Faculty Publications
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Item The influence of microwave sintering on the tribological performance of powder metallurgy based aluminum cenospheres composites(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Ananda Kumar, M.G.; Seetharamu, S.; Sampath Kumaran, P.; Nayak, J.The Metal Matrix Composites (MMCs) especially Aluminum based systems have unique advantages of having superior mechanical, chemical and electrical properties, in addition to light weight and high stiffness. In this work, composites comprising of Aluminum with varied concentrations of Cenospheres as reinforcement was produced by Powder Metallurgy (PM) route. The densification of the composites was effected both by conventional and Microwave (MW) sintering techniques. The microstructures of the sintered samples were observed through scanning electron microscope (SEM) and phases by x ray diffraction technique (XRD), followed by evaluation of tribological parameter namely slide wear behavior and solid particle erosion resistance. The densities and the Brinell hardness values for the samples were also evaluated. The results showed that microwave sintered samples exhibited higher hardness, lower erosion and slide wear loss. © (2015) Trans Tech Publications, Switzerland.Item Effect of chromium addition on properties of sinter-forged Fe-Cu-C alloy steel(World Scientific Publishing Co. Pte Ltd wspc@wspc.com.sg, 2018) Kulkarni, V.R.; Nayak, J.; Dabhade, V.V.The present work deals with sinter-forged powder metallurgical (P/M) steels alloyed with chromium by addition of ferrochrome powder, which allows a close control over the chromium contents of alloy steels. Chromium contents can be varied by adjusting appropriately weighed ferrochrome powder in the P/M mixtures. Fe-Cu (2%) and C (0.7%) is the base composition for this P/M alloy steel. Study with the addition of 0.5% and 3% chromium by weight in the form of ferrochrome powder is carried out. The P/M alloy steel of base composition with no chromium content is also prepared for comparative study. The paper deals with these three alloy steels formed by the sinter-forging technique of powder metallurgy. The results of hardness and wear in hardened and tempered condition are reported in the present work. © 2018 World Scientific Publishing Company.Item Effect of heat treatment on properties of sinter forged Fe-Cu-C-Cr steel(Zibeline International Publishing Sdn. Bhd., 2019) Kulkarni, V.R.; Nayak, J.; Dabhade, V.V.Powder metallurgy is industrially well appreciated manufacturing technique. Many components are now manufactured by powder metallurgical route than conventional manufacturing techniques. It is customary for wrought steels to compare the properties of alloy in austempered condition with that in hardened and tempered condition. However limited data is available for austempered powder metallurgical components. In this work sinter forging technique is used to prepare samples from metal powders and subjected to austempering as well as conventional hardening and tempering heat treatments. Effect of these heat treatments on the microstructure, hardness and wear properties of Fe-2Cu-0.7C-2Cr sinter forged alloy are studied. From the results it is concluded that though hardness in hardened and tempered condition is lower (26 HRc) than that of austempered condition (39 HRc) its wear performance is better. © 2019 Rockefeller University Press. All rights reserved.Item Tribocorrosion Behaviour of Biomedical Porous Ti–20Nb–5Ag Alloy in Simulated Body Fluid(Springer Science and Business Media Deutschland GmbH, 2021) Shivaram, M.J.; Arya, S.; Nayak, J.; Panigrahi, B.B.Porous Ti–20Nb–5Ag (wt.%) alloy was developed using powder metallurgy (PM) route with the porosity of 43% after sintering in a high vacuum atmosphere. The microstructure of the porous alloy revealed various micro, macro and interconnected pores with an average pore size of about 114 µm. Tribocorrosion behaviour of the porous alloy was examined in simulated body fluid under the various applied load of 1–10 N using DC electrochemical corrosion technique and kinetic parameters (corrosion potential, corrosion current density and breakdown potentials). After tribocorrosion test, the OCP values decreased from 0.17 to ? 0.49 VSCE as applied load was increased. The potentiodynamic polarization results revealed that the corrosion potential decreased, while corrosion current density increased under higher applied loads. Active–passive transition plots showed metastable passivity due to severe fluctuations of passive current density. After tribocorrosion, the surface morphology was analysed using SEM, and it exhibited the severity of wear tracks at higher applied loads. The results indicated that the developed porous Ti–20Nb–5Ag alloys exhibit better tribocorrosion properties in simulated body fluid. Through observations of SEM images of the worn surfaces, the visible scratches and deep grooves were observed along the sliding direction, indicating a predominant abrasive mechanism. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Development and Characterization of Biomedical Porous Ti–20Nb–5Ag Alloy: Microstructure, Mechanical Properties, Surface Bioactivity and Cell Viability Studies(Korean Institute of Metals and Materials, 2022) Shivaram, M.J.; Arya, S.B.; Nayak, J.; Panigrahi, B.B.Abstract: In this study, antibacterial Ag element added to synthesis of porous Ti–20Nb–5Ag (wt%) alloy using powder metallurgy space holder route. The microstructural, mechanical property, surface bioactivity and cytotoxicity behavior of porous Ti–20Nb–5Ag alloy have been investigated. The developed porous alloy obtained the porosities ranging from 22.5 to 68%. The porous sample having a porosity of about 43% is found to be in the optimum condition, which possess a modulus of about 5.8 GPa with an excellent compressive strength about 205 MPa. XRD result shows that the formation of small amount of α-Ti, β-Ti, along with α״ martensite and Ti2Ag are key phase constituents of sintered porous Ti–20Nb–5Ag alloys. The compression strength and elastic modulus of the sintered alloys were showed that decreased with increase of porosity. Surface bioactivity result revealed that the significant formation of hydroxyapatite on the alkali-heat treated (5 M NaOH) porous Ti–20Nb–5Ag alloy which is found after the in vitro test in SBF. Further, the cell viability test was conducted on as-synthesized porous Ti–20Nb–5Ag alloy for 1, 4, and 7 days using MG-63 human osteoblast cells and result shows an excellent cell proliferation, and the cytotoxicity test confirms the non-toxic nature of the porous alloy which is very much suitable for implant application. Graphic Abstract: [Figure not available: see fulltext.]. © 2021, The Korean Institute of Metals and Materials.