Browsing by Author "Udupa, K.R."

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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. Â© (2014) Trans Tech Publications, Switzerland.
A comparative study on wear properties of as cast, cast aged and forge aged A356 alloy with addition of grain refiner and/or modifier
(Masinski Fakultet - Kragujevac Sestre Janjic 6 Kragujevac 34000, 2015) Mallapur, D.G.; Udupa, K.R.
In the present work, a comparative wear behavior study of three categories of materials viz, as cast, cast aged (casting followed by T6) and forge aged (forging followed by T6) has been investigated. Neither melt treatment nor solid state processing (like aging and forging) seems to be altering the wear behavior of the materials drastically. Cast aged A356 materials exhibit higher wear resistance compared to as cast and forge aged A356 materials. Further, it was observed that cast aged samples register lower coefficient of friction compared to other samples. It is also noted that the difference in wear behavior is revealed only at conditions of higher load, higher speed and longer sliding distance of testing. At lower regimes the difference is marginal. Among cast aged samples, ones treated with combined addition exhibit better wear resistance compared to other materials. Samples treated with combined addition register lowest coefficient of friction followed by samples treated with Sr, those with B, those with Ti and untreated ones. Abrasive wear mechanism is found to be operative in the regime of higher loading and higher velocity of sliding. Adhesive wear mechanism seems to be dominating the wear process at the lower regime of load and velocity of sliding. © 2015 Published by Faculty of Engineering.
A comparative study on the wear behavior of cast and forge aged A356 alloy with addition of grain refiner and/or modifier
(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.
Corrosion behavior of high and low temperature austempered ductile iron (ADI) in iron ore slurry
(ASTM International, 2017) Aithal, P.M.; Vijayan, V.; Surendranathan, A.O.; Udupa, K.R.; Samuel, K.G.
Corrosion behavior of austempered ductile iron (ADI) and forged EN31 steel balls in a ground iron ore slurry was studied as a function of time in the slurry, while the microstructure of ADI developed due to different tempering temperature and tempering time. The corrosion rates of the grinding balls immersed in the iron ore slurry were determined using electrochemical analysis and weight loss methods. It was found that the pH of the iron ore slurry increased with time and the corrosion behavior was influenced by the pH of the slurry. The corrosion rate of forged EN31 steel balls increased with the increase in time and pH of the slurry, whereas the corrosion rate of ADI balls depended on the austempering treatment. In general, the forged EN31 steel ball offered better corrosion resistance than ADIs during the early stages of exposure in the slurry (low pH values of the slurry), but at higher pH values of the slurry, the ADIs yielded better corrosion resistance than forged EN31 steel balls. The ADI austempered at higher temperatures showed better corrosion resistance than the ones austempered at lower temperatures. © © 2017 by ASTM International.
Corrosion stability of electrodeposited cyclic multilayer Zn-Ni alloy coatings
(2011) Bhat, R.S.; Udupa, K.R.; Hegde, A.C.
This paper reports on a study of electrodeposition and characterisation of cyclic multilayer coatings of Zn-Ni alloy from a sulphate bath. Cyclic multilayer alloy coatings were deposited on mild steel through the single bath technique by appropriate manipulation of cathode current densities. The thickness and composition of the individual layers of the CMA deposits were altered precisely and conveniently by cyclic modulation of the cathode current during electrodeposition. Multilayer deposits with sharp change in composition were developed using square current pulses, using thiamine hydrochloride and citric acid as additives. Laminar deposits with different configurations were produced and their corrosion behaviours were studied by AC and DC methods in 5%NaCl solution. It was observed that the corrosion resistance of the CMA coating increased progressively with the number of layers (up to certain optimal numbers) and then decreased. The decrease in corrosion resistance at high degree of layering was attributed to interlayer diffusion due to less relaxation time for redistribution of metal ions at cathode during deposition. The coating configurations have been optimised for peak performance of the coatings against corrosion. It was found that CMA coating developed at cyclic cathode current densities of 3.0/5.0 A dm-2 with 300 layers showed the lowest corrosion rate (0.112×10-2 mm/year) which is ?54 times better than that of monolithic Zn-Ni alloy, deposited from the same bath. The protection efficacy of CMA coatings is attributed to the difference in phase structure of the alloys in successive layers, deposited at different current densities, evidenced by X-ray diffraction analysis. The formation of multilayers and corrosion mechanism were examined by scanning electron microscopy. © 2011 Institute of Metal Finishing.
Development of austempered ductile iron for high tensile and fracture toughness by two step austempering process
(2008) Ravishankar, K.S.; Udupa, K.R.; 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.
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.
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
Effect of hydrodynamics on the flow accelerated corrosion (FAC) and electrochemical impedance behavior of line pipe steel for petroleum industry
(Elsevier Ltd, 2019) Ajmal, T.S.; Arya, S.; Udupa, K.R.
The present work focuses on the flow accelerated corrosion (FAC) study of API X70 steel in a synthetic solution of oilfield water under a turbulent flow with 3 m/s velocity in a loop system. Multiple electrodes are located at intrados and extrados of the 90° pipe elbow. The influence of flow on corrosion and passivation were examined using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) tests. Corrosion current density for all the located specimens at intrados and extrados of the elbow are found to be increased however charge transfer resistances were significantly decreased along the fluid flow path. Corrosion rates of the electrodes located at the intrados are more than that at the extrados. Shear stresses are simulated using computational fluid dynamics (CFD) method and it is observed that the corrosion rate is inversely promotional to shear stresses. Surface morphology and corrosion products were examined using SEM and Raman spectroscopy. Raman spectroscopy indicates that the compositions of corrosion compounds formed by FAC are FeCO3, ?-Fe2O3, ?-Fe2O3, ? – FeOOH, and ? – FeOOH. © 2019
Effect of Multi Directional Forging on the Microstructure and Mechanical Properties of Zn-24 wt% Al-2 wt% Cu Alloy
(Springer India sanjiv.goswami@springer.co.in, 2017) Sharath, P.C.; Udupa, K.R.; Preetham Kumar, G.V.
Multi directional forging is an important process for producing fine grains in bulk materials by means of severe plastic deformation. Zn-Al alloy is used for making sleeves of plain bearings, but the presence of porosity degrades its usage in industrial application. In the present investigation, multi directional forging of Zn-24Al-2Cu alloy was carried out at 100 and 200 °C up to total strain of 0.6 and 1.2 respectively. Mechanical properties and microstructural characterization were carried out on the processed material. It was inferred that processing at 100 °C up to three passes increased ultimate tensile strength from 185 to 267 MPa with ductility of 14 %. The average grain size was reduced from 30 to 2 µm. In the case of samples processed at 200 °C up to six passes, the average grain size was reduced to 1 µm. The ultimate tensile strength increased to 276 MPa and ductility significantly improved to 21 %. The strength of the processed material increased due to strain hardening and grain refinement. Uniform distribution of various dispersed phases contributed to the enhancement of ductility during multi directional forging at 200 °C. Analysis of the fractured surface of the tensile samples revealed highly ductile nature of the fracture. © 2016, The Indian Institute of Metals - IIM.
Effect of T6 treatment on the coefficient of friction of Al25Mg2Si2Cu4Fe alloy
(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).
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. Â© 2018 Author(s).
Electron microscopic study of nodules formed during electrodeposition of copper on aluminium
(2015) Augustin, A.; Bhat, K.U.; 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 ?m to 8 ?m, 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.
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 Î¼m to 8 Î¼m, 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. Â© (2015) Trans Tech Publications, Switzerland.
Electroslag remelting experiments have been carried out on En 24 steel using two slag compositions in indigeneously constructed 350 KVA DC and 50 KVA AC ESR units. Detailed quantitative characterisation of the inclusions of different types has been carried out using Quantimet Image Analyser. The inclusion content in terms of volume fraction and density (No/mm2) and their size distribution in the refined ingot and the unrefined steel have been assessed. The chemical composition of selected inclusions has been established by electron probe microanalyser (EPMA). These studies are supplemented by scanning electron microscopy on typical fractured specimens. The present study shows that the DC reverse polarity mode of melting using a slag with higher silica content (10 wt%) offers the best conditions with particular reference to removal of inclusions and modification of inclusion morphology as compared to the ingots produced by DC straight polarity and AC modes of melting.
(Studies on inclusion characterization in electroslag refined En24 steel) Udupa, K.R.; Subramanian, S.; Sastry, D.H.; Iyengar, G.N.K.
1994
Experimental analysis of volumetric wear behavioural and mechanical properties study of as cast and 1Hr homogenized Al-25Mg2Si2Cu4Ni alloy at constant load
(2018) Harlapur, M.D.; Mallapur, D.G.; Udupa, K.R.
In the current study, an experimental analysis of volumetric wear behaviour and mechanical properties of aluminium (Al-25Mg2Si2Cu4Ni) alloy in as cast and 1Hr homogenized with T6 heat treatment is carried out at constant load. Pin-on-disc apparatus was used to carry out sliding wear test. Mechanical properties such as tensile, hardness and compression test on as-cast and 1 hr homogenized samples are measured. Universal testing machine was used to conduct the tensile and compressive test at room temperature. Brinell hardness tester was used to conduct the hardness test. The scanning electron microscope was used to analyze the worn-out wear surfaces. Wear results and mechanical properties shows that 1Hr homogenized Al-25Mg2Si2Cu4Ni alloy samples with T6 treated had better volumetric wear resistance, hardness, tensile and compressive strength as compared to as cast samples. � 2018 Author(s).
Experimental analysis of volumetric wear behavioural and mechanical properties study of as cast and 1Hr homogenized Al-25Mg2Si2Cu4Ni alloy at constant load
(American Institute of Physics Inc. subs@aip.org, 2018) Harlapur, M.D.; Mallapur, D.G.; Udupa, K.R.
In the current study, an experimental analysis of volumetric wear behaviour and mechanical properties of aluminium (Al-25Mg2Si2Cu4Ni) alloy in as cast and 1Hr homogenized with T6 heat treatment is carried out at constant load. Pin-on-disc apparatus was used to carry out sliding wear test. Mechanical properties such as tensile, hardness and compression test on as-cast and 1 hr homogenized samples are measured. Universal testing machine was used to conduct the tensile and compressive test at room temperature. Brinell hardness tester was used to conduct the hardness test. The scanning electron microscope was used to analyze the worn-out wear surfaces. Wear results and mechanical properties shows that 1Hr homogenized Al-25Mg2Si2Cu4Ni alloy samples with T6 treated had better volumetric wear resistance, hardness, tensile and compressive strength as compared to as cast samples. Â© 2018 Author(s).
Experimental studies on mechanical properties of T6 treated Al25Mg2Si2Cu4Fe alloy
(2018) Sondur, D.G.; Mallapur, D.G.; Udupa, K.R.
Effect of T6 treatment on the mechanical properties of Al25Mg2Si2Cu4Fe alloy was evaluated by conducting mechanical tests on test pieces using universal testing machine. Increase in the mechanical properties such as ultimate tensile strength, hardness and % elongation was observed. Microstructure characterization revealed the modification in the size and shapes of the precipitates formed during the homogenization process. This modification increases the anisotropy of the microstructure and the stresses in the as cast structure. The increase in the hardness of T6 treated alloy is due to the partial recrystallization, fragmentation and redistribution of primary Mg2Si phase, precipitation of fine ?, Q phases. The high volume fractions of uniformly dispersed hard ?-particles greatly increase the flow stress and provide an appreciable impediment to plastic deformation. Thus increasing the hardness of the alloy. � 2018 Author(s).
Experimental studies on mechanical properties of T6 treated 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 mechanical properties of Al25Mg2Si2Cu4Fe alloy was evaluated by conducting mechanical tests on test pieces using universal testing machine. Increase in the mechanical properties such as ultimate tensile strength, hardness and % elongation was observed. Microstructure characterization revealed the modification in the size and shapes of the precipitates formed during the homogenization process. This modification increases the anisotropy of the microstructure and the stresses in the as cast structure. The increase in the hardness of T6 treated alloy is due to the partial recrystallization, fragmentation and redistribution of primary Mg2Si phase, precipitation of fine Î¸, Q phases. The high volume fractions of uniformly dispersed hard Î²-particles greatly increase the flow stress and provide an appreciable impediment to plastic deformation. Thus increasing the hardness of the alloy. Â© 2018 Author(s).
Experimental wear behavioral studies of as-cast and 5 hr homogenized Al25Mg2Si2Cu4Ni alloy at constant load based on taguchi method
(2018) Harlapur, M.D.; Mallapur, D.G.; Udupa, K.R.
In the present study, an experimental study of the volumetric wear behaviour of Aluminium (Al-25Mg2Si2Cu4Ni) alloy in as cast and 5Hr homogenized with T6 heat treatment is carried out at constant load. The Pin on disc apparatus was used to carry out the sliding wear test. Taguchi method based on L-16 orthogonal array was employed to evaluate the data on the wear behavior. Signal-to-noise ratio among the objective of smaller the better and mean of means results were used. General regression model is obtained by correlation. Lastly confirmation test was completed to compose a comparison between the experimental results foreseen from the mention correlation. The mathematical model reveals the load has maximum contribution on the wear rate compared to speed. Scanning Electron Microscope was used to analyze the worn-out wear surfaces. Wear results show that 5Hr homogenized Al-25Mg2Si2Cu4Ni alloy samples with T6 treated had better volumetric wear resistance as compared to as cast samples. � 2018 Author(s).