Journal Articles
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Item Influence of Solid Lubricants on Microstructure and Tribological Performance of Nickel-Based Composite Coatings(Springer, 2022) Gudala, S.; Ramesh, M.R.; Siva Shanmugam, N.S.The present study investigates the microstructure and high-temperature tribological studies of solid lubricant encapsulated nickel alloy coatings developed by tungsten inert gas (TIG) cladding technique. The TIG current values of 90 A, 95 A, and 100 A were considered as process parameters. The microstructure of the coatings (coating A: NiCrSiB/WC/Ag/hBN, coating B: NiCrSiB/WC/MoS2/hBN) was characterized using the scanning electron microscopy, X-ray diffraction, X-ray energy dispersive spectroscopy and EBSD (electron backscatter diffraction) analysis. The dry sliding wear studies were conducted using a pin on disc apparatus, and the microhardness of the coating was assessed using Vicker’s indentation technique. The results show that coating A exhibited high hardness and excellent tribological properties than coating B. In particular, coating A presents the high average microhardness (950 HV), low coefficient of friction (0.34), and wear rate (2.96 × 1−3 mm3/N-m). Additionally, coating A showed three-fold higher hardness and a 2.43 times lower wear rate than the titanium substrate. The lubricant phases (Ag, BN, Mo2S3) and oxide phases (TiO, Ag2O, Ni (TiO3)) formed in both coatings were adequate to reduce the material loss. © 2022, ASM International.Item Microstructure Evolution and Mechanical and Corrosion Behavior of Accumulative Roll Bonded Mg-2%Zn/Al-7075 Multilayered Composite(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.B.; Sahu, S.Multilayered composite of Mg-2%Zn/Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and aluminum 7075 alloy. The Mg-2%Zn/Al-7075 multilayered composite exhibited density of 2295 kg/m3 and an average grain size of 1 and 1.3 ?m in Mg-2%Zn and Al-7075 layers, respectively. A thorough microstructural characterization was performed on the composites by scanning electron microscope, electron backscatter diffraction (EBSD), transmission electron microscope and phase analysis by x-ray diffraction. In addition, mechanical properties were evaluated by microhardness and tensile tests. Corrosion behavior of the multilayered composite was examined using electrochemical polarization test. EBSD analysis showed the presence of ultrafine grains with high-angle grain boundaries. The composite exhibited a significant improvement in ultimate tensile strength (~1.82 times) and elongation (~1.5 times) as compared with Mg-2%Zn alloy, after four-pass ARB process. © 2017, ASM International.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.Item Effect of zinc and rare-earth element addition on mechanical, corrosion, and biological properties of magnesium(Cambridge University Press, 2018) Kottuparambil, R.R.; Bontha, S.; Ramesh, M.R.; Arya, S.; Jana, A.; Das, M.; Balla, V.K.; Amrithalingam, S.; Prabhu, T.R.The present work aims to understand the effect of zinc and rare-earth element addition (i.e., 2 wt% Gd, 2 wt% Dy, and 2 wt% of Gd and Nd individually) on the microstructure evolution, mechanical properties, in vitro corrosion behavior, and cytotoxicity of Mg for biomedical application. The microstructure results indicate that the Mg-Zn-Gd alloy consists of the lamellar long period stacking ordered phase. The electrochemical and immersion corrosion behavior were studied in Hanks balanced salt solution. Enhanced corrosion resistance with reduced hydrogen evolution volume and magnesium (Mg2+) ion release were estimated for the Mg-Zn-Gd alloy as compared to the other two alloy systems. At the early stage of corrosion, formation of the oxide film inhibited the corrosion propagation. However, at the later stages, the breaking of the oxide film leads to shallow pitting mode of corrosion. The ultimate tensile strength of Mg-Zn-Gd-Nd is better than the other two alloys due to the uniform distribution of the Mg12Nd precipitate phase. The moderate strength in the Mg-Zn-Gd alloy is due to the low volume fraction of the secondary phase. The MTT (methylthiazoldiphenyl-tetrazolium bromide) assay study was carried out to understand the cell cytotoxicity on the alloy surfaces. Studies revealed that all three alloys had significant cellular adherence and no adverse effect on cells. © 2018 Materials Research Society.Item Experimental Investigation on Effects of Wire Electro Discharge Machining of Ti50Ni45Co5 Shape Memory Alloys(Springer Netherlands rbk@louisiana.edu, 2018) Soni, H.; Narendranath, S.; Ramesh, M.R.TiNiCo shape memory alloy is most popular shape memory alloy for biomedical applications due to their outstanding properties such as shape memory effect, pseudoelasticity and transformation temperature. Machining of such kind of alloys is very difficult through conventional machining process is very difficult because they may affect their internal properties of these alloys. However conventional machining processes give poor surface quality during the machining hence non-conventional machining processes such as (wire electro discharge machining, water jet machining and electro discharge machining etc.) are more suitable for machining of such kind of alloy. From the literature it has been found that Wire electro discharge machining (WEDM) is more suitable non-conventional machining process for such kind of alloy. Present study exhibits the effects WEDM characteristics of Ti50Ni45Co5 shape memory alloy. L-9 orthogonal array has been created by using Taguchi as a design method for machining of selected alloy and machined surface characterization has been carried out at the optimized process parameters with respect to microstructures, surface topography, microhardness, XRD analysis and residual stresses. To find the optimum setting of the input process parameters a couple of optimization techniques are used, namely principal component analysis (PCA) and Gray relational analysis (GRA) technique. 125?s pulse on time (Ton), 35?s pulse off time (Toff) and 40V servo voltage (SV) were found as an optimal setting for the higher material removal rate (MRR) with better surface roughness (SR) in the present study. Moreover, characterization of the machined surface is performed with respect to microstructures, surface topography, microhardness analysis, XRD and residual stresses. Harder surface observed near the cutting edge and TiNio3 Tio2 and CuZn were noticed on the surface of machined component through XRD analysis. However, compressive residual stress has been noticed on the machined surface during WEDM process. © 2018, Springer Science+Business Media B.V., part of Springer Nature.Item Microstructure and tribological characteristics of APS sprayed NiCrBSi/flyash cenosphere/Cr2O3 and NiCrBSi/flyash cenosphere/Mo composite coatings at elevated temperatures(Institute of Physics Publishing helen.craven@iop.org, 2019) Nagabhushana, N.; Rajanna, S.; Mathapati, M.; Ramesh, M.R.; Koppad, P.G.; Reddy, N.C.In the present investigation NiCrBSi/flyash/Cr2O3 and NiCrBSi/flyash/Mo composite coatings are developed using atmospheric plasma spray technique on superni 76 alloy. Coatings are characterized in terms of microstructure, phase analysis, and microhardness. Tribological properties of the coatings are evaluated using a pin on disc tribometer. Test is conducted under dry sliding conditions at room temperature, 200 °C, 400 °C, and 600 °C respectively. Microstructure and worn surfaces of the coatings are analyzed by utilizing Scanning Electron Microscope (SEM) where in phase analysis is carried out using x-ray diffractometer (XRD). XRD results revealed the presence of ?-Ni as primary phase along with Ni3B, Cr7C3, SiO2 and Al2O3 as minor phases in both the NiCrBSi/flyash/Cr2O3 and NiCrBSi/flyash/Mo coatings. Among the two coatings, Mo composite coating exhibited lower porosity and higher microhardness. The friction coefficient of both the coatings decreased with increasing temperature. The wear rate is found to decrease at lower temperatures but increased at a higher temperature (>400 °C) for Cr2O3 composite coating wherein Friction coefficient is decreased with increase in the temperature for Mo composite coatings. The worn surface analysis conducted revealed abrasive wear at lower temperatures while the transition from abrasive to adhesive is observed at higher temperatures. © 2019 IOP Publishing Ltd.Item Evaluation of Wear Behaviour of Metal Injection Moulded Nickel Based Metal Matrix Composite(Springer Netherlands rbk@louisiana.edu, 2019) Veeresh Nayak, V.N.; Ramesh, M.R.; Desai, V.; Kumar Samanta, S.K.Metal injection moulding (MIM) is a near-net shape manufacturing technology for producing intricate parts, cost-effectively. MIM comprises combined techniques of plastic injection moulding and powder metallurgy. The present study focused on the development of the binder and fabrication of defect free MIM component. A wax-based binder system consisting of paraffin wax (PW), low density polyethylene (LDPE), polyethylene glycol (PEG-600) and stearic acid was established for MIM of NiCrSiB (70% Wt.) + Cr3C2-NiCr (30% Wt.) nickel based metal matrix composite (NMMC) powder. The feedstock was characterised through rheological properties at different temperatures. Injection temperature was determined from the rheological investigation of the feedstock having the 56% powder loading and 44% binder by volume. Sintering process was carried out with the temperature cycle in the range of 1250–1300 ?C under hydrogen purged atmosphere. The MIM components showed good and acceptable shrinkage in linear dimensions. The mechanical properties and wear behaviour of NMMC was studied using a pin-on-disc apparatus with alumina disc.Tests were performed under dry sliding conditions at room temperature and elevated temperatures of 200 and 400 ?C. Results shows that wear rate is maximum at 400 ?C for 40 N and lowest at room temperature for 10 N. Further wear mechanism was analysed using scanning electron microscope (SEM). © 2018, Springer Science+Business Media B.V., part of Springer Nature.Item Sintering metal injection molding parts of tungsten-based steel using microwave and conventional heating methods(SAGE Publications Ltd info@sagepub.co.uk, 2019) Veeresh Nayak, C.; Ramesh, M.R.; Desai, V.; Kumar Samanta, S.K.In recent years, the near net shape metal injection molding process combines desirable features of plastic injection molding and powder metallurgy processes to gain high strength-to-weight ratio for manufacturing complex-shaped parts. The metal injection molding process consists of mixing, molding, debinding, and sintering. Microwave processing has attracted much attention in global research because of its unique features such as its ability to heat and sinter a wide variety of metals and its significant advantages in energy efficiency, processing speed, and compatibility. Also, it presents few environmental risks and can produce refined microstructures. The injected samples to be sintered are composed of fine tool steel metal powder and binders, stearic acid, paraffin wax, low-density polyethylene, and polyethylene glycol (600). In recent years, microwave-assisted post-treatment is considered a novel method for processing green parts. In this work, the green parts are subjected to high-intensity microwave fields which operate at a frequency of 2.45 GHz. Metal injection molding compacts were sintered using multi-mode microwave radiation. The sintering of a metal injection molding compact by microwaves has hardly been reported. The metal injection molding compact showed better results than those produced by sintering with conventional heating. This study evaluates the effect of conventional sintering and microwave sintering on mechanical properties. By optimizing the sintering process, increased sintered hardness, a more homogeneous microstructure, and greater shrinkage were obtained using microwave-assisted sintering. © IMechE 2018.Item Microstructural Characterization and Hot Corrosion Behavior of Plasma-Sprayed Fe17Cr2Ni0.18C/Fly Ash Cenosphere-Based Composite Coating(SAE International, 2021) Hanumanthlal, S.; Siddaraju, C.; Ramesh, M.R.; Thirtha Prasada, H.P.; Somasunder, B.; Virupakshappa, L.The current investigation studies the microstructure and high-temperature hot corrosion behavior of plasma-sprayed coatings. The composition of Fe17Cr2Ni0.18C and fly ash cenosphere powder is maintained in the 0%, 5%, 10%, and 15% ratio by weight percent, respectively. Both powder mixtures were thoroughly blended correspondingly and coated on T22 boiler steel tubings. Thermocyclic hot corrosion studies were examined in a liquid salt condition of Na2SO4 - 60% V2O5 for 17 cycles of 51 h at 600°C on bare and coated steels. Thermogravimetric practice was used to establish the kinetics of hot corrosion of uncoated and coated steels. As-coated samples are studied for microstructure and microhardness. X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy-dispersive spectroscopy, and X-ray mapping characterization techniques have been utilized for structural analysis of the as-coated and hot-corroded samples. It was observed that FeCrNiC/cenosphere-coated steels showed better hot corrosion resistance than the uncoated steels. The coated steels follow the parabolic rate law of oxidation, and parabolic rate constant values are lower in comparison to the uncoated steels. Better resistance is provided by the high-temperature permanence of mullite, alumina, and defensive oxide layer of silicon that is formed at elevated temperatures. ©Item Effect of Ball Milling on the Tensile Properties of Aluminum-Based Metal Matrix Nanocomposite Developed by Stir Casting Technique(SAE International, 2021) Ravikumar, K.S.; Ghanaraja, S.; Ramesh, M.R.Combining ball milling with stir casting in the synthesis of nanocomposites is found effective in increasing the strength and ductility of the nanocomposites. In the first step, the nanoparticles used as reinforcement are generated by milling a mixture of aluminum (Al) and manganese dioxide (MnO2) powders. A mixture of Al and MnO2 powders are mixed in the ratio of 1:2.4 by weight and milled at 300 rpm in a high-energy planetary ball mill for different durations of 120 min, 240 min, and 360 min to generate nano-sized alumina (Al2O3) particles. It is supposed that the powders have two different roles during milling, firstly, to generate nano-sized Al2O3 by oxidation at the high-energy impact points due to collision between Al and MnO2 particles, and secondly, to keep nano-sized Al2O3 particles physically separate by the presence of coarser particles. In the second step, 0.5 weight percent (wt%), 1 wt%, 1.5 wt%, and 2 wt% of the generated Al2O3 nanoparticles are reinforced in molten aluminum-magnesium (Al-Mg) alloy matrix via stir casting to synthesize nanocomposites. The effect of milling on the microstructure of the powder mixture before and after milling has been studied with the use of a scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). The microstructure of the cast composites is examined under SEM, and the fractured surface of the tensile specimens is analyzed through SEM fractographs. Ball milling of reinforcement before adding to the melt brings considerable improvement in the integration and uniform dispersion of the milled particle in the Al-Mg alloy matrix melt, which leads to improvement in the strength and ductility of the cast nanocomposites. ©