Faculty Publications

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    Studies on the surface oxidation of molten aluminium - Silicon alloys using laser as a probe
    (Materials Science and Technology, 2007) Udupa, K.R.; Chatterjee, S.
    An attempt has been made to study for the first time the surface oxidation of molten aluminium-silicon alloy using laser as a probe. A ray of low powered laser was made to fall on freshly prepared surface of molten aluminium-silicon alloy and intensity of the reflected beam was measured using a light detecting resistor (LDR). The change in intensity of reflected laser beam which was due to surface degradation of the molten liquid on oxidation was recorded. Intensity profile which showed variation of intensity (registered as reciprocal of resistance on LDR) with respect to time was generated for pure aluminium melt and molten aluminium-silicon alloy. The intensity profile revealed three regions indicating different mechanisms of oxidation in each stage. It was found that alloying addition influences the nature of intensity profile. Copyright © 2007 MS&T'07®.
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    Development of austempered ductile iron for high tensile and fracture toughness by two step austempering process
    (2008) Ravishankar, K.S.; Udupa, K.R.; Prasad Rao, P.P.
    During conventional austempering austempered ductile iron showed a decrease in fracture toughness with increasing austempering temperature, while the tensile toughness increased. Thus high fracture toughness was associated with low tensile toughness. A two step austempering treatment was then adopted where the samples were first au stem p ered at 3000e for sh ort peri 0 ds varyi ng from 10m in utes to 60 minutes, and then subsequently transferred to a second furnace at 4000e for further austempering for 2 hours. It was found that this resulted in fine ferrite grain size, high carbon content of the retained austenite together with increased stability of the austenite. Under such conditions it was possible to achieve an excellent combination of high fracture toughness and high tensile toughness.
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    Grinding wear behaviour of stepped austempered ductile Iron as media material during comminution of Iron ore in ball mills
    (2010) Raghavendra, H.; Bhat, K.L.; Udupa, K.R.; Rajath Hegde, M.M.R.
    An attempt has been made to evaluate the suitability of austempered ductile iron (ADI) as media material for grinding iron ore in a ball mill. Spheroidal graphite (S.G) iron balls are austenitised at 900°C for 60 minutes and given stepped austempering treatment at 280°C for 30 minutes and 60 minutes followed by 380°C for 60 minutes in each case. These materials are characterised by measuring hardness, analysing X-ray diffraction (X-RD), studying microstructure using optical and scanning electron microscope (SEM). Grinding wear behaviour of these materials was assessed for wear loss in wet condition at different pH value of the mineral slurry and found that the wear rate of grinding media material decreases with increase in pH of the slurry. The wear resistance of ADI balls were compared with forged En31 steel balls and found that the stepped austempered ductile iron is superior to forged En31 steel balls. © 2010 American Institute of Physics.
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    Probing the deterioration of 316L stainless steel welds due to ageing and creep by indentation creep tests
    (2011) Udaya Prasanna, H.U.; Udupa, K.R.
    Authors have probed into the creep behaviour of AISI 316L stainless steel welds through the indentation creep test methodology and assessed the deterioration effects of these welds under different ageing conditions subjecting them to different test conditions. Comparison is made between the parent metal and the weld metal for integrity at different levels of ageing and test loads. It is concluded that although the aged weld's deteriorated status is not revealed at low temperature and low load test conditions, it is explicitly revealed when tested at higher temperature and higher loads. Microstructural evidences have been given by the authors and they have suggested mechanisms of creep at different test conditions. © 2011 Elsevier B.V. All rights reserved.
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    Microbial effects on heat treated 316L weldments in marine water
    (2013) Suvarna, K.; Udupa, K.R.; Surendranathan, A.O.
    Austenitic stainless steels are susceptible to microbiologically influenced corrosion (MIC) when they are in contact with sea water. This is due to the changes in the chemistry of the environment at the metal surface because of the settlement and activities of microorganisms. The thrust of our work was in understanding the changes in the electrochemical behaviour of a type 316L stainless steel in the presence of a natural biofilm as well as the influence of metallurgical characteristics on microbial adhesion and MIC. The presence of a biofilm on material surface can influence the corrosion behaviour since the value of a given parameter such as temperature, pressure, concentration of a solute and pH at the water /substrate interface under the biofilm may be different from that in the bulk environment. The non-uniform nature of biofilm thus helps in generating heterogeneity in the environment at the surface. Thus, biofilms are known to aid in the initiation of corrosion, change the mode of corrosion or cause changes in the corrosion rate. Bacteria Arthobacter nicotinae (An) and algae Chlorella pyrenoidosa (Cp) were used for the study and bio film formed due to these showed pit initiation and increase in corrosion rate as time proceeds. 316L base metal (BM) and weld metal (WM) as received and after heat treated at 450°C for 10000 hours were studied and corrosion evaluation was done. Heat treated WM showed severe response to corrosion compared to as received WM. © (2013) Trans Tech Publications, Switzerland.
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    A comparative study on the wear behavior of cast and forge aged A356 alloy with addition of grain refiner and/or modifier
    (Trans Tech Publications Ltd ttp@transtec.ch, 2014) Mallapur, D.G.; Sondur, D.G.; Udupa, K.R.
    In the present work, a comparative study on the wear behavior of cast aged and forge aged A356 alloy has been investigated without and with the addition of grain refiner and modifier, under dry sliding conditions using a pin-on-disc wear testing machine. The comparison study reveals that tribological properties of A356 materials are highly influenced by T6 heat treatment process. It is found in the present study that, cast aged A356 materials possess higher wear resistance as compared to forge aged materials. Apart from this, the study also reveals that cast aged material is associated with lower frictional forces and coefficient of friction as compared to the forge aged category. It is further observed in the present investigation that abrasive wear mechanism is operative in both the categories of the materials when tested with lower load for lower sliding speed and lower distance of run. At higher values of external parameters the adhesive wear mechanism dominates the wear process. Lower values of wear properties recorded by the forge aged material are an unexpected result in the present studies. It is conceived to be due to the presence of micro cracks while forging. © (2014) Trans Tech Publications, Switzerland.
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    Electron microscopic study of nodules formed during electrodeposition of copper on aluminium
    (Trans Tech Publications Ltd ttp@transtec.ch, 2015) Augustin, A.; Bhat, K.; Udupa, K.R.; Hegde, A.C.
    Copper thin film was deposited on double zincated aluminium using electrodeposition route. To understand the growth behavior of copper nodules, deposition was done by varying coating current density. The topography and cross section of the coating was analyzed by using SEM. The structural details of copper nodules were studied by using TEM. Deposited copper thin film was made up of pomegranate like nodules with size varying from 5 μm to 8 μm, varying as a function of coating current density. At higher current density, the coating was made up of multiple layers of nodules having defects like twins, dislocations and stacking faults. The nodules had fine crystallites of size in the range of 50 nm. © (2015) Trans Tech Publications, Switzerland.
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    Optimization of control factors in tribological studies for as cast and 1Hr T6 treated Al25Mg2Si2Cu4Fe alloy using Taguchi methods
    (Elsevier Ltd, 2018) Sondur, D.G.; Mallapur, D.G.; Udupa, K.R.
    In this study, using the predictive model offered by Taguchi, optimization of wear parameters was carried out. Controlling factors such as sliding speed, load and T6 heat treatment (homogenizing hours) were considered. Pin on disc type friction monitor was used for determing the volumetric wear rate under constant speed for as cast and 1Hr T6 treated conditions. The L16 orthogonal array, signal to noise ratio (S/N) and regression results were used to arrive at optimal control factor values that affect the volumetric wear rate of the alloy. Combination of the dominating control factors has been predicted using Taguchi technique. Predicted combination of control factors were found to be close to the experimental observations i.e load was found to be a dominant factor for volumetric wear rate. Also 1Hr T6 treated alloy shows a higher volumetric wear resistance as compared to as cast alloy. © 2017 Elsevier Ltd.
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    Hot-dip Aluminizing of Low Carbon Steel in Al & Al-5wt % Cr Baths
    (Elsevier Ltd, 2018) Huilgol, P.; Bhat, K.U.; Udupa, K.R.
    Hot dip aluminizing of low carbon steel is carried out in pure aluminium bath and Al-5wt% Cr bath. The coating is characterized by scanning electron microscopy and chemical composition of the coating is analysed by EDS (energy dispersive spectroscopy) attached to SEM. The coating consists of three regions, viz., outer aluminium topcoat, intermediate Fe-Al intermetallics layer and the base alloy. The intermetallics layer consists of FeAl3 and Fe2Al5 phases. Fe2Al5 is the major phase in the intermetallics layer. The growth kinetics of intermetallics layer is parabolic in nature implying that it is diffusion controlled. Addition of chromium forms Al7Cr dispersed intermetallics phases in the aluminium topcoat. Addition of chromium has no influence on the morphology of the intermetallics layer. Scratch resistance of the coating is carried out to evaluate the scratch hardness of the coating. Chromium addition improves scratch resistance of the coating. © 2018 Elsevier Ltd.
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    Effect of T6 treatment on the coefficient of friction of Al25Mg2Si2Cu4Fe alloy
    (American Institute of Physics Inc. subs@aip.org, 2018) Sondur, D.G.; Mallapur, D.G.; Udupa, K.R.
    Effect of T6 treatment on the coefficient of friction of Al25Mg2Si2Cu4Fe alloy was evaluated by conducting wear test on pin on disc wear testing machine. Wear test parameters such as the load and the speed were varied by keeping one constant and varying the other respectively. It was observed that the coefficient of friction is high for as cast condition due to the brittle microstructure. After T6 heat treatment the precipitates formed such as the Chinese scripts and the Mg2Si blocks got modified that lead to improvement in the hardness and the wear resistance. This reduces the coefficient of friction. © 2018 Author(s).