Journal Articles

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884

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Author: search.filters.author.Dupadu, D.

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    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.
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    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.
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    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 Engineers
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    Multi objective optimisation of thermally enhanced machining parameters of Inconel 718 using grey relational analysis
    (Inderscience Publishers, 2017) Ganta, V.; Kalichetty, K.S.; Dupadu, D.
    The present work investigates an experimental study of thermally enhanced machining of nickel-based superalloy Inconel 718 using uncoated tungsten carbide inserts. An inexpensive flame heating technique using an oxyacetylene flame is used as a heat source for thermal enhancement of workpiece. The effects of cutting parameters like cutting speed, feed rate, depth of cut and temperature of workpiece on the performance characteristics like surface roughness, tool wear and material removal rate were studied. A L27 orthogonal array with four parameters and three levels was adopted for experimental design. Multi response optimisation was done using grey relation analysis to simultaneously minimise surface roughness, tool wear and to maximise material removal rate. It was observed that at cutting speed at 85.21 m/min, feed rate at 0.048 m/min, depth of cut at 0.6 mm and workpiece temperature at 600°C were optimal cutting parameters. It is clearly shown that the above performance characteristics in thermally enhanced machining can be improved effectively through this approach. © © 2017 Inderscience Enterprises Ltd.
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    Multi-objective optimisation of cryogenic turning process using Taguchi-based grey relational analysis
    (Inderscience Publishers, 2017) Sivaiah, P.; Dupadu, D.
    Cryogenic machining is a sustainable manufacturing approach; it eliminates coolant disposal cost, health problems compared to the conventional flood cooling. The present study investigates the multiple response optimisation of turning process while machining AISI 17-4 PH stainless steel under the cryogenic environment (jetting of liquid nitrogen at -196°C at the rake face of the tool) by using Taguchi-based grey relational analysis. The optimum levels of the machining parameters are cutting speed at 120.89 m/min, feed rate at 0.048 mm/rev, depth of cut 0.4 mm and physical vapour deposition (PVD) AlTiN coated tungsten carbide (WC). Taguchi-based grey relational analysis method reduced the cutting forces by 7.75%, improved the surface finish by 55.87%, and increased the material removal rate (MRR) by 154.76% and 25% increased the tool flank wear in cryogenic turning process. From the analysis of variance, it was identified that feed rate is the most influenced process parameter on turning performance characteristics. © © 2017 Inderscience Enterprises Ltd.
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    Influence of cryogenic coolant on turning performance characteristics: A comparison with wet machining
    (Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2017) Sivaiah, P.; Dupadu, D.
    Machining of 17-4 Precipitation Hardenable Stainless Steel (PH SS) is one of the difficult tasks because of its high cutting temperatures. Conventional cutting fluids are used to overcome the high cutting temperatures, but these are not acceptable from the health and environmental sustainable points of view. Cryogenic cooling is one of the potential techniques to overcome such problems. In the current work, comparison is made of cryogenic turning results, such as tool flank wear, cutting forces (feed force, main cutting force), cutting temperature, chip morphology and surface integrity characteristics with wet machining during machining of heat-treated 17-4 PH SS. The result showed that in cryogenic machining, a maximum of 53%, 78%, 35% and 16% reductions was observed in tool flank wear, cutting temperature, surface roughness and cutting force, respectively, when compared with wet machining. It was also evident from the experimental results that cryogenic machining significantly improved the machining performance and product quality even at high feed rates. © 2017 Taylor & Francis.
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    Influence of Thermally Assisted Machining Parameters on the Machinability of Inconel 718 Superalloy
    (Springer Netherlands, 2017) Ganta, G.; Dupadu, D.
    The present study describes the effect of thermally assisted machining (TAM) parameters on the cutting force, tool wear and surface integrity characteristics (surface roughness, surface topography, and microhardness) of Inconel 718. An inexpensive flame heating technique using oxy-acetylene flame is used to heat the workpiece material. The TAM parameters such as cutting speed, feed rate, depth of cut, and workpiece temperature were selected as process parameters over cutting force, tool wear and surface integrity characteristics.The experimental results reveal that the cutting forces and surface roughness decrease with increases in cutting speed and workpiece temperature, while the workpiece temperature increases as tool wear decreases. The tool wear mechanisms observed were abrasive, adhesive, diffusion and notch wear. The XRD results of thermally assisted machining reveal that neither phase change nor broadening of the peaks were observed at different machining conditions. © 2017, Springer Science+Business Media Dordrecht.
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    Machinability studies on 17-4 PH stainless steel under cryogenic cooling environment
    (Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2017) Sivaiah, P.; Dupadu, D.
    Under higher cutting conditions, machining of 17-4 precipitation hardenable stainless steel (PH SS) is a difficult task due to the high cutting temperatures as well as accumulation of chips at the machining zone, which causes tool damage and impairment of machined surface finish. Cryogenic machining is an efficient, eco-friendly manufacturing process. In the current work, cutting temperature, tool wear (flank wear (Vb) and rake wear), chip morphology, and surface integrity (surface topography, surface finish (Ra), white layer thickness (WLT)) were considered as investigative machinability characteristics under the cryogenic (liquid nitrogen), minimum quantity lubrication (MQL), wet and dry environments at varying cutting velocities while machining 17-4 PH SS. The results show that the maximum cutting temperature drop found in cryogenic machining was 72%, 62%, and 61%, respectively, in contrast to dry, wet, and MQL machining conditions. Similarly, the maximum tool wear reduction was found to be 60%, 55%, and 50% in cryogenic machining over the dry, wet, and MQL machining conditions, respectively. Among all the machining environments, better surface integrity was obtained by cryogenic machining, which could produce the functionally superior products. © 2017 Taylor & Francis.
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    Comparative evaluations of machining performance during turning of 17-4 PH stainless steel under cryogenic and wet machining conditions
    (Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2018) Sivaiah, P.; Dupadu, D.
    Productivity in machining of 17-4 PH stainless steel is adversely affected by the premature failure of tool and poor surface finish as a consequence of high cutting temperatures. Conventional cutting fluids not only create environmental and health problems but also fail to overcome the high cutting temperatures during machining. Cryogenic cooling is an environmentally clean cooling technology for attractive management of machining zone temperatures. The present study investigates the effect of cryogenic liquid nitrogen (LN2 at ?196°C) on cutting temperatures, cutting forces (main cutting force, feed force), surface roughness, tool flank wear and chip morphology in turning of 17-4 PH stainless steel with AlTiN PVD-coated tungsten-coated carbide inserts and results were compared to wet machining. In overall, cryogenic machining reduces the cutting temperature, cutting forces, surface roughness and tool flank wear to a maximum of 73.4, 17.62, 44.29 and 55.55%, respectively. Improved chip breakability was found in cryogenic machining. © 2018 Taylor & Francis Group, LLC.
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    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.