Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
19 results
Search Results
Item Heat transfer at the casting/chill interface during solidification of commercially pure Zn and Zn base alloy (ZA8)(2012) Ramesh, G.; Prabhu, K.N.Casting/chill interfacial heat transfer during solidification of commercially pure zinc and ZA8 alloy against copper, hot die steel, stainless steel and aluminiuminstrumented chills was investigated. The peak heat flux strongly depends on the thermophysical properties of chill, chill surface condition and superheat of the castingmaterial. Contact angles of alumina coatingmeasured on various substrates suggested that the adhesion of the coating material on copper chill was significantly better as compared to other chill materials. The heat flux curve in the case of coated chills is characterised by a double peak indicating remelting of the solidified casting shell. The second peak in the HTC curve is lower for high conductivity and higher for low conductivity chills as compared to the first peak. It is possible that solid shell formation and remelting occurred in the case of high thermal conductivity chills, whereas shell remelting did not happen in lower thermal conductivity chills. © 2012 W. S. Maney & Son Ltd.Item Behavior of Alloying Elements during Electro-Slag Remelting of Ultrahigh Strength Steel(2012) Bandyopadhyay, T.R.; Rao, P.K; Prabhu, N.The paper deals with the behavior of principal constituents of an ultrahigh strength steels during ESR. The multiple analyses show no significant variation in the concentrations of silicon, manganese, vanadium, molybdenum, sulphur and phosphorus while concentrations of carbon, chromium, aluminium and titanium in the ESR ingot are found to be within the range of ± 0.01, ± 0.12, ± 0.008 and ± 0.01% respectively. Silicon and manganese show a loss of 0- 55 and 2-13% respectively whereas the degree of desulphurization is in the range of 0 (in Ar shield) to 52 (in air). The lower carbon and chromium content of the electrode than the aimed value can be corrected by adding ferrochromium in-situ during ESR. The recovery of carbon from FeCr was nearly 100% in most of the melts while the recovery of chromium varied over a fairly wide range. The distributions of carbon and chromium are also uniform along the height and width of ESR ingots. The recovery of the inoculant titanium was relatively low at the bottom of the ingot and it increases with height and reached a constant value above 100-150 mm height. For the same addition of titanium, its recovery decreases during ESR with argon shielding. © Metallurgical and Mining Industry.Item Methodological and parametric studies of machinability of carbon and alloy steels(2013) Lalbondre, R.; Krishna, P.; Mohan Kumar, G.C.The carbon and alloy steels form an increasingly diverse variety and range of steels in manufacturing industries. The assessment of the machinability of an engineering material becomes a matter of prime activity to improve productivity. The machinability of carbon and alloy steels is affected by many factors, such as the composition, microstructure, and strength level of the steel; the feeds, speeds, and depth of cut; and the choice of cutting fluid, cutting tool material and its geometry. Thus the machinability is an intrinsic technological property which is complex to understand and difficult to determine. This paper discusses different methodology of determining the machinability and its rating/index. One of the methodologies, the face turning method in particular, shall be used to determine the machinability of carbon and alloy steel. Further it deals with identifying the appropriate cutting parameters to test the machinability in an effective, simple and easy way. The research work findings here provide useful economic machining solution of knowing, in advance, the machinability of steels to gain and maintain a competitive advantage. © 2013 CAFET-INNOVA TECHNICAL SOCIETY.Item The influence of the addition of 4.5 wt.% of copper on wear properties of Al-12Si eutectic alloy(Hashemite University huniv@hu.edu.jo, 2015) Channappagoudar, S.; Kiran Aithal, K.; Sannayallappa, N.; Desai, V.; Mukunda, P.G.The influence of 4.5 wt.% copper addition on wear behavior of as-cast Al-12Si alloy prepared by gravity casting is investigated in dry sliding against a steel counterface using a pin-on-disk apparatus. The microstructures of test alloys and worn surfaces were examined by scanning electron microscopy and energy dispersing X-ray spectroscopy. The addition of copper to the binary Al-12Si alloy led to the precipitation of CuAl2 phase. Copper addition resulted in a refinement of ?-Al and a minor modification of eutectic Si. The Al-12Si-4.5Cu alloy showed a higher wear resistance as compared to Al-12Si binary eutectic alloy. © 2015 Jordan Journal of Mechanical and Industrial Engineering. All rights reserved.Item Development of nanolaminated multilayer Ni-P alloy coatings for better corrosion protection(Royal Society of Chemistry, 2016) Elias, L.; Bhat, K.U.; Hegde, A.Nanolaminated multilayer Nickel-Phosphorous (Ni-P) alloy coatings were developed on mild steel from a citrate bath using glycerol as an additive. Multilayer Ni-P alloy coatings having nanolaminated layers of alloys of alternatively different compositions have been developed using pulsed direct current (DC) by cyclic modulation of the cathode current density. The composition and number (hence thickness) of the layers were tailored by periodic modulation of the current density (c.d.) and time using a programmable power source. The deposition conditions were optimized for both the composition and thickness of the individual layers for the best performance of the coatings against corrosion. Electrochemical corrosion study, evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the multilayer Ni-P alloy coating with 300 nanolaminated layers, represented as (Ni-P)1.0/4.0/300 showed several fold better corrosion resistance compared to its monolayer counterpart (deposited using regular DC) from the same electrolytic bath. Drastic improvement in the corrosion protection efficacy of the nanolaminated multilayer Ni-P alloy coatings were attributed to an increase in number of interfaces, separating layers of alloys having different morphologies, compositions and phase structures, which was supported by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, respectively. The corrosion rates of the multilayer Ni-P alloy coatings were decreased with increasing number of layers, only up to an optimal level and then increased. The increase in corrosion rates at a higher degree of layering were attributed to the diffusion of layers, due to the very short deposition time of each layer. © The Royal Society of Chemistry 2016.Item The Effect of Chilling and Ce Addition on the Microstructure and Mechanical Properties of Al-23Si Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Vijayan, V.; Prabhu, K.The present work involves the study of the effect of varying concentration of Ce addition on microstructure and mechanical properties of Al-23%Si alloys. Melt-treated alloys were solidified in copper, brass, stainless steel molds to assess the effect of cooling rate. The effect on microstructure was assessed by measuring the fineness of primary silicon and eutectic silicon particle characteristics. The Ce melt treatment transformed the coarse and irregular primary silicon into refined polyhedral silicon crystals, and the effect was more significant at higher cooling rates. Although the melt treatment had refined the eutectic silicon at lower cooling rates, it did not show any considerable effect on the eutectic silicon at higher cooling rates. The mechanical properties of the alloy increased significantly with increase in cooling rates and cerium concentration. Analysis of the results and literature reveals that the refined primary silicon was formed as a result of an invariant reaction between Ce compounds and primary silicon at higher temperatures. © 2016, ASM International.Item Effect of magnetic field on corrosion protection efficacy of Ni-W alloy coatings(Elsevier Ltd, 2017) Elias, L.; Hegde, A.C.High corrosion resistant Ni-W alloy coatings were developed using magnetoelectrodeposition (MED) approach for the protection of mild steel substrates. The conditions for the development of more corrosion resistant MED Ni-W alloy coatings were optimized by inducing a magnetic field (B) during deposition, in terms of intensity and direction. The applied magnetic field was used as a tool to alter the crystallinity, composition and thereby the corrosion resistance of the coatings. It was demonstrated that the corrosion resistance of Ni-W alloy coatings can be improved to many folds of its magnitude by MED approach. Significant increase in corrosion resistance exhibited by MED coatings (under both parallel and perpendicular magnetic field, B) is attributed to the increased W content of the alloy affected by an increase in limiting current density (iL). The high corrosion resistance of the MED Ni-W alloy coatings was explained in the light of magnetohydrodynamic (MHD) effect, responsible for the increased W content, brought about by the enhanced mass transport. The inherent limitations of the bath like low iL and induced type of codeposition which impedes the development of W rich alloy coatings has been successfully resolved by MED method. Drastic improvement in corrosion resistance is ascribed to the basic difference in the process of electrocrystallization and phases formed during MED, confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. The results are discussed with greater insight into binary alloy deposition and mass transfer process at cathode/electrolyte interface. © 2017 Elsevier B.V.Item Face milling tool condition monitoring using sound signal(Springer, 2017) Madhusudana, C.K.; Kumar, H.; Narendranath, S.This article presents the fault diagnosis of the face milling tool using sound signal. During milling, sound signals of the face milling tool under healthy and fault conditions are acquired. Discrete wavelet transform (DWT) features are extracted from the acquired sound signals. The support vector machine (SVM) technique is used to classify the face milling tool conditions using the extracted DWT features. Also, a comparison of classification efficiencies of different classifiers with respect to different features extraction methods is carried out. It is shown that, all extracted DWT features demonstrate better results than those obtained from selected statistical features and empirical mode decomposition features. The SVM technique is the best classifier as it has given an encouraging result in this study when compared to other classifiers, and it has provided 83% classification accuracy for the given experimental conditions and workpiece of steel alloy 42CrMo4. Hence, the SVM method and DWT technique can be put forward for the applications of condition monitoring of the face milling tool with sound signal. © 2017, The Society for Reliability Engineering, Quality and Operations Management (SREQOM), India and The Division of Operation and Maintenance, Lulea University of Technology, Sweden.Item Use of discrete wavelet features and support vector machine for fault diagnosis of face milling tool(Tech Science Press sale@techscience.com, 2018) Madhusudana, C.K.; Gangadhar, N.; Kumar, H.; Narendranath, S.This paper presents the fault diagnosis of face milling tool based on machine learning approach. While machining, spindle vibration signals in feed direction under healthy and faulty conditions of the milling tool are acquired. A set of discrete wavelet features is extracted from the vibration signals using discrete wavelet transform (DWT) technique. The decision tree technique is used to select significant features out of all extracted wavelet features. C-support vector classification (C-SVC) and ?-support vector classification (?-SVC) models with different kernel functions of support vector machine (SVM) are used to study and classify the tool condition based on selected features. From the results obtained, C-SVC is the best model than ?-SVC and it can be able to give 94.5% classification accuracy for face milling of special steel alloy 42CrMo4. © © 2018 Tech Science Press..Item HVOF sprayed Ni3Ti and Ni3Ti+(Cr3C2+20NiCr) coatings: Microstructure, microhardness and oxidation behaviour(Elsevier Ltd, 2018) Reddy, N.C.; Kumar, B.S.A.; Reddappa, H.N.; Ramesh, M.R.; Koppad, P.G.; Kord, S.This paper reports the development of Ni3Ti and Ni3Ti+(Cr3C2+20NiCr) coatings on AISI 420 stainless steel (MDN-420) and titanium alloy ASTM B265 (Ti-15) by HVOF technique. Microstructure, microhardness and high temperature oxidation behaviour of coatings were investigated. Microstructure of coatings was dense and displayed layers depicting lamellar structure. The microhardness of coatings was significantly higher than that of substrate owing to higher density and cohesive strength between individual splats of coating materials. Cyclic oxidation studies conducted on Ni3Ti and Ni3Ti+(Cr3C2+20NiCr) coatings showed oxide scale was composed of various oxides like NiO, NiCr2O4 and Cr2O3 phases. The formation of compact and protective NiO phase in case of Ni3Ti coatings; NiO and Cr2O3 phases in Ni3Ti+(Cr3C2+20NiCr) coatings stabilised the weight gain exhibited slow oxidation rate at higher temperatures. © 2017 Elsevier B.V.