Faculty Publications
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Item Micro-mechanical characterization and wear performance of TiAlN/NbN PVD coated carbide inserts during End milling of AISI 304 Austenitic Stainless Steel(Elsevier Ltd, 2018) Varghese, V.; Dupadu, D.; Ramesh, M.R.A multi-layer TiAlN/NbN coated on tungsten carbide insert by physical vapor deposition method (PVD) was selected for studying tool wear performance during end milling of AISI 304 Austenitic stainless steel. Stainless steel AISI 304 belongs to the class of difficult to machine materials, which tends to work harden during machining. The coating has been studied for its micro-mechanical characteristics using SEM/EDS, XRD, 3D confocal microscope & Nano indentation. Characterization results revealed that TiAlN/NbN coatings was well deposited. Dry milling experiments were carried out to evaluate tool life & failure mechanisms of coated tool. It was shown that micro chipping and peeling of coatings were major wear mechanisms observed during dry end milling of AISI 304 using coated inserts. © 2017 Elsevier Ltd. All rights reserved.Item 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. © 2018 Elsevier Ltd. All rights reserved.Item 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. © 2018 Elsevier Ltd. All rights reserved.Item Study on microstructure and tensile properties of fly ash AMCs welded by FSW(American Institute of Physics Inc. subs@aip.org, 2018) Patil, S.; Narendranath, S.; Dupadu, D.Aluminum matrix composite (AMCs) constitute a new class of light weight and high strength materials which have widespread applications in almost all engineering sectors. But the cost of AMCs is the only barrier to increase their applications still. Hence there is a huge demand for the composites containing low cost reinforcement with less weight, keeping this in mind, in the present work, Friction stir welding (FSW) of AA6061/SiC/fly ash was carried out successfully. Microstructural study on the welded specimens was performed using optical microscopy (OM) and scanning electron microscopy (SEM). Results indicate that fly ash particles were uniformly distributed in the weld nugget area because of the stirring action of the FSW tool also promoted the grain refinement of the matrix material with complete elimination of clusters present in matrix material which resulting in sound welds without any defects for AA6061/SiC/fly ash composites. 82% of joint efficiency is obtained for selected AMCs. Transverse tensile test results showed that all welds fractured in HAZ. © 2018 Author(s).Item 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. © Published under licence by IOP Publishing Ltd.Item Studies on microstructure and mechanical characteristics of as cast AA6061/SiC/fly ash hybrid AMCs produced by stir casting(Elsevier Ltd, 2020) Patil, S.; Narendranath, S.; Dupadu, D.Fly ash has been receiving the extensive concentration as a strong reinforcing element for Aluminum Matrix Composites (AMCs) to strengthen the properties and cut the price of manufacturing. AA6061 reinforced with various weight percentages of fly ash particulates and a constant weight percentage of SiC were prepared by stir casting technique as it is one of the simplest and cost-effective method for producing AMCs. Wettability of SiC and Fly ash particles with the aluminum was enhanced by fly ash itself. The microstructure, hardness and tensile properties of manufactured AMCs were analyzed. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) discovered a harmonized dispersion of SiC and fly ash particles with superior bonding with the matrix material. The inclusion of fly ash particles in to aluminum matrix enhanced the microhardness and Ultimate Tensile Strength (UTS) of the AMCs. © 2019 Elsevier Ltd. All rights reserved.Item 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. © 2020 Elsevier Ltd. All rights reserved.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 Engineers