Faculty Publications

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    Effect of purging gas on wetting behavior of Sn-3.5Ag lead-free solder on nickel-coated aluminum substrate
    (Springer Science and Business Media, LLC, 2013) Prabhu, K.; Varun, M.; Satyanarayan, S.
    The wetting characteristics of Sn-3.5Ag lead-free solder alloy on nickel-coated aluminum substrates in air (ambient), nitrogen, and argon atmospheres were investigated. The contact angles for the solder alloy obtained under air and argon atmospheres were in the range of 36 -38. With nitrogen atmosphere the contact angle was found to be significantly lower at about 26. Solder solidifying in air exhibited needle-shaped tin-rich dendrites surrounded by a eutectic matrix. The amount of tin dendrites decreased in argon atmosphere. However, the morphology of tin dendrites transformed from needle-shaped to nearly non-dendritic shape as the soldering atmosphere was changed from air to nitrogen. The interfacial microstructures revealed the presence of Ni 3Sn and Ni3Sn4 IMCs at the interface. The enhanced wettability observed under nitrogen atmosphere is attributed to the higher thermal conductivity of nitrogen gas and the formation of higher amount of Ni3Sn IMCs at the interface compared to air and argon atmospheres. © 2012 ASM International.
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    Effect of current density during electrodeposition on microstructure and hardness of textured Cu coating in the application of antimicrobial Al touch surface
    (Elsevier Ltd, 2016) Augustin, A.; Huilgol, P.; Udupa, K.R.; Bhat, K.U.
    Copper is a well proven antimicrobial material which can be used in the form of a coating on the touch surfaces. Those coating can offer a good service as touch surface for very long time if only they possess good mechanical properties like scratch resistance and microhardness. In the present work the above mentioned mechanical properties were determined on the electrodeposited copper thin film; deposited on double zincated aluminium. During deposition, current density was varied from 2 A dm?2 to 10 A dm?2, to produce crystallite size in the range of 33.5 nm to 66 nm. The crystallite size was calculated from the X-ray peak broadening (Scherrer?s formula) which were later confirmed by TEM micrographs. The scratch hardness and microhardness of the coating were measured and correlated with the crystallite size in the copper coating. Both characteristic values were found to increase with the reduction in crystallite size. Reduced crystallite size (Hall–Petch effect) and preferred growth of copper films along (111) plane play a significant role on the increase in the hardness of the coating. Further, TEM analysis reveals the presence of nano-twins in the film deposited at higher current density, which contributed to a large extent to the sharp increase of coating hardness compared to the mechanism of Hall–Petch effect. The antimicrobial ability of the coated sample has been evaluated against Escherichia coli bacteria and which is compared with that of commercially available bulk copper using the colony count method. 94% of E. coli cells were died after six hours of exposure to the copper coated surface. The morphology of the copper treated cells was studied using SEM. © 2016 Elsevier Ltd
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    Additive manufacturing of an aluminum matrix composite reinforced with nanocrystalline high-entropy alloy particles
    (Elsevier Ltd, 2017) Karthik, G.M.; Panikar, S.; Janaki Ram, G.D.J.; Kottada, R.S.
    In the present work, a metal-metal composite consisting of aluminum-magnesium alloy AA5083 matrix and nanocrystalline CoCrFeNi high-entropy alloy reinforcement particles in 12 vol% was successfully friction deposited in multiple layers. The layer interfaces or the reinforcement/matrix interfaces showed no brittle intermetallic formation – thanks to the inert nature as well as the high strength and hardness of the high-entropy alloy reinforcement particles. The composite showed significantly higher tensile and compressive strengths as compared to standard wrought-processed alloy AA5083-H112 and offered a much better combination of strength and ductility when compared to conventional aluminum matrix composites reinforced with ceramic particles. The current study establishes friction deposition as a viable technique for additive manufacturing of novel high-performance composite materials. © 2016 Elsevier B.V.
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    Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel
    (University of Science and Technology Beijing, 2018) Huilgol, P.; Rajendra Udupa, K.; Udaya Bhat, K.
    Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed. © 2018, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.
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    Effect of cutting parameters on tool wear, cutting force and surface roughness in machining of MDN431 alloy using Al and Fe coated tools
    (Institute of Physics Publishing helen.craven@iop.org, 2019) V Badiger, P.V.; Desai, V.; Ramesh, M.R.; Prajwala, B.K.; Raveendra, K.
    Thin solid films are used in cutting tools in order to improve its performance, reduce tool wear and improve tool life. Cathodic arc evaporation is the state of art PVD technique widely accepted in industries for the development of thin solid films. The turning cutting tool inserts are coated with AlCN/AlC and FeCrN monolayer thin solid films using cathodic arc evaporation technique. Quality characteristics of thin films are estimated using Calo and VDI3198 tests. Thickness of the coatings are found to be 1.430 and 1.475 ?m for AlCN/AlC and FeCrN coatings respectively and adhesion quality of HF1 is attained. Performance of the thin solid films are evaluated in machining MDN431 steel with range of cutting speed (59-118 m min-1), feed rate (0.062-0.125 mm/rev) and depth of cut (0.2-0.4 mm). Experiments are performed based on full factorial design and regression analysis. Optimization of the process parameters is carried out using combined techniques of desirability and Particle swarm optimisation (PSO). The objective of the study is to establish correlation between machining parameters with cutting force, tool wear and surface roughness. Optimal process parameter for least cutting force and surface roughness are obtained for coatings. ANN has been adopted to improve the coefficient of determination (CoD) and capability of predictive regression models. ANN trained model and mathematical regression models are adequate to predicted the responses, which follows the experimental data with minimum absolute error. The AlCN/AlC coatings exhibited lower cutting forces and surface roughness than FeCrN coated tools. Tool wear was reduced by 3.62 times in AlCN/AlC and 1.63 times in FeCrN coated tools compared to uncoated tool which is due to increased hardness and elastic modulus of the coating. © 2018 IOP Publishing Ltd.
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    High-temperature wear and frictional behavior of partially oxidized Al with NiCr composite coating
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Medabalimi, S.R.; Ramesh, M.R.; Kadoli, R.
    The influence of composite coating in improving wear and frictional behavior from room temperature to 600 °C was investigated. Partially oxidized Al powder was prepared with a flame spray process by spraying pure Al powder into distilled water. The composite powder is the mixture of 30 weight percent of partially oxidized Al and 70 weight percent of NiCr alloy powder. The composite powder was subsequently coated on MDN321 steel by air plasma spray process. The composite coatings are characterized with respect to adhesion strength, porosity, micro-hardness, and density. Wear and frictional behavior of coatings are evaluated under disc speed of 1 and 2 m s-1, loads of 10, 20 and 30 N and 3000 m sliding distance. The test results indicated that at room temperature, frictional heat generated due to applied load produce three-body abrasion at the interface caused to increase the wear and friction in the coating. The oxide film formed at high temperature due to plastic deformation avoids surface degradation at the interface and reduce the wear and friction. The worn surfaces at 600 °C consist phases of ?-Al2O3, NiO, and Cr3O. These phases are contributing to improving the wear resistance of the coating more than 4-times compared to uncoated steels under varying load and sliding velocities. The coefficient of friction reduced with increase in temperature due to generated oxides act as lubricants at the interface. © 2019 IOP Publishing Ltd.
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    Effect of simulated heating of plasma coating and ceramic firing on Ti and Ti-6Al-4V
    (Elsevier Editora Ltda, 2019) Kotian, R.; Rao, P.P.; Bangera, M.K.; Madhyastha, P.; Srikant, S.
    The study was performed to understand the impact of heat in plasma coating and ceramic firing of titanium (Ti) and titanium alloy (Ti-6Al-4V) on their mechanical properties, and microstructure. Standard specimens were prepared to measure tensile strength before and after simulated heating cycles using Instron machine of model 4206 at a crosshead speed of 1â»mm/min. Yield strength, ultimate strength, and elongation were recorded. The microstructure was studied using an optical microscope. The mechanical properties, microstructure, and grain size remained the same as that of as-received samples at temperatures of 600 and 700â»°C for both Ti and Ti-6Al-4V. At temperature 800 and 900â»°C decrease in yield strength, and ultimate tensile strength with a change in microstructure was observed. The temperature of plasma coating and ceramic firing that Ti and Ti-6Al-4V metal substrates encounter during the fabrication of coated implants and metal-ceramic restorations do not affect the mechanical properties and microstructure. Above 800â»°C, a significant change in mechanical properties and microstructure is observed. © 2019 The Authors.
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    Improvement of Anticorrosion Properties of Epoxy Primer Coating on Aluminum Alloy 2024-T3 by Thiosemicarbazone Derivatives
    (Springer, 2019) Prakashiah, B.G.; Nityananda Shetty, A.N.; Amitha Rani, B.E.
    The effect of adding thiosemicarbazone derivatives on the anticorrosion properties of epoxy primer coatings on aluminum alloy 2024-T3 was investigated. (E)-2-(2,4-dihydroxybenzylidene)hydrazinecarbothioamide (2,4-DHC), (E)-2-(3,4-dihydroxybenzylidene)hydrazinecarbothioamide (3,4-DHC), and (E)-2-(2,3,4-dihydroxybenzylidene)hydrazinecarbothioamide (2,3,4-THC) were supplemented to epoxy primer that is generally used in aircraft paint systems; and its anticorrosion property was examined by electrochemical impedance spectroscopy and salt spray test. Field emission scanning electron microscopy and energy dispersive x-ray analysis were used to study the surface topology of the coating system. 2,4-DHC and 3,4-DHC doped primer coating exhibits good barrier properties, while 2,3,4-THC doped primer coating exhibits good barrier properties along with active corrosion protection. © 2019, The Minerals, Metals & Materials Society.
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    Deposition of TiN and TiAlN Thin Films on Stainless Steel Tubes by a Cylindrical Magnetron Sputtering Method
    (ASTM International, 2021) Trivedi, K.; Rane, R.; Joseph, A.; Arya, S.B.
    Titanium nitride (TiN) and titanium aluminum nitride (TiAlN) coatings are very hard materials that are mostly coated on cutting tools to increase the tool life. These coatings have also been successfully applied as a coating material for biomedical applications mainly due to their tribological properties, biocompatibility, and affordable price. In an attempt to develop transition metal nitride coatings on specimens of cylindrical geometry, TiN and TiAlN thin films were deposited successfully on stainless steel tubes using a direct-current cylindrical magnetron cosputtering method. Both types of coatings were uniform in nature and had good adherence to the substrate. TiN and TiAlN thin films were characterized systematically to determine their structure, surface morphology, chemical states, chemical structure, and electrochemical behavior using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and potentiodynamic methods, respectively. The XRD patterns of the TiN and TiAlN coatings indicated (111) preferential orientation. Crosssectional SEM images revealed a columnar growth of the coatings with an arrow-headed geometry. XPS characterization showed the presence of TiN, Titanium dioxide, titanium oxynitride, aluminum oxide, and aluminum nitride phases. Potentiodynamic polarization tests in 3.5 % sodium chloride solution revealed that the TiAlN coating exhibited superior corrosion resistance compared with the TiN coating. Furthermore, TiAlN coating showed 94 % of average absorption in ultraviolet-visible region using photospectrometry. The cylindrical magnetron sputter deposition technique enables development of uniform protective coatings on tubular geometries, which are frequently employed in solar thermal and nuclear applications. © 2021 by ASTM International.
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    Solid Particle Erosion Behavior of Partially Oxidized Al with NiCr Composite Coating at Elevated Temperature
    (Springer, 2021) Subba Rao, M.; Ramesh, M.R.; Kadoli, R.
    The composite coating was developed and investigated the solid particle erosion performance at elevated temperature by varying impact angles. Al2O3 erodent of grit size 50 µm was used in air-jet erosion tester to investigate the resistance to erosion at RT, 200, 400, 600, and 800 °C by varying 30, 45, 60, 75, and 90° impact angles. The composite coating was deposited on MDN321 steel by plasma spray process with feedstock of “30 weight percent of partially oxidized Al powder and 70 wt.% of NiCr alloy powder.” The composite coating was characterized by bond strength, porosity, micro-hardness, and density. Volumetric erosion loss concerning temperature and impact angle was studied using SEM, EDAX, and XRD analysis. Non-contact three-dimensional optical profilometer was used to quantify the volumetric erosion loss. MDN321 steel showed better erosion resistance than composite coating at all the temperatures. Due to the formation of stable oxides at 800 °C the erosion resistance of the coating was improved. © 2021, ASM International.