Study and optimization of recast layer thickness and surface quality in laser trepan drilling of ZTA

Abstract An electrical discharge forms a crater on the workpiece surface. The crater morphology estimates the performance parameters of the electrical discharge machining process. The energy parameters (gap voltage, discharge current and the pulse on time), the plasma channel radius and the energy fraction coming to the workpiece determine the molten cavity radius and depth. The plasma flushes away a portion of material from the molten cavity forming a crater and resolidification of the remaining molten material forms a recast layer. The plasma flushing efficiency determines the crater’s radius and depth. Few researchers have successfully expressed the plasma radius, energy fraction and plasma flushing efficiency in relation to two of the energy parameters, namely, discharge current and pulse on time but not as a gap voltage function. This work attempted to develop a thermo-physical model to express plasma radius, energy fraction and plasma flushing efficiency as a function of all three energy parameters, such as gap voltage, discharge current and pulse on time. Plasma flushing efficiency was calculated and plasma radius and energy fraction were estimated by inverse finite element method from the measured values of crater radius, crater depth and recast layer thickness. The expressions for plasma radius, energy fraction and plasma flushing efficiency were found out from the regression equations obtained from the designed data set using the Taguchi method. Validation shows that the modeled and experimental values of crater radius, crater depth, and recast layer thickness agree well.

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Study on recast layer thickness and residual stress during WEDM of SMAs

Emerging Materials Research ◽

10.1680/jemmr.16.00120 ◽

2017 ◽

Vol 6 (1) ◽

pp. 82-88 ◽

Cited By ~ 3

Author(s):

Mallaiah Manjaiah ◽

Rudolph F. Laubscher

Keyword(s):

Residual Stress ◽

Layer Thickness ◽

Recast Layer ◽

Recast Layer Thickness

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Experimental investigations on surface integrity issues of Inconel-690 during wire-cut electrical discharge machining process

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture ◽

10.1177/0954405416654092 ◽

2016 ◽

Vol 232 (4) ◽

pp. 731-741 ◽

Cited By ~ 7

Author(s):

M Sreenivasa Rao ◽

N Venkaiah

Keyword(s):

Surface Roughness ◽

Layer Thickness ◽

Process Parameters ◽

Electrical Discharge ◽

Electrical Discharge Machining ◽

Recast Layer ◽

Machining Process ◽

Micro Hardness ◽

Recast Layer Thickness ◽

Inconel 690

Nickel-based alloys are finding a wide range of applications due to their superior properties of maintaining hardness at elevated temperatures, low thermal conductivity and resistance to corrosion. These materials are used in aircraft, power-generation turbines, rocket engines, automobiles, nuclear power and chemical processing plants. Machining of such alloys is difficult using conventional processes. Wire-cut electrical discharge machining is one of the advanced machining processes, which can cut any electrically conductive material irrespective of its hardness. One of the major disadvantages of this process is formation of recast layer as it affects the properties of the machined surfaces. In this study, experimental investigation has been carried out to study the effect of wire-cut electrical discharge machining process parameters on micro-hardness, surface roughness and recast layer while machining Inconel-690 material. Interestingly, hardness of the machined surface was found to be lower than that of the bulk material. The micro-hardness and recast layer thickness are inversely related to the variation of process parameters. Recast layer thickness, surface roughness and hardness of the wire-cut electrical discharge machined surfaces of Inconel-690 are found to be in the range of 10–50 µm, 0.276–3.253 µm and 122–171 HV, respectively, for different conditions. The research findings and the data generated for the first time on hardness and recast layer thickness for Inconel-690 will be useful to the industry.

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A Soft Computing-Based Analysis of Cutting Rate and Recast Layer Thickness for AZ31 Alloy on WEDM Using RSM-MOPSO

Materials ◽

10.3390/ma15020635 ◽

2022 ◽

Vol 15 (2) ◽

pp. 635

Author(s):

Kapil K. Goyal ◽

Neeraj Sharma ◽

Rahul Dev Gupta ◽

Gurpreet Singh ◽

Deepika Rani ◽

...

Keyword(s):

Layer Thickness ◽

Hybrid Approach ◽

Optimal Solution ◽

Az31 Alloy ◽

Recast Layer ◽

Response Characteristics ◽

Recast Layer Thickness ◽

Cutting Rate ◽

Pulse On Time ◽

Pulse Off Time

In the present research, the AZ31 alloy is machined by wire-cut electric discharge machining (WEDM). The experiments were designed according to the Box-Behnken design (BBD) of response surface methodology (RSM). The input process variables, namely servo feed (SF), pulse on-time (Ton), servo voltage (SV), and pulse off-time (Toff), were planned by BBD, and experiments were performed to investigate the cutting rate (CR) and recast layer thickness (RCL). The analysis of variance (ANOVA) was performed to determine the influence of machining variables on response characteristics. The empirical models developed for CR and RCL were solved using Multi-Objective Particle Swarm Optimization (MOPSO). Pareto optimal front is used for the collective optimization of CR and RCL. The optimal solution suggested by the hybrid approach of RSM-MOPSO is further verified using a confirmation test on the random setting indicated by the hybrid algorithm. It is found that the minimum RCL (6.34 µm) is obtained at SF: 1700; SV: 51 V; Toff: 10.5 µs; and Ton: 0.5 µs. However, maximum CR (3.18 m/min) is predicted at SF: 1900; SV: 40 V; Toff: 7 µs; and Ton: 0.9 µs. The error percentage of ±5.3% between the experimental results and predicted solutions confirms the suitability of the proposed hybrid approach for WEDM of AZ31.

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Correlation of surface roughness and recast layer thickness in electrical discharge machining

Proceedings of the Institution of Mechanical Engineers Part E Journal of Process Mechanical Engineering ◽

10.1177/0954408915600949 ◽

2015 ◽

Vol 231 (3) ◽

pp. 414-424 ◽

Cited By ~ 4

Author(s):

Yakup Yildiz ◽

Murali M Sundaram ◽

Kamlakar P Rajurkar ◽

Ahmet Altintas

Keyword(s):

Surface Roughness ◽

Layer Thickness ◽

Electrical Discharge ◽

Electrical Discharge Machining ◽

White Layer ◽

Processing Technique ◽

Recast Layer ◽

Image Processing Technique ◽

Recast Layer Thickness ◽

Two Parameters

Electrical discharge machining (EDM) is an extensively used method in the machining of electrically conductive materials. Recast or white layer formation is undesirable, but inevitable, result of EDM and needs to be understood and accurately determined to efficiently perform post-treatment processes for removing the recast layer caused by EDM process. In this study, recast layer thickness and surface roughness data obtained from experimental study were analyzed and a correlation between these two parameters has been established. Image-processing technique has been used for obtaining of recast layer thickness data. It was observed that the correlation between recast layer thickness and surface roughness increases remarkably with the increase of working current and pulse time. The correlation obtained in this study has the potential to predict the recast layer thickness on spark-eroded surfaces from simple surface roughness values instead of using the prevailing time-consuming and tedious etching and polishing method. The possible approximation of the recast layer thickness using a thermal model is also discussed.

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