Papers by Keyword: Recast Layer

Abstract: 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.

Abstract: In this study, a series of deep micro holes were machined on thick GH4169 super alloy by the trepan drilling, using a millisecond pulsed laser which equipped to the numerical control processing system. The microstructure of the holes including surface and longitudinal morphologies, diameter, taper, circularity, micro cracks and recast layer were systematically characterized. The surface morphology and the longitudinal section of the drilled holes were observed by Scanning Electron Microscope and 3D Laser Scanning Confocal Microscope. The method of Minimum circumcircle method was employed to evaluate the entrance and exit end circularity. The results showed that the melt and spattering accumulating around the holes decreased with the augment of laser power. The diameter of the entrance showed an increasing tendency with the growing of laser power, but the exit end was not seriously affected by the power. The micro cracks and recast layer could be found obviously, the micro cracks appeared in those zones which thermal stress concentrated, the thickness of recast layer is about 20μm and the taper and circularity were optimized at a laser power of 80-100W.

Abstract: In this study, the optimization of cutting width (Kerf), material removal rate (MRR), surface roughness (SR) and recast layer (RL) in WEDM was investigated by using Taguchi-Grey-Fuzzy logic method. The experiments have been conducted under varying arc on time, on time, off time, open voltage and servo voltage. An orthogonal array, signal-to-noise (S/N) ratio, grey relational analysis, grey-fuzzy reasoning grade and analysis of variance were employed to study the performance characteristics in the WEDM process of Buderus 2379 ISO-B tool steel. Experimental results show that on time gives the highest contribution for reducing the total variation of the multiple responses, followed by off time, open voltage, servo voltage and arc on time. The optimum performance characteristics could be obtained by using the values of AN, ON, OFF, OV and SV of 1 A, 1 µs, 15 µs, 95 V and 55 V respectively.

Abstract: In this study, the effects of cutting parameter on surface quality was investigated experimentally in wire electrical discharge machining (WEDM) process of ASSAB XW-42 and ASSAB 8407 2M tool steels. The surface quality of WEDMachined (WEDMed) was usually characterized by its roughness, recast layer and cracks. The experiments were conducted under different setting of pulse on time and arc on time on. It can be concluded that surface roughness, recast layer thickness and density of microcracks increased proportionally with pulse on time and arc on time. Thin recast layer and low crack density in the surface of ASSAB XW-42 tool steel was due to the low thermal conductivity of work piece material.

Abstract: Nimonic-80A is a nickel based super alloy which is specifically used in aerospace industry for its high strength to weight ratio and corrosion resistance. This paper presents the influence of process parameters of wire cut Electrical Discharge Machining (WEDM) during the machining of Nimonic 80A with brass wire as electrode and optimization of machining parameters on kerf width. Process parameters (pulse-on time, pulse-off time, peak current, spark gap set voltage, wire feed and wire tension) have been investigated using L₂₇ orthogonal array. With the assistance of Taguchi quality design, ANOVA and F-test, significant parameters affecting the kerf have been identified. The surface topography of machined samples has been studied in correlation with the rate of input energy into the spark.

Abstract: Wire Electrical Discharge Machining (WEDM) is an very accurate non-traditional machining process for producing parts with accurate dimensions and complex shapes. The performance of WEDM is measured by evaluating the parameters like Material Removal Rate (MRR), Surface Roughness (Ra), cracks, voids, pores and recast layer. In this paper, an attempt is made to improve the machining performance by adding multi wall carbon nanotube (MWCNT) with dielectric fluid. The MRR, Ra and surface characteristics are compared with surface that is machined using dielectric fluid with and without MWCNT. The results show that addition of MWCNT improves the MRR and surface finish.

Abstract: 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.

Abstract: Femtosecond laser with the features of ultrashort pulse duration and ultrahigh peak power can achieve “cold” machining. The recast layer and micro-cracks of the hole wall can be ruduced effectively by applying femtosecond laser in processing air-film holes on turbine blades, and the machining accuracy and consistency of the hole shape will increase. In this paper, the high-speed rotating femtosecond laser beam is adopted in several currently used turbine blade materials for air-film holes machining, and high quality air-film holes without hole wall recast layer and micro-cracks are processed through a large number of experiments to optimize machining technology and technological parameter.

Abstract: In order to improve the surface quality of titanium alloy in electric discharge machining (EDM) milling, presents electrode ultrasonic vibration assisted EDM milling in the kerosene fluid which fills with 12g/L SiC abrasive particles. By the comparison test of surface roughness between EDM milling and abrasive particle ultrasonic vibration assisted EDM milling in short pulse(pulse width less than 1μs), it is found that ultrasonic vibration role of SiC particle could effectively improve surface roughness from Ra 0.5μm to 0.2μm. The recast layer and surface crack are analyzed by scanning electron microscope (SEM).Results show the thickness of recast layer reduced 20-30μm and surface crack decreased obviously under the role of abrasive particle ultrasonic vibration. It shows that the combined action of ultrasonic vibration and abrasive particle can dramatically improve the surface quality of titanium alloy in EDM milling.

Abstract: The technology to produce micro-holes without recast layer on nickel-based alloy is studied in this work. The holes are firstly drilled with Nd: YAG laser, a millisecond pulsed laser of high power and efficiency. For the reason of thermal effect, however, holes drilled by this laser always have the defect of recast layer, which is a serious problem, especially in the application as aviation and aerospace engine. In order to remove the recast layer, laser parameters are optimized to produce micro-holes with the least recast layer, and then a kind of chemical etching is used to clear the residual recast layer completely.