ceramics. But to enhance the durability and performance of these components, study of material properties became essential after laser machining because this process involves intense heat or thermal energy. Present study investigates the material characteristics of laser trepanned ZTA plate with the aim to explore the effects of process parameters on recast layer thickness, microcrack width and microhardness. The outcome of study may be helpful in setting the processing regime for laser trepanning of ZTA ceramic which may furnish the products with minimum recast layer thickness and microcrack width along with minimum change in microhardness. The experimental results show that lower pulse width or trepanning speed, and higher air pressure reduce the recast layer thickness and microcrack width.

Prediction Modelling of Recast Layer and Circularity for Laser Drilling of Polyethylene Terephthalate (PETG) Thermoplastic

Laser drilling is a promising industrial machining application. However, the recast layer and improper circularity are the two important drawbacks for the practical manufacturing industry. The aim of this study is to develop prediction models of the recast layer and circularity by using Taguchi method. For the design of experiment (DOE) aspects, an L9 orthogonal array design has been chosen and conducted nine experiments with three runs for each experiment. Experimental results indicated minimum recast layer at laser power 700 watts, gas pressure at 1.5 bars and cutting speed at 4000 mm/s. Whereas average circularity has been found at laser power 700 watts, gas pressure at 1.0 bar and cutting speed at 3500 mm/s. In addition, the percentage of contribution for recast layer of laser power is 27.66%, gas pressure is 23.68% and cutting speed is 48.66%. Whereas for circularity, laser power contribution is 23.89%, gas pressure is 26.00%, and cutting speed is 50.11%. Moreover, the 2nd order prediction models have been found excellent agreement with the experimental data. This research will extend knowledge to predict the desired circularity and minimum recast layer of the Polyethylene terephthalate (PETG) thermoplastic which is very important in the field of medical and packaging industry.

Effect of temporally modulated pulse on reducing recast layer in laser drilling

Temporally modulated-pulse laser is a promising technique; it has many advantages compared with normal pulse laser. The modulated pulse studied in this work was comprised of a wide pre-heating pulse front and a sharp pulse trail. The experiments were carried out mainly to study the influence of pre-heating subpulse energy and duration, while the trail subpulse was invariant. Both blind-hole and through-hole drillings were carried out, finding that there were some important differences between them. In blind-hole drillings, the deep melting caused by pre-heating subpulses greatly enhanced the absorptivity of laser energy of the sharp pulse trail, which increased the vaporization rate and pressure, and eventually expelled most of the liquid melt from the cave, leaving a very small quantity to resolidify as recast layer. In through-hole drillings, although the minimum recast layer thickness was reduced to 2.5 μm, the hole quality was found to be very sensitive to sample thickness. Once the pre-melting depth exceeds the sample thickness, it would be very difficult for the remnant pulses to expel the melt chunk. High-quality holes can only be drilled when the pre-melting depth is close to the back surface but melt through does not happen. Even so, the recast layer at the hole exit was always thicker than that at the other parts of the hole due to the sudden slump of recoil pressure when the hole was drilled through.

WEDM of nickel based aerospace alloy: optimization of process parameters and modelling

This article presents the experimental data for the machining of Nimonic-90 on wire electrical discharge machining (WEDM). It is a nickel based alloy which possessing creep resistance and high rupture strength at high temperature (up to $$950~^{\circ }\hbox {C}$$ ). Four input process parameters, viz., peak current (Ip), pulse-on time (Ton), pulse-off time (Toff), and servo voltage (SV) were investigated and modelled for three response variables namely cutting speed (CS), surface roughness (SR) and radial overcut (RoC) utilizing Response Surface Methodology (RSM). In present experimentation, quadratic model is suggested for all three responses. Analysis of Variance (ANOVA) indicate that Ip, Ton, Toff and SV are significant process parameters influencing the CS and SR while Ip, Ton and SV were highly significant parameters influencing the RoC. Desirability function was employed to optimize the multi-performance characteristics. Using SEM micrographs and micro-hardness profile, effect of discharge energy (DE) on surface morphology was examined. Topography of machined surface; corresponds to different levels of DE; suggests that high discharge energy results in overlapped and deep craters of large size diameters and high thickness of recast layer whereas low discharge energy results into fine surface with minimum recast layer.

Micro-electro discharge machining of non-conductive zirconia ceramic: investigation of MRR and recast layer hardness

Increasing material removal rate (MRR) and minimizing recast layer hardness are critical issues in machining non-conductive ceramic using micro-electro discharge machining (micro-EDM). This paper presents the analysis of MRR and recast layer hardness of zirconium oxide (ZrO2) due to micro-EDM using EDM-3 dielectric fluid and tungsten tool electrodes. The two main parts of this research are process development and the analysis of MRR and recast layer hardness. In process development, the appropriate use of assisting electrode (AE), polarity, flushing, feed rate, gap voltage, and tool electrode rotational speed are identified. The better machinability of ZrO2 was found to be with copper adhesive as AE, positive workpiece polarity, 3-μm/s feed rate, and workpiece submerged in dielectric fluid with one-way circulation. Empirical models are developed for the estimation of MRR and recast layer hardness. The optimum parameters for maximum MRR and minimum recast layer hardness are found to be at a 370-rpm rotational speed and at 80-V gap voltage.

Investigation of Recast Layer of Non-Conductive Ceramic due to Micro-EDM

This paper presents the investigation of minimum recast layer of zirconium oxide (ZrO2) due to micro-EDM using EDM-3 synthetic oil as dielectric fluid and tungsten as the tool electrode with control parameters of rotational speed and gap voltage. The investigation was performed using multi-process micro machine tools DT 110. The recast layer thickness was observed using scanning electron microscope and its hardness was measured using micro-Vickers hardness tester. The hardness data were analyzed and an empirical model was developed. The optimum value for minimum recast layer hardness was 873.46 Hv with rotational speed of 395 rpm and gap voltage of 110 V.

Investigating the recast layer formed during the laser trepan drilling of Inconel 718 using the Taguchi method

This paper presents an investigation into the recast layer formed during the laser trepan drilling of Inconel 718 by a Nd:YAG laser. Laser drilling has evolved into the method of choice for the drilling of cooling holes in aerospace components. However, holes drilled with this particular technique are liable to display a variety of defects, including spattering, tapering, microcracks, and a recast layer. In order to meet the standards specified by the original engine manufacturer, this paper investigates the effects of the various laser drilling parameters on the recast layer thickness in the trepan drilling mode. A total of eight laser drilling parameters are considered in a series of experiments arranged using a Taguchi L18 orthogonal array. Taguchi analytical techniques are employed to establish the optimum set of parameters which yields a minimum recast layer thickness. The results indicate that the assist gas pressure, the peak power, and the focal position exert the greatest influence on the recast layer thickness. Having performed a confirmation experiment based on the initial Taguchi design experiments, the recast layer thickness is reduced further by adjusting the values of the assist gas pressure and the trepanning speed.

Effects of intrapulse structure on hole geometry in laser drilling

Lasers have been established as a commercial tool for drilling holes in a variety of materials. The beam quality and temporal shape of the laser pulse have been identified as critical parameters to create high quality (deeper holes, minimum taper angle, and minimum recast layer) holes. However, little attention has been directed toward an analytic investigation of the effect of different temporal pulse shapes on these product variables. In this study, a leading-edge, sharp-spiked, and a rectangular Nd:YAG laser pulse were used to drill holes in stainless steel 304 to examine the effects of these temporally different laser pulses on the drilling process. It is found that holes drilled with the sharp-spiked laser pulse are significantly deeper than for the case of rectangular pulses. Also an optimum processing regime is identified to drill holes with minimum taper angle and recast layer. A mathematical model describing the drilling process is presented in this article for different temporal profiles of the pulsed laser beams. The model assumes one-dimensional heat conduction in the material and it incorporates the Stefan conditions at the solid–liquid and liquid–vapor interfaces. The predicted drill depth and recast layer thickness are larger than the experimental data but follow the same trend.