Faculty Publications
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Item Evaluation of WEDM performance characteristics of Inconel 706 for turbine disk application(Elsevier Ltd, 2015) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 is a newly developed superalloy, which offers high mechanical strength alongwith easy fabricability thus making it suitable for turbine disk applications. Although Inconel 706 exhibits a substantial increase in stress rupture and tensile yield strength compared to other superalloys, its conventional machining yields poor surface finish and low dimensional accuracy of the machined components. Hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed and various performance attributes such as material removal rate (MRR), surface roughness (SR), recast surface, topography, microhardness, microstructural and metallurgical changes of the machined components have been evaluated. The experimental results revealed that servo voltage, pulse on time, and pulse off time greatly influence the MRR and SR. Due to high toughness of Inconel 706, no micro cracks were observed on the machined surface. Micro voids and micro globules are significantly reduced at low pulse on time and high servo voltage. But, there is a propensity of thick recast layer formation at high pulse on time and low servo voltage. EDAX analysis of recast surface exposed the existence of Cu and Zn which have migrated from the brass wire. The subsurface microhardness was changed to 80. ?m due to significant thermal degradation. © 2015 Elsevier Ltd.Item Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected. © 2016, ASM International.Item Effect of wire diameter on surface integrity of wire electrical discharge machined Inconel 706 for gas turbine application(Elsevier Ltd, 2016) Sharma, P.; Dupadu, D.; Narendranath, S.Inconel 706 superalloy has established itself in the field of gas turbine industry because of its easy fabricability combined with high mechanical strength. Due to its high stress rupture and tensile yield strength, conventional machining of this superalloy exhibits poor surface and low dimensional accuracy of the machined components. It is well known that most of the gas turbine components include complex shaped profile with high precision and hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed to achieve the feasibility in manufacturing of complex shaped components for gas turbine application. In the current investigation, the effect of wire diameter on WEDM performance characteristics such as cutting speed, surface roughness, surface topography, recast layer formation, microhardness, microstructural and metallurgical changes have been evaluated. It was investigated that smaller diameter wire is advantageous over the larger diameter wire since it improves productivity as well as surface quality of the machined components under the same settings of control parameters. In addition, smaller diameter wire has shown comparatively lower recast layer thickness, minimum hardness alteration and shorter manufacturing time. The XRD result has confirmed the presence of residual stress within WED machined component. © 2016 The Society of Manufacturing EngineersItem Analysis and Optimization of WEDM Performance Characteristics of Inconel 706 for Aerospace Application(Springer Netherlands rbk@louisiana.edu, 2018) Sharma, P.; Dupadu, D.; Narendranath, S.Wire Electrical Discharge Machining (WEDM) has established itself for manufacturing of precise and complex shape components for aerospace application due to the high quality requirement of aerospace components such as normal residual stress, no cracks, no recast layer, no porosity; still there is a need to optimize the control parameter settings and evaluate the performance characteristics of the WEDM process. The experiments have been conducted on Inconel 706 which is a newly-developed superalloy specially for aircraft application. A hybrid approach has been used to optimize the material removal rate (MRR) as well as surface roughness (SR) and significant control parameters have been identified using analysis of variance (ANOVA). Microstructure analysis revealed the formation of microglobules, melted debris and microholes on the machined surface, but no microcrack was detected due to the high toughness of the alloy. Energy dispersive X-ray spectroscopy (EDAX) has been carried out to study the metallurgical changes in the WED machined surface. The topography analysis of the curved surface revealed the best surface quality of the machined component at low pulse on time and high pulse off time. A thick recast layer of 39.6 µm was observed at high pulse on time and low servo voltage. Microhardness of the machined surface was changed up to a depth of 70 µm due to cyclic thermal loading during the WEDM process. © 2017, Springer Science+Business Media Dordrecht.Item Performance evaluation of mechanical micro-drilling, electrical discharge machining and laser beam machining on nimonic 80A alloy(National Institute of Science Communication and Information Resources (NISCAIR) ijact.editor@gmail.com Dr. K. S. Krishnan Marg (Near Pusa Gate) New Delhi 110-012, 2018) Sudhakar, S.; Kumar, P.; Srinivas, G.; Ravishankar, S.; Dupadu, D.; Barshilia, H.C.Micromachining techniques such as mechanical micro-drilling, electrical discharge machining (EDM) and laser beam machining (LBM) play an important role in the manufacturing of micro-devices used in mechanical, electronics, aerospace and medical applications. In this paper, an effort has been made to compare the performance of these micromachining techniques with regard to tool wear, burr formation and surface integrity. This is done by producing 20 micro-holes of approximately 800 ?m diameter on a rectangular block (90×30×3 mm3) of Nimonic 80A superalloy. TiAlN coated WC micro-drills, Cu electrodes and CO2 laser beam are used to produce these holes in conventional micro-drilling, EDM and LBM, respectively. The quality of the drilled hole (diameter, surface roughness and micro-burr formation), tool diameter analysis, taper angle and material removal rate (MRR) are compared and reported. A comprehensive analysis is also carried out on overcut, which leads to hole inaccuracy. Results show that mechanical micro-drilling produces better results in the above mentioned characteristics in comparison to LBM and EDM techniques. The relatively better performance of mechanical micro-drilling is attributed to the usage of TiAlN coating on WC tool. © 2018, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Item Measurement of WEDM performance characteristics of aero-engine alloy using RSM-based TLBO algorithm(Elsevier B.V., 2021) Sharma, P.; Dupadu, D.; Narendranath, N.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. © 2021 Elsevier LtdItem Precision manufacturing of turbine wheel slots by trim-offset approach of WEDM(Elsevier Inc., 2021) Sharma, P.; Dupadu, D.; Narendranath, S.The present study aims to precisely manufacture the turbine wheel slot using a novel trim-offset approach of wire-electrical-discharge-machining (WEDM) in order to overcome the challenges of a conventional broaching process. Two dimensional model of turbine wheel slot is prepared in ‘ELCAM’ software to generate the computer-numerical-control (CNC) code of fir-tree-profile geometry. The experimental plan based on a trim-offset approach is executed to minimize the thermal damage and to improve the surface fatigue strength, which is most desirable for a long operating life of the jet engine. An average cutting speed of ~1.5 mm/min is observed for rough-cut and ~5 mm/min for trim-cut operation. Six categories of wires are used to manufacture the turbine wheel slots without any wire breakage and gap-short issue. The fabricated profile slots have demonstrated an average roughness (Ra) of 0.65 ?m, profile accuracy within ±5 ?m, minimum hardness alteration (34.87 Hv), and negligible recast layer (<5 ?m) using B-150 wire and fulfilled the essential requirements of the gas turbine industries. Compared to wire-electrochemical-machining (WECM), WEDM trim-offset approach is quite advantageous and should be beneficial for the researchers working in ‘Precision machining of aerospace materials’. © 2021 Elsevier Inc.