Browsing by Author "Dupadu, D."

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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.
Analysis of surface hardness and surface roughness in diamond burnishing of 17-4 PH stainless steel
(IOP Publishing Ltd, 2019) Sachin, B.; Narendranath, S.; Dupadu, D.
Burnishing is a chipless secondary finishing operation which yields excellent surface finish. The present work focuses on multi-response optimization of diamond burnishing on 17-4 precipitation hardenable stainless steel under dry environment by using Taguchi based grey relation analysis (TGRA) to simultaneously minimize surface roughness and maximize surface hardness. The effect of the process parameters such as burnishing speed, burnishing feed and burnishing force on performance characteristics like surface roughness and surface hardness were studied. Taguchi's L9 orthogonal array has been adopted for the experimental design. The optimal burnishing process parameters were found to be burnishing speed of 73 m/min, burnishing feed of 0.048 mm/rev and burnishing force of 150 N. Burnishing feed is the most significant parameter on burnishing performance characteristics. It has been proved that the performance characteristics of a diamond burnishing process have been improved by effective use of this technique. Â© Published under licence by IOP Publishing Ltd.
Analysis of the Effect of Friction Stir Welding Parameters on Characteristics of AA6061 Composites using Response Surface Methodology
(Springer, 2021) Patil, S.; Dupadu, D.; Narendranath, N.
Response surface methodology (RSM) is used for mathematical modeling of friction stir welding parameters for joining AA6061 composite material. Characteristics of joints were examined through response characteristics such as ultimate tensile strength (UTS) and microhardness (HV) using RSM. Microstructure examination was carried out using optical microscopy, scanning electron microscopy and electron backscattered diffraction, and results exhibit variation in the grain size diameter. Specifically, lower nugget exhibits fine grains with maximum hardness compared to middle nugget and upper nugget. Analysis of variance (ANOVA) results indicate good match between actual values and predicted values with R2 of 0.91 and 0.96, respectively, for UTS and HV, and better joint efficiency of 90% is obtained. © 2021, The Indian Institute of Metals - IIM.
Application of Desirability Approach to Optimize the Control Factors in Cryogenic Diamond Burnishing
(Springer, 2020) Sachin, B.; Narendranath, S.; Dupadu, D.
Cryogenic diamond burnishing is an impactful method to enhance the functional performance of the product. In this article, an experimental study on the diamond burnishing of 17-4 precipitation hardenable stainless steel in a cryogenic cooling condition has been presented. This material has excellent corrosion resistance, high strength and enormous applications in the manufacturing industries. The control variables were namely burnishing force, burnishing feed and burnishing force have been studied and modeled for the output responses explicitly surface hardness and surface roughness. The influence of control variables on performance features has been analyzed using response surface graphs. The significant influence of burnishing conditions on the output responses was established by analysis of variance. Desirability function approach has been employed to optimize the multi-performance characteristics. At the corresponding highest desirability, the optimal process parameter combination was found to be burnishing feed = 0.053 mm/rev, burnishing speed = 31.29 m/min and burnishing force = 200 N which yields a minimum surface roughness = 0.199 µm and maximum surface hardness = 397.48 HV. The maximum percentage of error among the predicted and experimental results was found to be 10% and 2%, respectively, for surface roughness and surface hardness. The investigational findings were observed to be in agreement with the predicted value with permissible deviation. © 2020, King Fahd University of Petroleum & Minerals.
Characterisation and performance evaluation of TiSiN &tiAlSiN coatings by RF magnetron sputtering deposition during end milling of maraging steel
(Institute of Physics Publishing helen.craven@iop.org, 2019) Varghese, V.; Ramesh, M.R.; Dupadu, D.; Shaik, H.
Monolayer nanostructured thin films of TiSiN & TiAlSiN were deposited on WC-Co milling inserts using RF magnetron sputtering for metal cutting. The alloy targets of TiSi (80/20 at%) & TiAlSi (34/56/10 at%) were used for the deposition in an Ar + N atmosphere. The deposition time and parameters are optimized to develop a uniform and homogenous coating. The mechanical and metallurgical properties are characterized to analyze the wear resistance of the coating. The machinability studies on MDN 250 maraging steel is carried out using TiSiN and TiAlSiN coated WC-Co inserts under dry and wet environment. The machining responses such as surface roughness, cutting force, tool wear and tool life are analyzed by varying spindle speed. The results showed that TiAlSiN coating had a higher wear resistance and machining performance compared to the TiSiN coating owing to the high hardness and plasticity index of the coating. © 2020 IOP Publishing Ltd.
Characterization and Evaluation of Joint Properties of FSWed AA6061/SiC/FA Hybrid AMCs Using Different Tool Pin Profiles
(Springer, 2020) Patil, S.; Narendranath, S.; Dupadu, D.
This work reports the characterization of AA6061/SiC/FA hybrid composites joined using friction stir welding (FSW). FSW was conducted by employing various tool pin profiles such as straight cylindrical (SC), tapered conical, straight square (SS) and cylindrical threaded. Microstructure and mechanical characteristics of joints were investigated using these tool pin profiles. Microstructure study of the weld joints was carried out through scanning electron microscopy and electron backscattered diffraction (EBSD) analysis. The results show equiaxed distribution of grains in the nugget zone. EBSD analysis indicates that the average grain size reduces to 3 µm after FSW with the presence of high-angle grain boundaries. Higher joint efficiency (85%) is obtained for joints obtained using SS tool pin compared to their counterparts, and SC tool yields minimum joint efficiency (77%). Overall 8% enhancement of the joint efficiency is achieved using SS tool pin profile. © 2020, The Indian Institute of Metals - IIM.
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.
Effect of cryogenic diamond burnishing on residual stress and microhardness of 17-4 PH stainless steel
(Elsevier Ltd, 2018) Sachin, B.; Narendranath, S.; Dupadu, D.
Diamond burnishing is a cold working process, which produces a work hardened and uniform surface by plastic deformation. The aim of the present work is to study the behavior of diamond burnishing on surface integrity of 17-4 precipitation hardenable stainless steel (PH-SS) under cryogenic, minimum quantity lubrication (MQL) and dry environments. Surface modification was achieved by the application of liquid nitrogen during diamond burnishing. The process parameters considered were speed, feed, burnishing depth and number of passes. Surface integrity characteristics such as microhardness and residual stresses were investigated after diamond burnishing under cryogenic, MQL and dry environments. In cryogenic diamond burnishing, the surface integrity characteristics of 17-4 PH stainless steel has been significantly improved when compared to MQL and dry environments. Maximum microhardness of 395 HV, 369 HV, and 357 HV respectively was observed under cryogenic, MQL and dry environment. The maximum residual stress of -352 MPa, -282 MPa and -195 MPa respectively were recorded for cryogenic, MQL and dry environment. Â© 2018 Elsevier Ltd. All rights reserved.
Effect of FSW on microstructure and hardness of AA6061/SiC/fly ash MMCs
(Elsevier Ltd, 2018) Patil, S.; Narendranath, S.; Dupadu, D.
In this study 6 mm thick plates of aluminum matrix composites (AMCs) composed of AA6061/SiC (10 Wt. %) /fly ash (7.5 Wt. %) were butt welded using friction stir welding (FSW. Microstructural characterization of weld joints was conducted by using optical microscopy (OM) and scanning electron microscopy (SEM). The microstructure of the weld revealed the presence of four different zones like nugget zone (NZ), thermo mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM). Nugget zone reveals homogenous distribution of fly ash and SiC particles. Rotating effect of FSW tool results in breaking of some array of grains present in the parent AMCs. Needle like phases present in the parent AMCs eliminated successfully by the incorporation of fly ash particles. Higher hardness is observed in the nugget zone compared to other zones. Â© 2018 Elsevier Ltd. All rights reserved.
Effect of traverse speed on joint characteristics of FSWed HAMCs
(Elsevier Ltd, 2020) Patil, S.; Narendranath, S.; Dupadu, D.
The present work describes the evolution of microstructure and enhancement of mechanical properties of friction stir welded AA6061/SiC/FA Hybrid AMCs (HAMCs). Various joints were produced using different traverse speed from 30 mm/min to 80 mm/min. Microstructural analysis was carried out using Optical microscopy and scanning electron microscopy. Mechanical characteristics such as ultimate tensile strength (UTS) and microhardness (Hv) were studied. Sound quality joints were obtained by FSW without any defects. Results showed that the microstructure zones are divided in to nugget zone, thermomechanically affected zone, heat affected zone and base material zone. Uniform and fine grain formation took place at traverse speed of 60 mm/min indicating sufficient amount of heat input at this speed. Accordingly maximum joint efficiency of 90% is obtained at this traverse speed. Â© 2020 Elsevier Ltd. All rights reserved.
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
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.
Effect of working parameters on the surface integrity in cryogenic diamond burnishing of 17-4 PH stainless steel with a novel diamond burnishing tool
(Elsevier Ltd, 2019) Sachin, B.; S, N.; Dupadu, D.
The productivity of the components is adversely affected by the poor surface integrity characteristics as a consequence of the generation of high temperature in the burnishing zone. The abundant use of conventional lubricants causes environmental pollution and health problems. To overcome these issues, cryogenic cooling has been used across the world to reduce the temperature generated in the burnishing zone. It is well known that most of the accidents which involve aero engines have revealed that the reason for this may be due to the failure of the first stage of compressor blades. Hence aerospace material, 17-4 precipitation hardenable (PH) stainless steel can be used in aero engines to minimize the failure occurring due to foreign object damage. In the present study, the effect of cryogenic diamond burnishing on the surface integrity characteristics such as surface roughness, surface hardness, surface morphology, surface topography, subsurface microhardness, and residual stress of 17-4 pH stainless steel have been investigated with a novel diamond burnishing tool and also it has been related to dry and minimum quantity lubrication (MQL) environments. From the experimental results of diamond burnishing process, surface roughness was observed to be reduced by 33%–50%, 34%–51% and 25%–40% in the cryogenic cooling environment in contrast with MQL and dry environments. Similarly, the surface hardness improvement in a cryogenic cooling environment was found to be 5%–7%, 6%–10%, and 6%–9%, in comparison with MQL and dry environments respectively. © 2019 The Society of Manufacturing Engineers
Enhancement of surface integrity by cryogenic diamond burnishing toward the improved functional performance of the components
(Springer Verlag service@springer.de, 2019) Sachin, B.; Narendranath, S.; Dupadu, D.
17-4 precipitation-hardenable (PH) stainless steel is one of the widely used materials in various applications of engineering practices owing to their excellent corrosion resistance and high strength. The components such as automotive body, aerospace compressor blades, turbine blades and molds demand higher load carrying capacity and improved fatigue strength, which is possible to achieve by surface severe plastic deformation. Diamond burnishing process is an appropriate technique to produce such components which improves the surface integrity characteristics of the material. This article presents a comprehensive examination of the surface integrity of cryogenic diamond burnished 17-4 PH stainless steel using a novel diamond burnishing tool. The impact of diamond burnishing control factors on subsurface microhardness, surface roughness, surface hardness, surface topography, residual stress and surface morphology has been analyzed. The optimal control factor setting ensures the least surface roughness of 0.03 µm by the application of one factor at a time approach. Cryogenic diamond burnished surface achieves the exceptional surface finish and the surface hardness in tool-tip of 8 mm and 6 mm, respectively. The maximum surface hardness of 413 HV was attained using 6-mm tool-tip diameter. The subsurface microhardness improvement of 2% and 4% has been observed while using a tool-tip diameter of 6 mm in contrast to 8 mm and 10 mm. Compressive residual stresses have been generated at the top surface layer of the specimen. The attained experimental results prove that cryogenic diamond burnishing can be successfully applied to 17-4 PH stainless steel to enhance its surface integrity characteristics. © 2019, The Brazilian Society of Mechanical Sciences and Engineering.
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.
Experimental evaluation of diamond burnishing for sustainable manufacturing
(Institute of Physics Publishing helen.craven@iop.org, 2018) Sachin, B.; Narendranath, S.; Dupadu, D.
Diamond burnishing is one of the most popular surface finishing technique used to achieve an excellent surface finish. The aim of the present study is to investigate the effect of process parameters in diamond burnishing of 17-4 PH stainless steel (PH SS) under cryogenic environment. The requirement of a sustainable environment for various machining processes urged to explore the importance of cryogenic burnishing over other cooling techniques. Surface modification was achieved by the application of liquid nitrogen (LN2) during diamond burnishing. The process parameters considered to reduce the surface roughness (Ra) and increase the surface hardness (H) are burnishing speed, burnishing feed and burnishing force. The diamond burnishing experiments were conducted based on the L9 orthogonal array. The significant parameters and the optimal level of each parameters were determined by using analysis of variance (ANOVA) and main effect plots respectively. Multi-response optimization has been carried out for cryogenic diamond burnishing of 17-4 PH stainless steel by using Taguchi's grey relation analysis (TGRA). From the TGRA, it was observed that at burnishing speed 73 m min-1, burnishing feed 0.048 mm/rev and burnishing force 150 N, improved diamond burnishing performance characteristics were obtained. An improvement in grey relation grade (GRG) was found to be 38.47%. Cryogenic diamond burnishing has led to modifications in the microstructure and also an improvement in the subsurface hardness of the material. © 2018 IOP Publishing Ltd.
Experimental investigation and optimization of machining parameters for sustainable machining
(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2018) Varghese, V.; Ramesh, M.R.; Dupadu, D.
A detailed investigation on the effects of cutting parameters and different cooling environments on machinability of austenitic stainless steel AISI 304 is presented in this study. The need for sustainable manufacturing and better surface quality urged to explore the merits of cryogenic cooling over the other conventional cooling techniques. The end milling experiments were designed based on three parameter and three-level design considering dry, wet, and cryogenic machining environments to have a comparative study. The machinability studies such as surface roughness, tool wear, cutting forces, chip morphology, and chip reduction coefficient were investigated and compared with different machining environments. The machining parameters were optimized using Taguchi-based grey relational analysis. The cryogenic machining had the most influence on milling of AISI 304 steel and resulted in the reduction of cutting forces, surface roughness, and chip reduction coefficient in comparison with the conventional wet and dry machining. © 2018, © 2018 Taylor & Francis.
Experimental investigation of cryogenic end milling on maraging steel using cryogenically treated tungsten carbide-cobalt inserts
(Springer, 2019) Varghese, V.; Ramesh, M.R.; Dupadu, D.
The cryogenic machining and cryogenic treatment have already emerged as the sustainable manufacturing process of the future generation. The cryogenic treatment improves the cutting tool life, but the high cutting temperature developed during high-speed machining reduces the effect of cryogenic treatment of cutting tool. This study investigates the possible improvements in cutting tool life by combining cryogenic cooling and cryogenic treatment. The authors believe that these two techniques can replace conventional machining approaches using dry and wet machining conditions using coated carbide tools. The tungsten carbide-cobalt inserts are cryogenically treated (CT) at a soaking temperature of ? 195.8 °C for a period of 24 h and are used to evaluate milling performance under dry, wet, and cryogenic cutting environments. The machining experiments are conducted on maraging steel MDN 250 using one factor at a time approach by varying spindle speed and keeping feed rate and depth of cut as constant. The cutting force, surface roughness, tool wear, and subsurface microhardness are some of the machining responses evaluated and compared with an untreated cutting tool (UT). The tool life improved up to 24% during cryogenic machining using CT tools at a spindle speed of 270 rpm. © 2019, Springer-Verlag London Ltd., part of Springer Nature.
Experimental Investigation on Surface Integrity in Cryogenic Machining of Maraging Steel
(Springer, 2025) Varghese, V.; Sharma, P.; Ramesh, M.R.; Dupadu, D.; Sunilkumar, S.
The study investigated the effect of machining environments such as cryogenic, wet, and dry conditions on the surface integrity of machined surfaces during end milling of MDN 250 maraging steel. During the machining of maraging steel, cutting temperatures and strain rates increased, resulting in a loss of mechanical properties and surface integrity of the machined surface. Surface integrity was an important factor influencing the components’ functional performance and quality, just like dimensional accuracy. In this study, the machining parameters such as spindle speed, feed rate, and depth of cut were kept constant, and the cutting environment was varied between cryogenic, dry, and wet conditions respectively. Surface integrity metrics such as surface roughness, microstructure evolution, residual stress, and microhardness were analyzed using Talysurf, electron back-scattered diffraction, x-ray diffraction, and Vickers microhardness test respectively. The correlated results conceded that cryogenic machining improved surface integrity compared to dry and wet machining. It also demonstrated that cryogenic machining was a viable manufacturing substitute to traditional machining using cutting fluids. The average grain size of the machined surface of the maraging steel under cryogenic, wet, and dry conditions was found to be 20.56, 24.92, and 11.54 µm respectively. The surface roughness was also reduced by up to 50% under the cryogenic environment compared to the dry environment. The residual stress results showed that stresses were compressive under dry, wet, and cryogenic environments, and the highest compressive stress was reported under a cryogenic environment (? 355 MPa). © ASM International 2025.
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.